Cytherissa calva Mazepova, 1990

Alekseeva, Tatyana M., Krivorotkin, Roman S. & Timoshkin, Oleg A., 2025, Redescriptions of ten endemic Cytherissa species (Ostracoda, Podocopida, Cytherideidae) from the coastal and deep-water zones of Lake Baikal, Zootaxa 5673 (3), pp. 301-354 : 330-351

Cytherissa calva Mazepova, 1990

Figs. 23–26 ; 38H ; 39G ; 40L .

Type locality. Lake Baikal , middle basin, underwater Academichesky Ridge (approximate coordinates 53º37’10.42” N, 108º10’11.69” E) .

Type material. Lectotype No. O14 (female): dwm No. O1-060872. Paralectotypes Nos. 1–6 (6 females): dwm No. O2-060872. Paralectotypes Nos. 7, 8 (2 males): dwm No. O3-060872. Paralectotypes Nos. 9–18 (7 females; 3 males): swm No. 34. Paralectotypes Nos. 19 (male): swm No. 34 (valves) and wm No. O4-060872 (limbs). Paralectotype No. 20 (male): swm No. 34 (valves) and wm No. O5-060872 (limbs). Paralectotype No. 21 (male): wm No. O6-060872 (limbs). Paralectotype No. 22 (female): swm No. 34 (valves) and wm No. O7-060872 (limbs).

All ostracods were collected in the middle basin of Lake Baikal, underwater Academichesky Ridge, August 6, 1972, depth 230 m, sample No. 337 from the collection of taxocoenoses of G.F. Mazepova.

Description. Female. Carapace ( Figs. 23A–23D ; 24A–24F ; 39G ) laterally rectangular-ovate: L=780–830 µm (mean 800 µm, n=7), largest H=495–520 µm (mean 515 µm, n=7), located at posterior border of anterior 1/3 of L. Dorsal margins of valves slightly arcuate. Anterior end of carapace broadly rounded, posterior end almost straight, narrowly rounded.Ventral margins of both valves equally concave on inner side, and almost straight, slightly concave on outer side. LV slightly overlaps RV throughout. Inner lamella very broad. Marginal pore canals long, occupying 65–100% of width of inner lamella and ending in sensilla. Inner lamella of each valve with 25–27 marginal pore canals. Pore canals of outer lamella sieve-type, branching, grouped (up to four canals in a group), single near margin of valves; each canal with one sensillum. Outer lamella of each valve with at least 125–130 pore canals. Inner side of each valve with about 30–32 canal apertures. Hinge teeth on RV, slightly crenulated, not extending beyond valve margin; bar on LV, slightly crenulated. Microrelief of valves surface heterogeneous. Most of valves smooth, but in center small depressions corresponding to adductor muscle scars (located on inner side) ( Fig. 26A ). Posterior part of dorsal and ventral margins of valves with long ridges (ventral one longer) covered with pitted microrelief ( Fig. 26B, 26C ). Microrelief appears deeper and more evenly spaced on dorsal side, while on ventral side less deep but more frequent. Site of greatest carapace width on ventral and dorsal views at central part of L ( Fig. 24C, 24D ).

A1, A2, Md, Mxl, L5–L7 as in C. heckyi , but distal segments of L5 partially fused.

Male. Carapace ( Figs. 23E–23H ; 25A–25E ; 39G ) slightly longer than in female: L=805–830 µm (mean 820 µm, n=6), H=495–520 µm (mean 515 µm, n=6). Site of greatest width on dorsal ( Fig. 25C ) and ventral views expressed much weaker than in female ( Fig. 24C, 24D ). Geniculate (transformed) legs on right side of body. Other morphological features of carapace structure, microrelief, A1, A2, Md, Mxl, left (non-geniculate) legs L5 and L6 as in female; distal segments of L5 partially fused. Both legs of L7 and right (geniculate) L5 as in male C. heckyi .

L6. Right leg. Protopod with four setae and one group of pseudochaetae. Endopod two-segmented ( Fig. 40L ), first segment with small seta. Distal part of second segment with gently pointed outgrowth.

