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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Aspidisca

Aspidisca Ehrenberg, 1830 (ref. ID; 2014, 7400)

From Dr. Inaki

From Dr. Inaki

From Dr. Ouchiyama

Class Polyhymenophora: Subclass Spirotricha: Order Hypotrichida: Suborder Sporadotrichina: Family Aspidiscidae (ref. ID; 2014)
Order Euplotida: Family Aspidiscidae (ref. ID; 7354)
Family Aspidiscidae Ehrenberg, 1838 (ref. ID; 4905) reported year? (ref. ID; 4813)

Synonym Aspidicopsis Ghosh, 1921 (ref. ID; 2014); Coccudina Dujardin, 1841 (ref. ID; 2014); Onychaspis Stein, 1859 (ref. ID; 2014)

[ref. ID; 2014]
Small, irregularly ovoid, inflexible body with dorsal ridges. The AZM is reduced or rudimentary, consisting usually of two parts separated on the left margin of the body. The more posterior is the larger, and is associated with the cytostome. Undulating membrane absent. Marginal and caudal cirri absent. The cirri in two groups; a transverse set of 5 or more large cirri located posteriorly and an anterior group (often 7). The macronucleus C-, horseshoe-shaped or is in two parts. 1 or 2 micronuclei. The contractile vacuole posterior to the transverse cirri.
Quote; Colin R. Curds, Michael A. Gates and David McL. Roberts "British and other freshwater ciliated protozoa Part II Ciliophora: Oligohymenophora and Polyhymenophora" Cambridge University Press, 1983 (ref. ID; 2014)

[ref. ID; 7354]
Ciliates in the genus Aspidisca have 7-15 FVC and five or more TC. There are no right caudal cirri or dorsal cilia. The AZM is reduced to a few collar membranelle with in a ventral fossa, and lapel membranelles located within a ventral buccal cavity. Spines or spurs commonly occur on both the dorsal surface and left edge of the cell. All species are free-living. (ref. ID; 7354) Wu and Curds (1979) divided the genus Aspidisca into three sections. Type species; Aspidisca lynceus (Muller, 1773) Ehrenberg, 1831 (ref. ID; 7354)

