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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Pinaciophora

Pinaciophora Greeff, 1873 (ref. ID; 3541, 4747) reported year? (ref. ID; 1618) or Greeff, 1873 emend. Penard (ref. ID; 3691) reported author and year? (ref. ID: 7207)
Pinacophora (ref. ID; 2240)

Phylum Rhizopoda von Siebold, 1845: Class Filosea Leidy, 1879: Order Cristidiscoidida Page, 1987: Family Pompholyxophryidae Page, 1987 (ref. ID; 4747)

Synonym Pinaciocystis ("Penaciocystis") Roskin, 1929 (ref. ID; 4747)

[ref. ID; 1618]
Spherical; outer envelope composed of circular discs, each being perforated with 19 minute pores; cytoplasm reddish; fresh water. (ref. ID; 1618)

[ref. ID; 4747]
Diagnosis; Cells globose to ovoid, covered with a layer of overlapping circular or oblong plate-scales. The cell diameter is variable (14-80 um); the diameter of the scales is 3-6 um. The plate-scales consist of 2 layers fused peripherally, elsewhere connected by intercalary material appearing as hexagonally arranged black dots. The proximal plate is perforated by many very minute pores and the distal plate is perforated by 4-24 large pores. The cytoplasm is colourless or reddish brown. The filopodia are small and thin. (ref. ID; 4747)
Remarks; Since the description of 8 new species of the genus Pinaciophora Greeff, 1873, by Thomsen (1978), little attention has been paid to this genus (Thomsen 1979) and its delimitation from the closely related genus Rabdiophrys (Nicholls 1983). As Thomsen (1978) mentioned, the taxonomic position of the 8 new species was very uncertain and further study was needed. Among the species included in the genus Pinaciophora (Thomsen 1978, 1979) are 2 groups differing in type of scales. The first group, represented by the type species itself and by P. stammeri, bears only plate-scales. The second group, containing all the other species, is characterised by the possession of both plate- and spine-scales. (ref. ID; 4747)
Type species; Pinaciophora fluviatilis Greeff (ref. ID; 4723, 4747)

[ref. ID; 7207]
The twelve species of Pinaciophora known from electron microscopy all show some similarity of structure of plate-scales and spine-scales which clearly sets this genus apart from other related heliozoean genera such as Raphidocystis (Rees et al. 1980) and Acanthocystis (Nicholls 1983). The typical Pinaciophora plate-scale is characterized by a three-layered structure (Manton and Sutherland 1979; Thomsen 1978) consisting of two main plates separated by an intercalary structure (the third layer) of ridges, circular rims of nodules often forming hexagonal patterns. Minor deviations from this typical structure are found in five of the twelve species. Pinaciophora reticulata lacks that distal layer; P. spiculata, P. paucipora and P. multicosta lack the middle layer of intercalary structures. The middle layer of P. triangula from Ontario is much reduced to a series of short rods encircling the central large holes of the distal surface, while in the Swedish type material it is much denser and forms a continuous thickened rim around all three of the large central holes. No taxonomic importance should be attached to these minor differences in morphology since other important structural features of P. triangula scales from both localities are identical. As mentioned by both Thomsen (1978) and Manton and Sutherland (1979), there has been some risk in assigning all of the spine-bearing forms to the genus Pinaciophora. The type species, P. fluviatilis apparently lacks spine scales and nothing is known of the protoplast structure in any of the species except. P. fluviatilis. It is conceivable that all Pinaciophora species described recently with spine-scales will eventually be transferred to the genus Rabdiophrys Rainer. No mention of this possibility (or even reference to Rainer 1968) was made by either Thomsen (1978) or Manton and Sutherland (1979); however, this revision will be necessary should one of the three presently known Rabdiophrys species be rediscovered with the light microscope and be shown by electron microscopy to possess scales identical to one of the spine-scaled Pinaciophora species. Of the spine-scaled Pinaciophora, P. pinea is closest to Rabdiophrys annulifera Rainer with its long and short spine-scales and plate scales with a large central hole. Discovery of whole cells, with scale structure identical to that of P. pinea but identical to R. annulifera as regards the absence of a centroplast and other structural details described by Rainer with the light microscope, will be evidence to substantiate the transfer of the 11 spine-scale Pinaciophora species of the genus Rabdiophrys. (ref. ID; 7207)

