Camptocercus vietnamensis Than 1980

16. Camptocercus vietnamensis Than, 1980

Fig. 22

Synonymy. Camptocercus vietnamensis Than in Than et al., 1980, p. 233–234, Fig 144; Sinev 2011, p. 52–58, Figs 1–2. Camptocercus rectirostris (Schoedler) in Yoon 2010, p. 118–119, Fig. 63.

Type locality. "Hanoi region”, Vietnam.

Locality in Korea. 14 (see Fig. 1 and Table 1).

Parthenogenetic female. Body ovoid, high in lateral view (Fig. 22 A); strongly compressed laterally and having a well-expressed dorsal keel both on carapace and head. Dorsal margin without depression between valves and head shield, postero-dorsal angle broadly rounded, posterior margin convex, postero-ventral angles broadly rounded. Ventral margin almost straight. Rostrum acute, pointed downward (Fig. 22 B). Three connected main head pores, lateral pores minute. Labrum with sub-triangular keel with rounded apex; its posterior margin with denticle and a group of fine setules (Fig. 22 B–C). Row of ventral setae followed by a row of fine setules, in dorsal portion of posterior margin they are strong, denticle-like (Fig. 22 D). Postabdomen very long, narrowing distally, length about 4.5–5 height (Fig. 22 E). Preanal portion straight, preanal angle well-developed, anal margin concave, postanal angle expressed, postanal margin straight; postanal portion 2.5 times longer than anal one. Postanal margin with 15–18 small triangular, postanal denticles, each distal one with a small additional denticle proximally to its base. Laterally, about 15 lateral series of fine setules. Postabdominal claw long, straight, with slightly curved tip; basal spine short, slightly bent, about 0.2 length of claw itself; setules at the end of proximal pecten as strong spines (Fig. 22 F). Antenna I with length about 4–5 width, with three groups of fine setules at anterior face; among nine aesthetascs two longer than the rest, longest aesthetascs as long as antenna I; antennular seta thin, about 1/3-1/ 4 length of antenna I, protruding somewhat distally to middle (Fig. 22 B). Antenna II short, antennal formula: setae 0-0-3/0-1-3, spines 1-0-1/0-0-1. Apical setae subequal in size, apical spines very short, spine on proximal exopod segment also very short (Fig. 22 G). Limb I with ODL bearing a long seta, armed with long setules; IDL with four clusters of setules and three setae; seta 1 large, well developed, about 1/3 length of ODL seta; setae 2 and 3 thick, curved, hook-like, with a setulated distal portion (Fig. 22 H). Size in our material 0.39–0.50 mm.

Notes. Camptocercus vietnamensis differs from C. uncinatus in: (1) a smaller size (Sinev 2011), although such comparison should be based on ample samples; (2) higher body; (3) presence of a denticle on labral keel; (4) postanal teeth consisting of a strong denticle and one small additional denticle proximally to its base. Until recently it was known only from Vietnam, but Sinev (2011) proposed that some tropical populations earlier identified as C.

uncinatus could also belong to C. vietnamensis. It is a rheophylic species (Sinev 2011), but we found it in an oxbow lake. After our finding, it is clear that it is widely distributed in Pacific Asia. We regard it as a tropical-subtropical species that deeply penetrating the Palaearctic. Korea may be the northernmost area of its distribution, because it is apparently absent from the Amur basin (Kotov et al. 2011a).