Caligus calotomi Shiino, 1954

Venmathi Maran, B. A., Ohtsuka, Susumu & Shang, Xu, 2012, Records of Adult Caligiform Copepods (Crustacea: Copepoda: Siphonostomatoida) in Marine Plankton from East Asia, Including Descriptions of Two New Species of Caligus (Caligidae), Species Diversity 17 (2), pp. 201-219 : 202-203

Caligus calotomi Shiino, 1954 ( Fig. 2A )

Caligus calotomi Shiino, 1954a: 16 ; Yamaguti 1963: 55; Lin and Ho 2007: 51.

Caligus sp.: Venmathi Maran and Ohtsuka 2008: 209; Nagasawa et al. 2010: 103.

Material examined. One adult ♂ (KMNH IvR

500,499), Tokushima Port, Tokushima Prefecture, Japan (St.

5), 4 October 2008 ( Table 1).

Description. Male. Body ( Fig. 2A ) 3.09 mm long, excluding caudal setae. Cephalothorax suborbicular, longer than wide, 2.25× 1.68 mm. Fourth pediger wider than long, 0.21× 0.37 mm. Genital complex with triangular posterior corners representing legs 5 and 6, 0.50× 0.71 mm, ornamented dorsolaterally with conspicuous sensilla. Abdomen small, rectangular, wider than long, 0.14× 0.31 mm. Caudal ramus longer than wide, 0.12× 0.10 mm, armed with 3 short subterminal and 3 long terminal setae.

Remarks. The present species was originally recorded in plankton from the Nansei Islands, southwestern Japan, as an unidentified species of Caligus ( Venmathi Maran and Ohtsuka 2008) , but we now refer it to C. calotomi based on the redescription of Lin and Ho (2007). This is the second record of this species from Japan from plankton samples, although males have not so far been reported on any fish host as parasites in Japan ( Shiino 1954a; Nagasawa et al. 2010). The present specimen is slightly smaller (3.09 mm) than the previous one (3.13 mm, cf. Venmathi Maran and Ohtsuka 2008), 3.16 mm which itself was similarly shorter than the original specimen from Taiwan ( Lin and Ho 2007). A close comparison with the original description shows a minor difference in the shape of the maxillule. According to Lin and Ho (2007), the base of the maxillule nearby the setae is not curved (=straight), but it is curved in our specimens (cf. Venmathi Maran and Ohtsuka 2008).

Distribution. Caligus calotomi was first found as a parasite on the Japanese parrotfish Calotomus japonicus (Valenciennes, 1840) collected from Nagashima, Mie Prefecture and a few additional specimens were found freely swimming in the public aquarium at the Seto Marine Biological Laboratory, Shirahama, Wakayama Prefecture ( Shiino 1954a). These were all females, and the male remained unreported from Japan until we found it in the plankton ( Venmathi Maran and Ohtsuka 2008). We recently examined the host fish C. japonicus from Uwajima in Ehime Prefecture, but, none was found with caligids (Venmathi Maran, personal observation). Hence, the present find is the second report of male of this species from Japan following our previous report ( Venmathi Maran and Ohtsuka 2008; Nagasawa et al. 2010). Around Taiwan, a female and a male were found on a torpedo scad, Megalaspis cordyla (Linnaeus, 1758) , and a striped bonito, Sarda orientalis (Temminck and Schlegel, 1844) , respectively ( Lin and Ho 2007).

Figures

Fig. 2. Two species of Caligus from plankton samples. A, Caligus calotomi Shiino, 1954, male (KMNH IvR 500,409), habitus, dorsal view. B–G, Caligus quadrigenitalis sp. nov., holotype, female (KMNH IvR 500,500): B, habitus; C, frontal plate enlarged; D, lateral region of genital complex showing setules and leg 5; E, abdomen; F, caudal ramus; G, antennule. Scale bars: 1mm (A, B), 0.2mm (C), 0.1mm (D–G).