With shell. The strength of the shell which is dependent on the arrangement of particles and the binding matrix. Three categories are readily identified, robust, intermediate and fragile. Species with robust shells often have irregular outlines as in D. oblonga. They appear to be non-selective with regards to size or shape of particles, often assembling these materials to be more than one layer deep, and rarely are areas of organic cement seen as part of the surface pattern. Those in intermediate category are probably the largest group and include D. pyriformis, D. gigantea, D. claviformis and others that construct smooth or regular shells and have areas of organic cement showing as part of the surface pattern. Those of fragile category include D. bacillariarum, D. bacillifera, D. brevicolla and D. lacustris, have shells that are fragile or delicate. The shells are constructed mainly of diatom frustules. The choice of shell materials influenced of pH (Heal 1961). (ref. ID; 890)
ref. ID; 1618
Test variable in shape, but generally circular in cross-section; composed of cemented quartz-sand, diatoms, and other foreign bodies; aperture terminal; often with zoochlorellae; cytoplasmic body almost fills the test; typically a single nucleus; many contractile vacuoles; pseudopodia cylindrical, simple or branching; end rounded or pointed; fresh water, woodland soil, etc. (ref. ID; 1618)
ref. ID; 1923
Shell varying from globular to elongated pyriform or acuminate. Aperture without diaphragm. (ref. ID; 1923)
ref. ID; 3686
Shell colourless, yellow or brown; circular, ovoid, pyriform or acuminate; composed of agglutinated mineral particles and diatom-frustules; aperture terminal, circular or lobed, sometimes with an organic border. (ref. ID; 3686)
Shell surface rarely smooth, frequently carrying an incrustation of sand grains. End of fundus acute or with a knoblike process. Widely distributed, usually associated with the preceding species. Habitat ooze of sands and marshy ground. (ref. ID; 1923)
Shell outline; rough, elongate pyriform with a distinct aboral horn. Shell composition; small to large pieces of angular quartz, rarely incorporates diatoms. Shell organic cement; small network. Shell aperture; circular, surrounded by regular arrangement of small particles. (ref. ID; 2024)
The shell is brown, cylindrical with a pointed or acuminate aboral region. The surface is rough and covered with quartz particles and occasionally with fragments of diatoms. The aperture is circular and often covered with a thin layer of organic cement which gives it a smooth outline. (ref. ID; 3686)
Comments
Cash (1909) suggested that there was such a gradation of shape and size between specimens that they could not be considered as varieties. Nevertheless, he did list two varieties D. a. var. inflata and D. a. var. curvata. (ref. ID; 3686)
Measurements
Length from 100-300 µm. (ref. ID; 1923)
Length(L) 224-382; breadth(B) 76-123; diameter of aperture(Da) 40-48 µm; B/L 0.36+/-0.03; Da/L 0.15+/-0.03. (ref. ID; 2024)
This cosmopolitan species is very variable in size. Length 180-455 µm. (ref. ID; 2356)
Total length of the test 190; maximum width 65; diameter of the pseudostome 40 µm. (ref. ID; 2683)
Length of shell 232; breadth of shell 72; diameter of aperture 36 µm (n=1). (ref. ID; 3686)
The shell is brown, elongated oval in shape tapering towards the aperture, and laterally compressed. The aboral region curves in a graceful arc. It is composed of sand grains. The aperture is oval or circular, and is surrounded by a regular array of small particles which sometimes vary in size. The size of the particles used to construct an individual shell is variable, but the general outline can easily be distinguished. (ref. ID; 3686)
Measurements
Length of shell 130-162; breadth of shell 105-130; depth of shell 86-95; diameter of aperture 36-43 µm (n=7). (ref. ID; 3686)
The shell is transparent, colourless or light yellow-brown, ovoid or pyriform usually with a distinct aboral protuberance or horn. The aboral horn is usually pointed, of varying length, and positioned centrally, but it may be deflected to the side when the tapering is uneven. Diatom frustules united by organic cement appear to make up the bulk of the shell, and the compact nature of the shell material only leaves small areas in which either organic cement or small siliceous plates can be seen. It is thought, however, that the basic shell is made or small shell plates and that the diatoms act as reinforcement. The organic cement is seen either as area of a patterned structure of small rings, or as strands between particles. The shape of the aperture is dependent on the arrangement and size of the diatoms which surround it. Small diatoms are usually used and the shape is circular, but it may vary to the extent of being triangular. Chardez (1978) observed that the aboral horn was either present or absent in specimens of D. australis (Playfair, 1918), a species that was initially described as a variety of D. bacillariarum. Although D. australis is alleged to differ from D. bacillariarum in size, the range of measurements given by Playfair (1918) for Australian species of both species are similar. Furthermore, Playfair noted that one specimen of D. bacillariarum australis was formed entirely to nebeloid plates, which supports the observation made above regarding the inner shell and diatom reinforcements. (ref. ID; 890)
The shell is colourless, ovoid and circular in transverse section. It is composed of thin siliceous plates overlaid by diatom frustules. The aperture is circular, but the shape is often masked by diatom shells. There has been considerable confusion between this species and Difflugia elegans. The main differences are that D. elegans is composed mainly of sand-grains overlaid with diatom shells, and has a distinct constriction just posterior to the aperture. The presence or absence of a terminal protuberance as a diagnostic character is questionable. It is absent on our two specimens of D. bacillariarum, but most of our specimens of D. elegans have a pronounced horn. (ref. ID; 3686)
Measurements
Length 73-103 µm; breadth 37-47 µm; diameter of aperture 17-24 µm. (ref. ID; 890)
Their tests were heavily beset with diatom frustules, and the total length was 70 µm. (ref. ID; 2683)
Length of shell 67-69; breadth of shell 40-44; diameter of aperture 22-24 µm (n=2). (ref. ID; 3686)
Difflugia pyriformis var. bacillifera Levander, 1895 (ref. ID; 1316); Difflugia septentrionalis var. bacillifera Averintzev, 1900 (ref. ID; 1316)
Descriptions
The shell is usually transparent, light brown or yellow, ovoid or elongate with a distinct, long, cylindrical neck. The outline, however, is often masked by the diversity of diatom frustules that are incorporated into the structure, and in some instances the whole of the shell may appear to be an amalgamation of diatoms. The siliceous materials used vary from diatom frustules almost equal in length to the body of the shell, to small frustules about 10 µm long, and spherical siliceous cysts of chrysomonad flagellates. The smaller frustules and cysts are usually found surrounding the aperture and at interstices between the larger frustules. The organic cement that binds the shell materials together is in the form of rings, similar to those for D. curvicaulis and D. elegans, but differing in having a perforated membrane inside the rings. These organic rings may often be pushed together so that they overlap. The aperture is usually circular, but may even be triangular if the large diatom frustules of the main shell body are incorporated as they occasionally are. Chardez (1966) stated that this species was considered to be rare, but that it was typical of certain environments. However, Ogden stated that D. bacillifera is not rare in Britain. (ref. ID; 890)
Shell variable in form, usually with a rounded fundus tapering into a narrow, often cylindrical neck; membrane hyaline, covered wholly or in part with diatoms, which are sometimes scattered with sand particles or foreign bodies such as minute tests of siliceous flagellates or rhizopoda, e.g. Euglypha laevis. Habitat Sphagnum pools and mosses. (ref. ID; 1923)
The shell is brown, ovoid or elongate, and the outline is often concealed by adhering diatom frustules. Cash (1909) suggested that the extent to which diatom frustules are incorporated was dependent on the season. Our specimens have attached various diatoms from the genera, Tabellaria, Frustulia, Pinnularia and Eunotia, but we have not observed any seasonal trends. The aperture is circular and surrounded by small quartz particles. (ref. ID; 3686)
Measurements
Length 117-176 µm; breadth 54-80 µm; diameter of aperture 17-27 µm. (ref. ID; 890)
Length 145-160 µm. (ref. ID; 1923)
Length of shell 130-194; breadth of shell 59-91; diameter of aperture 25-36 µm (n=8). (ref. ID; 3686)
This variety differs from the species by its smaller size and the extreme narrowness of the shell. It has thus an almost cylindrical and tubular appearance. (ref. ID; 2392)
Measurements
Its measurements vary from 80-90 µm for the length, diameter of the shell 28-30, and of the aperture 10-12 µm. (ref. ID; 2392)
