Pleuroxus (Picripleuroxus) quasidenticulatus

Lee, Sue Yeon, Yoo, Jung Sun & Kim, Seung Tae, 2017, Recent progress in studies of the Cladocera (Crustacea: Branchiopoda) of South Korea with seven new records for the Korean Peninsula, Journal of Species Research 6, pp. 227-246 : 232-235

4. Pleuroxus (Picripleuroxus) quasidenticulatus

(Smirnov, 1996) ( Figs. 4-6)

Material deposited to NIBR. 5 parthenogenetic females from a pond 1 (N 33.43251°, E 126.5998°) in Halla Eco-forest , Jeju-do, coll. in Nov 2012 by A.A. Kotov and. H.G. Jeong, NIBRIV0000812487 .

Parthenogenetic female. Body without any sculpture, low in juveniles ( Fig. 4A) and high in adults ( Fig. 4B), somewhat compressed laterally ( Fig. 4C, D), posterior margin regularly curved from tip of rostrum to rounded postero-dorsal angle, posterior margin slightly convex, ventral margin with exactly marginal setae of different length in different portions of it ( Fig. 4E, F), postero-ventral angle with 1-2 blunt and closely located denticles (distance between them is obviously smaller than the denticle thickness at its base ( Fig. 4 G-J). Head ( Fig. 4K) with a regularly curved, elongated rostrum, its tip sharp ( Fig. 4L) and projected postero-ventrally, ocellus somewhat smaller than compound eye. Head shield with two major head pores, postpore distance subequal to two interpore distance, two minute pores in midline, located somewhat closely to anterior major pore ( Fig. 4M). Labral keel large, with rounded apex ( Fig. 4N). Postabdomen moderately long, somewhat narrowing distally, ventral margin straight to somewhat convex, preanal margin longer than anal one, undulated; preanal angle well-expressed; anal margin concave; postanal angle expressed; postanal margin straight, dorso-distal angle well-expressed ( Fig. 4O, P). On distal portion, 10-12 postanal teeth with size slightly increasing distally, each tooth accompanied of short series of additional small denticles. Postabdominal claw massive, slightly curved, with two basal spines, length of the distal spine about 0.3 claw length, proximal spine very short. Antenna I short, with antennular sensory seta approximately in middle and nine terminal aesthetascs of subequal size ( Fig. 4Q). Antenna II short, with two short sensory setae in coxal portion, basal segment with a minute spine distally ( Fig. 4R, S). Antennal formula: setae 0-0-3/0-1-3, spines 1-0- 1/0-0-1; a spine on proximal segment of exopod minute; apical spines shorter than apical segments. Limb I with ODL supplied with a long seta and a small lateral seta; IDL with two large setae setulated distally ( Fig. 5A, B: 2 and 3) and a shorter naked seta (1). Size in our material 0.4-0.5 mm.

Ephippial female. As parthenogenetic female, the only dorsal portion of valves additionally pigmented in yellow-brown ( Fig. 5C).

Adult male. Body elongated, dorsal margin regularly convex, postero-dorsal angle well-expressed ( Fig. 6A, B), denticles at postero-ventral angle as in female ( Fig. 6C, D). Rostrum widely round, short ( Fig. 6F). Labrum somewhat shorter than in females ( Fig. 6G, H). Postabdomen comparatively long, postanal margin slightly convex, distal portion rounded, gonopore openings large, located subdistally ( Fig. 6I, J), postanal portion armed with series of fine setules instead of postanal teeth. Postabdominal claw thick, distalmost basal spine shorter than in female. Antenna I thick, with additional male seta ( Fig. 6K). Antenna II ( Fig. 6L) as in female. Limb I with U-shaped copulatory hook, IDL with four setae, seta 1 shorter than others, male seta somewhat shorter than seta 2 ( Fig. 6M, N: ms).

Notes. Only P. (P.) quasidenticulatus was illustrated by Yoon (2000, fig. 75) as P. (P.) denticulatus . The former differs from the latter in: (1) absence of a sculpture on valves and head shield; (2) blunt and closely located denticles (distance between them is obviously smaller than the denticle thickness at its base) at the postero-ventral angle; (3) presence of a cluster of larger postanal teeth at the distal angle of postabdomen; (4) shorter and more robust postabdominal claw ( Sinev and Sanoamuang, 2013). Both taxa are found on the Korean Peninsula.

P. (P.) quasidenticulatus is a new record for Korea. This is a relatively common taxon in SE Asia and the southern portion of Far East of Russia. This taxon should be regarded as a member of the southern thermophilic complex sensu Kotov (2016).