[ref. ID; 7400]
Taxonomic backgroud; Ehrenberg established the genus Aspidisca in 1830 using A. lynceus (Muller, 1773) as the type species. A second species, A. turrita (Ehrenberg, 1838) Claparede and Lachmann 1858, closely resembles A. lynceus in size, shape, and ciliature except for the possession of a dorsal thorn-like structure. My students and I discovered A. turrita coexisting with the large predacious ciliate Urostyla grandis and hypothesized that the dorsal thorn of A. turrita was an anti-predator structure induced by a cue released by U. grandis. Urostyla-factor (U-factor) induces defensive morphological changes in species of Euplotes and Sterkiella. (ref. ID; 7400)
  1. Aspidisca aculeata (Ehrenberg, 1838) (ref. ID; 1621) reported year? (ref. ID; 3771), (Ehrenberg, 1883) Kahl, 1932 (ref. ID; 7354)
    Syn; Aspidisca aculeata Mansfeld, 1926 (ref. ID; 1621)
  2. Aspidisca andrewi Mereschkowski, 1877 (ref. ID; 1621)
  3. Aspidisca antarctica Corliss & Snyder, 1986 (ref. ID; 7603 original paper)
  4. Aspidisca baltica Kahl, 1932 (ref. ID; 3119)
  5. Aspidisca bengalensis (Ghosh, 1921) (ref. ID; 1621)
  6. Aspidisca binucleata Kahl, 1932 (ref. ID; 1621, 2316)
  7. Aspidisca caspica Agamaliev, 1967
    See; Aspidisca leptaspis (ref. ID; 4905)
  8. Aspidisca cicada (O.F. Muller, 1786) (ref. ID; 662) or (Mueller, 1786) Claparede & Lachmann, 1858 (ref. ID; 4488, 4609, 4813) reported author and year? (ref. ID; 191, 1629, 1896)
    Syn; Aspidisca sulcata Kahl, 1932 (ref. ID; 4609); Coccudina costata Dujardin, 1841 (ref. ID; 4609, 4813); Trichoda cicada O.F. Muller, 1786 (ref. ID; 4609, 4813)
  9. Aspidisca costata Dujardin, 1842 (ref. ID; 3116, 4654) reported year? (ref. ID; 1219, 3342, 3698, 5624), (Dujardin, 1842) Kahl, 1932 (ref. ID; 1621, 2245) or (Dujardin, 1841) Stein, 1859 (ref. ID; 3790)
    Syn; Aspidisca cicada Claparede & Lachmann, 1859 (ref. ID; 1621); Coccudina costata Dujardin, 1842
  10. Aspidisca crenata Fabre-Domergue, 1885 (ref. ID; 1621)
    See; Aspidisca leptaspis (ref. ID; 4905, 4909)
  11. Aspidisca dentata Kahl, 1928 (ref. ID; 1621)
  12. Aspidisca fjeldi Dragesco, 1960 (ref. ID; 3690 original paper)
  13. Aspidisca fusca Kahl, 1928 (ref. ID; 1621, 2112, 3119)
  14. Aspidisca herbicola Kahl, 1932 (ref. ID; 7354) reported author and year? (ref. ID; 1621)
  15. Aspidisca hexeris Quennerstedt, 1869 (ref. ID; 4905, 4909) reported author and year? (ref. ID; 2249)
    See; Aspidisca leptaspis (ref. ID; 4905, 4909)
  16. Aspidisca hyalina Dragesco, 1960 (ref. ID; 3690 original paper)
  17. Aspidisca irinae Burkovsky, 1970 (ref. ID; 2112 original paper, 3119)
  18. Aspidisca leptaspis Fresenius, 1865 (ref. ID; 1621, 4905 redescribed paper, 4909)
    Syn; Aspidisca baltica sensu Borror, 1968 (ref. ID; 4905); Aspidisca caspica Agamaliev, 1967 (ref. ID; 4905); Aspidisca crenata Fabre-Domergue, 1885 (ref. ID; 4905); Aspidisca hexeris Quennerstedt, 1869 (ref. ID; 4905); Aspidisca lyncaster sensu Fleury et al., 1986 (ref. ID; 4905) or sensu Tuffrau, 1964 (ref. ID; 4905); Aspidisca orthopogon Deroux & Tuffrau, 1965 (?) (ref. ID; 4905); Aspidisca psammobiotica Burkovsky, 1970 (ref. ID; 4905); Aspidisca pulcherrima Kahl, 1932 (ref. ID; 4905) or sensu Tuffrau, 1964 (ref. ID; 4905); Aspidisca pulcherrima var. baltica Kahl, 1932 (ref. ID; 4905); Aspidisca sedigita Quennerstedt, 1867 (ref. ID; 4905) or sensu Dragesco, 1960 (ref. ID; 4905); Aspidisca tridentata Dragesco, 1963(?) (ref. ID; 4905)
  19. Aspidisca lincaster Stein (ref. ID; 2117)
  20. Aspidisca lyncaster (O.F. Muller) Stein, 1859 (ref. ID; 1621, 3119) or Stein, 1859 (ref. ID; 7605) reported year? (ref. ID; 3690) reported author and year? (ref. ID; 191)
  21. Aspidisca lynceus Ehrenberg, 1838 (ref. ID; 662, 1308, 1621, 1629, 1896, 2245) reported year? (ref. ID; 1219, 1618, 3698), (Mueller, 1773) Ehrenberg, 1830 (ref. ID; 4488, 4609, 4813, 7400) or (Mueller, 1773) Ehrenberg, 1831 (ref. ID; 7354) reported author and year? (ref. ID; 191)
    Syn; Trichoda lynceus O.F. Muller, 1773 (ref. ID; 4609, 4813)
  22. Aspidisca magna Kahl, 1932 (ref. ID; 7354) reported author and year? (ref. ID; 1621)
  23. Aspidisca major Madsen, 1931 (ref. ID; 7354) reported year? (ref. ID; 1621, 3119)
  24. Aspidisca major Madsen var. faurei Dragesco, 1960 (ref. ID; 3690 original paper)
  25. Aspidisca marsupialis Penard, 1922 (ref. ID; 1621)
  26. Aspidisca mutans Kahl, 1932 (ref. ID; 7354) reported author and year? (ref. ID; 1621)
  27. Aspidisca orthopogon Deroux & Tuffrau, 1965 (ref. ID; 7354) reported author and year? (ref. ID; 191)
  28. Aspidisca polypoda Dujardin, 1841 (ref. ID; 3690) or 1842 (ref. ID; 1621), (Dujardin, 1841) Kahl, 1932 (ref. ID; 7354)
  29. Aspidisca polystyla Stein, 1859 (ref. ID; 1335, 1621) reported year? (ref. ID; 1618)
  30. Aspidisca psammobiotica Burkovsky, 1970
    See; Aspidisca leptaspis (ref. ID; 4905)
  31. Aspidisca pulcherrima Kahl, 1932 (ref. ID; 3119, 4905, 4909) reported author and year? (ref. ID; 1621)
    See; Aspidisca leptaspis (ref. ID; 4905, 4909)
  32. Aspidisca pulcherrima var. baltica Kahl, 1932 (ref. ID; 4905) reported author and year? (ref. ID; 1621)
    See; Aspidisca leptaspis (ref. ID; 4905)
  33. Aspidisca quadrilineata (ref. ID; 1621)
  34. Aspidisca robusta (ref. ID; 1621)
  35. Aspidisca sedigita Quennerstedt, 1867 (ref. ID; 1621, 3119, 4905, 4909, 7603) reported year? (ref. ID; 3690)
    See; Aspidisca leptaspis (ref. ID; 4905, 4909)
  36. Aspidisca steini (V. Buddenbrock, 1920) (ref. ID; 1621, 4905)
    Syn; Aspidisca aculeata sensu Agamaliev, 1974 (ref. ID; 4905); Aspidisca aculeata sensu Borror, 1965 (ref. ID; 4905); Aspidisca glabra Kahl, 1928 (ref. ID; 1621)
  37. Aspidisca steini var. major Madsen, 1931 (ref. ID; 1621)
  38. Aspidisca sulcata Kahl, 1932 (ref. ID; 4609)
    See; Aspidisca cicada (ref. ID; 4609)
  39. Aspidisca tridentata Dragesco, 1963
    See; Aspidisca leptaspis (ref. ID; 4909)
  40. Aspidisca tuberosa Kahl, 1932 (ref. ID; 7354) reported author and year? (ref. ID; 1621)
  41. Aspidisca turrita (Ehrenberg, 1831) Claparede & Lachmann, 1858 (ref. ID; 4609, 4813) or (Ehrenberg, 1838) Claparede & Lachmann, 1858 (ref. ID; 7400) reported year? (ref. ID; 1335, 1621, 1629, 2245)
    Syn; Euplotes? turritus Ehrenberg, 1831 (ref. ID; 4609, 4813); Euplotes turritus Ehrenberg, 1838 (ref. ID; 4609, 4813)