Hemipenis ( Figs 26D ; 38H ) small, elongate-triangular; outer appendage lanceolate. Length of hemipenis in quiescent state 365 µm (n=1), greatest width 235 µm. Diameter of copulatory process 115–135 µm.

Brush organ. Both rami with 14 apical setae, rows of small pseudochaetae in medial, subapical and apical parts.

Differential diagnosis. The carapace outlines of C. calva are vaguely similar to the individuals of C. dextima . The species are discriminated by dinstict shell microrelief: the valves of C. calva are to a larger extent smooth with pits on the posterior part of the dorsal and ventral margins, whereas the microrelief in C. dextima is almost homogenous and consists of large cells.

Notes. The type specimen list ( Mazepova 2001 pp. 552) of C. calva shows 24 paratypes (15 females and 9 males), which is consistent with the handwritten version and the tube label. Paratype designation is not valid without a holotype, therefore, all individuals are referred to as syntypes. We found and examined only 23 syntypes (15 females and 8 males). The location of the remaining syntype is unknown, and probably it is lost.

Geographic distribution. Endemic to Lake Baikal, found in the northern and middle basins at depths from 10 to 20 m (for details see Mazepova 1990: p. 389) and on the underwater Academichesky Ridge (depth unknown). Inhabits various substrates, including silt with sand.

Cytherissa plena Mazepova, 1985

Figs. 27–29 ; 33A, 33B ; 38D ; 39H ; 40E, 40N .

Type locality. Lake Baikal , Maloye More Strait , one of two locations: 1) near Ulan-Baysan Cape (second name Zantyk Cape) (approximate coordinates 53º19’24.92” N, 107º38’45.39” E); 2) near the Kharansa Island (approximate coordinates 53º14’17.09” N, 107º24’42.42” E) .

Type material. Lectotype No. O15 (female) and paralectotype No. 1: dwm No. O32-130868. Paralectotypes Nos. 2–14 (13 females): dwm No. O33-130868. Paralectotypes Nos. 15–20 (6 males): dwm No. O34-130868. Paralectotypes Nos. 21–28, 32 (5 females; 4 males): swm No. 32. Paralectotype No. 29 (male): swm No. 32 (valves) and wm No. O35-130868 (limbs). Paralectotype No. 30 (male): swm No. 32 (valves) and wm No. O36-130868 (limbs). Paralectotype No. 31 (female): swm No. 32 (valves) and wm No. O37-130868 (limbs).

All ostracods were collected in the Maloye More Strait, in one of two locations: 1) near Ulan-Baysan Cape (second name Zantyk Cape), August 13, 1968, depth 25 m, sand with chara algae, sample No. 175 from the collection of taxocoenoses of G.F. Mazepova; 2) near Kharansa Island, August 16, 1968, depth 25 m, sand with detritus, sample No. 182 from the collection of taxocoenoses of G.F. Mazepova. Since all specimens were in one tube with a common label, we did not determine where each specimen was collected from.

Description. Female. Carapace ( Figs. 27A–27D ; 28A–28G ; 39H ) laterally elongate-ovate: L=730–780 µm (mean 760 µm, n=10), largest H=470–495 µm (mean 485 µm, n=10), located on posterior border of anterior 1/ 3 L. Dorsal margins of valves slightly arched at center. Anterior end of carapace broadly rounded, posterior end almost straight, narrowly rounded. Ventral margins of both valves equally concave on inner side and straight with small protrusions on outer side. LV overlaps RV throughout except for the center of dorsal margin. Inner lamella broad. Marginal pore canals may be short and not reach margin of inner lamella or occupy 100% of width of inner lamella; some marginal pore canals branching, especially in anterior part of valves. Inner lamella of each valve with 30–31 marginal pore canals (8–9 short, 22 long). Pore canals of outer lamella sieve-type, branching, grouped (up to six canals in a group), single near margin of valves; each canal with one sensillum. Outer lamella of each valve with at least 230–245 pore canals. Inner side of each valve with approximately 45 canal apertures. Hinge teeth on RV, distinctly crenulated, posterior tooth slightly extending beyond margin of valve; bar on LV, crenulated. Microrelief of valves surface heterogeneous, consisting of pits of different diameter and depth. In central part of valves ( Fig. 33A ), diameter and depth of pits significantly larger than in anterior ( Fig. 33B ) and posterior parts. Site of greatest carapace width in ventral and dorsal views is at posterior border of 2/3 L ( Fig. 28C, 28D ).