[ref. ID; 7519]
The genus Pinaciophora is retained within the Heliozoa also in more recent taxonomic treatments. Thus Tregouboff (1953) places it within the heliozoan order Centrohelidia in the suborder Chalarothoraca. (ref. ID; 7519)
  1. Pinaciophora apora Croome, 1987 (ref. ID; 4723 original paper)
  2. Pinaciophora bifurcata Thomsen, 1978 (ref. ID; 7519 original paper)
  3. Pinaciophora candelabrum Thomsen, 1978 (ref. ID; 7519 original paper) reported year? (ref. ID; 7207)
  4. Pinaciophora columna Croome, 1987 (ref. ID; 4723 original paper)
  5. Pinaciophora denticulata Thomsen, 1978 (ref. ID; 7519 original paper)
  6. Pinaciophora fluviatilis Greeff, 1873 (ref. ID; 3541, 3691) reported year? (ref. ID; 1618, 4723, 4796, 7207, 7519) or Greeff, 1873, sensu Penard, 1904 (ref. ID; 4747), Pinacophora fluviatilis Greeff (ref. ID; 2240)
    Syn; Pinaciocystis duboscqi ("Penaciocystis dubosqui") Roskin, 1929 (ref. ID; 4747)
  7. Pinaciophora monopora Thomsen, 1978 (ref. ID; 7519 original paper) reported year? (ref. ID; 4741)
  8. Pinaciophora multicosta Thomsen, 1978 (ref. ID; 7519 original paper) reported author and year? (ref. ID; 7207)
  9. Pinaciophora ovalis Croome, 1987 (ref. ID; 4741 original paper)
  10. Pinaciophora paucipora Thomsen, 1978 (ref. ID; 7519 original paper) reported author and year? (ref. ID; 7207)
  11. Pinaciophora pinea Nicholls, 1983 (ref. ID; 7207 original paper) reported year? (ref. ID; 4741)
    See; Rabdiophrys anulifera (ref. ID; 4747)
  12. Pinaciophora reticulata Thomsen (ref. ID; 7207)
  13. Pinaciophora rubicunda Hertwig & Lesser (ref. ID; 4796) or (Hertwig & Lesser, 1874) emend. Roijackers & Siemensma, 1988 (ref. ID; 4747 described paper)
  14. Pinaciophora spiculata Manton & Sutherland (ref. ID; 7207), Manton (ref. ID; 7519)
  15. Pinaciophora stammeri Rainer, 1968 (ref. ID; 3541 original paper)
  16. Pinaciophora tasmanica Croome, 1987 (ref. ID; 4723 original paper)
  17. Pinaciophora triangula Thomsen, 1978 (ref. ID; 7519 original paper) reported year? (ref. ID; 4741, 7207)
  18. Pinaciophora tridentata Thomsen, 1978 (ref. ID; 7519 original paper) reported year? (ref. ID; 7207)

Pinaciophora apora Croome, 1987 (ref. ID; 4723 original paper)

Diagnosis

Periplast comprising scales of two kinds. Protoplast unknown. Plate-scales circular to slightly ovoid, ca. 2.3 um in diameter, comprising proximal and distal plates connected by an intercalary layer of polygonal thickenings across the middle two thirds of the scale, giving a mesh-like appearance to the scale centre. The distal plate has fine perforations throughout but lacks the larger pores characteristic of many species of Pinaciophora (hence the specific epithet). Around the circumference of the scale there is a narrow, patternless rim. Spine-scales cylindrical, with a flared base and tip, ca. 3.0 um long, 0.7 um wide at the base, 0.2 um wide at the narrowest point and distally drawn out into five small spines. (ref. ID; 4723)

Type locality

From sites in Tasmania sampled during an Australia-wide survey of freshwater habitats. (ref. ID; 4723)