Aspidisca antarctica Corliss & Snyder, 1986 (ref. ID; 7603 original paper)

Descriptions

Oval body with concave left side, 40 (30-50) um long, 24 (21-38) um wide (n=10). Prominent prostomial spur on left margin. Four dorsal ridges extending anterior to posterior. The single macronucleus is wishbone-shaped, 4-6 um in diameter. Single micronucleus, 4 um in diameter. Cytostome and oral polykinetids are oriented along a nearly transverse axis, anterior to the prostomial spur. Seven frontoventral cirri are arranged as a loose group of five anteriorly and a group of two closer to the center of the body. An eighth frontventral cirrus lies subequatorially along the right margin, close to the transeverse cirri, which are five in number. Four rows of paired kinetosomes lie between the ridges on the dorsal surface. (ref. ID; 7603)

Remarks

Aspidisca antarctica n. sp. most closely resembles A. sedigita Quennerstedt, 1867; but it differs in the number of frontoventral cirri, the pattern of the frontoventral cirri, the number of transverse cirri, and the number of dorsal kineties (from A. sedigita as well as from other species of this long known genus). (ref. ID; 7603)

Etymology

Its new name is based on its general area of collection. (ref. ID; 7603)

Type locality

Samples of sea-ice pore water from the Weddell Sea, Antarctica. (ref. ID; 7603)