The shell is transparent, yellow or light brown, spherical with a short neck. The neck, in ventral view, varies from being easily visible to being obscured by shell components, but at either extreme it is usually apparent in apertural view. It is composed mainly of a mixture of small diatom frustules, small pieces of quartz and siliceous cysts of chrysomonad flagellates. In addition, the empty shell cases of smaller testate amoebae, for example Trinema, are often attached to the shell and aggregations of material are sometimes attached to the aboral extremity. The organic cement is only occasionally visible because the shell material is so well packed, but it appears either as a matrix with small rings or as small spheres and rings. The aperture is circular, borded by an arrangement of small particles and diatoms, and it usually has a regular even outline. A smooth cyst membrane seals the mouth of the aperture in some specimens. The description given here differ from Heal's (1962) observation that D. brevicolla incorporates "much mineral matter" in its shell. Using the terminology given by Heal, D. brevicolla should be listed with D. bacillariarum and D. bacillifera in having "little mineral matter". (ref. ID; 890)
Its transverse section being slightly compressed; however, the presence of a carina built up by a single row of sand-grains gives to the whole an aspect as if it were much more compressed than it actually is; indeed, without carina, the body is but very slightly compressed. On the fundus of the test, the carina may be built out of two rows of sand-grains, while there is but a single row on the lateral sides. The sand-grains on the body-surface are as numerous as in most Difflugia-species. The mouth-margin is built up by an irregular series of sand-grains. The keel makes a circle around the body, and continues till 1/4 of the length of the test, beginning from the mouth. (ref. ID; 2233)
See Difflugia gigantea. (ref. ID; 2022)
Shell outline; smooth, pyriform with a conical aboral cone (cone sometimes reduced or absent). Shell composition; small to large pieces of flat quartz, plus occasional diatom. Shell organic cement; regular network. Shell aperture; circular surrounded by regular arrangement of small particles. (ref. ID; 2024)
The shell is brown, pyriform with the apical region having a terminal conical protuberance. The sides swell evenly from the aperture to reach their widest diameter and then curve gracefully to the conical protuberance. It has a smooth outline and is composed mainly of sand-grains held together by a mesh of organic cement. The aperture is circular and surrounded by an even arrangement of small particles. (ref. ID; 3686)
Measurements
Length(L) 288-316; breadth(B) 105-123; diameter of aperture(Da) 34-40 µm; B/L 0.43+/-0.07; Da/L 0.14+/-0.01. (ref. ID; 2024)
Length of shell 247-393; breadth of shell 97-196; diameter of aperture 33-62 µm (n=12). (ref. ID; 3686)
Difflugia compressa (Leidy) Gauthier-Lievre & Thomas (ref. ID; 2147, 2152) or Leidy (ref. ID; 3496)
Test laterally ovoid, fundus more or less prolonged obliquely upward, rounded, and simple or provided with spines; soil forms generally spineless aperture antero-inferior, large, circular or oval and its edge inverted; test composed of quartz grains; colorless to brown; cytoplasm colorless; in the ooze of ponds and in soil. (ref. ID; 1618)
Test ovoid to spheroid, circular in cross-section; crown broadly rounded, with a variable number of spines, aperture more or less convex in profile, central and it border multidentate of multilobate; test with fine sand-grains, opaque cytoplasm colorless; pseudopodia numerous, long, branching or bifurcating; in fresh water. (ref. ID; 1618)
Shell ovoid inclining to spheroid, composed of large sand grains or flattened silicious plates, smooth and regular in outline. Teeth usually more than 12 in number, evenly arranged or not. Fundus with 6 to 9 spines, but sometimes with 1 to 4, or none at all. Nucleus single. One of the best known species of Difflugia, used by Jennings in his genetical research. Common in ooze of ponds. (ref. ID; 1923)
The shell is brown, spherical or ovoid and has a variable number of spines on the aboral region. It is composed of quartz particles, with the small pieces being cemented into the gaps between larger pieces to reproduce a relatively uniform surface. The aperture is circular and surrounded by a denticular collar. The tooth-like structures are evenly spaced, number between 12 to 20, and are composed of small particles cemented together. A study of cultured and wild specimens of D. corona by Jennings (1916 and 1937) showed that this species varied considerably in size and shape. The aboral spines are easily broken because they project some distance from the shell, so that variation of this feature should be expected. (ref. ID; 3686)
Test barrel-shaped, oval, gray, not transparent. Horns are situated at the base of the fundus, they are stout and pointed down. Aperture 12-13-lobed, lobes raised above test and form a small, differentiated collar that is distinctly visible laterally. Inner part of each lobe extends keel-like and forms a longitudinal riblike tooth the height of which is equal to that of the collar. In this way, the inner costate structure of the collar is formed where the number of equally large riblike teeth is equal to the number of lobes. In addition, on each tooth, a distinctly formed small triangular denticle with the tip directed upward is situated apically. The so-called dentate pseudostome (aperture) of D. corona is formed in connection with the transformation of the lobes of the collar. A diaphragm under the teeth is absent or there may be fragments. Diameter of the pseudostome is always more than 0.50 times maximum diameter of the test. The test consists of equally large sand grains densely packed next to each other, at the junctions between them the cement film with open pores is visible. (ref. ID; 7923)
Remarks
In our collections from the Snov River floodplain (15 km up from the mouth) Difflugia specimens had the dentate pseudostome typical of D. corona, but they differed in the presence or absence of a diaphragm rudiment beneath its teeth. SEM of the structure of the tests of these two forms, with and without a diaphragm, raised a question on the validity of the species Protocucurbitella coroniformis and the taxonomic status of both its forms. The genus Protocucurbitella Gauthier-Lievre & Thomas, with the single species P. coroniformis and its two forms, pussila and ecornis, was described from material from Central Africa in 1960. We know of no other mentions of these taxa. The principal characters used to distinguish the genus and place it between Difflugia and Cucurbitella include the presence of a diaphragm rudiment beneath the teeth of the pseudostome and the absence of a collar or a little-differentiated collar. But based on the shape and size of the test, the structure of the collar, the number and nature of the teeth of the pseudostome, Protocucurbitella coroniformis and Difflugia corona are extremely similar. For both species, ecornis forms have been identified (Gauthier-Lievre & Thomas, 1958) that have the same distinctive characters, including absence of horns on the test. As a result, the significance of a diaphragm rudiment as the basis of the genus Protocucurbitella is questionable. Analysis of our own data and the literature suggests that the presence or absence of a diaphragm rudiment is not a consistent character, that it is variable even within a single population (for example, the Snov River floodplain). Thus, in Fig.(a), a form is shown with a diaphragm rudiment and in Fig.4(c) one without. At the same time, in the photographs of D. corona presented by Ogden and Hedley (1980: 120, Figs.A, B), we see fragments of the diaphragm, which is the decisive character in the description of the genus Protocucurbitella. Evidently, fragments of the diaphragm beneath the teeth of the pseudostome between its lobes may be present during formation of the pseudostome or encystment, but are not a consistently present structure. The fact of the presence of a diaphragm rudiment is not sufficient, in our view, to separate the genus Protocucurbitella or for a species within the genus Difflugia. Thus I synonymize Protocucurbitella with Difflugia and the species P. coroniformis Gauthier-Lievre & Thomas, 1960, with the species D. corona Wallich, 1864. (ref. ID; 7923)
Ecology
Eutrophic waters, on the substrate and periphyton on aquatic plants. Widespread in Ukraine. Cosmopolitan. (ref. ID; 7923)
Examined materials
Difflugia were collected in the Snov River floodplain on higher aquatic plants, Chernigov Oblast, 14.IX.1989; in the Dnieper floodplain in the region of Kiev on macrophytes, 3.IX.1987; abundant. (ref. ID; 7923)
Measurements
180-230 µm by about 150 µm. (ref. ID; 1618)
Length without spines 180-230 µm. (ref. ID; 1923)
Length of shell 137-189; breadth of shell 141-176; diameter of aperture 51-83 µm (n=12). (ref. ID; 3686)
Long. testae(L) 112.3-128.2 (average 119.7) µm, Lat. testae(B) 112.0-120.0 (average 114.7) µm, Diam. pseudost. inter dent.(d') 46.0-56.0 (average 51.7) µm, Diam. pseudost. inter lob.(d") 59.4-66.7 (average 63.0) µm, Dentis (long.) average 24.0 µm, Aculeus (long.) 24-32 (average 26.7) µm, d":B 0.53-0.56 (average 0.55) (n=10). (ref. ID; 7923)
