Zivkovicia
Zivkovicia Ogden, 1983 (ref. ID; 3567, 7701 original paper) or 1987 (ref. ID; 6793)
[ref. ID; 7701]
Diagnosis; Shell pyriform, often with a distinct constriction of the neck region, either circular or compressed in transverse section; composed mainly of quartz particles bound by an organic cement network; aperture terminal usually circular; internally the shell is partitioned into two regions by an extension of the walls of form a diaphragm, the latter having either one or two small circular openings. (ref. ID; 7701)
Etymology; The genus is named in honour of Andjelija and Dragana Zivkovic, whose company the author shared whilst collecting some of the samples on a visit to Lake Vlasina, Yugoslavia. (ref. ID; 7701)
- Zivkovicia bryophila (Penard, 1902) Ogden, 1983 (ref. ID; 7701 redescribed paper)
Syn; Pontigulasia bryophila Penard, 1902 (ref. ID; 7701); Pontigulasia bryophila var. elachys Jung, 1942 (ref. ID; 7701); Pontigulasia varadi Godeanu, 1972 (ref. ID; 7701)
- Zivkovicia compressa (Carter, 1864) Ogden, 1983 (ref. ID; 7701 redescribed paper) reported year? (ref. ID; 2125, 2152)
Syn; Difflugia compressa Carter, 1864 (ref. ID; 7701); Difflugia pyriformis var. vas sub-var. bigibossa Penard, 1899 (ref. ID; 7701); Pontigulasia bigibossa Penard, 1902 (ref. ID; 7701)
- Zivkovicia epiouxi Chardez, 1984 (ref. ID; 2151 original paper, 2152)
Syn; Pontigulasia epiouxi Chardez, 1983 (ref. ID; 2151)
- Zivkovicia flexa (Cash & Hopkinson) Ogden, 1983 (ref. ID; 2125, 2151, 7701 redescribed paper)
Syn; Pontigulasia compressa var. flexa Cash & Hopkinson, 1909 (ref. ID; 2151) reported author and year? (ref. ID; 7701)
- Zivkovicia gigas (Vucetich, 1978) Ogden, 1983 (ref. ID; 7701 redescribed paper)
- Zivkovicia montana (Ogden & Zivkovic, 1983) Ogden, 1983 (ref. ID; 7701 redescribed paper)
- Zivkovicia sarrazinensis Chardez, 1984 (ref. ID; 2125)
- Zivkovicia vas (Leidy, 1874) Ogden, 1983 (ref. ID; 7701 redescribed paper)
Syn; Difflugia pyriformis var. vas Leidy, 1879 (ref. ID; 7701); Difflugia vas Leidy, 1874 (ref. ID; 7701); Pontigulasia spectabilis Penard, 1902 (ref. ID; 7701); Pontigulasia vas (Leidy) Schouteden, 1906 (ref. ID; 7701)
Zivkovicia bryophila (Penard, 1902) Ogden, 1983 (ref. ID; 7701 redescribed paper)
Synonym
Pontigulasia bryophila Penard, 1902 (ref. ID; 7701); Pontigulasia bryophila var. elachys Jung, 1942 (ref. ID; 7701); Pontigulasia varadi Godeanu, 1972 (ref. ID; 7701)
Descriptions
The shell is elongate pyriform, tapering evenly from the aperture to the widest breadth at about two-thirds of the body-length, then curving gradually to the aboral extremity, and is circular in cross section. It has a rough surface composed mainly of smooth of medium pieces of quartz, but with some randomly scattered larger particles. Small areas of organic cement are sometimes seen between the particles. Often these appear to be spheres with a patterned or perforated surface, and sometimes they are fused to form a network of rings, each ring having a perforated centre. The spheres are about 300 nm in diameter and the pores or perforations are 20 nm in diameter. The external aperture is circular and usually surrounded by a relatively regular arrangement of particles to give a notched or tooth-like appearance. The internal opening is seen through the external aperture, when viewed directly, as a smaller circular orifice. However, examination of a specimen broken at a level with the internal openig shows that the so-called diaphragm is an integral part of the shell which divides it into two compartments. This dividing wall is made mainly of small particles cemented together with the central circular opening surrounded by a raised lip of particles. In on specimen this internal opening was covered by a smooth membrane, possibly a cyst plug. (ref. ID; 7701)
Remarks