Aspidisca binucleata Kahl, 1932 (ref. ID; 1621, 2316)

Descriptions

Nine frontoventral and six transverse cirri present, together with two macronuclei. (ref. ID; 2316)

Measurements

Oval body 50 um in diameter. Kahl (1932) gave measurements of 70-90 um. (ref. ID; 2316)

Aspidisca costata Dujardin, 1842 (ref. ID; 3116, 4654) reported year? (ref. ID; 1219, 3342, 3698, 5624), (Dujardin, 1842) Kahl, 1932 (ref. ID; 1621, 2245) or (Dujardin, 1841) Stein, 1859 (ref. ID; 3790)

Synonym

Aspidisca cicada Claparede & Lachmann, 1859 (ref. ID; 1621); Coccudina costata Dujardin, 1842

Descriptions

Body not plastic because of the armour-like pellicle; ventral side flattened and furnished with 7 front-ventral cirri and 5 transversal, 2 of which are located immediately behinds the buccal area; the adoral zone of membranelles is reduced in comparison with Stylonychia and other hypotrichs; the buccal area bears a rather small group of membranelles and is located in the left posterior part of the ventral side, its membranelles are covered by a this transparent fold; on the left anterior part of the ventral side there is a group of 3 small membranelles-a remnant of a greater adoral zone. Dorsal side convex and conspicuously ridged, the 6 longitudinal ridges vary in side. Macronucleus horseshoe-shaped; 1 small spherical micronucleus anteriorly; contractile vacuole near the right side in the vicinity of the first transverse cirrus. (ref. ID; 1219)
Aspidisca costata is a colorless fresh-water species. According to most observers, A. costata is characterized by the presence on the domed dorsal surface of 6 prominent longitudinal ridges. Probably the majority of our specimens had 6 or 7 dorsal ridges, but there was considerable variation in their number, from 3 to 10. Often it was difficult to be certain about their number because of confusion with the ventral rim which encircles the animals. Brown stated that the dorsal surface lacked cilia. We have seen indications in the preparations stained by the Holmes technic that there are dorsal bristles. In side view, A. costata resembles a bisected orange, with the cur flat surface being the ventral surface and the almost hemispherical scalloped (ridged) convex outline, the dorsal site. The organism is almost as high as it is wide. Ventral view: the suboval trilateral shape; the lip on the organism's right side under which are spaced 4 (frontal) cirri; 5 transverse or anal cirri, 3 on the contractile vacuole side and a group of 2 behind the AZM, with a row of 3 ventral cirri between them; the AZM in the animal's left posterior quadrant; the horseshoe-shaped macronucleus; the micronucleus; and a rather prominent cortical diagonal ridge extending anteriorly from the bases of the group of 3 anal cirri. These is also another cortical ridge (skeletal?) parallel to the region of alignment of the 2 left anal cirri, between them and the AZM. The membranelles of the AZM are arranged in closely packed parallel rows and partially enclosed in the buccal cavity. The exact number of membranelles comprising this organelle is difficult to determine precisely, but is ~15. The longest membranelles are in the center of the AZM, their length decreasing anteriorly and posteriorly. The complex structure of the AZM has not been satisfactorily analyzed. There are probably paroral membranelles. The length of the AZM is 8-10 um. The most anterior ciliary structure in the cell is a tuft of 3 parallel units, always tapering to a point, which lies in a ventral notch at the front of the organism near the anterior-most frontal cirrus. This ventral ciliated notch, is indicated from a dorsal view by an identification in the left anterior outline. The macronucleus is very characteristic and consistently oriented in the cell. It is horseshoe-shaped and symmetrically situated on the ventral surface with the opening toward the right latero-posterior border of the organism and the center of the curve toward the left anterior side. Often the right arm is shorter and more slender than the left arm. These morphologic landmarks usually enable the observer to tell at a glance whether a ciliate is being viewed lying on its dorsal or its ventral side, e.g. if the open end of the C is on the observer's left the organism's ventral side is up. The position of the AZM is also decisive in this respect. The micronucleus is located slightly to the left of and peripheral to the apex of the curve of the C, ventral to the macronucleus. It is of fair size, the slightly ovoid envelope measuring ~3.0 um and the endosomes ~20 um. The movements of our A. costata were quite characteristic of this creeping bottom-dwelling form. Its jerky, nervous, almost ceaseless circling to the right, probably by walking on its cirri, enables one to distinguish it easily under the dissecting microscope from other small forms, such as Chilodonella spp. (ref. ID; 3790)