Test almost round or barrel-shaped, slightly narrowed toward the pseudostome, light, not transparent. Horns small, situated at the base of the fundus, directed down and to the side, their structure analogous to the structure of the test. Pseudostome 12-13-lobed, slightly raised lobes form a small collar visible laterally. On the inner side of the lobes, as in the type form of D. corona, costate teeth are formed that are as high as the collar. Triangular small denticles and the costate teeth are lacking. Beneath the teeth of the pseudostome, there may be fragments of a diaphragm. Diameter of the pseudostome is always less than the greatest diameter of the test. The test consists of densely packed sand grains that are covered with a film of cement. At the junctions of the sand grains, the test is provided with rows of pores. The cement is abundant and its film uniformly covers the entire test. On an encysted specimen, which has an aperture plug, it is evident that the plug forms at the base of the teeth, that is, at the place where the so-called diaphragm rudiments may be observed. (ref. ID; 7923)
Remarks
These Difflugia were found together with the type form of D. corona. This similarity in test structure, aperture, and type of cement is obvious. They differ from D. corona is having a smaller pseudostome, smaller processes on the fundus, and absence on the costate teeth of small denticles. In many of them, there were fragments of a diaphragm beneath the teeth of the pseudostome. As we indicated above, the presence of a so-called diaphragm is not sufficient to separate the genus Protocucurbitella or a species within the genus Difflugia. The individuals described here are also close in shape to var. pussila of the species Protocucurbitella coroniformis (Gauthier-Lievre & Thomas, 1960), since they have small processes on the fundus and their pseudostome is always less than 0.50 times the greatest diameter of the test. These characters are sufficient grounds for separating the variant pusilla within the species D. corona. In our case, the dimensions of the test were less than those indicated for the African specimens (L without horns 110-150 µm, L with horns 135-185 µm, B: 120-150 µm, D(pseud): 45-50 µm. In 1987, a second species of Protocucurbitella, P. mitrata Chardez, from ponds in Belgium was described (Chardez 1987). The description and drawings provided by the author make it possible to postulate that, in this case, we are most likely dealing with an undetermined form of the species D. corona. Thus P. mitrata (Chardez) requires clarification (a species inquirenda). (ref. ID; 7923)
Ecology
Eutrophic waters, in the littoral, on the bottom and aquatic plants; substrate-muddy sand, black mud smelling of hydrogen sulfide; pH 6-6.5. (ref. ID; 7923)
Examined materials
Difflugia were collected in the Snov River floodplain 15 km up from the mouth, on higher aquatic plants, Chernigov Oblast, 14.IX.1989 (45 specimens); in the Dnieper River floodplain in the region of Kiev, on macrophytes, 3.IX.1987 (3 specimens). (ref. ID; 7923)
Difflugia acuminata f. curvicaulis (ref. ID; 2352)
Descriptions
Shell outline; smooth, pyriform with a distinct aboral hone, often curved and perforated at apex. Shell composition; small and medium pieces of flat quartz. Shell organic cement; regular network. Shell aperture; circular surrounded by regular arrangement of small particles. (ref. ID; 2024)
The shell is colourless or brown, elongate or ovoid, circular in transverse section, and the aboral region terminates with a tubular horn which is often curved and perforated at its apex. It is composed of siliceous particles, often interspersed with a mesh of organic cement, arranged to give a smooth outline to the shell. The aperture is circular and surrounded by a rim of small particles. This species was considered by Cash (1909) to differ from D. acuminata only in the form of the terminal horn. Examination of our specimens shows that D. curvicaulis differs from D. acuminata and D. elegans in the smoothness of the shell, the shape, and in the form of the aperture. (ref. ID; 3686)
Measurements
Length(L) 159-232; breadth(B) 70-97; diameter of aperture(Da) 35-44 µm; B/L 0.47+/-0.05; Da/L 0.22+/-0.02. (ref. ID; 2024)
Length of shell 146-191; breadth of shell 74-88; diameter of aperture 34-42 µm (n=7). (ref. ID; 3686)
Shell outline; rough, pyriform usually with a constriction near the aperture to form a neck, and an aboral horn often curved and perforated at apex. Shell composition; small to large pieces of angular quartz and often diatom. Shell organic cement; unconnected rings. Shell aperture; circular or oval, surrounded by an irregular mixture of particles. (ref. ID; 2024)
The apex of the test sometimes has two spines more or less symmetrically placed instead of a single spine. (ref. ID; 2356)
The shell is brown, ovoid with an acuminate aboral region which terminates in a tubular horn, and there is a distinct constriction posterior to the aperture. In transverse section it is circular, and composed of sand-grains and diatom frustules. The aperture is circular and surrounded by an irregular arrangement of particles and diatoms. Variation in the construction of the test is considerable, as is the length of the tubular horn, but the constriction behind the aperture distinguishes this species from D. bacillariarum which it closely resembles. (ref. ID; 3686)
Measurements
Length(L) 113-151; breadth(B) 75-95; diameter of aperture(Da) 35-48 µm; B/L 0.59+/-0.07; Da/L 0.33+/-0.04. (ref. ID; 2024)
Length 80-162 µm. (ref. ID; 2356)
Length of shell 117-158; breadth of shell 69-99; diameter of aperture 39-55 µm (n=14). (ref. ID; 3686)
Difflugia elegans var. parva Chardez, 1969 (ref. ID; 2126, 2555, 3568)
Descriptions
The test is shortly pear-shaped, not compressed. The rear part of the test is pointed. The cover consists of xenosomata of different size which mostly do not touch each other. The aperture is circular. (ref. ID; 2555)
Measurements
Length of the test 45-60 (Chardez 1969), 58 (Opravilova 1989); width of the test 30-35 (Chardez 1969), 29 (Opravilova 1989); diameter of the aperture 18 µm (Opravilova 1989). (ref. ID; 2555)
Shell ovoid, circular in cross section, with a well defined apertural rim; walls constructed of an organic matrix with siliceous particles added; aperture large, circular; cytoplasm does not fill casing, nucleus with many peripheral nucleoli, two or three contractile vacuoles, peroxisomes and symbiotic bacteria present; lobose pseudopodia. (ref. ID; 4799)
Descriptions
Active individuals usually extend one large lobose pseudopod from which one or two smaller branches may develop near the point of extrusion. Such pseudopods may extend for one and a half times the body length, about 80 µm, and may be up to 10 µm in diameter. Bands of filaments are often seen running along the length of large pseudopods; their appearance corresponds to the dimensions of microtubules but they could equally be bands of microfilaments. The cytoplasmic body occupies about two-thirds of half of the anterior shell volume around the aperture in moving animals, the posterior portion of the shell being unoccupied. A central nucleus and two to three contractile vacuoles are clearly visible in the cytoplasm. Pseudopodia in the vicinity of the aperture consist of a range of cytoplasmic strands which vary in size from 0.5 µm to about 5 µm in diameter. (ref. ID; 4799)
Specific designation
Due to the confusion surrounding earlier descriptions of globular forms of Difflugia, the species studied here was previously considered by Ogden (1988) to represent Difflugia globulosa sensu Penard, 1902, based on general size, shape and composition of the shell. Nevertheless, it was noted then that there were differences such as the presence of a distinct organic apertural collar and the regular size of the body and aperture. Further investigation of the cytoplasmic features of these specimens shows that they also differ from the earlier forms reviewed by Penard (1902) and Cash & Hopkinson (1909), in one important feature, the shape and structure of the nucleus. These earlier authors described most globular forms as having a single nucleus with a large central nucleolus. One spherical species, Difflugia subequalis, was described by Penard (1910) to have a single nucleus and several nucleoli. Nevertheless this species has substantially different measurements, on average a body length of 81 µm compared with 55 µm, a breadth of 88 µm compared with 52 µm and an aperture diameter of 53 µm compared with 23 µm. In addition aperture was not perpendicular with axis of the shell, hence the specific name. The specimens examined here are now considered to be sufficiently distinct to justify designation as a new species, the diagnostic features of which are: a distinct organic apertural collar, regular body size and aperture, and a single nucleus with several, mainly peripheral, well defined nucleoli. (ref. ID; 4799)
Etymology
The name being Greek, ge = earth and sphaira = ball. (ref. ID; 4799)
Difflugia oblonga var. gigantea Chardez, 1967 (ref. ID; 2151)
Descriptions
This species has the typical pyriform shell with a spherical fundus, and tapers towards the aperture for about half of the total shell length. The shell surface is smooth and constructed of medium pieces of flattened quartz. The aperture is circular or oval, and surrounded by small particle of quartz. Areas of organic cement are often seen binding the quartz together and the surface of this cement is perforated by small regularly spaced opening. This species is similar to D. claviformis in having a smooth shell, but it lacks the aboral cone and has a structurally different organic cement. (ref. ID; 2022)
The shell is brown, spherical or hemispherical, usually composed of large quartz particles but may also include diatom frustules. The general appearance is a rough shell although some smoother forms have been seen. The aperture is circular, and surrounded by smaller particles which often appear smooth due to the overlaying cement. Variation in this species is prolific, both in the composition of the shell and the size of the aperture in relation to the diameter of the shell. (ref. ID; 3686)