Pinaciophora bifurcata Thomsen, 1978 (ref. ID; 7519 original paper)

Diagnosis

Periplast ca. 20x12 um when flattened, covered with scales of two kinds. Details of protoplast unknown. Plate-scales circular, 2.0-2.5 um in diameter. A small number of differently sized larger perforations penetrate the distal plate, mainly clustered around the centre of the scales. The major part of the distal scale surface is occupied by hexagonally close-packed fine perforations. A narrow band along the scale edge is patternless. The lower scale plate -visible through the larger distal plate perforations- appears to be patternless. The two scale plates are fused peripherally, elsewhere connected by intercalary material appearing as black dots with some tendency towards a hexagonal arrangement. Spine-scale 2.5-3.0 um long and 0.8-0.9 um wide at the distal bifurcate end (0.6-0.7 um wide proximally and ca. 0.2 um at the narrowest point). The spine-scales are flattened distally into a very conspicuous bifurcation (hence the specific epithet). The triangular area between the branches is the only non-perforated part of the whole spine-scale. Proximally a number of struts attach the spine proper to an oval base plate. Large holes appear between these struts. (ref. ID; 7519)

Habitat of the type

Marine (15 degrees C, 32 0/00 S), North Sea (Denmark). Collected June 1975. Surface water sample. (ref. ID; 7519)

Pinaciophora candelabrum Thomsen, 1978 (ref. ID; 7519 original paper) reported year? (ref. ID; 7207)

Diagnosis

Periplast ca. 30x30 um when flattened, covered with scales of two kinds. Details of protoplast unknown. Plate-scales circular to oval, occasionally with a median constriction. Scale dismensions ranging from 2.0 to 3.1 um. Distal scale surface perforated by 6-8 differently sized larger pores occupying the centre of the scale. Between these larger pores and a conspicuous patternless rim the distal scale surface is perforated by minute hexagonally arranged holes. The lower plate -visible through the larger perforations of the distal plate- shows a rather indistinct pattern of minute perforations. The two plates of the scale are fused peripherally, elsewhere connected by intercalary material appearing as black dots, sometimes in a distinct hexgonal arrangement. Spine-scales (2-9 um long, ca. 0.8 um wide at the base) flattened distally into a bifurcate tip. Decurrent ridges, mutually connected by irregularly perforated scale material, are proximally attached by a number of struts to a basketlike scale base with perforations arranged in distinct lines. The transition from the spine proper to the scale base is subject to some variation; in some cases it appears like a banister encircling a depression from the centre of which the spine emerges. (ref. ID; 7519)

Remarks

The scales of P. candelabrum from the Sound (Elsinore January 1976; 10 meters; 2.7 degrees C, 26.3 0/00 S) differ in some details from those collected from Dybso Fjord. Whereas the plate-scales from Dybso are quasicircular, those from the Sound are oval with a distinct median constriction. The spine-scales show bases perforated by several horizontal rows of rounded perforations and a spine emerging from a slight depression encircled by a "banister". Those from Dybso Fjord show a reduction in the number of rows of perforations encircling the basal part of the scale. Moreover, the individual perforation is somewhat elongated rather than circular. The transition between the basal part of the scale and the spine proper being dominated by a limited number of struts with large holes in between. Because of the general similarity between both plate- and spine-scales from the two localities the variation noted is for the time being considered to be intraspecific variation within P. candelabrum, probably an expression of clonal differences. (ref. ID; 7519)

Habitat of the type

Marine, Dybso Fjord (Denmark). Collected 1 March 1977. Surface water sample. (ref. ID; 7519)

Pinaciophora columna Croome, 1987 (ref. ID; 4723 original paper)

