Redescription of Apocyclops dengizicus (Lepeschkin, 1900) from Central Asia (Crustacea, Copepoda)

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Eudiaptomus transylvanicus

Eudiaptomus transylvanicus (Daday, 1891) (Figs 1, 2) Material examined. Russia, Chuvash Republic, near Atrat Vill., “kopan’” water body, 54.9991°N 46.6685°E, 3 July 2019, 9 males, 8 females; same locality, quarry pond, 54.97798°N 46.72082°E, 26 May 2020, 2 males, 2 females; same locality, carr lakelet, 54.97798°N 46.72082°E, 26 May 2020, 4 males (all E. Osmelkin leg.). Redescription. Female (Fig. 1a). Body length 1.60–1.66 mm (n = 8). Last thoracic segment with well-developed asymmetrical wings. Genital compound somite gently dilated in central part, with medium-sized hyaline spines (Fig. 1b, arrowed). Antennules extending closely to apices of apical caudal setae (Fig. 1a). Rostrum with two strong long curved asymmetrical processes (Fig. 1d). Edge of mandibular incision with single-vertex teeth: one ventral and six or seven central (Fig. 1c, 1c′). Ventral tooth separated from other teeth by a deep diastema (Fig. 1c′). Rather deep diastema present between outer ventral central tooth and other teeth. Central teeth acute, with wide base (Fig. 1c′). Dorsal teeth double-vertex, acute, with narrow base. Maxilla and maxilliped with long plumose setae increasing filtration; these setae situated on sympodite compounds (precoxopodite, coxopodite), basipodite and endopodite. In leg 2, endopod segment 2 with Schmeilsche lobus (Fig. 1e, arrowed). In leg 5, coxa with triangular lateral projection, with wide base, nearly as large as basipod (Fig. 1f); exopod segment 1 rectangular; exopod segment 2 with spine (bearing row of spinules) at base of segment 3 (Fig. 1g′) and with terminal claw bearing row of spinules on lateral and medial margins (Fig. 1g); exopod segment 3 with two apical spines (Fig. 1g), longest spine extending to apex of terminal claw; endopod two-segmented, as long as exopod segment 1 or even longer, with distal row of setulae and with relatively long unequal setae: one apical and one subapical (Fig. 1h). Male (Fig. 2a). Body length 1.40–1.55 mm (n = 9). Rostrum with two strong long curved processes and one distinct lateral process (Fig. 2c). Left antennule extending to middle of urosome. Right antennule with spiniform projections on segments 10, 11 and 13–16; segment 13 with longest projection (Fig. 2b); antepenultimate segment with small hyaline process (Fig. 2b′, arrowed). In right leg 5 (Fig. 2d), coxa with elongate projection supplied with hyaline spine; basis with two well-visible hyaline processes in proximal and distal parts of medial margin and with a small hook-shaped process between them (Fig. 2e, arrowed), with granulate (not spinulate) surface near distal process (Fig. 2e); exopod segment 1 wider than long, with distinct acute dilation at outer distal corner; exopod segment 2 about 1.7 times as long as wide, with strong slightly curved claw and granulate (not spinulate) surface near it (Fig. 2f, arrowed), with lateral dentate spine inserted in distal part of lateral margin (Fig. 2f); endopod two-segmented, reaching one-third of proximal part of exopod segment 2, with distal brush of setulae and three apical setulae (Fig. 2g). In left leg 5 (Fig. 2d), basis slightly narrowing distally, with small lateral process near distal margin; exopod two-segmented, with thick setae in middle of segment 1 and in proximal part of segment 2; proximal part of exopod segment 1 wider than its distal part; exopod segment 2 with long dentate spine (exopod 3, according to Dussart & Defaye, 2001) being slightly curved in proximal part, with tiny hairs on anterior surface and with five overlapping membranous folds on distomedial surface (Fig. 2h); endopod two-segmented, weak.Published as part of Podshivalina, V. N., Sheveleva, N. G., Semenova, A. S. & Mirabdullayev, I. M., 2022, Eudiaptomus transylvanicus and E. vulgaris (Copepoda: Calanoida: Diaptomidae): comparative morphology, distribution and ecology, pp. 42-54 in Zoosystematica Rossica 31 (1) on page 44, DOI: 10.31610/zsr/2022.31.1.4