Measurements

Length 25-40 um. (ref. ID; 1219)
20-25x20 um. (ref. ID; 3342)
Modal length of 26 um (n=46); another race had a consistent length of ~20 um and maximum width of ~17 um. In all other respects the larger and smaller "races," probably nutritionally induced, seemed identical. (ref. ID; 3790)

Aspidisca hexeris Quennerstedt, 1869 (ref. ID; 4905, 4909) reported author and year? (ref. ID; 2249)

See

Aspidisca leptaspis (ref. ID; 4905, 4909)

Descriptions

In marine. (ref. ID; 2249)

Aspidisca leptaspis Fresenius, 1865 (ref. ID; 1621, 4905 redescribed paper, 4909)

Synonym

Aspidisca baltica sensu Borror, 1968 (ref. ID; 4905); Aspidisca caspica Agamaliev, 1967 (ref. ID; 4905); Aspidisca crenata Fabre-Domergue, 1885 (ref. ID; 4905); Aspidisca hexeris Quennerstedt, 1869 (ref. ID; 4905); Aspidisca lyncaster sensu Fleury et al., 1986 (ref. ID; 4905) or sensu Tuffrau, 1964 (ref. ID; 4905); Aspidisca orthopogon Deroux & Tuffrau, 1965 (?) (ref. ID; 4905); Aspidisca psammobiotica Burkovsky, 1970 (ref. ID; 4905); Aspidisca pulcherrima Kahl, 1932 (ref. ID; 4905) or sensu Tuffrau, 1964 (ref. ID; 4905); Aspidisca pulcherrima var. baltica Kahl, 1932 (ref. ID; 4905); Aspidisca sedigita Quennerstedt, 1867 (ref. ID; 4905) or sensu Dragesco, 1960 (ref. ID; 4905); Aspidisca tridentata Dragesco, 1963(?) (ref. ID; 4905)

Improved diagnosis

Ellipsoid, large marine Aspidisca, in vivo 60-90 um long, characterized by 4 dorsal ribs and often pronounced lateral and posterior spur-like protrusions on cell border; 7 strong and one small frontoventral cirri; 6-7 transverse cirri, of which the left-most cirrus always closely positioned; 4 dorsal kineties with densely spaced basal bodies; 7-8 membranelles in AZM1 while 16-19 in AZM2. (ref. ID; 4905)

Redescription

Size of our populations in vivo about 60-80x40-50 um, body elliptical with snout-shaped anterior end; broadest in or behind mid-body, right margin convex, let almost straight, anteriorly broadly rounded; dorso-ventrally highly flattened (ca. 1:2.5-3). Outline associated with indentation or protrusion of cell, one lateral spur subapically located, which is usually smaller than prostomial one even inconspicuous in some specimens. Additionally, several (4-6) posterior spurs on border of caudal portion, which make the cell usually rugged (q.v. Borror 1968; Dragesco 1960; Kahl 1932; Tuffrau 1964). Ventral surface generally flattened, on dorsal always 4 dominant ridges. Buccal area with 1 distinct thorn-like projection (prostomial spur) on left subcaudally, which covers the AZM2. Pellicle rigid. Cytoplasm hyaline. Contractile vacuole right of median, at level of adoral zone of membranelles. Macronucleus C-shaped, with many spherical nucleoli (ca. 1-2 um). Micronuclei several in number (usually 3-5), always located in depressions of macronucleus. Movement crawling on substrate, quite fast compared with other congeners. When disturbed, always attached to substrate firmly for quite a while. Ciliary pattern stable. Frontoventral cirri rather stiff and strong, cilia of 7 large ones about 12-15 um long; one small, satellite-like cirrus close to right-most (posteriormost) cirrus, which is easy to be overlooked (q.v. Agamaliev 1967). Transverse cirri usually strong, tightly arranged in oblique row, base of right-most cirrus always splitting (but mostly imperfectly) into closely spaced 2-3 ones or even more, which are in vivo clearly recognizable. Cilia of transverse cirri about 15-20 um long. Anterior portion of adoral zone (AZM1) containing 7-8 membranelles, located in deep concave. Posterior part (AZM2) significantly long, as usual beneath lid-like prostomial spur. Paroral membrane (PM) small, difficult to observe. Pharyngeal fibres curved anteriorly. Constant 4 dorsal kineties with tightly spaced basal body pairs. Very characteristically, both basal bodies ciliated with rossete-shaped granules at bases of cilia. Each kinety along dorsal ridge and generally extending from end to end of cell (yet 2 central rows may be slightly shortened at posterior end). (ref. ID; 4905)

