Leberis diaphanus (King, 1853)

Sinev, Artem Y. & Sanoamuang, La-Orsri, 2011, Hormonal induction of males as a method for studying tropical cladocerans: description of males of four chydorid species (Cladocera: Anomopoda: Chydoridae), Zootaxa 2826, pp. 45-56 : 50-51

Leberis diaphanus (King, 1853)

King, 1853: 260, Pl.8, fig. D ( Alona diaphana ); Sars, 1888: 47–50, Pl. 5, fig. 5–7 ( Alonella diaphana ) Smirnov, 1971: 368–371, Fig 430–431 ( Alona davidi partum); Smirnov & Timms, 1983: 41, Fig. 41 ( Alona davidi ); Frey, 1991: 12–23, Fig. 2 –41 ( Alona diaphana ); Sinev, Van Damme & Kotov, 2005: 187–193, Fig. 14–59.

Description. Male. Length of studied specimens 0.37 mm. Body rounded, moderately high ( Fig. 3 A), height/ length ratio about 0.75. Maximum height before the middle of the body. Dorsal margin of valves highly arched, posterior margin almost straight, posteroventral and posterodorsal angles broadly rounded. Ventral margin of valves convex. Head large, moderately broad. Rostrum short, truncated. Eye 3 times larger than ocellus.

Postabdomen ( Fig. 3 B) short, moderately broad, narrowing in postanal portion, length about 2.5 height. Ventral margin straight, sperm duct openings located at the end of postabdomen above the base of claws. Distal part of postabdomen rounded, with no defined distal angle. Distal part of postabdomen 2.3 times longer than preanal, postanal portion 1.5 times longer than anal. Both anal and postanal margins straight. Both postanal and preanal angles weakly defined. Dorsal margin with 11–12 clusters of short setules, distalmost clusters consisting of 6–8 setules, number of setules in cluster increase basally. Postabdomen bears 9–10 lateral fascicles of setules in the main row, 4–5 distalmost fascicles broad, moderately long, other much shorter. Additional fascicles located at the end of postabdomen and in anal portion.. Postabdominal claw short, curved, about 2/3 length of preanal margin, with long thin basal spine about 0.4 length of claw, and a pecten of long spinules.

Antennule ( Fig. 3 C) moderately broad, length/width ratio about 2.5, with 10 terminal aesthetascs of variable length, longest about 2/3 length of antennule, and two lateral aesthetascs, about half length of antennule. Male seta moderately long, about 1/2 length of antennule, arising almost at 1/4 antennule length from the tip.

Thoracic limb I ( Fig. 3 D,E) massive, much broader than that of female, copulatory hook U-shaped, small, 2.5 times shorter than limb itself. Copulatory brush present, four clusters of numerous moderately long setules located below it on ventral face of limb. Copulatory brush seta short, thin. IDL seta 1 absent (as typical for the genus), setae 2 and 3 subequal in size, 1.5 times shorter than ODL seta, male seta little smaller than IDL seta 2, weakly curved. Morphology of endites as in female.

Taxonomical notes. The genus Leberis was recently revised ( Sinev et al. 2005), but no reliable description of L. diaphanus males from Asia was available so far (see also Smirnov & Timms, 1983, Smirnov, 1971). The morphology of Leberis diaphanus male is typical for the genus ( Sinev et al. 2005), general shape, outline of postabdomen, morphology of antennula and the first thoracic limb are similar to those of the two related species, L. davidi (Richard, 1895) and L. chichuachuensis Elias-Guttieres & Valdes-Morena, 2008 (see Sinev et al. 2005, Elias-Guttieres & Valdes-Morena 2008). Male of L. diaphanus differs by the proportions of postabdomen (in both other species postabdomen long and narrow, its length/height ratio is about 3, and preanal portion of dorsal margin about two times longer than anal) and by smaller number of lateral groups of setules on postabdomen (14–16 in both other species). Also, the male of L. diaphanus has a longer basal spine of the postabdominal claw than L. davidi , being similar to L. chichuachuensis .

Figures

FIGURE 2. Oxyurella singalensis Daday 1898, specimens from culture from Loeng Yai reservoir, Khon Kaen area: A – Bpostabdomens of instar I and 2 juvenile males; C—postabdomen of adult male; D – E—distal denticles of adult male postabdomen. Scale bars 0.05 mm for A-C, 0.01 mm for D-E.

FIGURE 3. Leberis diaphanus (King, 1853), adult male from culture from Loeng Yai reservoir, Khon Kaen area: A—lateral view, B—postabdomen, C—antennule, D — thoracic limb I, E—copulatory hook and IDL of limb I. Scale bars: 0.1 mm for A, 0.05 mm for B – E.