Cytherissa calva Mazepova, 1990

Cytherissa calva Mazepova, 1990

Figs. 23–26 View FIGURE 23 View FIGURE 24 View FIGURE 25 View FIGURE 26 ; 38H View FIGURE 38 ; 39G View FIGURE 39 ; 40L View FIGURE 40 .

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

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

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 View FIGURE 23 ; 24A–24F View FIGURE 24 ; 39G View FIGURE 39 ) 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 View FIGURE 26 ). Posterior part of dorsal and ventral margins of valves with long ridges (ventral one longer) covered with pitted microrelief ( Fig. 26B, 26C View FIGURE 26 ). 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 View FIGURE 24 ).

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

Male. Carapace ( Figs. 23E–23H View FIGURE 23 ; 25A–25E View FIGURE 25 ; 39G View FIGURE 39 ) 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 View FIGURE 25 ) and ventral views expressed much weaker than in female ( Fig. 24C, 24D View FIGURE 24 ). 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 View FIGURE 40 ), first segment with small seta. Distal part of second segment with gently pointed outgrowth.

Hemipenis ( Figs 26D View FIGURE 26 ; 38H View FIGURE 38 ) 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 View FIGURE 27 View FIGURE 28 View FIGURE 29 ; 33A, 33B View FIGURE 33 ; 38D View FIGURE 38 ; 39H View FIGURE 39 ; 40E, 40N View FIGURE 40 .

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) GoogleMaps .

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

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 View FIGURE 27 ; 28A–28G View FIGURE 28 ; 39H View FIGURE 39 ) 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 View FIGURE 33 ), diameter and depth of pits significantly larger than in anterior ( Fig. 33B View FIGURE 33 ) and posterior parts. Site of greatest carapace width in ventral and dorsal views is at posterior border of 2/3 L ( Fig. 28C, 28D View FIGURE 28 ).

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

Male. Carapace ( Figs. 27E–27H View FIGURE 27 ; 29A–29F View FIGURE 29 ; 39H View FIGURE 39 ) 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 View FIGURE 29 ) than in female ( Fig. 28C, 28D View FIGURE 28 ). 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 View FIGURE 40 ) 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 View FIGURE 40 ). First segment with small seta. Distal part of second segment with gently pointed outgrowth.

Hemipenis ( Fig. 38D View FIGURE 38 ) 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 View FIGURE 30 View FIGURE 31 View FIGURE 32 ; 33C, 33D View FIGURE 33 ; 38I View FIGURE 38 ; 39I View FIGURE 39 ; 40M, 40R View FIGURE 40 ; 41A, 41E View FIGURE 41 .

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) GoogleMaps .

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

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 View FIGURE 30 ; 31A–31F View FIGURE 31 ; 39I View FIGURE 39 ) 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 View FIGURE 33 ). Site of greatest carapace width on ventral and dorsal views at posterior border of 2/3 L ( Fig. 31C, 31D View FIGURE 31 ).

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

Male. Carapace ( Figs. 30E–30H View FIGURE 30 ; 32A–32F View FIGURE 32 ; 39I View FIGURE 39 ) 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 View FIGURE 32 ) than in female ( Fig. 31C, 31D View FIGURE 31 ) 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 View FIGURE 40 ). First segment with small seta. Second segment with distal pointed outgrowth.

Hemipenis ( Fig. 38I View FIGURE 38 ) 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 View FIGURE 40 ). 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.