This species can easily be confused with specimens of Difflugia bryophila because their shells are of a similar size and composition, whilst sharing the same type of ecological niche (Ogden 1983). The difference between these two species is the presence of an internal diaphragm an different organic cement pattern of Z. bryophila. There is insufficient detail to warrant recognition of either the variety Pontigulasia bryophila var. elachys Jung, 1942 or the species Pontigulasia varadi Godeanu, 1972 the descriptions of both being based only on external features, and as these show little difference from the features of Z. bryophila they are considered as synonyms. Specimens from Yugoslavia recently decribed by Ogden & Zivkovic (1983) as Pontigulasia bryophila, had a slightly differ orgnaic cement pattern from that seen in the British specimen described here, but in all other respects were identical with Z. bryophila and are so designated. A single slide identified as Pontigulasia bryophila by Penard, BM (NH) 20.12.8.564, shows the dark band of the diaphragm across the width of the shell and in all other respects agrees with the present description. (ref. ID; 7701)
Material examined
Specimens were collected from samples of Sphagnum moss gathered at Holmsley Lodge, Burley, New Forest, Hampshire in May 1977 and 1978, Subberthwaite, Broughton-in-Furness, Cumbria in June 1979, Matley Bog, Hampshire in March, 1980 and Myndd Hiraethog, Denbigh, Clwyd, North Wales in August, 1980. (ref. ID; 7701)
Geographical distribution
Argentina (Vucetich 1974), Belgium (Couteaux 1969), Britain (Cash & Hopkinson 1909), Germany (Grospietsch 1958), Roumania (Godeanu 1972), Russia (Tarnogradskij 1961), Switzerland (Penard 1902). (ref. ID; 7701)
Zivkovicia compressa (Carter, 1864) Ogden, 1983 (ref. ID; 7701 redescribed paper) reported year? (ref. ID; 2125, 2152)
Synonym
Difflugia compressa Carter, 1864 (ref. ID; 7701); Difflugia pyriformis var. vas sub-var. bigibossa Penard, 1899 (ref. ID; 7701); Pontigulasia bigibossa Penard, 1902 (ref. ID; 7701)
Descriptions
The shell is pyriform, divided into an anterior wedge-shaped neck, one-third, with a large circular, posterior body, two-thirds, laterally compressed. It has a rough surface composed mainly of small to medium pieces of quartz, but often with some large particles added. Organic cement binds these particles together and is sometimes seen as part of the shell matrix. The cement forms a regular pattern of thick walled circles arranged in a network. Each circle has a mesh covering which is perforated by about fourteen small openings. The positioning of these perforation do not appear to be in a regular manner, although this may be due to the close packing of the circular elements and the strength of the covering mesh. The external aperture is usually oval, rarely circular, and surrounded by small or medium particles. The two internal openings, usually one on either side of the shell, are not visible through the external aperture when viewed directly, although the thickened edges surrounding them are just visible at the periphery. The three micrographs of the broken anterior portion of the shell, show the size of these internal openings, their position close to the shell wall, the thickness of the dividing wall, which may include large particles, and that both sides of the dividing structures are constructed in a similar manner to the shell wall. The apertural face of this internal structure is maked by two rims of particles, which surround the internal openings, and are seen clearly when the specimen is tilted to either side. One specimen differed in having three internal openings. The additional opening being a small centrally positioned feature, but to further complicate this specimen the openings were covered or partially covered by a smooth organic membrane. This smooth covering is probably a cyst membrane and has been seen to cover either the internal openings, as in the specimen described above, or the external opening. Only four examples of encysted specimens were present in the samples examined, these were divided equally between having either internal or external cyst membrane, so no preference can be established. (ref. ID; 7701)
Remarks
