Macrothrix triserialis Brady, 1886

Kotov, Alexey A., Jeong, Hyun Gi & Lee, Wonchoel, 2012, Cladocera (Crustacea: Branchiopoda) of the south-east of the Korean Peninsula, with twenty new records for Korea *, Zootaxa 3368, pp. 50-90 : 65-67

10. Macrothrix triserialis Brady, 1886

Fig. 11–12

Synonymy. Macrothrix triserialis Brady, 1886 , p. 295, Pl. 37: figs 16–20; Smirnov 1992, p. 51–55, Figs 191 –205, 219, 225; Dumont et al. 2002, p. 6–7, Figs 18–20.

Not M. triserialis Brady in Chiang & Du 1979, Fig. 127.

See intensive synonymy in Smirnov (1992).

Type locality. "Colombo" ( Brady 1886), Sri Lanka.

Locality in Korea. 6 a (see Fig. 1 and Table 1).

Parthenogenetic female. Body subovoid, dorsal margin in general regularly curved, with well-expressed ocular dome, shallow depression behind dorsal head pore, postero-dorsal as a pointed angle, lying somewhat above longitudinal body axis ( Fig. 11 A). Whole surface of head and valves covered with striae, with rare or numerous anastomousings. Body significantly compressed laterally, with sharp dorsal keel. Ventral head margin somewhat convex, with a projection anterior to labrum, which is sub-rectangular, with a series of tubercles at apex; ocellus small ( Fig. 11 B). Setae at ventral margin plumose, organized in short series of three setae of different size located at different angles, the first seta thick ( Fig. 11 C). Postabdomen subovoid, with rounded distal extremity, distinct heel basally, preanal margin with short transversal series of short to medium-sized setules; in basal portion these setules always longer and more robust ( Fig. 11 D). Postabdominal claw small, outer dorsal row of two large denticles: a ‘basal spine’ and second denticle, plus a small denticles distally; inner dorsal row with numerous denticles, two of them remarkably more robust than the rest; ventral row of two denticles ( Fig. 11 D–F). Postabdominal seta with a very short distal segment, no setules on basal segment ( Fig. 11 G–H). Antenna I rod-like, sensory seta externally at a distance more than antennular diameter from antennule joint, about 7 transverse rows of denticles on anterior surface of antennule; nine short aesthetascs, two of them significantly larger than the rest ( Fig. 11 B, 12 A). Antenna II with two small basal sensory setae of subequal size. Basal segment with distal burrowing spine equal in length to basal segment of exopod, naked; swimming setae 0- 0-1 - 3 / 1 - 1-3, spines 0-1 - 0-1 /0- 0-1 ( Fig. 12 B). Largest seta (on basal endopod segment) with three strong spinules in middle portion, and a row of short setules in basal and distal portions ( Fig. 12 C). True spine on second segment of exopod with third length of this segment. Additional spines on exopod segments small, decreasing gradually in dorsal direction ( Fig. 12 B). On limb I, ODL with long apical seta, and small lateral seta; IDL with tree series of strong setules, and three bisegmented setae of different size, unilaterally setulated distally, two smaller two smaller ones hook-shaped ( Fig. 12 D). Other limbs as in females from type locality as described by Dumont et al. (2002). Size in our material 0.55–0.73 mm.

Notes. The Macrothrix rosea-triserialis group was revised during the last decade, and it was found that M. triserialis lives only in the tropics and subtropics of the Old World ( Dumont et al. 2002; Kotov et al. 2004). Kim & Yoon (1987) and Yoon (2010) reported for Korea only a single species from this group, the palaearctic M. rosea (Jurine, 1820) (as Echinisca ). We confirm its presence in Korea (see Figs 13–14 of M. rosea from Ho Tan wetland). M. triserialis differs from the latter in: (1) more expressed projection anterior to labrum; (2) thinner first seta in each triplet on valve; (3) very short distal segment of postabdominal seta; (4) three strong spinules in the middle of largest antennal seta. The finding of M. triserialis in Korea‘s non-subtropical climate (i.e. winters with negative temperatures) was quite surprising. Taking into consideration that " M. triserialis " in Fig. 192 by Chiang & Du 1979 is apparently M. rosea , the presence of M. triserialis in China needs to be confirmed. The latter we now consider as a tropicopolitan species (=species widely distributed in the tropics, but capable of penetrating more northern territories).