A1, A2, Md, Mxl, L5–L7 ( Fig. 28E ) as in C. heckyi , but distal segments of L5 partially fused.

Male. Carapace ( Figs. 27E–27H ; 29A–29F ; 39H ) slightly longer and lower than in female: L=805–860 µm (mean 830 µm, n=10), H=450–480 µm (mean 470 µm, n=10). On dorsal and ventral views, site of greatest width pronounced much more weakly ( Fig. 29C, 29D ) than in female ( Fig. 28C, 28D ). Geniculate (transformed) legs on right side of body. Other morphological features of carapace structure, microrelief, A1, A2, Md, Mxl, left (non-geniculate) legs L5 and L6 as in female; distal segments of L5 ( Fig. 40E ) partially fused. Both legs of L7 and right (geniculate) L5 as in male C. heckyi .

L6. Right leg. Protopod with four setae and several groups of pseudochaetae. Endopod two-segmented ( Fig. 40N ). First segment with small seta. Distal part of second segment with gently pointed outgrowth.

Hemipenis ( Fig. 38D ) small, triangular; outer appendage triangular. Length of hemipenis in quiescent state 315 µm (n=1), greatest width 255 µm. Diameter of copulatory process 70–90 µm.

Brush organ. Both rami with 12 apical setae, rows of small pseudochaetae in medial, subapical and apical parts.

Differential diagnosis. The broadly oval outline of C. plena valves, dorsally and ventrally, remotely resembles Cytherissa sernovi ovata Bronstein, 1947 , yet they differ in the valve shape laterally.

Notes. The list of type specimens ( Mazepova 2001: pp. 543) includes 29 paratypes (21 females and 8 males), that as a whole coincides with the handwritten catalog and the label inside the tube. However, the handwritten version locates sampling site of 29 individuals opposite Ulan-Baysan Cape, but there is no indication of the number of specimens found near Kharansa Island. For the most part, G.F. Mazepova indicated the number of type specimens collected for the type series at each of the sampling sites except for this case. The tube contained 32 individuals (3 more than indicated in all sources). We assume that 29 specimens were collected opposite Ulan-Baysan Cape, and 3 at Kharansa Island. Paratype designation is not valid without a holotype, hence, all the individuals are syntypes ( ICZN 1999).

Geographic distribution. Endemic to Lake Baikal, found in the northern basin and in the Maloye More Strait at depths from 10 to 28 m (for details see Mazepova 1990: p. 325). Inhabits on sand.

Cytherissa bisetosa Mazepova, 1984

Figs. 30–32 ; 33C, 33D ; 38I ; 39I ; 40M, 40R ; 41A, 41E .

Type locality. Lake Baikal , Angara River source, Listvennichny Bay , Listvyanka Settlement , opposite the Baikal Museum of the Siberian Branch of the Russian Academy of Sciences (approximate coordinates 51º52’03.76” N, 104º49’50.57” E) .

Type material. Lectotype No. O16 (female) and paralectotype No. 1 (male): dwm No. O1-260368. Paralectotypes Nos. 2–5 (4 females): dwm No. O2-260368. Paralectotypes Nos. 6, 7 (2 males): dwm No. O3- 260368. Paralectotypes Nos. 8–15 (4 females; 4 males): swm No. 27. Paralectotype No. 16 (female): swm No. 27 (valves) and wm No. O4-260368 (limbs). Paralectotype No. 17 (male): swm No. 27 (valves) and wm No. O5- 260368 (limbs). Paralectotype No. 18 (male): swm No. 27 (valves) and wm No. O6-260368 (limbs).

All specimens were collected near the source of the Angara River, Listvennichny Bay, opposite the building of the Baikal Museum (Listvyanka Settlement), on March 26, 1968. The specimens are from two samples: 1) 4.5–5 m depth, gravel and sand, sample No. 109 from the collection of taxocoenoses of G.F. Mazepova; 2) 12 m depth, stone with sponges and gravel, sample No. 111 from the collection of taxocoenoses of G.F. Mazepova. Since all specimens were in one tube with a common label, we did not determine where each specimen was collected from.

