Caligus orientalis Gusev, 1951

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 : 210-211

Caligus orientalis Gusev, 1951

( Fig. 8A, B )

Caligus orientalis Gusev, 1951: 411 ; Brandes 1956: 173; Markevich 1956: 184; Yin 1962: 41; Yamaguti 1963: 57; Hwa 1965: 48; Margolis and Parker 1966: 311; Suzumoto 1974: 23; Urawa et al. 1979: 139; Matumoto 1980: 143; Li 1984: 157; Urawa and Kato 1991: 161; Nagasawa 1994: 83; Kim 1998: 664; Lin and Ho 1998a: 200, 1998b: 96.

Caligus laticorpus Shen, 1957: 354 ; Yamaguti 1963: 55; Yoda 1973: 98; Nagasawa et al. 2010: 103.

Material examined. One adult ♀ (XOB-PC 11), Amoy (=Xiamen), Fujian Province, China (St. 1), 20 September 2008; 1 adult ♂ (KMNH IvR 500,504), Ariake Sea , Saga Prefecture, Japan (St. 2), 6 July 2008 ( Table 1) .

Description. Female. Body ( Fig. 8A ) 2.68 mm long,

excluding caudal setae. Cepahalothorax slightly longer than wide, 1.60× 1.57 mm. Fourth pediger wider than long, 0.15× 0.32 mm. Genital complex subrectangular, slightly wider than long, 0.64× 0.76 mm, with rounded posterolateral corners. Abdomen small, 0.28× 0.31 mm, unsegmented. Caudal ramus wider than long, armed with 3 short and 3 long plumose setae.

Male. Body ( Fig. 8B ) 3.01 mm long, excluding caudal setae. Cephalothorax longer than wide, 1.98× 1.71 mm. Fourth pediger wider than long, 0.17× 0.40 mm. Genital complex wider than long, 0.51× 0.70 mm, with indented lateral margins and sharp, acute posterolateral projections marking leg 5. Abdomen small, 0.32× 0.40 mm, distinctly 2-segmented with large anal somite. Caudal ramus as in female.

Remarks. This is the first record of male Caligus orientalis from Japan and the second report from China in plankton samples. Both sexes of C. orientalis were reported recently from plankton samples at the mouth of the Mankyong River, Korea ( Venmathi Maran and Ohtsuka 2008), where the number of males exceeded that of females. The present male (3.01 mm) is larger than the present female (2.68 mm), in accordance with previous reports ( Ho and Lin 2004a; Venmathi Maran and Ohtsuka 2008).

Distribution. Caligus orientalis is a serious pest of cultured mullet Mugil cephalus Linnaeus, 1758 in Korea ( Kim 1998). It is a common parasite in Asia, severely infecting the freshwater fish common carp Cyprinus carpio Linnaeus, 1758 in aquaculture facilities ( Suzumoto 1974; Matumoto 1980), and also in marine waters ( Hwa 1965; Urawa et al. 1979; Urawa and Kato 1991; Kim 1998; Lin and Ho 1998a, b), sometimes causing mass mortality ( Kim 1998). The hosts of C. orientalis and its biology have been reviewed ( Nagasawa 2004). It is well distributed in Japan ( Nagasawa et al. 2010), Korea ( Kim 1998; Venmathi Maran and Ohtsuka 2008), China ( Shen 1957; Hwa 1965; present study), Taiwan ( Lin and Ho 1998a, b) and the Russian Far-East ( Gusev 1951). The regular occurrence of this species in plankton suggests that it readily detaches from the host and actively swims in the water column.

Figures

Fig. 8. Three previously described species of Caligus found in plankton samples. A, Caligus orientalis Gusev, 1951, female (KMNH IvR 500,503), habitus, dorsal view; B, C. orientalis, male (KMNH IvR 500,504), habitus, dorsal view; C, C. rotundigenitalis Yu, 1933, male (XOB- PC12), habitus, dorsal view; D, C. undulatus Shen and Li, 1959, female (KMNH IvR 500,505), habitus, dorsal view; E, C. undulatus, male (KMNH IvR 500,506), habitus, dorsal view.Scale bars: 1mm (A–E), 0.5mm (C).