Metacaligus uruguayensis ( Thomsen, 1949 )

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 : 193-196

Metacaligus uruguayensis ( Thomsen, 1949)

( Figs. 13 , 14 )

Caligus (Metacaligus) uruguayensis Thomsen, 1949, p. 3 , pl. 2, figs. 1-25; pl. 3, figs. 1-21.

Caligus longicorvicis Gnanamuthu, 1950 . p. 115, pl. 3, figs. 31-46; Kirtisinghe, 1964, p. 65, fig. 57; Pillai, 1966, p. 125, fig. 2.

Metacaligus uruguayensis : Ho and Bashirullah, 1977. p. 707, figs. 3, 4; Lin and Ho, 2000, p. 206, figs. 4-6; Ho and Lin, 2004, p. 302, figs. 159-161.

Material examined. 2¥¥, 1J from Trichurus lepturus, Linnaeus at Sorae Port (the fish was imported from Jeju Island ), S. Y. Moon, 10 October 2009 .

Female. Body ( Fig. 13A ) large and narrow, 6.08 mm long. Cephalothoracic shield subcircular, 2.30× 2.10 mm; lateral zone with weakly curved ventral rib and small posterolateral pit; posterior sinus deep. Thoracic zone extending to level of posterior end of lateral zone. Urosome longer than prosome. Fourth pedigerous somite narrow and fused with genital complex. Genital complex large, ovoid, widest in middle, 2.10× 1.56 mm. Abdomen about 600×362 µm, 1-segmented, with slightly convex lateral margins. Caudal ramus ( Fig. 13C ) weakly tepering, 185×85 µm, 2.18 times as long as wide, with 6 setae; longest one of caudal setae 300 µm.

Antennule ( Fig. 13D ) 2-segmented; proximal segment 228 µm long, with 27 setae; distal segment elongated, 208 µm long, with 12 naked setae and 2 aesthetascs. Antenna 3-segmented; first segment without proximal process; second segment nearly quadrangular; third segment longer than segment, forming long, with 2 small setae ( Fig. 13E ). Postantennal process small, triangular, with 2 papillae each tipped with 1 or 2 setules ( Fig. 13E ); another papilla located posterior to postantennal process tipped with 1 setule.

Mandible with 12 teeth distally. Maxillule consisting of anterior papilla bearing 3 unequal setae and tapering posterior process. Maxilla ( Fig. 13F ) 2-segmented; proximal segment unarmed; distal segment with large subdistal membrane (flabellum) on inner margin; calamus about 1.3 times longer than canna, both with serrate margins. Maxilliped ( Fig. 13G ) 3-segmented and stocky; first segment strongly tapering distally; second segment with 1 small setiform process distally; third segment almost fused with second, forming strong claw. Sternal furca absent.

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; I,I,5; endopod 0-1; 0-2; 6

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

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

Leg 1 ( Fig. 13H ) coxa with simple outer setule; basis with pinnate outer and inner setae. Proximal exopodal segment with 1 small outer distal naked seta and row of spinules on inner margin; distal segment 113×88 µm, broad, three distal spines very unequal in size, 165, 105, and 75 µm from outer to inner, each accompanied by pectin near base; inner distal seta naked; 3 inner setae small, not longer than distal segment; endopod small, knob-like. Leg 2 ( Fig. 14A ) coxa with large seta on inner posterior margin; basis with small outer seta and 1 inner setule. Outer spine of second exopodal segment and outer proximal spine on third segment small ( Fig. 14B ). Second and third endopodal segments with spinules on outer surface. Leg 3 ( Fig. 14C ) protopod (apron) with spinules on mid-ventral and outer ventral surfaces. Leg 4 ( Fig. 14D ) protopod longer than exopod, with small outer distal seta. Exopod 2-segmented; proximal segment longer than distal segment, its distal spine 110 µm; 4 spines on distal segment 105, 115, 134, and 210 µm, from proximal to distal. Leg 5 represented by 1 and 3 small setae on posterolateral area of genital complex ( Fig. 13B ).

Male. Body ( Fig. 14E ) 4.19 mm long, with narrow urosome. Cephalic shield 1.98× 1.83 mm. Genital complex 808×529 µm, nearly fusiform. Abdomen 2-segmented, 385×337 (proximal) and 288×232 µm (distal segment).

Antennule as in female. Antenna ( Fig. 14G ) 3-segment- ed as in female; first segment unarmed; second segment with 2 weak adhesion pads; third segment short, with 2 inner proximal setae and distally forming several layers of leaf-like flaps. Postantennal process ( Fig. 14F ) large and very different from that of female.

Mandible and maxilla as in female. Maxillule ( Fig. 14H ) with 1 small subdistal seta on posterior process. Maxillip- ed as in female. Sternal furca absent.

Legs 1-5 as in female. Leg 6 represented by 2 small setae on each posterolateral corner of genital complex.

Distribution and hosts. Known hosts of Metacaligus uruguayensis are Trichiurus haemula (Forskål) in India, T. lepturus Linnaeus in Uruguay, Venezuela, Taiwan and Korea (present study), T. savala Cuvier in India and Sri Lanka, and Trichiurus sp. in Brazil ( Lin and Ho, 2000).

Remarks. The genus Metacaligus is distinguished from other genera of the Caligidae by the combination of the following characters (Ho and Bashiru-llah, 1977; Ho and Lin, 2002): 1) the absence of sternal furca; 2) the absence of accessory process on two mid-terminal spines of the second exopodal segment of leg 1; 3) the possession of only one outer spine (instead of two) on the terminal exopodal segment of leg 2.

The cutlassfish Trichiurus lepturus harbors another species of Metacaligus , M. latus described by Ho and Lin (2002) from Taiwan. According to Ho and Lin (2002), in M. latus the genital complex of both sexes is globular and almost as long as wide, the caudal ramus is 1.63 times as long as wide in the female, the postantennary process has papillae tipped with 4 setules, and the anal somite of the male is distinctly longer than the proximal abdominal somite. C. uruguayensis may be easily differentiated from M. latus based on those features of the latter species.

Figures

Fig. 13. Metacaligus uruguyensis (Thomsen), fmale. A. habitus, dorsal. B. abdomen, ventral. C. caudal rami. D. antennule. E. antenna, postantennal process, and maxillule. F. maxilla. G. maxilliped. H. leg 1. Scales=A. 1 mm. B. 0.5 mm. C-F, H. 0.1 mm. G. 0.2 mm.

Fig. 14. Metacaligus uruguyensis (Thomsen), female. A. leg 2. B. second and third exopodal segment of leg 2. C. leg 3. D. leg 4. Male. E. habitus, dorsal. F. postantennal process. G. antenna. H. maxillule. Scales=A, C, F-H. 0.1 mm. B. 0.05 mm. D. 0.2 mm. E. 0.5 mm.