Caligus undulatus Shen & Li, 1959

Lee, Jimin, Chang, Cheon Young & Kim, Il-Hoi, 2022, Symbiotic copepods (Cyclopoida and Siphonostomatoida) collected by light trap from Korea, ZooKeys 1115, pp. 1-71 : 1

Caligus undulatus Shen & Li, 1959

Fig. 33

Material examined.

Four ♀♀, 1 ♂, Site 11, 16 Apr. 2014; 1 ♀, 1 ♂, Site 20, 05 Jun. 2020; 1 ♀, Site 26, 06 Jul. 2016; 1 ♀, 2 ♂♂, Site 31, 15 Nov. 2020.

Other material from fish host.

1 ♀ and 1 chalimus from the skin of the fish Konosirus punctatus (Temminck & Schlegel, 1846), at a market at Gonam, Hadong, south coast (34˚59'47"N, 126˚48'37"E), 25 Jul. 2012, leg. I.-H. Kim.

Supplementary description of female.

Body (Fig. 33A ) narrow. Body length 3.92 mm. Cephalothoracic shield distinctly longer than wide (1.76 × 1.36 mm); thoracic zone extending beyond posterior tips of lateral zones. Urosome longer than cephalothoracic shield. Genital complex nearly fusiform, ~ 1.4 × longer than wide (1.07 × 0.77 mm), incompletely articulated from fourth pedigerous somite, truncate posteriorly. Abdomen 0.61 × 0.26 mm, unsegmented, elongate, not articulated from genital complex, with wrinkled cuticle at proximal region. Caudal rami (Fig. 33B ) slightly convergent, 2.50 × longer than wide (195 × 78 μm), armed with three large and three small setae; one of small setae positioned ventrally.

Sternal furca (Fig. 33C ) narrow; tines gradually narrowed distally, with blunt apex. Distal exopodal segment of leg 1 (Fig. 33D ) with three large, pinnate setae on inner margin and four distal armature elements comprising, from outer to inner, claw-like spine 1, smaller claw-like spine 2 bearing accessory process, transparent, aesthetasc-like seta, and long, naked seta. Leg 4 (Fig. 33E ) consisting of protopod and two-segmented endopod; protopod with one small seta distally; proximal exopodal segment armed with one spine of 114 μm long; distal exopodal segment armed with four spines of 64, 62, 75, and 101 μm long, respectively, from proximal to distal.

Description.

Male. Body (Fig. 33F ) smaller than that of female, 3.30 mm long. Cephalic shield 1.75 × 1.24 mm. Genital complex longer than wide. Abdomen two-segmented; proximal and distal abdominal somites 310 × 250 μm and 360 × 185 μm, respectively. Caudal ramus 2.57 × longer than wide (185 × 72 μm).

Remarks.

Caligus undulatus is distributed in tropical and warm waters of the world, and has been frequently found from plankton samples. Moon and Park (2019) also recorded its occurrence in plankton samples from Korea. Ohtsuka et al. (2020) recorded the fish Sardinella zunasi (Bleeker, 1854) as a host of C. undulatus , which was the first host record. In the present study, we report Konosirus punctatus as an additional host record. The fish hosts S. zunasi and K. punctatus live on East Asian coasts, sometimes entering bays or brackish waters. It is conceivable that C. undulatus and other caligids may detach from the hosts due to the salinity change when the hosts approach brackish waters.

A female specimen from Site 11 exhibited a shrunken genital complex with undulated lateral margins as observed in the type material of Shen and Li (1959). This form of the genital complex may occur immediately after oviposition.

Figures

Figure 33. Caligus undulatus Shen & Li, 1959 Female A habitus, dorsal B caudal rami, dorsal C sternal furca D distal exopodal segment of leg 1 E leg 4. Male F habitus, dorsal. Scale bars: 0.5 mm (A, F); 0.1 mm (B, C, F); 0.05 mm (D).