Diagnosis

Periplast comprising scales of two kinds. Protoplast unknown. Plate-scales round, 1.5-1.9 um in diameter, with a large pore 0.5-0.7 um in diameter in the centre of the distal surface. In this pore there is a central column (hence the specific eithet) ca. 0.20 um in diameter. The column is usually "free-standing" but is sometimes connected to the distal plate by a narrow bridge. The scales occasionally have a second smaller perforation adjacent to the main central structure. Small irregular perforations are present in the distal layer towards the edge of the scale. The proximal layer of the scale can be seen beneath the large central perforation and is not obviously perforate. The intercalary layer appears as a series of short dark lines and a prominent dark circle around the edge of the large central pore. Around the circumference of the scale there is a narrow, raised, patternless rim. The very edge of the scale appears slightly darker and dotted. Spine-scales 1.4-2.5 um long, with a base 0.5-0.7 um wide and a longitudinally tripartite shaft ending in three small teeth at the apex. (ref. ID; 4723)

Type locality

From sites in Tasmania sampled during an Australia-wide survey of freshwater habitats. (ref. ID; 4723)

Pinaciophora denticulata Thomsen, 1978 (ref. ID; 7519 original paper)

Diagnosis

Scales of two kinds. Protoplast unknown. Plate-scales circular to oval, 3-4 um in diameter. Central part of distal scale surface with mostly six large perforations in a hexagonal arrangement. Between a narrow patternless rim and the large central perforations is a band of small hexagonally arranged perforations. Lower scale plate (visible through the larger perforations of the distal surface) is perforated by minute holes in hexagonal close packing. The two main plates of the scale are fused peripherally, elsewhere connected by intercalary material appearing as hexagonally arranged black dots. Spine-scales tubular, commonly 1 (0.8-1.8) um long and 0.6 (0.5-0.8) um wide, with an approximately median narrowing (ca. 0.3 um). At the distal end the dilated tube rim is extended into minute spines (hence the specific epithet). The spine-scale is proximally attached to a base-plate by a series of struts. (ref. ID; 7519)

Habitat of the type

Marine (2 degrees C, 16 0/00 S). Collected 27 January 1977 in Dybso Fjord (Denmark). Surface water sample. (ref. ID; 7519)

Pinaciophora fluviatilis Greeff, 1873 (ref. ID; 3541, 3691) reported year? (ref. ID; 1618, 4723, 4796, 7207, 7519) or Greeff, 1873, sensu Penard, 1904 (ref. ID; 4747), Pinacophora fluviatilis Greeff (ref. ID; 2240)

Synonym

Pinaciocystis duboscqi ("Penaciocystis dubosqui") Roskin, 1929 (ref. ID; 4747)

Descriptions

In freshwater ponds. (ref. ID; 1618)
Cells globose to ovoid with a diameter ranging from 45-50 um. The plate-scales are circular, discoid, 4-6 um in diameter; they are flat and have commonly a distinct hexagonal pattern of large holes, 17-24 in number, mostly arranged in a regular 3-4-5-4-3 or a 4-5-6-5-4 sequence. Smaller perforations are irregularly distributed along the periphery. (ref. ID; 4747)
The large size of the plate scales with their numerous large holes in the distal surface allows P. fluviatilis to be easily distinguished from other species. The outer portion of the distal surface is patterned with small (0.05-0.07 um in diameter) holes confined mainly between the central area of large holes and the patternless rim. The intercalary layer consists of reticulated ridges and columnar structures, appearing as dark dots in the outer portion of the scales. (ref. ID; 7207)