Description. Female. Carapace ( Figs. 30A–30D ; 31A–31F ; 39I ) laterally rectangular-trapezoidal: L=960– 1015 µm (mean 980 µm, n=7), largest H=600–625 µm (mean 615 µm, n=7), located on posterior border of anterior 1/ 4 L. Dorsal margins of valves slightly arched at center. Anterior end of carapace broadly rounded, posterior end almost straight, narrowly rounded. Ventral margins of both valves on inner and outer sides almost equally concave. LV overlaps RV throughout except for dorsal and posterior margins. Small posterior-ventral protrusion on RV (much larger in male). Inner lamella narrow. Marginal pore canals occupying 60–100% of width of inner lamella and ending in sensilla. Inner lamella of each valve with 21–22 marginal pore canals. Pore canals of outer lamella sieve-type, branching, grouped (up to five canals in a group), single near margin of valves; each canal with one sensillum. Outer lamella of each valve with at least 140–160 pore canals. Inner side of each valve with about 45–48 canal apertures. Hinge teeth on RV, weakly crenulated, posterior tooth slightly extending beyond margin of valves; bar on LV, slightly crenulated. Microrelief of the valve surface elatively homogeneous and complex, consisting of large cells of different shapes with smaller cells of rounded shape ( Fig. 33C, 33D ). Site of greatest carapace width on ventral and dorsal views at posterior border of 2/3 L ( Fig. 31C, 31D ).

A1, A2, Md, Mxl, L5–L7 as in C. heckyi , but distal segments of L5 partially fused.

Male. Carapace ( Figs. 30E–30H ; 32A–32F ; 39I ) slightly longer and lower than in female: L=960–1015 µm (mean 990 µm, n=10), H=545–570 µm (mean 565 µm, n=7). In dorsal and ventral views, site of greatest width much less pronounced ( Fig. 32C, 32D ) than in female ( Fig. 31C, 31D ) and shifted to posterior 4/ 5 L. The posterior-ventral protrusion more pronounced than in female. Geniculate (transformed) legs on right side of body. Other morphological features of carapace structure, microrelief, A1, A2, Md, Mxl, left (non-geniculate) legs L5 and L6 as in female; distal segments of L5 partially fused. Both legs of L7 and right (geniculate) L5 as in male C. heckyi .

L6. Right leg. Protopod with four setae and several groups of pseudochaetae. Endopod two-segmented ( Fig. 40M ). First segment with small seta. Second segment with distal pointed outgrowth.

Hemipenis ( Fig. 38I ) medium-sized, elongate-triangular; outer appendage long, elongate-lanceolate. Length of hemipenis in quiescent state 475 µm (n=1), greatest width 325 µm. Diameter of copulatory process 140 µm.

Brush organ ( Fig. 40R ). Both rami with 15 apical setae, rows of small pseudochaetae in medial, subapical and apical parts.

Differential diagnosis. The outlines of C. bisetosa carapace and valves are similar to many Baikalian species of this genus, however, the surface microrelief is unique. According to G.F. Mazepova’s monograph (1990: pp. 411), only this species has a complex microrelief composed of large cells of irregular shape, inside of which we find smaller cells. Examination of G.F. Mazepova’s collection of taxocoenoses revealed at least two more Cytherissa spp. species with analogous type of microrelief, but with markedly distinct valve outlines in contrast to C. bisetosa .

Notes. The list of type specimens ( Mazepova 2001: pp. 553, 554) includes 21 paratypes (10 females and 11 males) that corresponds to the handwritten catalog of type specimens and the label in the tube. Inside of the tube we found and examined only 19 type specimens (10 females and 9 males). The location of two more syntypes is unknown, they are most likely lost.

Geographic distribution. Endemic to Lake Baikal, found in the southern basin at depths from 3.5 to 5 m (for details see Mazepova 1990: p. 399). Inhabits on stones with sponges.

Cytherissa sinistra Mazepova, 1984

Figs. 34–37 ; 38J ; 39J ; 40D, 40O .