The description of this species as Difflugia compressa given by Carter (1864), was so precise that Cash and Hopkinson (1909) considered that it was 'beyond question' identical with Pontigulasia bigibossa Penard, 1902 and therefore a synonym of their new combination Pontigulasia compressa (Carter 1864). This treatment was accepted by Penard when identifying specimens for the Clare Island Survey (Wailes & Penard 1911). This is probably the most common of those having an internal diaphragm and is usually easy to identify because this feature is often seen as a dense 'v' or 'u' shape positioned at the base of the neck, this may frequently be accompanied by a winged appearance of the shell body as it expands from the diaphragm position. It is interesting to note that the present specimens agree well with Penard's (1902) dimensions for specimens from Lake Leman, Switzerland, body length 200-250 um, whilst those given by Cash & Hopkinson (1909) for specimens from Britain are smaller, body length 130-150 um. Seven slides identified by Penard as Pontigulasia bigibossa, BM(NH) 20.12.8. 557-563, are in good agreement with the description of Z. compressa given here. (ref. ID; 7701)
Material examined
Specimens were collected from samples of Sphagnum moss gathered at three sites in the New Forest, Hampshire, namely Cranes Moor, Holmsley Lodge and Matley Bog in May, 1979, 1978 and March, 1979, 1980. (ref. ID; 7701)
Geographical distribution
Argentina (Vucetich 1974), Austria (Laminger 1972, 1973, 1975), Belgium (Couteaux 1969; Chardez & Hellebaut 1978), Britain (Cash & Hopkinson 1909), France (Thomas 1954), Germany (Grospietsh 1958; Schonborn 1962, 1965; Voeltz-Hohn 1971), Poland (Moraczewski 1965), Russia (Tarnogradskij 1961), Switzerland (Penard 1902), United States of America (Laminger et al. 1979). (ref. ID; 7701)
Zivkovicia flexa (Cash & Hopkinson) Ogden, 1983 (ref. ID; 2125, 2151, 7701 redescribed paper)
Synonym
Pontigulasia compressa var. flexa Cash & Hopkinson, 1909 (ref. ID; 2151) reported author and year? (ref. ID; 7701)
Descriptions
The shell is elongate, tapering slightly and evenly from the aperture to the mid-body region and then gradually to the gracefully curved aboral extremity, laterally compressed. An occasional specimen is curved laterally, hence the origin of the specific name, but more frequently they have a clean regular outline. It usually has a smooth surface composed mainly of medium flat pieces of quartz with smaller particles filling the interstices. Small areas of organic cement in the form of a regular patterned sheet are frequently seen between the particles. Each pattern is made of a circle of perforations, which are about 500 nm in diameter, with two or more central perforations. These perforations are about 80 nm in diameter although they may sometimes fuse to form larger holes or elongated slots. The external aperture is circular and surrounded by small or medium particles. There is no external indications to show the position of the internal wall, but it is positioned about one-third of the body length from the aperture. This inner wall has two opening situated equidistant from the lateral walls and the midbody position of the shell, so that when viewed directly through the external aperture only the edges of each is visible. Although most specimens have an elongate, smooth shell, a small percentage have either a more pyriform outline and others a rougher shell matrix composed of angular quartz. (ref. ID; 7701)
Remarks
This species is similar to Z. compressa but can easily be distinguished from it by the smooth, more transparent, narrow elongate shell which rarely has any indication of a neck constriction. The occasional specimens may have a rough surface, but this is usually confined to the addition of small angular particles and is in no way similar to the arrangement of larger particles seen in the shell of Z. compressa. It may be significant that the present specimens came from North Wales as did those from the original description, although this can only be resolved by further investigations. (ref. ID; 7701)
Material examined
Specimens were collected from Sphagnum moss gathered at Myndd Hiraethog, Denbigh, Clwyd, North Wales in August, 1980. (ref. ID; 7701)
Geographical distribution
Britain (Cash & Hopkinson 1909). (ref. ID; 7701)
Zivkovicia gigas (Vucetich, 1978) Ogden, 1983 (ref. ID; 7701 redescribed paper)
Descriptions
This species is similar to Z. compressa in general outline but has much larger dimensions, for example the body length is 420-470 um. The diaphragm is reported as having a single apertural opening similar to Z. vas. Although this species is known only from Argentina (Vucetich 1978), a single large specimen identified as Pontigulasia has been recorded from the New Forest, England (West 1901). (ref. ID; 7701)