Comments

The variation within this species and the difficulty of identifying species based on single scales has been discussed by Thomsen (1978). The report from Antarctica (Takahashi 1981) is interesting, as the illustrated scales differ from all other known scales in having 3 central holes which are smaller than the surrounding holes. Pinaciocystis duboscqi is badly described. The species is unrecognisable and indistinguishable from a number of cristidiscoidid amoebae. For convenience it is here considered as minor synonym of Pinaciophora fluviatilis. (ref. ID; 4747)
This organism was briefly described by Greeff (1873) and more thoroughly by Greeff (1875). As implied by the choice of specific epithet, the type material orginated from a freshwater locality - the river Rhine at Bonn. According to Greeff the cells of P. fluviatilis are spherical, approximately 50 um in diameter, and covered with "epinem Gerust" of closely packed siliceous plates. Each plate is oval with pointed ends, and perforated by minute holes. A close look at Greeff's makes it evident that the perforations are not randomly distributed, but locally arranged in a hexagonal pattern. According to Greeff very delicate axopodia apparently penetrate these scale pores as well as a hyaline space just inside the scalecase. The central cytoplasm of the cell is reddish brown. Whereas Greeff (1875) considered P. fluviatilis to be closely related to the Radiolaria, Penard (1904) and later authors grouped P. fluviatilis with the Heliozoa. On the basis of material collected from lake Geneva, Penard gave an emended description which differed from that of Greeff mainly regarding details of the scales. According to Penard each scale is regularly circular, 4.5-6 um in diameter, and perforated by 19 minute pores. The scale perforation forms a pattern which consists of holes in a 3-4-5-4-3 sequence arranged in a hexagonal pattern. While the two authors disagree on the outline of the individual scale and the arrangement of the perforations, there is good agreement as regards the side view. The average cell diameter of P. fluviatilis from lake Geneva was 45-50 um. The highly characteristic and frequent presence of adventitious pseudpodia in P. fluviatilis is another observation added in the emended description of the genus (Penard 1904). It seems very likely, as suggested by Penard (1904), that the differences in scale morphology between his and Greeff's material are mainly due to a misinterpretation by Greeff. As Greeff does not mention air-dried material, it is very likely that his description is based solely on the examination of living cells. According to Penard (1904) details in the periplast are extremely difficult to observe in living material. It seems probable that the rather unusual scale type pictured by Greeff may be explained as a misinterpretation of a pattern of irregularly imbricated scales which are circular or nearly so. The overlappins of neighbouring scales is tantamount to only sections of scales being visible; sections which may well attain a shape reminiscent of that pictured by Greeff (1875). (ref. ID; 7519)

Comparison between Pinaciophora fluviatilis Greeff and Potamodiscus kalbei Gerloff

Measurements

Diameter 45-50 um, but somewhat variable. (ref. ID; 1618)

Pinaciophora monopora Thomsen, 1978 (ref. ID; 7519 original paper) reported year? (ref. ID; 4741)

Diagnosis

Scales of two types. Protoplast unknown. Plate-scales circular, ca. 2.5 um in diameter, with one big central hole through the distal scale surface. Between a patternless scale rim and the central hole is an area perforated by hexagonally packed minute holes. The lower scale-plate -visible through the central hole- is likewise perforated by small holes arranged in distinct hexagonal pattern. The two scale-plates are fused peripherally, elsewhere interconnected by material which appears in places as hexagonally arranged black dots. Spine-scales ca. 1.5 um long and 0.7 um broad at the base, flattened distally into a bifurcate tip, proximally attached by extensions from the two decurrent ridges to an oval base-plate. Occasionally a large hole is present just above the base of the spine-scale. (ref. ID; 7519)

Habitat of the type

Freshwater (5 degrees C). Appeared in a three weeks old crude culture set up from a surface water sample collected from lake Esrom (Denmark) 19 February 1974. (ref. ID; 7519)

Pinaciophora multicosta Thomsen, 1978 (ref. ID; 7519 original paper) reported author and year? (ref. ID; 7207)

Diagnosis

Scales of two kinds. Protoplast unknown. Plate-scales circular, ca. 1.5-2.0 um in diameter, with a broad patternless rim. More heavily silicified towards the centre of the scale. A less silicified central area is delimited by a circle of small perforations. A number of tiny circular structures are distributed over the central scale area. Spine-scales 2.5-6.0 um long and ca. 0.8 um wide at the base. The spine-scale is composed of a long shaft (ca. 0.1 um in diameter) which is distally flattened into a conspicuous bifurcation, proximally abruptly widened into a circular basal plate. A number of curved costae interconnect the two branches of each bifurcation. (ref. ID; 7519)

Habitat of the type

Marine, Dybso Fjord (Denmark). Collected 1 March 1977. Surface water sample. (ref. ID; 7519)

Pinaciophora ovalis Croome, 1987 (ref. ID; 4741 original paper)