Comments
Penard (1902) described this species as having two distinct forms, the typical form and one varying between 135 and 155 µm. He also described two smaller forms 50 to 70 µm in size. Cash et al. (1909) described a small form (15-50 µm) under the name D. globulus, and suggested that Dujardin's original description of D. globulosa was ambiguous. In agreement with recent descriptions we have accepted Penard's (1902) re-description of D. globulosa. (ref. ID; 3686)
Measurements
Diameter of shell 91-119; depth of shell 79-113; diameter of aperture 33-58 µm (n=13). (ref. ID; 3686)
In culture: In the absence of mineral particles D. globulosa can construct a complete shell casing composed of organic building units. This represents the first evidence that a hitherto agglutinate Difflugia is capable of totally covering itself in a secreted organic shell. This shell is spherical, with a regular outline, and has a small, smooth, raised collar surrounding a circular aperture. It is usually slightly longer than wide, the aperture being about half the diameter of the body. Examination of the surface detail shows that in culture it is composed of an aggregation of small, often circular organic building units, packed together in random order. It would appear that most of these units are of similar dimensions, and have a slightly raised, variable sized central zone. In some instances a circular opening is present often at the centre and occasionally at the edge of this central zone. The units may closely abut to each other in small areas to form an alomst regular tessellated group. Similar units are present on the apertural lip, but here they are compressed to give a smooth layer, with some units apparently fused to their neighbours. Sections through the apertural lip show that there are several units making up this region. In parts the overlapping of the units here are such that they are curved to reconnect with the shell wall and form an enclosure. At others there is a distinct separation between the single wall layer and the thickening of the lip which just arches over. In both of these micrographs waste products have been enclosed within the curvature of the lip, in other sections whole bacteria have been seen. It is assumed therefore, that in these specimens there is some continuity between the lip enclosure and the surrounding environment. These shells are considered to be "young", having thin walls surrounding relatively compressed units. In a recently formed shell the wall units are often so compressed that they appear to have opposing walls that almost meet. Ageing of the shells results in the expansion of the units which are then seen to contain an inner fibrous concentration. These contents are lost in sectioning and staining, hence the while appearance seen in the figured sections. Fractured portions of older shells show that there has been some strengthening of the walls of individual units because they are seen as straight, clean structures, with an aggregation of other material close to the external surface. It is assumed that the contents from those units showing such clear cut walls have been torn cleanly out of the unit, to leave an empty compartment. This is consistent with the earlier opinion (Hedley et al. 1976) that these contents were mainly inorganic chemical elements with a fibrous or crystalline appearance and easily lost. Although the inner face of the shell is seen as a smooth, continuous sheet, the units here having fused without leaving any signs of junctions between adjacent walls, the outer surface is overlaid with a thin additional layer with seems to cover all the folds and hollows. Close to the aperture these units may be compressed into discs and a gradual overlapping of the units takes place. The smooth protrusions seen are thought to be inorganic inclusions. Smaller round concentrations are also seen attached to the faces of the inner walls, these may represent nucleating sites for elemental deposition. When sterilised soil was introduced into fresh culture, the animal promptly included mineral grains into the fabric of the shell. A clean unmarked collar is still clearly visible, with the mineral grains arranged so that the coarser angular pieces were confined to the aboral extremity, and only the smaller smoother grains are used in the anterior region. Detailed examination of the surface shows that they are almost entirely covered with agglutinate material and only small areas of organic cement are seen. These are usually restricted to strands of cement and the occasional unit with a central opening. Fractured edges of such shells show that the basic unit layer remains the same, with the inner surface having a regular smooth lining. The outer wall of the units adhere to and hold the mineral grains, and it seems that in some instances this facet has moulded itself to the contours of the grain. A culture of diatoms, grown from the initial isolate, was introduced into a fresh culture of Difflugia. Although some frustules were incorporated into the shell matrix they were not generally used. Initially it was considered that as this was a mixture of live diatoms and empty shell, perhaps only empty shells were used. However, when there were mainly empty shells there was no observable change in the numbers used in the shell architecture. The main body is still composed almost exclusively of organic building units, with the frustules scattered sparsely over the surface. Whole frustules are usually seen at the aboral position, but sometimes they are positioned to run the length of the shell apparently embedded in the building units. Although such frustules appear to rest only on the surface of the outer face of the building units, the edges are seen to be held by thick and thin strands of cement. There seems to be no strand of cement holding the central zone of such frustules and no internal depression of the inner, curved surface of the shell, which remains as a smooth lining. This unaltered contour of the inner lining is achieved by slightly compressing the underlying units. The cavity formed by the building units curving over to make the apertural lip, is seen in these older specimens, to be filled with a smooth, structureless substance. Elemental chemical analysis was carried out on some organic shells which did not have any agglutinate particles, using an X-ray dispersive system attached to an Hitachi S500 scanning electron microscope. The main elements detected were calcium, iron, manganese and phosphorus, with traces of chlorine and potassium, and questionable traces of silicon, sulphur and zinc. Such results indicate that calcium, iron and manganese are the principal ions used to strengthen the organic matrix, the high value for phosphorus is probably associated with calcium, as alkali phopshates are soluble in water and tertiary phosphates of other metals are insolbule. (ref. ID; 7506)
Examined materials
Collected at the edge of a drainage dyke near Pedwell, King's Sedgemoor, Somerset in July 1984. (ref. ID; 7506)
The description given by Cash & Hopkinson (1909) for D. globulus (Ehrenberg, 1848): "Test ordinarily globular or hemispherical, but subject to variation, truncated on the broad ventral surface; composed of chitinous membrane, with an incrustation of sand-grains or diatom frustules, or both of these; the mouth circular, its margins not invaginated, often large proportionately to the size of the structure". As Cash & Hopkinson stated a great deal of confusion had arisen regarding the name and description of this species, the name globulosa being given by Dujardin (1837) to a species with a small aperture and a chitinous shell, under their reproduction of Dujardin's text figure of D. globulosa (their Fig.51, p.36) they suggest that it is a synonym of "?=D. lobostoma". A further complication was the description by Wallich (1864) of a heavily encrusted species as D. globularis Duj., which was considered by Cash & Hopkinson (1909) to be an error for D. globulosa Duj. Fortunately, this error can easily by confirmed because Wallich's copy of Leidy (1879) monograph is held in the British Museum (Natural History) and contains Wallich's pencilled comments alongside Leidy's text. Against the sentence that the name D. globularis was evidently a mistake for that of D. globulosa, Wallich has written "quite true, it was a mistake". Leidy's work joined several forms together under the name D. globulosa Duj., including some of the smaller shelled specimens which probably belong to the genera Phryganella Penard, 1902, Pseudodifflugia Schlumberger, 1845 and Cyclopyxis Deflandre, 1929, these forms differ mainly from Difflugia in the character of their pseudopodia. The breadth of Leidy's (1879) description was such that no specific identification is possible although two comments are worth noting - "the smallest specimens frequently consist of a chitinous membrane incorporated with variable proportions of sand grains, and are more commonly of a yellowish hue" and that in his "experience it has occurred to meet with dead shells of D. globulosa more frequently than with living specimens". The range of measurements he gave for this species, 36 µm to 300 µm long with an aperture varying from 30 µm to 160 µm wide, are an unlikely range of parameteres.
