Macrothrix vietnamensis Silva-Briano, Dieu and

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 : 228-230

1. Macrothrix vietnamensis Silva-Briano, Dieu and

Dumont, 1999 ( Fig. 1)

Material deposited to NIBR. 3 parthenogenetic females from rice paddy (N 37.675°, E 127.96°) near Hongcheon, Gangwon-do, coll. in 19 Apr 2016 by Y.D. Han, H.M. Yang and A.A. Kotov, NIBRIV0000812485 .

Other localities. Rice paddy (N 34.6528°, E 126.7761°) next to Gangjin Shinpoong road, Jeollanam-do, coll. in 17 Jul 2017 by A.A. Kotov and K.S. Chae; Puddle 1 (N 34.9331°, E127.4988°), a remnant of a wetland pond, Suncheon city, Jeollanam-do, coll. 16 Jul 2017 by A.A. Kotov and K.S. Chae; Rice paddy (N 37.9089°, E 127.2107°) near Myun-Am road, Gyeonggi-do, coll. in 07 May 2016 by H.G. Jeong, A.A. Kotov, M.A. Gololobova and M.A. Kotova .

Parthenogenetic female. Body subovoid, not high, dorsal margin regularly curved, without an ocular dome, no depression behind dorsal head pore, dorsal portion of carapace not elevated above head level, postero-dorsal angle as a rounded triangle, lying at level of longitudinal body axis ( Fig. 1A). Body moderately compressed laterally, without lateral bulges, dorsal keel poorly expressed, minute serration on dorsal rim of carapace ( Fig. 1B), reticulation on valves not seen under light microscope. Ventral head margin depressed, labrum sub-rectangular ( Fig. 2C). Compound eye located near antero-dorsa head margin, ocellus diameter two times smaller than eye diameter. Dorsal head pore small. Ventral margin of valve serrated, with plumose setae, organized in short series of three setae of different size located at different angles, the first seta thick ( Fig. 1D). Postabdomen subrectangular, no heel proximally, preanal margin with transversal series of short setules ( Fig. 1E). Postabdominal seta with a relatively long distal segment, long setules present on proximal segment ( Fig. 1E). Postabdominal claw small, outer dorsal row composed of small spinules only, ventral row as a series of fine spinules ( Fig. 1G). Antenna I relatively robust, dilated distally, with about seven transverse rows of denticles on anterior surface, sensory seta externally at a distance of two antennular diameters at base, nine terminal aesthetascs, two of them significantly larger than the rest ( Fig. 1H). Antenna II with two small proximal sensory setae of subequal size, basal segment short, endopod and exopod subequal in size ( Fig. 1I), swimming setae 0-0-1-3/1-1-3, spines 0-1-0-1/0- 0-1. Largest seta (on proximal endopod segment) with long, thin short setules in middle portion ( Fig. 1J). True spine on second segment of exopod reaches middle of next segment. Additional spines on exopod and exopod segments absent. On limb I, outer distal lobe ( Fig. 1K: ODL) with long apical seta armed by rare, stiff setules, and a very short lateral seta; inner distal lobe ( Fig. 1K: IDL with tree series of strong setules, and three bisegmented setae of different size, unilaterally setulated distally. Limb I corm ( Fig. 1L) and other limbs as described by Silva-Briano et al. (1999). Size 0.37-0.42 mm.

Notes. We identified these populations as M. vietnamensis , initially described from Vietnam ( Silva-Briano et al., 1999). M. vietnamensis differs from the closest species, M. laticornis Jurine in: (1) a relatively low body with dorsal margin of carapace not elevated above the head level; (2) a slight dorsal keel with very fine serration; (3) absence of a distinct reticulation and lateral bulges on valves; (4) presence of long setules on proximal segment of the postabdominal seta. But, in contrast to the description by Silva-Briano et al. (1999), females from Korean populations have: (1) a small dorsal head pore; (2) very small epipodites on all thoracic limbs. If the second character could be variable in different environmental conditions (see Kotov et al., 2004), the first character could indicate specific status for the Korean populations. This is a new record for the Korean Peninsula. This taxon should regarded as a member of the southern thermophilic complex sensu Kotov (2016). Note that M. cf. laticornis is also present in Korea - it was described and illustrated in detail by Yoon (2000, P. 99-101, fig. 52). But the head pore is large in females from Korean populations, as illustrated by Yoon, in contrast to M. laticornis s. str. (see Silva-Briano et al., 1999), in addition, Yoon (2000) illustrated a very specific armature of the seta on the proximal endopod segment (which could be an artifact, it needs to be re-checked). Therefore, these populations also could belong to a specific undescribed taxon from the M. laticornis group which needs to be revised in Korea and all East Asia.

Family Chydoridae Dybowski and Grochowski, 1894 emend. Frey 1967

Subfamily Chydorinae Dybowski and Grochowski, 1894 emend. Frey 1967