Diagnosis

Protoplast spherical after fixation, 20-25 um in diameter, internal details unknown. Periplast comprising scales of two kinds. Plate-scales oval (hence the specific epithet) 4.4-6.5 um x 2.9-4.1 um, usually with two lines of pores in the distal surface, each pore around 0.3 um in diameter. Under TEM the intercalary layer appears as a longitudinal mesh, mostly within the lines of pores. Around the circumference of the scale there is a narrow patternless rim. The very edge of the scale appears slightly darker, Spine-scales 5.0-14.0 um long, with a base 1.2-1.7 um across, and a shaft about 0.3 um across, which tapers just below the apex and then flares slightly. (ref. ID; 4741)

Comments

The description of P. ovalis brings the number of species of Pinaciophora to 17, 15 other species having been described from observations by electron microscopy and one from light microscopy. P. ovalis is unusual in having plate-scales with a bilateral symmetry, made particularly obvious by the two parallel lines of pores in the distal surface. Most species of Pinaciophora have plate-scales which are circular or nearly circular, the marked exception being P. triangula Thomsen, which has triangular plate scales and is taken to represent a unique line of evolution within the genus (Thomsen 1978). Oval plate-scales have been described for P. fluviatilis Greeff, P. denticulata Thomsen, P. spiculata Manton and Sutherland and P. candelabrum Thomsen, but no bilateral symmetry has been noted in them. The distinct bilateral symmetry of the plate-scales of P. ovalis is therefore unusual, and perhaps illustrates another line of evolution within the genus. Ecologically, P. ovalis is most closely related to P. fluviatilis Greeff, P. triangula Thomsen, P. stammeri Rainer, P. pinea Nicholls, P. monopora Thomsen, P. columna Croome, P. tasmanica Croome and P. apora Croome, these being the other species reported from freshwater. (ref. ID; 4741)

Type material

Collected from Basin Lake in Western Tasmania (41 degrees 59'S, 145 degrees 33'E), a small (ca. 20 ha), high altitude (580 m) freshwater lake, on 10. August 1984. (ref. ID; 4741)

Pinaciophora paucipora Thomsen, 1978 (ref. ID; 7519 original paper) reported author and year? (ref. ID; 7207)

Diagnosis

Periplast circular when flattened, ca. 17 um in diameter, with two kinds of scales. Details of protoplast unknown. Plate-scales circular, ca. 1.5-2.0 um in diameter, patternless apart from a pentagonal arrangement of perforations at the scale centre. The central scale area circumscribed by the "pentagon" appears less heavily silicified than the immediate surroundings. Spine-scales ca. 1.5-2.0 um long and ca. 0.5 um wide at the base, composed of a cylindrical shaft (ca. 0.1 um in diameter), distally terminating in a multi-spined tip while proximally widened gradually into a circular base-plate. Small perforations are occasionally present at the base of the spine-scale. (ref. ID; 7519)

Habitat and the type

Marine, Dybso Fjord (Denmark). Collected 1 March 1977. Surface water sample. (ref. ID; 7519)

Pinaciophora pinea Nicholls, 1983 (ref. ID; 7207 original paper) reported year? (ref. ID; 4741)

See

Rabdiophrys anulifera (ref. ID; 4747)

Diagnosis

Periplast consisting of scales of two kinds. Plate-scales circular, 2.5-3.0 um in diameter with a large (0.8-1.2 um diameter) hole, centrally located in the distal surface through which can be seen the hexagonal pattern of tiny pores ornamenting the proximal surface of the scale. The distal surface of the scale is raised into a thickened rim approximately 0.15 um high around the central hole. A second, not significantly raised, about 0.05 um wide encircles the scale about midway between the central hole and the outer patternless rim of the scale. Spine-scales hollow, 2-20 um long; midsection of shaft 0.25-0.6 um in diameter and flared to 1 um at the apex of large spines. The baseplate of the spine scale consists of a circular disc with a thick (0.1-0.15 um) outer rim which is attached to the shaft of the spine by a network of radiating "spokes" which are sometimes branched. The "spokes" are less well developed in the short spines and the base of the spine shaft is more closely associated with the rim of the base plate than in the long spines. A thin membrane envelops the base of the shaft and its base plate. Protoplast unknown. (ref. ID; 7207)