Type locality. According to the label, specimens were collected from three different locations of Lake Baikal: 1) the underwater Academichesky Ridge (approximate coordinates 53º37’10.42” N, 108º10’11.69” E) ; 2) southern basin, near Bugul’deika Village (approximate coordinates 52º30’47.88” N, 106º04’03.66” E) ; 3) between Eligey and Gorevoi Utes Cape (approximate coordinates 53º22’56.97” N, 108º21’44.49’’ E) .

Type material. Lectotype No. O17 (female) and paralectotype No. 1 (male): dwm No. O16-060872. Paralectotypes Nos. 2–9 (8 females): dwm No. O17-060872. Paralectotypes Nos. 10–16 (7 males): dwm No. O18- 060872. Paralectotypes Nos. 17–24 (4 females; 4 males): swm No. 33. Paralectotype No. 25 (female): swm No. 33 (valves) and wm No. O19-060872 (limbs). Paralectotype No. 26 (male): swm No. 33 (valves) and wm No. O20- 060872 (limbs). Paralectotype No. 27 (male): swm No. 33 (valves) and wm No. O21-060872 (limbs).

According to the label, specimens were collected in three different locations of Lake Baikal: 1) 11 females and 9 males: the underwater Academichesky Ridge , August 6, 1972, depth 230 m, sample No. 337 from the collection of taxocoenoses of G.F. Mazepova; 2 ) 14 females: southern basin, near Bugul’deika Village , September 13, 1991, 360 m depth, brown silt, sampled using a research deep-submergence vehicle “Pisces”; 3 ) 3 males: between Eligey River and Gorevoi Utes Cape, August 9, 1972, 520 m depth. Since all specimens were in one tube with a common label, we did not determine where each particular specimen was collected from .

Description. Female. Carapace ( Figs. 34A–34D ; 35A–35F ; 39J ) laterally oval-ovate: L=730–780 µm (mean 755 µm, n=10), largest H=495–520 µm (mean 510 µm, n=10), located on posterior border of anterior 1/ 3 L. Dorsal margins of valves slightly arcuate at center.Anterior end of carapace broadly rounded, posterior end almost straight, narrowly rounded. Ventral margins of both valves equally concave on inner side and arcuate on outer side; ventral margin protrudes more strongly on RV than on LV. RV overlaps LV throughout. Inner lamella broad. Marginal pore canals may be short and not reach margin of inner lamella or occupy 100% of width of inner lamella; some marginal pore canals branching (in anterior part of valves). Inner lamella of each valve with 26–33 marginal pore canals (8–12 short, 18–21 long). Pore canals of outer lamella sieve-type, branching, grouped (up to five canals in group), single near margin of valves; each canal with one sensillum ( Fig. 37B, 37D, 37E ). Single pore canals near valve margin may be elongate ( Fig. 37D ) or round ( Fig. 37E ). Outer lamella of each valve with at least 125–155 pore canals. Inner side of each valve with approximately 40 canal apertures. Hinge teeth on LV, crenulated, posterior tooth slightly extending beyond margin of valve; bar on RV, almost smooth. Microrelief of valves surface almost homogeneous, consisting of large pits, diameter almost equal on entire surface of valves ( Fig. 37A ). Dorsal margin almost smooth, with highly smoothed microrelief. Ventral margin with highly elongated pits; row of very small pits along valve margin ( Fig. 37C ). Site of greatest carapace width on ventral and dorsal views in central part of L ( Fig. 35C, 35D ).

A1, A2, Md, Mxl, L5–L7 as in female C. heckyi .

Male. Carapace ( Figs. 34E–34H ; 36A–36F ; 39J ) slightly longer and taller than in female: L=805–860 µm (mean 835 µm, n=10), H=495–520 µm (mean 515 µm, n=10). In dorsal and ventral views, males ( Fig. 36C, 36D ) significantly narrower than females ( Fig. 35C, 35D ). Microrelief on dorsal margin more pronounced ( Fig. 36D ) than in females ( Fig. 35D ). Inner lamella of each valve with 29–31 marginal pore canals. Geniculate (transformed) legs on left side of body. Other morphological features of carapace structure, microrelief, A1, A2, Md, Mxl, right (non-geniculate) legs L5 ( Fig. 40D ) and L6 as in female. Both legs L7 and geniculate L5 as in male C. heckyi .