Penard (1902) reiterated the earlier comments on nomenclature problems and considered that Leidy (1879) had included too many different types of rhizopods under the name D. globulosa. He considered that there were two quite distinct varieties of D. globulosa, the first "genuine" form was 70-110 µm long, with a chitinoid shell, covered with small grains, sometimes diatoms; with a round mouth about half the diameter of the width of the shell: the second form he likened to Wallich's description of D. globularis, it ranged from 135-155 µm in length; composed mainly of angular grains with a little cement; the round mouth surrounded by an arrangement of smaller grains than those making up the body. Penard also described two other variants, the first was hemispherical, mainly chitinoid with a diameter of 50 µm, the aperture being almost the same diameter; and the other was 65-70 µm long, spherical, covered with large grains and having an aperture with a width about a quarter that of the diameter of the body, the further commented that it would have been interesting to study live animals but these were not easily found. (ref. ID; 7506)
The shell is brown or purplish-grey, spherical or ovoid. The surface is rough and covered with sand-grains, but like D. corona the gaps between large particles are often filled with smaller fragments. The aperture is trilobed and is surrounded by a slightly raised collar of small particles cemented together. (ref. ID; 3686)
Comments
This species varies in size and in the composition of the shell, according to Cash (1909) who stated that sometimes the shell was made of thin siliceous plates. Leidy (1879) described a specimen with five lobes surrounding the aperture, whereas Penard (1902) described both curved and rectangular shaped lobes. (ref. ID; 3686)
Measurements
The length of the test was 70 µm and the diameter 45 µm. (ref. ID; 2683)
Length of shell 80-98; breadth of shell 68-95; diameter of aperture 28-36 µm (n=4). (ref. ID; 3686)
The new species differs from known species of collared Difflugia first of all in the presence of teeth on the inside of the collar. In addition to this distinctive character, the new species differs from Difflugia hydrostatica Zacharias, 1897, to which it is closest in shape and size of the test, in the presence of the inner layer of cement lining the collar, which along with the teeth imparts great structural distinction to this element of the test. The new species differs from Difflugia rubescens Penard, 1891, the only species in the genus known to me having similar teeth, by the shape of the test. (ref. ID; 7923)
Descriptions
Test light, trasparent, mostly round, sometimes somewhat laterally compressed. Low collar distinctly defined, cylindrical, edges the round aperture, always armed on the inside with teeth, the number of which and the extent to which they are formed vary. In most cases, there are 6-8 teeth, but there may be 1-2 large, well formed teeth and rudiments of others in the form of a small point or tubercle. From the inside, the line connecting the collar and test is sharply defined. In one specimen, small teeth are distinctly visible on this line while only one large tooth was formed on the apical edge of the collar. At the junction of the test and collar, a groove is distinctly defined on the outside. The outer covering of the test consists of flat sand grains, densely packed and embedded in the matrix; sometimes sections of the cement are visible at the junctions of the form of a group of compressed cone-shaped elements with a central opening. The organic material of the test also forms knobs and rods which may entirely cover the sand grains. Above this structure are diatom valves which are numerous, always present in the test composition and form a second layer of the skeleton. The collar has a similar structure, that is, its outer part consists of exogenous material embedded in a matrix. Apically, the collar is covered with a layer of cement on which there may be groups of grains; this may be the idiosome. From the inside, the collar is lined with a smooth layer of cement which evidently forms the apical structure of the test, including the tooth. Formation of pseudopodia not observed. (ref. ID; 7923)
Ecology
Wet Sphagnum bogs, primarily on the substrate inside hummocks, pH not higher than 5; common. (ref. ID; 7923)
Etymology
The name heterodentata is given because of its most characteristic feature. (ref. ID; 7923)
Examined materials
Shelled amoebas from substrate in the "Mokh" sedge-Sphagnum bog, Chernigov Oblast, 19.XI.1989 (45 specimens). (ref. ID; 7923)
The lateral compression of the test and presence on the lateral corners of the fundus of two arched horns or conelike tubercles, in the case of underdevelopment of the horns, sharply distinguishes this species from other species of the genus with processes, including the most closely related, D. elegans Penard, 1890, which also has two processes, but the test of D. elegans and its forms are not laterally compressed. (ref. ID; 7923)
Descriptions
Test light, gray, transparent, laterally compressed, in cross section oval, aperture also slightly oval. At the base of test symmetrically along the sides are two processes or horns closed by plugs. They are either distinctly formed and turned down or not entirely formed, in which case the test is trapeziform. The fundus is slightly pointed. The aperture is large, its edge uneven because of various-sized sand grains arranged along the edge of the aperture. The test consists of various exogenous material, including sand grains, diatom valves, cysts, and plates of other species of Rhizopoda; they are tightly packed and the surface of the test is uneven. The cement matrix holding the test elements is abundant, particularly close to the aperture, visible only at the junction of individual particles and appears like small plates consisting of densely packed projecting cone-shaped ridges with an opening in the center of each. Forms without the outgrowths and with curved horns were found, but the latter dominate (ratio of 2:1). Formation of pseudopodia was not observed. (ref. ID; 7923)
Remarks
Despite the great difference in dimensions, a similarity between the new species and Difflugia nodosa var. crassa (Cash, 1909) (Chardez, 1960), may be seen. In the latter, the test is laterally compressed, the number of horns is two or more; the fundus, if it bears no more than two horns, may be extended wedgelike. However, D. nodosa var. crassa is a very large form with a test 250-450 µm long (Chardez 1960). The new species most likely is a smaller Difflugia. In addition, in D. nodosa and its forms, the organic cement matrix is of a different type. It consists of porous, comparatively large plates, the pores are simple, small, without ridges and thickenings. Thus, D. juzephiniensis has features distingushing it from other species of the genus. (ref. ID; 7923)
Ecology
Found in sedge-Sphagnum bogs, on mosses and inside hummocks in the substrate, wet moss, pH not higher than 5; density is high. (ref. ID; 7923)
Etymology
Species named afther the type locality. (ref. ID; 7923)
Examined materials
Shelled amoebas from wet moss in the "Yuzefinovskaya" sedge-Sphagnum bog, Rovno Oblast, 8.VII.1988 (20 specimens); from the "Mokh" and "Gal'skiy Mokh" sedge-Sphagnum bogs, Chernigov Oblast, 19.XI.1989 (many specimens). (ref. ID; 7923)
The shell is brown, ovoid with the apertural end truncate, and is composed of assorted quartz particles and diatom frustules. The aperture is surrounded by a shallow undulating lip, which may appear lobed, whilst the neck of the aperture is often recessed into the body of the shell. This species can be distinguished from D. amphoralis Hopkinson, 1908 by the presence of a recess at the base of the neck. (ref. ID; 3686)
Measurements
Length of shell 158; breadth of shell 118; diameter of aperture 52 µm (n=1). (ref. ID; 3686)