[ref. ID; 4909]
As observed by the present and previous authors (Kahl 1932; Wu and Curds 1979; Song & Wilbert 1997), its morphology and infraciliature have revealed extremely high stability, except for the posterior spines, which appear to vary from insignificant to conspicuous. Based on the present observations and descriptions obtained on populations/strains all over the world, this species is characterized by 1) oval body shape with 2 conspicuous left-lateral and several smaller posterior spines; 2) seven large (including one "buccal cirrus") and one small frontoventral (FV) cirri, of which the latter is posteriorly adjacent to the rightmost large FV cirrus; 3) five transverse cirri, of which the leftmost one is slender and often divided in vivo into 2-3 subunits; 4) long adoral zone part 2 (AZM2) consisting of ca. 20 membranelles; 5) seven to eight small membranelles in AZM1 which is positioned typically in the left-frontal area and 6) 4 densely ciliated dorsal kineties, which are arranged along the inconspicuous dorsal ridges. (ref. ID; 4909)
  • Morphogenesis: The earliest cortical morphogenetic event is the appearance of a small patch of basal bodies (kinetosomes) in irregular arrangement, the oral primordium (OP), which occurs de novo beneath the cortex of the ventral surface, conspicuously posterior to the AZM2 and to the left of the transverse cirri. After initial OP formation, there is rapid proliferation of basal bodies with development of a subsurface pouch, in which growth of the OP continues. By this time, a small patch of basal bodies has appeared near the AZM2 as a new anlage of the buccal cirrus for the proter. At about the same time as the OP appears, basal bodies for cirral anlagen (CP) develop as 3 fine and short streaks anterior to the transverse cirri on the cell surface. No parental ciliatures are involved in the formation of these new streaks. Slightly later, two other cirral anlagen are formed de novo to the right of the parental rightmost FV-cirrus. In the end of this stage, each of 5 cirral anlagen extends to its maximum length. The ciliature on the dorsal surface is unchanged at this time. At the centre of the macronucleus two replication bands are recognizable, these subsequently move along the arms simultaneously to both ends of the macronucleus. Division continues with the formation of cirral anlagen fields of the proter and opisthe. These steaks then slightly broaden and become completely separated into anterior and posterior groups. As the pouch of the OP enlarges, the basal bodies align into membranelles from the leftmost end and organize towards the right. A new independent anlage for the buccal cirrus of the opisthe is formed, which seems to be on the ventral wall of the subcortical pouch, while clearly not derived from the OP. In the next stage the two sets of cirral anlagen enlarge and begin to break apart and envelop as distinct cirri. The buccal cirrus develops in both the proter and the opisthe. The resorption of some parental cirri is about to begin, while the ciliature on the dorsal side remains unchanged. In the following period, the anterior end (left-most end) of the opisthe's adoral zone of membranelle emerges onto the cortical surface. The posterior part, as well as the buccal cirrus, is stil within the subsurface pouch; both of these will soon completely migrate outside. At this morphogenetic stage the formation of all adoral membranelles in the opisthe is still in process, while the segregation of new frontoventral-transverse (FVT) cirri (including the buccal cirrus) from the FVT-anlagen is nearly finished. At about the same time, the proliferation of new basal bodies occurs separately in both anterior and posterior portions of each parental dorsal kinety. Later these well develop into 2 groups of kinetal rows (anlagen) for both dividers. The migration of replication bands in the micronucleus is about completed by this stage. Conspicuous events in this period are the separation of the two cirral sets from each other and the formation of the paroral membrane in the opisthe, which is clearly derived from the posterior-most part of the oral primordium. The formation of the membranelles of the opisthe in the OP is almost completed and the final number of membranelles can now be recognized. The AZM2 moves on the cell surface following elongation of the cell. The anterior part (the leftmost portion, the developing AZM1 of the opisthe), which has separated from the main part by migrating anteriorly, seems to be still lying within the subsurface pouch. The buccal cirrus of the opisthe moves anteriorly on the cell surface to the level of the other frontoventral cirri. On the dorsal side, the proliferation of new basal bodies occurs at two levels in the dorsal kineties, which are then rapidly elongated. The macronucleus has shortened and thickened into a compact sausage-shaped mass. As division proceeds all cirri migrate to their final positions. In both proter and opisthe the five FVT-cirral anlagen are seen to have given rise to 3:3:2:2:2 mature frontoventral and transverse cirri, respectively. The buccal cirrus in both dividers has already reached the final size. The AZM1 in the opisthe is still beneath the cell surface. Along with the formation of the division furrow, development and migration of all cirri and other ciliary organelles are completed. Also finished is the division of the macronucleus. The resorption of parental cirri is well advanced. Each of the dorsal kineties extends to the ends of both cells. Morphogenetic events of all cortical structures have been completed except that the body shape, size and general position of some ciliary organelles are still not exactly the same as in the trophic cell. The resorption of parental cirri is almost completed. The macronucleus will soon re-extend to the shape and position of their form in interphase. In summary, all parental cirri are replaced by new structures during morphogenesis. The proter retains both parts of the parental membranelles, with new membranelles of both AZM1 and AZM2 being developed in the opisthe. In both proter and opisthe a buccal cirrus originates from an anlage formed de novo. Additional cilia are developed intrakinetally within the dorsal kineties of both proter and opisthe. (ref. ID; 4909)

