Pseudocandona glauci Mazepova, 1990

Figs. 27–32; 40D; 41F; 42D; 43C, 43D

Type locality. Lake Baikal, coastal zone of Peschanaya Bay (approximate coordinates: 52°15′37 N, 105°42′17 E).

Type material. Lectotype No. O3 (male) and paralectotype No. 1 (female): dwm No. O1–040866. Paralectotypes Nos. 2–6 (3 females, 2 males): dwm No. O2–040866. Paralectotypes Nos. 7–11 (3 females, 2 males): dwm No. O3–040866. Paralectotypes Nos. 12–21 (5 females, 5 males): swm No. x945. Paralectotypes Nos. 22, 23 (male and female in copula): swm No. x945. Paralectotype No. 24 (female): swm No. x945 (valves) and wm No. O4–040866 (limbs). Paralectotype No. 25 (male): swm No. x945 (valves) and wm No. O5–040866 (limbs).

Additional material. Specimens Nos. 1–3 (two females, one male): swm No. x964 (valves).

All specimens were collected in Lake Baikal, southern basin, in coastal zone of Peschanaya Bay, August 4, 1966, depth 18–20 m, sand, sample No. 13 from the collection of G.F. Mazepova.

Description. Female. Carapace (Fig. 27A–27D; 28A–28F; 40D) laterally broadly trapezoidal; L = 930–990 µm (average 955 µm, n = 6), greatest H = 555–580 µm (average 570 µm, n = 6) located on posterior border of 1/ 4 L. Dorsal margin straight, anterior margin widely rounded, posterior margin rounded-angular. LV overlaps RV throughout. Ventral margin of valves on inner side is more concave than on outer side. Inner lamella broad, marginal pore canals occupy 80–100% of width of inner lamella. Inner lamella of each valve with 50–70 marginal pore canals. Sensillae of outer lamella relatively sparse and emerging from small outgrowths. Microrelief of valve surface relatively homogenous, consisting of large cells (Fig. 30D). Diameter of cells larger in center of carapace and slightly smaller at margins of valves (Fig. 30A, 30B). Site of greatest width (both on ventral and dorsal sides) at 2/3 L of carapace.

A1 (Fig. 31A) seven-segmented. First segment with one finely plumed seta. Second segment with three setae, two of same length, one shorter and finely plumed. Third segment with one seta. Fourth segment with two small setae. Fifth segment with two setae of different lengths. Sixth segment with four setae of different lengths and one claw. Seventh segment with two claws of different lengths, one seta and stick-shaped aesthetasc (ya).

A2 (Fig. 31B–31D). Five-segmented. Coxal segment with three setae, one of them inserted on this segment, two located between coxal and basal segments. One of them pappose. Basal segment with one ventro-distal seta. Exopod with three setae (one of them plumose distally to base). Endopod three-segmented. First endopodal segment with posteromedial club-shaped aesthetasc (Y) and two posterodistal setae. Second endopodal segment with one ventromedial seta, small dorsal-medial aesthetasc (y1), two t-setae of different lengths (t1 thick and plumose, t2 slightly shorter and smooth), three z-setae (z1 three times shorter than z2 and four times shorter than z3), three G-claws (G1 and G3 two times long G2), and small distal aesthetasc (y2). Terminal segment with two G-claws of nearly equal length (GM and Gm) and two setae, one of them basally fused with stick-shaped aesthetasc (y3).

Md (Fig. 31G). Coxa with one subapical seta and several setae between teeth of endite and on apical inner corner. Branchial plate with seven plumose setae and one smooth seta. Palp four-segmented. First segment with four setae: S1 (long, plumose), S2 (short, pappose), α (short and thin), and proximal seta. Second segment with six posterior setae (β-seta very small), two anterior setae, and row of pseudochaetae. Third segment with four posterodistal setae (γ-seta long and plumose), three anterior setae, and groups of small pseudochaetae. Distal segment with two claws, three setae, and group of small pseudochaetae.

Mxl. Protopod without setae. First endite with 14 setae, two at base of endite, 12 at apex. Second endite with nine apical setae. Third endite with eight setae and two claws. Palp two-segmented, first segment with four plumose setae. Distal segment with two claws and seta apically and three setae medially (two plumose and one smooth). Branchial plate with 23 setae and row of pseudochaetae.