The shell is transparent, colourless, ovoid with a long, thin neck that makes up about half of the shell length. It is composed of a mixture of flattish pieces of quartz, fragments of diatom frustules and some small siliceous plates. The neck has an encrustation of quartz particles just anterior to the junction with the body. Small isolations of organic cement, in the form of small rings, are sometimes seen. The aperture is circular and surrounded by small pieces of quartz. (ref. ID; 890)
The shell is yellow or hyaline, elongate and tapering at both ends. It is composed of siliceous angular particles arranged so that the sides appear polished and smooth. The aperture is circular and surrounded by an organic collar. The shell may sometimes be more sharply pointed in the aboral region, but the clean outline of this species is the main distinguishing feature. (ref. ID; 3686)
Measurements
Length -260 µm. (ref. ID; 2356)
Length of shell 116-159; breadth of shell 46-72; diameter of aperture 23-28 µm (n=4). (ref. ID; 3686)
Difflugia urceolata var. lebes Penard, 1893 (ref. ID; 3693)
Descriptions
Neck sometimes indistinct, aperture large and entire. Shell very fragile, covered with silicious flattened particles. Collar straight, rarely recurved (= var. elongata Penard). Sometimes more than 100 nuclei. Feeds on large diatoms. Habitat ooze at the bottom of lakes, ponds. (ref. ID; 1923)
Measurements
One of the greatest Difflugia, some reaching 400 µm in length, or more. (ref. ID; 1923)
Difflugia lobostoma Leidy var. limnetica Levander, 1900 (ref. ID; 3693)
Descriptions
The tests of D. limnetica consist of xenosomes, i.e. of polymorphic mineral particles (grains of sand, frustules of diatoms, etc.) of different origin and organic "cement" in the interstices. (ref. ID; 2028)
The oral opening is always trilobated, the three lobes varying in distinctness from case to case. Mostly the lobes are shallow, but in L. Bocksjon (Tiveden, northern Vastergotland) they were deep and relatively narrow. The shape of the shell varies, being sometimes spheroidal, sometimes slightly elongated. Often a collar is distinctly set off, but in some cases this character is hardly discernible. Mineral particles are cemented together in the shell, sometimes also small diatoms. The cementing substance of the shell may be yellowish or brown, but more often it is colourless. D. limnetica was found in oligotrophic as well as eutrophic lakes. (ref. ID; 2554)
The shell is brown, ovoid with a slight constriction near the aperture to form a small collar, and is circular in transverse section. It is composed of small quartz particles and some diatom shells. The aperture is circular and has an uneven outline. Penard (1902) thought that the small collar of this species might easily be overlooked. (ref. ID; 3686)
Measurements
Length 62-75 µm. (ref. ID; 3496)
Length of shell 126; breadth of shell 99; diameter of aperture 47 µm (n=1). (ref. ID; 3686)
Test ovoid to subspherical; aperture terminal; with three to six lobes; test usually composed of sand-grains, rarely with diatoms endoplasm colorless or greenish; in fresh water. Sexual fusion and life cycle. (ref. ID; 1618)
Shell ovoid or nearly spheric, usually with a quadrilobate (rarely trilobate) aperture. Pseudopods few. Cytoplasm sometimes with chlorellar. Habitat ponds, ditches, and marshy places; common. (ref. ID; 1923)
The shell is brown, pyriform, the fundus is usually rounded and the neck tapers evenly to the aperture. The surface is rough and encrusted with sand-grains of various sizes. The aperture is circular and surrounded by a regular arrangement of small particles. (ref. ID; 3686)
Comments
This species was considered by Gassowsky (1936) to be a variety of D. oblonga because of its small size. It is similar to D. oblonga in shape, but we have found both species together in the same moss sample and have easily identified D. longicollis on size. Note that the reports of this species by Gauthier-Lievre & Thomas (1958) and Chardez (1967) are omitted because the measurements given (length 240-476 µm) are not comparable with the original description. (ref. ID; 3686)
Measurements
Length of shell 91-109; breadth of shell 47-55; diameter of aperture 16-21 µm (n=11). (ref. ID; 3686)
Shell slightly compressed, covered with flat quartz particles. Living individuals accumulate mainly inorganic material round the elliptic aperture. This aggregation of particles is probably drawn into the shell when the amoebae encysts and is lost when the cell dies. Schonborn (1966) believes that they represent stored reserve xenostomes. Recently, Schonborn et al. (1987) described food-bundles in Schoenbornia humicola which look rather similar to the particle aggregation observed by us in D. lucida and P. fascicularis. We suggest that it is a peculiar kind of apertural "plug" to avoid desiccation of the cytoplasma during short periods of dryness. Nucleus with a central nucleolus. (ref. ID; 4755)
The shell is yellow or brown, oval, circular in transverse section and in the apical region tapers evenly to the aperture. It is covered with small sand grains which are usually packed closely together, but often the aboral region has a broken outline due to an addition of larger particles. The aperture is small, circular and usually surrounded by small particles, the regularity being occasionally broken by the inclusion of larger particles. Variation appears to be restricted to the size of the materials used in shell formation. (ref. ID; 3686)
Measurements
Length of shell 75-88; breadth of shell 47-54; diameter of aperture 15-20 µm (n=15). (ref. ID; 3686)
Difflugia manicata var. langhovdensis Sudzuki, 1964 (ref. ID; 3491, 3536 original paper)
Descriptions
The shell constantly pyriform, slightly compressed and the posterior end more or less pointed. With a rounded posterior border in the lateral view. The aperture circular, without neck. The sand grains concentrated around the aperture, very rarely or never at the posterior half of the shell, except for the sandy particles. The main protoplasm usually located at the posterior half of the body, and in the cyst very often wholly spherical in form, away from the shell. The nucleus, one in number. (ref. ID; 3536)
Comments
The present species is much like D. lucida, fallax and pristis in general features and size, but different in lacking the remarkable ridge usually present around the aperture, and the lateral outline of the shell (parallel in lucida) from the first, different in the condition of the large sand grains attached from the second, and different in the nature of the material stuck to the shell from the third. The present species could be identical with D. manicata Penard, but clearly different from its type by its having a compressed shell. (ref. ID; 3536)
Measurements
Size 55-62x19-32x20-25 µm, the aperture 29x19 µm. (ref. ID; 3536)
Test pyriform, flask-shaped, or ovoid; neck variable in length; fundus rounded, with occasionally one to three conical processes; aperture terminal, typically circular; test composed of angular sand-grains, diatoms; bright green with chlorophyllous bodies; in the ooze of fresh water ponds, ditches and bogs; also in moist soil. (ref. ID; 1618)
A very common species that seems to be exceedingly variable in form and size, but that really comprises a number of elementary species and varieties not yet discriminated. Habitat ooze of ponds, lakes, and among aquatic vegetation. (ref. ID; 1923)
The neck is long, about one-third of the shell length, and in D. petricola Cash, 1909 it is short about one-sixth of the shell length. In each case the aperture is circular and usually surrounded by a regular assortment of small quartz particles. The remainder of shell is composed of randomly arranged quartz particles and a few diatoms frustules. The surface has a rough appearance and only the occasional strand of organic cement can be seen binding these particles together, although the aperture of D. petricola often has a margin of patterned organic cement. The feature that separates these two species is the size of the neck. The difficulty of defining the junction of the neck with the main body of the shell, especially as this often be obscured by extra large particles, made us forgo trying to measure this feature. The shell D. petricola is usually shorter and broader than D. oblonga, and in both shell breadth appears to vary with shell length. (ref. ID; 2022)