    Remarks

    As we observed both from newly collected samples and in culture, the dorsal ridges and spurs in caudal region, which form the rugged body outline, could vary from less to very conspicuous. Since those characters are so variable and depend so much on description of the observers, we appraise these as weak characters for species separation. Alike is the number of transverse cirri: since the left-most one is only partly divided (the bases are closely connected), the number of those cirri might depend in a large scale on the quality of impregnation. Due to these factors, we suggest that forms with 5-8 transverse cirri, with or without appearance rugged body outline but similar in all other morphological (in vivo and at infraciliature level), biological (habitat, behaviour) and morphometric features should be considered as the same species. Based on the reasons stated above, we synonymize with Aspidisca leptaspis the following species (see; Syn) simply because they show basically no differences but the number of transverse cirri and "absence" of spurs at caudal end of cell. In Aspidisca sedigita, A. hexeris and A. crenata, no satellite-cirrus was mentioned in original descriptions (Quennerstedt 1867, 1869; Fabre-Domergue 1885). We suppose, however, that it was overlooked by the authors since this cirrus is very fine and not easy to recognize with "classical" methods used a century ago. We consider Aspidisca pulcherrima Kahl, 1932 as an extreme morphotype of A. leptaspis with highly developed spurs and ridges. By contrast are A. tridentata, A. caspica and A. psammobiotica (Dragesco 1963; Agamaliev 1967; Burkovsky 1970), which have less rugged body outlines. Since this feature is not regarded as a diagnostic character, the identification of all those "varieties" seems fairly certain. We are not quite sure whether the Aspidisca orthopogon should be synonymized with A. leptapsis because, according to original illustrations (Deroux & Tuffrau 1965), the satellite-like cirrus is located close to the anterior (instead of posterior) right-most cirrus (optic illusion or misinterpretation?), and its general pattern of infraciliature on dorsal side seems somewhat different (dorsal kinety 1 and 2 possibly having higher number of basal body pairs), so the identification is uncertain. In the same way, A. tridentata Dragesco, 1963 is very similar to A. leptapsis, except for no mention of the satellite-like cirrus (overlooked?). We set in the synonym-list tentatively and await further support. (ref. ID; 4905)