L6. Left leg. Protopod with four setae and several groups of pseudochaetae. Endopod one-segmented ( Fig. 40O ), most probably without seta (or very small), distal part with gently pointed outgrowth.

Hemipenis ( Fig. 38J ) small, elongate-triangular; outer appendage lanceolate, with slightly curved main axis. Length of hemipenis in quiescent state 370 µm (n=1), greatest width 265 µm. Diameter of copulatory process 105–125 µm.

Brush organ. Both rami with 25 apical setae, rows of small pseudochaetae in medial, subapical and apical parts.

Differential diagnosis. The hinge teeth on the left valve and cellular microrelief of the valves of C. sinistra are identical with the individuals of the recently redescribed Cytherissa latirecta Mazepova, 1985 ( Alekseeva et al. 2025c). The species have well-distinguished valve outlines (in lateral view) and carapace shape in dorsal and ventral views. The outlines of C. sinistra shells are generally similar to C. dextima individuals, but the first species has hinge teeth on the left valve and the second, on the right valve.

Notes. The list of type specimens ( Mazepova 2001: pp. 551, 552) includes 20 paratypes (11 females and 9 males). The handwritten version of G.F. Mazepova’s catalog lists many more— 37 type specimens (25 females and 12 males); among them 11 females and 9 males were collected at the underwater Akademicheskiy Ridge, 14 females opposite Bugul’deyka Village and 3 males between Eligey River and Gorevoy Utes Cape. The label on the tube shows 27 types specimens (15 females and 12 males), indicating the same three sampling sites mentioned above. Paratype designation is not valid without a holotype, thus all the specimens are referred to as syntypes. Inside of the tube we found and analyzed 28 type specimens (14 females and 14 males).

Geographic distribution. Endemic to Lake Baikal, found in the northern and southern basins, in the Maloye More Strait, at depths from 50 to 900 m (for details see Mazepova 1990: p. 386). Inhabits silty sand, silt and clay.

Figures

FIGURE 23. Cytherissa calva Mazepova, 1990, schematic drawings of the valves of females (A–D) and males (E–H), outer (A, B, E, F) and inner (C, D, G, H) sides, laterally. Arrows point towards the anterior. A–D—paralectotype No. 22; E–H— paralectotype No. 19. Scale 500 µm.

FIGURE 24. Cytherissa calva Mazepova, 1990, SEM photographs of carapaces (A–D) and valves (E, F) of females: A, B— laterally, outer side; C—ventrally; D—dorsally; E—LV laterally, inner side; F—RV laterally, inner side. Arrows point towards the anterior. A—paralectotype No. 10; B—paralectotype No. 9; C—paralectotype No. 12; D—paralectotype No. 11; E, F— paralectotype No. 22. Scale 500 µm.

FIGURE 25. Cytherissa calva Mazepova, 1990, SEM photographs of carapaces (A–D) and valves (E, F) of males: A, B— laterally, outer side; C—dorsally; D—LV laterally, inner side; E—RV laterally, inner side. Arrows point towards the anterior. A—paralectotype No. 14; B—paralectotype No. 13; C—paralectotype No. 15; D, E—paralectotype No. 19. Scale 500 µm.

FIGURE 26. Cytherissa calva Mazepova, 1990, SEM photographs of some elements of female carapace structure (A–C) and male body (D): A—central part of LV, laterally; B—posterior part of the carapace, dorsally; C—posterior part of the carapace, ventrally; D—hemipenis. In A–C, arrows point towards the anterior. A—paralectotype No. 9; B—paralectotype No. 11; C— paralectotype No. 12; D—paralectotype No. 13. Scale 100 µm.

FIGURE 27. Cytherissa plena Mazepova, 1985, schematic drawings of the valves of females (A–D) and males (E–H), outer (A, B, E, F) and inner (C, D, G, H) sides, laterally. Arrows point towards the anterior. A–D—paralectotype no. 31; E–H— paralectotype No. 29. Scale 500 µm.