The shell is brown, pyriform and composed of quartz particles. The neck is often clearly defined and the circular aperture is surrounded by small particles cemented together. (ref. ID; 3686)
Comments
D. oblonga has been the subject of controversy regarding its correct description for some time. For example, there has been doubt expressed by Chardez and Decloitre (1973) regarding the synonymy of D. pyriformis with D. oblonga. The argument, it seems to Ogden et al. (1979), reflects difficulties encountered when critically comparing original descriptions which are often inadequate or vague, with recent observations on similar specimens. Ogden et al. (1979) acknowledge that there is a problem is reconciling the descriptions of D. oblonga given by Ehrenberg (1838) with that given by Perty (1841) for D. pyriformis. Nevertheless, most authors have accepted the synonymy initially proposed by Ehrenberg (1871) and reinforced by Cash and Hopkinson (1909), the latter authors detailing all the earlier literature and their judgment on the problem. As Ogden et al. (1979) do not consider that Chardez and Decloitre (1973) have established the validity of the two species, Ogden et al. (1979) concur with the synonymy proposed by Ehrenberg (1871). (ref. ID; 2022)
Several varieties were described by Penard (1890 and 1902) and Cash et al. (1909), which illustrate the considerable variation exhibited by this species. The description given by Cash appears to embrace several varieties described by Penard (1890), including D. longicollis, so we refer in the measurements to Penard's (1890) description. Nevertheless, the discussion given by Cash (1909) concerning the priority of the name D. oblonga over D. pyriformis of Perty (1849) is accepted. (ref. ID; 3686)
Measurements
60-580 by 40-240 µm. (ref. ID; 1618)
Length(L) 128-232; breadth(B) 60-99; diameter of aperture(Da) 19-38 µm; B/L 0.45+/-0.04; Da/L 0.15+/-0.02. (ref. ID; 2022)
Length of shell 190-237; breadth of shell 92-146; diameter of aperture 32-42 µm (n=7). (ref. ID; 3686)
Shell oval, with a circular cross-section. The aperture is truncated at a right angle; the border shows a slight swelling (rim), sometimes slightly recurved to the interior. The organic cement is transparent with a yellowish tint, encrusted with small flattish pieces, and with a few siliceous elements and diatoms added. Cytoplasm limpid, lobose pseudopodia, spherical nucleus. (ref. ID; 2392)
Comments
This small species resembles Difflugia saxicola Penard, but differs mainly from the latter by aperture which is truncated at a right angle and provided with a slight, mostly recurved rim. (ref. ID; 2392)
Measurements
Length of shell 25-29; diameter of shell 18-28; diameter of pseudostome 9-15; height of rim 1.5-2.2; diameter of nucleus 15 µm (n=8). (ref. ID; 2392)
The shell is light brown, sub-spherical or ovoid, tapering evenly to the aperture. It is composed of small siliceous elements, and occasionally some diatom shells, irregularly arranged and bound by cement to produce a smooth surface. Small pores are often seen in the cement between adjacent elements. The aperture is surrounded by a thick collar of organic cement, which divides the opening into either three or four lobes. Specimens with five or six lobes surrounding the aperture have been reported (Chardez 1967). The arrangement of siliceous elements to produce a daughter cell at division have been described by Netzel (1976, 1977). (ref. ID; 3686)
Measurements
Length of shell 79-87; breadth of shell 57-67; diameter of aperture 25-26 µm (n=4). (ref. ID; 3686)
The species is closest to Difflugia nodosa (Leidy, 1879) Ogden, 1983, from which it differs sharply in the shape of the test (Ogden and Zivkovic, 1983). The test of D. nodosa is trapeziform, its base is extended wedgelike or roundedly convex, but is not concave. The corners of the fundus are produced or form tubercles, the neck expands smoothly to the base of the test and accounts for a fifth or quarter of the test. In the new species, the fundus is rounded, cordiform, concave, the subcylindrical neck visually is distinctly delimited from the fundus, its length accounts for one third of the length of the test. (ref. ID; 7923)
Descriptions
Test large, laterally compressed, consists of broadly flattened fundus and cylindrical, narrow, sharply delimited neck. Aperture round. Width of narrow side of fundus equal to diameter of neck. Test dark gray or brown, not transparent, surface smooth, consists of densely packed sand grains primarily small and medium size. Between sand grains are narrow plates of cement. The cement is abundant, particularly on the neck, constitutes part of the test surface, appears as spongy porous plates; pores are simple, small open. Sometimes the cement of this structure forms a film covering the exogenous material, in which case there are numerous rod-like short formations, curved or straight, resembling idiosomes, under the film and on it. The edge of the fundus is straight, resembling idiosomes, under the film and on it. The edge of the fundus is straight or concave, the neck may be inclined relative to the longitudinal axis, but does not form any kind of structure resembling the spiral of Lesquereusia. The edge of the pseudostome is flat, consists of densely packed small sand grains embedded in the cement. We did not observe formation of pseudopodia. (ref. ID; 7923)
Ecology
Littoral of the lake, on the bottom, substrate of yellow viscous mud, pH 6, depth 0.5 m, temperature 12 degrees C. (ref. ID; 7923)
Examined materials
Difflugia collected from the littoral of Lake Maricharika (Carpathian National Park) on the bottom among aquatic plants, 14.VIII.1990 (3 specimens). (ref. ID; 7923)
Measurements
Long. testae(L) 384, 336, and 328 µm, Lat. testae(B) 352, 368, and 308 µm, Neck height(l) 104, 120, and 112 µm, Neck diameter 128 µm, Diam. psd.(dp) 90, 64, and 72 µm, B:L 0.92, 1.10, and 0.94, l:L 0.27, 0.36, and 0.34 (n=3). (ref. ID; 7923)
In general shape (of the shell) D. pelagica agrees with D. limnetica, being slightly oviform or almost spheroidal. A collar is sometimes set off. The oral opening has four lobes, contrary to conditions in D. limnetica. However, exceptionally two of the lobes tend to merge giving the impression that only three lobes exist. In the encountered populations the lobes were always shallow. The shell is made up of mineral grains cemented by a colourless substance. Zoochlorellae were found in the protoplasm. D. pelagica agrees in most respects with D. lobostoma Leidy. However, the latter species is considerably larger (140-170 µm according to Penard), and it is not said to be planktic. D. pelagica occurred as a purely planktic species. (ref. ID; 2554)
Measurements
The length of the shell varied between 60 and 100 µm in the four localities. (ref. ID; 2554)
The shell is transparent or yellow, ovoid and circular in transverse section. It is thin, usually has a regular outline, and is composed mainly of small diatom frustules arranged on an organic matrix. Although the major part of the shell is made of specimens belonging to the diatom genera Cocconeis and Achnanthes, larger diatom shells and spherical siliceous cysts of chrysomonad flagellates may also be incorporated. The aperture is small and circular. (ref. ID; 3686)
Comments
This species was initially described under the name D. fallax by Penard (1890), who suggested that the animal may have made the siliceous plates. It would appear from our observations that the density of the organic cement masks the fine detail of the diatom frustules, but emphasises the outlines so that they seem to be siliceous plates. (ref. ID; 3686)
Measurements
Length 78 µm. (ref. ID; 2356)
Length of shell 75-94; breadth of shell 47-54; diameter of aperture 17-19 µm (n=4). (ref. ID; 3686)