Zivkovicia montana (Ogden & Zivkovic, 1983) Ogden, 1983 (ref. ID; 7701 redescribed paper)
Descriptions
This species is similar to Z. bryophila in having a single centrally positioned opening of the diaphragm, but differs in being broader, having a larger apertural opening and often a distinct constriction of the neck. Doubtful species. (ref. ID; 7701)
Zivkovicia vas (Leidy, 1874) Ogden, 1983 (ref. ID; 7701 redescribed paper)
Synonym
Difflugia pyriformis var. vas Leidy, 1879 (ref. ID; 7701); Difflugia vas Leidy, 1874 (ref. ID; 7701); Pontigulasia spectabilis Penard, 1902 (ref. ID; 7701); Pontigulasia vas (Leidy) Schouteden, 1906 (ref. ID; 7701)
Descriptions
The shell is pyriform, usually divided into two distinct but unequal halves, a smaller, anterior wedge-shaped portion which terminates at a usually pronounced junction with the larger posterior rounded portion. It is usually composed of medium angular quartz particles, often with some diatom frustules incorporated into the matrix and frequently with larger particles near to or at the position of the constriction. One specimen in the present sample was composed entirely of diatom frustules and fragments of them, but this is considered to be unusual and not significant. Smaller particles are often packed at the junctions of larger particles to give a compact, but irregular appearance, to the extent that the binding organic cement is infrequently seen. The organic cement that the typical thick walled network, with each mesh perforated with smaller openings. This network is seen as either single elements or in the 'diatom' specimen as a line of elements. The external aperture is usually circular but sometimes may be oval in outline and is surrounded by the small or medium particles. The inner wall or diaphragm is composed of small quartz, siliceous shell plates and some larger, flat pieces of quartz. The internal openings, of which there are two, are situated off-centre close to the shell wall and are not visible from a direct examination. Often only one these openings is visible, the other being camouflaged by a large siliceous plate. (ref. ID; 7701)
Remarks
The synonym of Diffulgia vas Leidy, 1874 with Pontigulasia spectabilis Penard, 1902 was proposed by Schouteden (1906) and has been accepted by most authors, this is in accord with Penard (1902) who considered his specimens were similar but proposed a new name spectabilis with vas as a synonym. Eight slides, identified by Penard as P. vas, BM(NH) 20.12.8.565-572, are in good agreement with the present description. An interisting observation by Penard was apparent sealing of one of the two internal openings of the diaphragm, which has also been in the present material. The structure of the diaphragm is not as robust as that seen in Z. compressa, because it incoporates siliceous shell plates and flat pieces of quartz with the openings appearing as ragged breaks situated towards the lateral margins. One opening is visible in all specimens, but two in only a few, although in a specimen of the former group another partial opening was seen when the specimen was broken for examination. This partial opening was sealed with a large flat plate, similar to that described as covering the second opening by Penard (1902). The reason for the closure of the second opening is difficult to understand, although it may be associated with encystment. Nevertheless, as already noted organic membranes cover both diaphragm and apertural openings in Z. compressa, whilst some specimens of Z. vas have an organic cyst membrane over the apertural opening, it could be assumed that a similar membrane would cover the diaphragm opening. (ref. ID; 7701)
Material examined
Specimen were collected from samples of Sphagnum moss which formed part of a mat of vegetation floating across an isolated corner at Lake Vlasina, Serbia, Yugoslavia in September, 1982. (ref. ID; 7701)
Geographical distribution
Argentina (Lena & Zaidenwerg 1975), Austria (Laminger 1973, 1975), Belgium (Chardez & Hellebaut 1978), Britain (Cash & Hopkinson 1909), France (Thomas 1954), Germany (Grospietsch 1958; Voeltz-Hohn 1971), Poland (Moraczewski 1965), Russia (Tarnogradskij 1961), United States of America (Laminger et al. 1979). (ref. ID; 7701)