FIGURE 28. Cytherissa plena Mazepova, 1985, SEM photographs of carapaces (A–D) and valves (E–F) of females: A, B— laterally, outer side; C—ventrally; D—dorsally; E—RV with soft parts, inner side; F—LV laterally, inner side; G—RV laterally, inner side. Arrows point towards the anterior. A—paralectotype No. 22; B—paralectotype No. 21; C—paralectotype No. 24; D—paralectotype No. 23; E—paralectotype No. 32; F, G—paralectotype No. 31. Scale 500 µm.

FIGURE 29. Cytherissa plena Mazepova, 1985, SEM photographs of carapaces (A–D) and valves (E, F) of males: A, B— laterally, outer side; C—ventrally; D—dorsally; E—LV laterally, inner side; F—RV laterally, inner side. Arrows point towards the anterior. A—paralectotype No. 26; B—paralectotype No. 25; C—paralectotype No. 28; D—paralectotype No. 27; E, F— paralectotype No. 29. Scale 500 µm.

FIGURE 30. Cytherissa bisetosa Mazepova, 1984, schematic drawings of the valves of females (A–D) and males (E–H), outer (A, B, E, F) and inner (C, D, G, H) sides, laterally. Arrows point towards the anterior. A–D—paralectotype No. 16; E–H— paralectotype No. 17. Scale 500 µm.

FIGURE 31. Cytherissa bisetosa Mazepova, 1984, SEM photographs of carapaces (A–D) and valves (E, F) of females: A, B—laterally, outer side; C—ventrally; D—dorsally; E—LV laterally, inner side; F—RV laterally, inner side. Arrows point towards the anterior. A—paralectotype No. 9; B—paralectotype No. 8; C—paralectotype No. 11; D—paralectotype No. 10; E, F—paralectotype No. 16. Scale 500 µm.

FIGURE 32. Cytherissa bisetosa Mazepova, 1984, SEM photographs of carapaces (A–D) and valves (E, F) of males: A, B—laterally, outer side; C—ventrally; D—dorsally; E—LV laterally, inner side; F—RV laterally, inner side. Arrows point towards the anterior. A—paralectotype No. 13; B—paralectotype No. 12; C—paralectotype No. 15; D—paralectotype No. 14; E, F—paralectotype No. 17. Scale 500 µm.

FIGURE 33. Cytherissa plena Mazepova, 1985 (A, B) and Cytherissa bisetosa Mazepova, 1984 (C, D), SEM photographs of some elements of the carapace structure of females (A, B, D) and males (C): A—dorsal part of LV, laterally; B—anterior part of RV, laterally; C—central part of LV, laterally; D—central part of carapace, ventrally. Arrows point towards the anterior. A—paralectotype No. 21; B—paralectotype No. 22; C—paralectotype No. 12; D—paralectotype No. 11. Scale 100 µm.

FIGURE 34. Cytherissa sinistra Mazepova, 1984, schematic drawings of the valves of females (A–D) and males (E–H), outer (A, B, E, F) and inner (C, D, G, H) sides, laterally. Arrows point towards the anterior. A–D—paralectotype No. 25; E–H— paralectotype No. 26. Scale 500 µm.

FIGURE 35. Cytherissa sinistra Mazepova, 1984, SEM photographs of carapaces (A–D) and valves (E, F) of females: A, B—laterally, outer side; C—ventrally; D—dorsally; E—LV laterally, inner side; F—RV laterally, inner side. Arrows point towards the anterior. A—paralectotype No. 18; B—paralectotype No. 17; C—paralectotype No. 20; D—paralectotype No. 19; E, F—paralectotype No. 25. Scale 500 µm.

FIGURE 36. Cytherissa sinistra Mazepova, 1984, SEM photographs of carapaces (A–D) and valves (E, F) of males: A, B— laterally, outer side; C—ventrally; D—dorsally; E—LV laterally, inner side; F—RV laterally, inner side. Arrows point towards the anterior. A—paralectotype No. 22; B—paralectotype No. 21; C—paralectotype No. 24; D—paralectotype No. 23; E, F— paralectotype No. 26. Scale 500 µm.