L5 (Fig. 32C–32E). Protopod with three setae (a, b, d). Endite with 14 setae, arranged in two groups of four and ten setae. Palp with three setae. Branchial plate reduced to two setae of different lengths.

L6 (Fig. 32A). Five-segmented. First segment with d1-seta. Second and third segments with one distal seta (e, f) each and rows of pseudochaetae. Fourth segment with two distal g-setae and rows of pseudochaetae. Fifth segment with long claw (h2) and two small setae (h1 and h3) of different lengths.

L7 (Fig. 32B) four-segmented. First segment with anterior d1-seta and posterior dp-seta; d2-seta absent. Second segment without pseudochaetae. Third segment with one posterodistal g-seta and rows of pseudochaetae. Fourth segment with three serrate setae (h1–h3) of different lengths.

UR (Fig. 32H). Symmetrical, with smoothly curved main axis. Each ramus with one posterior seta distal to middle of ramus, one short anterodistal seta, and two thin distal claws of nearly equal length.

Male. Carapace (Figs. 27E–27H; 29A–29F; 40D) laterally broadly trapezoidal, as large as that of female; L = 940–990 µm (average 955 µm, n = 5), greatest H = 565–595 µm (average 575 µm, n = 5). Site of greatest H at 3/4 of L and more pronounced than in female. Dorsal margin slightly inclined towards the anterior end of body.Anterior margin widely rounded; posterior margin rounded more smoothly. Ventral margin of each valve with two triangular projections: one in central part of L, second in posterior 1/3 of L. Length of anterior projections 25–30 µm, width of their bases 85–120 µm; length of posterior projection on RV 50 µm, and on LV 20 µm, width of their bases 90–100 µm. Projections arranged symmetrically, main axis directed toward the posterior end of body and slightly toward the opposite valve (Fig. 30C). Microrelief of carapace, A1, A2 (protopod, exopod, first endopodal segment), Md, Mxl, L5 protopod, L6, L7 as in female.

A2 (Fig. 31E, 31F). Second endopodal segment with one ventromedial seta, small dorsal-medial aesthetasc (y1), two t-setae (t1, t2) of different lengths, three z-setae (z2 and z3 of almost equal length, and z1 modified into claw), three G-claws (G1 and G2 2.5 times long G3), and small distal aesthetasc (y2). Terminal segment with two G-claws (GM and Gm; Gm longer than GM) and two setae, one of them basally fused with stick-shaped aesthetasc (y3).

Prehensile palps of L5 (Fig. 32F, 32G) almost symmetrical, crescent-shaped. Main axis of palps arcuately curved distally to insertion of two setae. Left palp with outgrowth in form of “ear”. Distal tip of both palps with thin seta.

Hemipenis (Fig. 41F) small, oval-rectangular, 315 µm long and 185 µm wide; lobes oval, weakly protruding.

Zenker organ (Fig. 42D) 315 µm long, with 4+2 rings of spines 85 µm in diameter, diameter of central tube 35 µm, vesicle large, 90 µm in diameter.

UR (Fig. 32I) as in female, but rami thinner.

Comparisons. P. glauci is clearly distinguished from most Baikalian representatives of the genus by the appearance of the ventral margins of the valves of males, which are armed with four projections (two on each valve). Similar projections are present in males of Pseudocandona academica Mazepova, 1982, but this species is clearly different in the shell’s outline and the morphology of its appendages.

Notes. Similar to the previous species, G.F. Mazepova did not designate a holotype, but only indicated paratypes (Mazepova 2001: p. 529), which are not valid without designation of a holotype and should be considered as syntypes, which was undertaken in the present work.

Males and females in copula were found (Fig. 43C, 43D). The valves of the male grasp the posteroventral margin of the female's shell by outgrowths on the ventral margin of the valves.

Geographic distribution. Endemic to Lake Baikal, found in all three basins, on the Ushkany Islands and in the Maloye More Strait at depths of 5–20 m on silted sand, and sandy and stony substrates (Mazepova 1990: p. 181).