Notes

Pinaciophora pinea's closest relative is P. monopora which has plate-scales of nearly identical size and a single large hole in the distal surface of the scale. The main features distinguishing the two species are the presence of the thickened rim between the central hole and the outer margin of the scale of P. pinea and the presence of the long (up to 2 um) spine-scales of P. pinea. Spine scales of both species appear to be bilaterally symmetrical with apices similar in structure to those of P. candelabrum Thomsen and P. spiculata in that all show some weak bifurcation. Unfortunately, scales from only a single specimen of each of P. monopora and P. pinea have been found. The apparently distinctive features separating these two species may become less relevant if, for example, long spine-scales are found on specimens having P. monopora-type plate-scales. (ref. ID; 7207)

Type material

Collected 5 May 1981 from Pigeon Creek, the outflow of Pine Lake, Muskoka District, Ontario (44 degrees 57'N, 79 degrees 26'W). (ref. ID; 7207)

Pinaciophora rubicunda Hertwig & Lesser (ref. ID; 4796) or (Hertwig & Lesser, 1874) emend. Roijackers & Siemensma, 1988 (ref. ID; 4747 described paper)

Emended diagnosis

Cells globose with a diameter ranging from 15-25 um (mean 22 um). The plate-scales are broadly elliptical, discoid, 3.6-5.3 um in diameter, with a distinct pattern of large perforations, 4-9 in number; usually there is one central hole, surrounded by 6 equal holes, showing a hexagonal pattern. The cytoplasm contains many small brown-reddish coloured granules. (ref. ID; 4747)

Comments

The specimens we found are identical with those described by Hertwig & Lesser (1874) and are easily distinguished from P. fluviatilis by the smaller cell diameter and the smaller plate-scales with fewer than 10 perforations. The broad elliptical plate-scales are distinguishable from the circular ones of P. fluviatilis. The plate-scales are almost identical to those of Rhabdiophrys thomseni n. sp., which species, however, also possesses spine-scales. Therefore, single plate-scales are not sufficient for distinguishing between these two species. The single plate-scales illustrated by Thomsen (1979) and identified as Pinaciophora denticulata may belong to either R. thomseni or P. rubicunda. (ref. ID; 4747)

Pinaciophora spiculata Manton & Sutherland (ref. ID; 7207), Manton (ref. ID; 7519)

Remarks

P. spiculata was described on material collected from the North American Arctic (Manton 1978). During the examination of material from Dybso Fjord collected in January and March, 1977, a number of broken periplasts were observed, very similar to P. spiculata except in the shape of the plate-scales which were oval rather than circular and in the structure of the base-plates of the spine-scales. In Manton's specimens the base-plate centre appeared to be reticulate, but in those from Dybso Fjord the plate was apparently replaced by rather heavily silicified oval rings. However, the general similarity between the material from Denmark and the type material is so convincing that the Danish material can safely be referred to P. spiculata. It is also clear that the single plate-scale illustrated by Gaarder, Fryxell and Hasle (1976, loc. cit., fig.14) originates from a P. spiculata periplast. As will appear from the discussion, in which the different plate- and spine-scales of Pinaciophora are compared, those of P. spiculata and in particular those of the two species described below represent scale types which are not readily derived from more typical Pinaciophora scales, as represented by e.g. P. fluviatilis, P. denticulata, P. candelabrum, and P. bifurcata; this applies in particular to the plate-scales which in comparison with the spine-scales show less variation within the genus. As, however, both the following species are electron microscopically highly characterstic members of brackish waters, it is most convenient to have a name for these organisms, even though future investigations may make some taxonomic alterations necessary. (ref. ID; 7519)

Pinaciophora tasmanica Croome, 1987 (ref. ID; 4723 original paper)