The shell is opaque, pyriform, tapering evenly form the aperture to about the mid-body position and curving gracefully in the aboral region. It is composed of an assortment of quartz particles, so arranged that the outline in usually regular whilst the surface is intermediate between rough and smooth, the anterior region is most frequently restricted to small pieces of quartz and rarely has large irregular particles. Areas of organic cement are often seen at the junction between particles, and the surface of the cement is characterized by a distinctive rosette-like pattern. The aperture is circular and surrounded by a regular arrangement of small quartz particles. A smooth cyst membrane seals the mouth of the aperture in some specimens. D. pyriformis is similar D. oblonga. The total length of the shell is similar but it differs significantly in both breadth and diameter of aperture, either by direct comparison or by using the rations breadth/length and diameter of aperture/length. Besides size, the main difference is the texture of the shell. In D. oblonga the shell is irregular in outline, rough, composed of small to large pieces of angular quartz with only strands of organic cement visible, whereas the shell in D. performs has a regular outline, intermediate between rough and smooth, rarely incorporates large irregular pieces of quartz, and has visible areas of organic cement. According Penard's (1902) description of D. pyriformis, he described that the shell was made mainly of angular pieces of quartz often with two or three larger pieces around the junction of the neck and body, that it seldom incorporated sediment or diatoms, and that the materials were joined by a clear cement which was not abundant and allowed the shell to break easily under pressure. (ref. ID; 890)
Pyriform, yellowish in color; membrane chitinous, encrusted with foreign particles and diatoms. Aperture circular, bordered by a incurved crenulate margin; protoplasm containing numerous granules of brick-red color; cyst equally red or brownish-red in color. Habitat aquatic vegetation and among Sphagnum or moss. (ref. ID; 1923)
The shell is yellow or light brown, pyriform. It is usually encrusted with sand-grains or diatom frustules. The aperture is circular and bordered by an organic collar, the inner margin of which is crenulated to form tooth-like structures. The outer covering of this species varies considerably in having either few or numerous diatom-frustules attached to the shell, often to the extent that they disguise the pyriform shape. (ref. ID; 3686)
The ultrastructure study. (ref. ID; 4810)
Type locality
From specimens collected in the Rocky Mountains of America. (ref. ID; 4810)
Measurements
Length 65-105 µm. (ref. ID; 1923)
Length of shell 70-91; breadth of shell 38-54; diameter of aperture 14-20 µm (n=11). (ref. ID; 3686)
The shell is colourless and usually almost transparent, especially in the aboral region. It is elongate, tubular, swelling gradually from the aperture to the mid-body region and then tapering rapidly to end in a fine point. Small pieces of quartz and thin, flat portions of diatom shells are arranged to make a surface which for the most part is smooth. Although gaps appear to be present between particles when viewed under the optical microscope, only small areas of cement have been seen using the scanning electron microscope. This cement is similar in structure to that of D. curvicaulis. The aperture is circular and surrounded by a fairly regular arrangement of small quartz particles. The aboral region of this species may be curved to resembles the cutting edge of knife, hence the specific name, but as Penard (1899) stated this does not appear to be a constant feature. (ref. ID; 2024)
Collection
Slide (Reg.No.20.12.8.28) in the collections of the Zoology Department, British Museum (Natural History). (ref. ID; 2024)
The shell is flask-shaped with an almost spherical part and a distinct slender cylindrical neck. The aperture is circular and bordered by a slight rim. The shell is almost entirely covered by diatoms, embedded in the transparent organic cement. (ref. ID; 2392)
Measurements
Length of shell 140-158; diameter of shell 66-79; diameter of aperture 20-23 µm (n=3). (ref. ID; 2392)
In general appearance they have a similar shape to specimens of Pontigulasia compressa (Carter, 1864), but can be distinguished from the latter but the absence of an external constriction which defines the neck and the associated internal diaphragm. The shell in broad view is pyriform and laterally it is flattened. From about the mid-body region the shell tapers towards the aperture, and often there is a collar or ring of large particles at a position near the beginning of the slope. This is evident in one specimens as a ring of flattened particles when viewed from the aperture, similar to that shown by Chardez (1969). Small medium pieces of flattened quartz are arranged in the shell to produce a smooth outline, but larger pieces may be present in the collar, and large areas of organic cement are often visible between the quartz. The surface of the cement is characterised by having numerous small rosettes, each of which usually has a central opening and is surrounded by a circle of six to eight equally spaced openings. (ref. ID; 2022)
Measurements
Length of shell 175 (Jung 1942), 185-220 (Chardez 1967), 173-183 (Ogden et al. 1979); breadth of shell 145 (Jung 1942), 110-150 (Chardez 1967), 112-142 (Ogden et al. 1979); depth of shell 80-100 (Chardez 1967), 90-108 (Ogden et al. 1979); diameter of aperture 50 (Jung 1942), 39-46 µm (Ogden et al. 1979). (ref. ID; 2022)
Neck distinct, aperture lobated or with undulating margin. Shell brownish, mammillated in outline. Ovoid, in transverse section circular, with subhemispheric elevations exteriorly and corresponding depressions interiorly, the surface having a mulberry-shaped appearance. Membrane chitinous, covered with irregularly-sized minute sand grains. Aperture hexilobate, with a narrow collar. One nucleus. Habitat marshes and ponds. (ref. ID; 1923)
The shell is brown, ovoid or circular and composed of quartz particles. The surface is characterized by having an almost regular arrangement of small protuberances, which are composed of aggregates of small particles. The aperture is circular and is bordered by a narrow collar of small pieces of quartz. (ref. ID; 3686)
Measurements
Length 120-140 µm. (ref. ID; 1923)
Length of shell 102-140; breadth of shell 98-140; diameter of aperture 39-44 µm (n=6). (ref. ID; 3686)
A large ovoid, rotund test, with a short neck and a rim around aperture; multinucleate; in ditches, ponds, sphagnous swamps, etc. (ref. ID; 1618)
Neck deeply constricted, with outer margin always recurved. Shell ovoid or spherical, generally without spines, but a variety, D. urceolata var. olla Leidy, possesses a few short stubby spines developed from the fundus. Forty to 60 nuclei. Habitat ooze of pond water. (ref. ID; 1923)
The shell is opaque, ovoid or circular, with irregular, blunt, aboral protuberances and a pronounced apical rim or collar. It is composed of assorted sand grains to give a relative smooth and regular outline. The aperture is circular with the surrounding rim made of small quartz particles cemented together to form a regular structure. Variation in this species appears to be restricted to the presence or absence of aboral spines, and differences in size. (ref. ID; 3686)
Measurements
200-230 µm by 150-200 µm. (ref. ID; 1618)
Dimensions 200-350 µm, mostly 220-250 µm. (ref. ID; 1923)
Length of shell 313-394; breadth of shell 250-426; diameter of aperture 122-198 µm (n=4). (ref. ID; 3686)
The shell is opaque, ovoid, elongate and circular in transverse section. It is composed of a mixture of large and small particles of quartz. The aperture is circular, has a regular outline and is surrounded by small particles. This species was originally described from depths of 20 to 40 meters in Lake Geneva by Penard (1902), who considered it to have a fragile shell. Our specimens, are robust, but otherwise agree well with his description. (ref. ID; 3686)
Measurements
Length of shell 256-284; breadth of shell 188-215; diameter of aperture 82-89 µm (n=5). (ref. ID; 3686)