    Aspidisca lynceus Ehrenberg, 1838 (ref. ID; 662, 1308, 1621, 1629, 1896, 2245) reported year? (ref. ID; 1219, 1618, 3698), (Mueller, 1773) Ehrenberg, 1830 (ref. ID; 4488, 4609, 4813, 7400) or (Mueller, 1773) Ehrenberg, 1831 (ref. ID; 7354) reported author and year? (ref. ID; 191)

    Synonym

    Trichoda lynceus O.F. Muller, 1773 (ref. ID; 4609, 4813)

    Descriptions

    Dorsal side smooth and without ribs, a short distinct spine between the two left transverse cirri. (ref. ID; 1219)
    Predotor-induced phenotypic changes. (ref. ID; 7400)

    Measurements

    Length 30-50 um. (ref. ID; 1219, 1618)

    Aspidisca polystyla Stein, 1859 (ref. ID; 1335, 1621) reported year? (ref. ID; 1618)

    Descriptions

    In marine. (ref. ID; 1618)

    Measurements

    About 50 um long. (ref. ID; 1618)

    Aspidisca steini (V. Buddenbrock, 1920) (ref. ID; 1621, 4905)

    Synonym

    Aspidisca aculeata sensu Agamaliev, 1974 (ref. ID; 4905); Aspidisca aculeata sensu Borror, 1965 (ref. ID; 4905); Aspidisca glabra Kahl, 1928 (ref. ID; 1621)

    Redescription

    In vivo about 20-35x15-17 um, but mostly less than 30 um long; outline more or less bean-shaped with slightly snout-like anterior end; broadest in or behind mid-body, right margin convex, left almost straight, anteriorly broadly rounded. Posteriorly with 1 distinct thorn-like projection (prostomial spur) on left, associated with indentation of cell. Dorso-ventrally flattened about 2:1. Pellicle rigid, 4 dorsal ridges (rightmost one on cell margin), slightly curved. Those ridges usually low but clearly visible even at low magnification. Cytoplasm colourless and hyaline, feeds likely on pennate diatoms. Contractile vacuole (not always visible) small, right of median, at level of transverse cirri. Macronucleus about 20 um long, without conspicuous nucleoli. 2-3 micronuclei (Mi) spherical, close to macronucleus. Movement very slow, crawling on substrate. When disturbed always attached to substrate firmly. Cirral pattern stable. Cilia of frontoventral cirri about 10 um long. Transverse cirri relatively weak, subcaudally arranged in oblique row; rightmost cirrus often splitting into two closely spaced ones. Adoral zone of membranelles bipartite (genus characteristic), anterior portion (AZM1) with mostly 4 membranelles located in deep concave while posterior part (AZM2) beneath lid-like spur. Paroral membrane (PM) close to proximal end of AZM2. Pharyngeal fibres curved anteriorly. Dorsal kineties with sparsely arranged basal body pairs, each along dorsal ridge and generally extending from end to end of cell. Cilia of kineties about 2 um long, as in most other hypotrichs, only anterior basal body ciliated. (ref. ID; 4905)

    Remarks

    We found this organism quite frequently, and all of its morphological features correspond very well with the original and later descriptions (Buddenbrock 1920; Dragesco & Dragesco-Kerneis 1986). Though Kahl (1932) insisted that Aspidisca steini should be smooth (no ridges) on dorsal side, we are convinced that our identification is correct because the appearance of ridges in this genus is clearly a population-dependent character. Aspidisca setini differs from A. aculeata in the absence of the dorsal backward curving hook (dorsal thorn) (Kahl 1932; Curds & Wu 1983). Borror (1965) described a form with 5 dorsal kineties (the left-most one possessing only 2 basal body pairs) and smooth dorsal surface under the name of A. steini, while another similar form was described as A. aculeata, which differs only in lower number of dorsal kineties (4 vs. 5), with or without dorsal ridges. Because of these weak difference, the latter is regarded conspecific with the former. Agamaliev described a new species, Aspidisca fuscoides, which was isolated from the Caspian Sea (1975). It generally has the same appearance and infraciliature (also the overall pattern on dorsal side) as in A. steini and differs only in larger cell size (50-60 vs. 20-35 um long). We assume that this might concern a "size-variety" and identify it with A. steini. (ref. ID; 4905)