Caligus rotundigenitalis Yü, 1933

Moon, S. - Y. & Kim, I. - H., 2012, Sea lice (Copepoda, Siphonostomatoida, Caligidae) new to Korea, including three new species, Journal of Species Research 1 (2), pp. 175-217 : 187-190

Caligus rotundigenitalis Yü, 1933

( Figs. 9 , 10)

Caligus rotundigenitalis Yü, 1933, p. 118 , pl. 1, pl. 2, figs. 1-4; Rangnekar, 1959, p. 43, fig. 1a-m; Pillai and Natarajan, 1977, p. 55; Ho et al., 2000, p. 177; Ho and Lin, 2004, p. 268, figs. 3-14; Venmathi Maran et al., 2009; p. 797.

Caligus multispinosus : Lin et al., 1994, p. 259, figs. 5-7.

Caligus seriolae Yamaguti, 1936, p. 2 , pl. 1; Kim, 1998, p. 681, figs. 324, 325.

Material examined. 3¥¥, 2JJ from gills of Hapalogenys mucronatus (Eydoux and Souleyet) , at Wando Island , in the southern coast of Korea, S. Y. Moon, 11 October 2009 .

Female. Body ( Fig. 9A ) 2.63 mm long. Cephalothoracic shield circular, 1.24× 1.20 mm; lunules small; ventral rib of lateral zone ramified distally; posterolateral pit present; posterior sinus moderately deep; thoracic zone extending far beyond lateral zone. Fourth pedigerous somite fused with genital complex. Urosome longer than prosome. Genital complex 568×851 µm, wider than long, with rounded anterolateral and posterolateral corners. Abdomen fused with genital complex, 421×254 µm, 1- segmented, its anterior half broader and posterior half narrower. Caudal rami slightly incurved, 112×74 µm, 1.51 times as long as wide, with 6 setae, and setules on inner margin ( Fig. 9B ).

Antennule ( Fig. 9C ) 232 µm long and 2-segmented; proximal segment occupying 64% length of antennule, with 27 pinnate and 2 naked setae; distal segment with 12 naked setae and 2 aesthetascs. Antenna 3-segmented; first segment lacking proximal process ( Fig. 9D ); second segment nearly quadrangular; third segment forming large, distally bent claw bearing 2 small setae. Postantennal process small, bearing 2 papillae each tipped with 2 or 3 setules; another papilla located posterior to postantennal process tipped with 3 setules.

Mandible with 12 teeth. Maxillule consisting of anterior papilla bearing 3 setae and posterior elongate process bearing small denticle on side ( Fig. 9D ). Maxilla ( Fig. 9E ) 2-segmented; proximal segment (lacertus) slightly curved and unarmed; slender distal segment (brachium) with subdistal membrane (flabellum) at about 65% region of inner margin; calamus about about 1.3 times longer than canna. Maxilliped ( Fig. 9F ) 3-segmented; first segment (corpus) gradually narrowed distally; second segment (shaft) short, with 1 distal seta; third segment forming strongly curved claw. Sternal furca ( Fig. 9G ) with broad tines bearing blunt and oblique distal end.

Armature on rami of legs 1-4 as follows:

Leg 1: exopod 1-0; III,1,3; endopod (vestigial)

Leg 2: exopod I-1; I-1; II,I,5; endopod 0-1; 0-2; 6

Leg 3: exopod I-0; I-1; III,4; endopod 0-1; 6

Leg 4: exopod I-0; I-0; III; endopod (lacking)