FIGURE 37. Cytherissa sinistra Mazepova, 1984, SEM photographs of some elements of carapace structure of females (A, B, E) and males (C, D): A—central part of RV, laterally; B—pore canals and sensilla; C—central part of the carapace, ventrally; D, E—sensilla and variations in pore canal shape in the ventral part of the carapace. In A, C, arrows point towards the anterior. A, B—paralectotype No. 18; C, D—paralectotype No. 24; E—paralectotype No. 20. Scale, µm: A, C—100; B, D, E—20.

FIGURE 38. Microphotographs of male hemipenes of the studied species: A—Cytherissa glomerata Mazepova, 1990, paralectotype No. 19; B—Cytherissa dubitabilis (Bronstein, 1947) Mazepova 1990, specimen No. 11; C—Cytherissa derupta Mazepova, 1984, paralectotype No. 11; D—Cytherissa plena Mazepova, 1985, paralectotype No. 29; E—Cytherissa cytheriformis Bronstein, 1947, specimen No. 20; F—Cytherissa golyschkinae Mazepova, 1990, paralectotype No. 26; G— Cytherissa obrutshevi Mazepova, 1990, paralectotype No. 16; H—Cytherissa calva Mazepova, 1990, paralectotype No. 20; I—Cytherissa bisetosa Mazepova, 1984, paralectotype No. 17; J—Cytherissa sinistra Mazepova, 1984, paralectotype No. 26. Scale 100 µm.

FIGURE 39. Microphotographs of valves of the studied species: A—Cytherissa glomerata Mazepova, 1990; B—Cytherissa dubitabilis (Bronstein, 1947) Mazepova, 1990; C—Cytherissa derupta Mazepova, 1984; D—Cytherissa cytheriformis Bronstein, 1947; E—Cytherissa golyschkinae Mazepova, 1990; F—Cytherissa obrutshevi Mazepova, 1990; G—Cytherissa calva Mazepova, 1990; H—Cytherissa plena Mazepova, 1985; I—Cytherissa bisetosa Mazepova, 1984; J—Cytherissa sinistra Mazepova, 1984. Sex designations for A are as for B–J. Arrows point towards the anterior. Specimens figured are the same as those used to prepare the schematic darwings of the valves. Scale 500 µm.

FIGURE 40. Drawings of non-geniculate L5 (A), L5 endopods (B–F), geniculate L6 (G), endopods of geniculate L6 (H–P) and brush organs(Q–S) ofmales:A,G,Q—Cytherissaglomerata Mazepova,1990,paralectotype No.19;B,H—Cytherissaobrutshevi Mazepova, 1990, paralectotype No. 16; C, K—Cytherissa dubitabilis (Bronstein, 1947) Mazepova 1990, specimen No. 21; D, O—Cytherissa sinistra Mazepova, 1984, paralectotype No. 27; E, N—Cytherissa plena Mazepova, 1985, paralectotype No. 29; F, J—Cytherissa derupta Mazepova, 1984, paralectotypes Nos. 11 (F) and 22 (J); I, S—Cytherissa cytheriformis Bronstein, 1947, specimen No. 20; L—Cytherissa calva Mazepova, 1990, paralectotype No. 20; M, R—Cytherissa bisetosa Mazepova, 1984, paralectotype No. 17; P—Cytherissa golyschkinae Mazepova, 1990, paralectotype No. 26. On A–F, the arrows show clear separation (D, F) and partial fusion (A–C, E) of distal segments of non-geniculate L5. The arrangement of pseudochaetae on A is characteristic of B–F but is not drawn. Scale 100 µm.

FIGURE 41. SEM photographs of the body (A–D) and geniculate L6 of males (E–H), ventrally (A, D, E, H) and laterally (B, C, F, G): A, E—Cytherissa bisetosa Mazepova, 1984, additional specimen; B, F—Cytherissa cf. burchani Mazepova, 1990; C, D, G, H—Cytherissa sinistrodentata Bronstein, 1930. On A, B, E, F the geniculate L6 is located on the right side of the body, on C, D, G, H—on the left side. The arrow points towards the anterior for all photographs.Abbreviations: Rs—right side; Ls—left side. Scale, µm: A–D—500; E–H—100