Diagnosis

Periplast comprising scales of two kinds. Protoplast unknown. Plate-scales circular or nearly so, 1.9-2.4 cm (um spelling miss?) in diameter. The central part of the distal surface with 6-10 perforations 0.15-0.20 um in diameter. A small cluster of minute perforations (ca. 0.04 um in diameter) is present at the very centre of the scale. Other small, less regular perforations are present in the distal layer outside the circumference of the large perforations. The proximal layer of the scale can be seen beneath the large perforations in the distal layer, and is not obviously perforate. The intercalary layer appears as small dots and thickenings across the scale with a well defined periphery comprising a ring of uniform and closely spaced dots towards the scale edge. Around the circumference of the scale there is a narrow, patternless, raised rim. Spine-scales 2.9-5.1 um long, with a base 0.7-0.8 um wide, a shaft 0.11-0.18 um wide at its narrowest point, and either a slightly flared or pointed apex. (ref. ID; 4723)

Type locality

From sites in Tasmania sampled during an Australia-wide survey of freshwater habitats. (ref. ID; 4723)

Pinaciophora triangula Thomsen, 1978 (ref. ID; 7519 original paper) reported year? (ref. ID; 4741, 7207)

Diagnosis

Scales of two kinds. Protoplast unknown. Plate-scales rounded-triangular with concave sides (ca. 1.5 um). Between a patternless rim and three large central perforations is an area dominated by hexagonally arranged fine perforations. The edge of the plate-scale appears finely serrate. "Spine-scales" commonly 1-2 um long and 0.8 um wide at the base. Base-plate angular with raised rims, supporting an irregular obconical structure with a distal cavity. Parts of the "spine-scale", including the fan-shaped connections between tube and base-plate, show rather irregular perfortaions as does the bottom of the angular base-plate. (ref. ID; 7519)

Descriptions

This species is the only one with plate scales which are not circular or oval; the rounded triangular scales from Mouse Lake, Ontario agree well in size and structure with those reported from Lake Straken, Sweden, the only other known locality (Thomsen 1978). The triad of large (0.3-0.5 um diameter) holes in the distal surface of the scale is surrounded by a thickened rim which, in the Mouse Lake scales, is interrupted at regular intervals and thus has the appearance of a series of several short (0.06-0.12 um) bars encircling each hole. The short spine scales found with the Swedish material were not visible in the Ontario specimen. (ref. ID; 7207)

Remarks

Unfortunately only a somewhat insufficient description can at the moment be given of P. triangula. As these scales represent a unique line of evolution within the genus, it has, however, been included here in spite of the lack of details in the description. The structure of the plate-scales is in accordance with that found in typical members of the genus Pinaciophora. The distal surface shows a triad of large holes in the centre of the scale, followed by an area with finer perforations in hexagonal arrangement and an always patternless edge. (ref. ID; 7519)

Habitat of the type

Freshwater, lake Straken (Sweden). (ref. ID; 7519)

Pinaciophora tridentata Thomsen, 1978 (ref. ID; 7519 original paper) reported year? (ref. ID; 7207)

Diagnosis

Scales of two kinds. Protoplast unknown. Plate-scales circular to oval, 2-3 um in diameter. Central part of the distal scale surface with a ring of five larger perforations. A single smaller perforation occasionally present in the centre of the scale. Between a rather broad rugose rim and the central ring of perforations is an area perforated by small hexagonally arranged pores. The two plates of the scale are fused peripherally, elsewhere connected by intercalary material appearing as hexagonally arranged black dots. Spine-scale ca. 3 um long and ca. 0.2 um wide at the narrowest point. The middle part appears cylindrical. Distally the spine is split into a trifurcate tip (hence the specific epithet). It is supported at the base by short struts that attach to an oval base-plate ca. 0.6 um wide and composed of an oval ring and approximately three cross-beams. Apart from the spaces between the struts, and a few smaller perforations through the trifurcate tip, the spine-scale appears patternless. (ref. ID; 7519)

Habitat of the type

Marine, Dybso Fjord (Denmark). Collected 1 March 1977. Surface water sample. (ref. ID; 7519)