Leg 1 ( Fig. 9H ) coxa with branched outer setule; basis with pinnate outer seta, smaller pinnate inner seta. Proximal exopodal segment with 1 small outer distal naked seta and row of setules on inner margin; outermost distal spine distinctly smaller than nearby elements and bearing spinules; other 3 distal element setiform, naked, and subequal in size, without setule or subsidiary element. Leg 2 ( Fig. 10A) coxa with large seta on inner posterior margin; basis with small outer seta and 1 inner setule and membrane on inner part of posterior margin; second and third endopodal segments with patch of minute spinules on outer surface; outer side of basis and first exopodal segment with broad membrane (not illustrated in Fig. 10A). Leg 3 ( Fig. 10B) protopod (apron) with broad membrane on outer and inner margins; outer spines of second and third exopodal segments setiform; outer proximal spine on third exopodal segment markedly smaller than distal 2 spines; distal endopodal segment with vestige of articulation. Leg 4 ( Fig. 10C) stocky; protopod with small outer distal seta. Exopod of leg 4 3-segmented; first segment longest, with 1 small setule on outer margin; third segment tapering; distalmost spine on third segment 110 µm long, distinctly longer than other spines; other 4 spines on exopod setiform, dissimilar in form to distalmost spine, plumose, and distally curved; all spines on exopod accompanied by membrane near base. Leg 5 represented by 1 and 3 small setae on posterolateral margin of genital complex.

C B A F H D G E

Male. Body ( Fig. 10D) 1.61 mm long. Cephalic shield 919×863 µm, resembling that of female. Genital complex slightly longer than wide. Abdomen 2-segmented, segmentation incomplete; distal somite about twice as long as proximal one. Caudal ramus 88×61 µm.

Antennule armed as in female. Antenna ( Fig. 10F) 3- segmented; first segment with 1 adhesion pad; second segment with 2 weak adhesion pads; third segment with 2 inner proximal setae and forming strong claw bearing large subsidiary claw near middle. Postantennal process more slender and longer than that of female.

Mandible, maxillule and maxilla as in female. Maxilliped ( Fig. 10G) with 1 corrugation on inner margin of first segment. Sternal furca as in female.

Legs 1-4 also as in female. Leg 5 represented by 4 small setae on lateral margin of genital complex ( Fig. 10H). Leg 6 represented by 3 small setae on each posterolateral corner of genital complex ( Fig. 10H).

Distribution and hosts. Very diverse species of fishes have been reported as hosts of C. rotundigenitalis from Persian Gulf, India, China, Taiwan, and Malaysia. It is parasitic on 33 species of fishes belonging to 19 families in Taiwan ( Ho et al., 2000).

Remarks. Ho et al. (2000) mentioned the similarity of C. rotundigenitalis with C. tanago Yamaguti, 1939 and C. mutispinosus Shen, 1957 . To this group, we could also keep C. seriolae Yamaguti, 1936 . These four species are similar to one another in most of the morphological aspects. However, C. tanago can be separated from the other three by having a narrow abdomen with its nearly parallel lateral margins and a simple (not ramified) ventral rib of the lateral zones of the cephalic shield which can be detected in the dorsal view of body under the microscope. A close comparison of the remaining three species based on the previous records and our available specimens fail- ed to distinguish them. We consider C. multispinosus and C. seriolae as junior synomyms of C. rotundigenitalis . They share the following characteristic features: 1) the ventral rib of the lateral zones of the cephalic shield ramified distally; 2) the antenna lacks a proximal spine on the first segment; 3) the postantennal process is small in the female; 4) the distal tines of the sterna furca are broad, with blunt tip; 5) the rudimentary endopod of leg 1 is blunt; 6) the outermost distal spine (spine I) of the distal exopodal segment of leg 1 is spiniform and much smaller than other 3 distal spines which are naked, setiform, and similar in length, without accessory element; and 7) the distalmost spine of leg 4 is nearly smooth and distinctly longer than four proximal spines which are plumose and setiform.

Figures

Fig. 9. Caligus rotundigenitalis Yü, female. A. habitus, dorsal. B. caudal rami, dorsal. C. antennule. D. antenna, postantennal process, and maxillule. E. maxilla. F. maxilliped. G. sternal furca. H. leg 1. Scales=A. 0.5 mm. B, D, F. 0.1 mm. C, E, G, H. 0.05 mm.