Lepeophtheirus atypicus Lin, Ho and Chen, 1996

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 : 196-198

Lepeophtheirus atypicus Lin, Ho and Chen, 1996

( Figs. 15 , 16 )

Lepeophtheirus atypicus Lin et al., 1996, p. 130 , figs. 1- 3; Ho and Lin, 2004, p. 277, figs. 145-147.

Material examined. 2¥¥ from Siganus fuscesens (Houttuyn) , at Sagye, Jeju Island, M.-K. Choe, 16 August 2009 .

Female. Body ( Fig. 15A ) flat, 2.18 mm long. Cephalothoracic shield subcircular, 1.45× 1.34 mm; lateral zone with weakly curved, simple ventral rib and minute setules along lateral margin; posterior sinus deep. Thoracic zone broad and extending over posterior end of lateral zone. Fourth pedigerous somite short. Genital complex much wider than long, 421×719 µm, with rounded corners. Abdomen 108×163 µm and 1-segmented ( Fig. 17B ). Caudal rami widely separated from each other; each ramus ( Fig. 15C ) 106×40 µm, 2.65 times as long as wide, with 6 setae, 2 proximal ones of them located on ventral surface.

Antennule ( Fig. 15D ) 199 µm long and 2-segmented; proximal segment occupying 72% length of antennules, with 1 pointed process and 26 setae; distal segment stout, with 11 naked setae and 2 aesthetascs. Antenna 3-segmented; first segment with distinct proximal process ( Fig. 15E ); second segment nearly quadrangular, with 1 adhesion pad; third segment forming large, distally strongly bent claw bearing 2 small setae. Postantennal process 2 papillae each tipped with 4 or 5 setules ( Fig. 15E ); anoth- er papilla located posterior to postantennal process also tipped with 5 setules.

Mandible with 12 teeth distally. Maxillule consisting of anterior papilla bearing 3 small setae and posterior process bearing 2 tines ( Fig. 15E ). Maxilla ( Fig. 15F ) very slender and 2-segmented; proximal segment (lacertus) unarmed; distal segment (brachium) elongated, distinctly longer than proximal segment, with long membrane (flabellum) at region slightly proximal to middle of on inner margin; calamus about twice as long as canna. Maxilliped ( Fig. 15G ) 3-segmented; first segment (corpus) widest in middle, with almost straight inner margin; second segment (shaft) short, with 1 distal seta; third segment nearly as long as second segment, forming curved claw. Sternal furca ( Fig. 15H ) with divergent tines; each tine straight, tapering, but with blunt tip.

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-1; IV,4; endopod 0-1; 4

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

Leg 1 ( Fig. 15I ) basis with pinnate outer seta and small- er pinnate inner seta. Proximal exopodal segment with 1 small outer distal naked seta and row of setules on inner margin; distal segment broadened distally; three distal spines broad, somewhat scalpel-form and not branched; distal seta much smaller than distal spines. Leg 2 ( Fig. 16A ) coxa with large seta on inner posterior margin and 1 setule on ventral surface; basis with outer seta and 1 inner setule and membrane on inner part of posterior margin; Leg 3 ( Fig. 16B ) with 2-segmented rami; first exopodal segment with large distal spines and 1 setule on outer margin. Leg 4 ( Fig. 16C ) protopod with small outer distal seta. Exopod slender and distinctly longer than protopod; outer spine on first segment small and recurved, hooklike; second segment longer than first or third segments, its distal spine 79 µm; three spines on third segment 83, 175, and 177 µm from outer to inner; all spines on exopodal segments accompanied with flabelliform membranes near base. Leg 5 represented by 1 seta on small papilla and 3 setae on elongate plate (this plate well extending over posterior margin of genital complex) on posterolateral side of genital complex ( Fig. 15B ).

Male. Unknown in Korea.

Distribution and host. Only from Siganus fuscesens (Houttuyn) in Taiwan and Japan ( Lin et al., 1996) and Korea (present study).

Remarks. The close relative of Lepeophtherirus atypicus is L. goniistii Yamaguti, 1936 ( Lin et al., 1996). However, L. atypicus obviously differ from L. goniistii in the following features of the female: 1) caudal rami are widely separated from each other and 2.65 times as long as wide (both closed and 1.30 times as long as wide in L. goniistii , according to Kim, 2008); 2) tines of sternal furca are blunt at tip (pointed in L. goniistii ); 3) two middle spines on terminal margin of distal exopodal segment of leg 1 are simple, not bifurcated; 4) the distal endopodal segment of leg 3 bears 4 setae (6 setae in L. goniistii ); and 5) two inner terminal spines on leg 4 are similar in length.

Figures

Fig. 15. Lepeophtheirus atypicus Lin, Ho and Chen, female. A. habitus, dorsal. B. abdomen, ventral. C. caudal ramus, ventral. D. antennule. E. antenna, postantennal process, and maxillule. F. maxilla. G. maxilliped. H. sternal furca. I. leg 1. Scales=A. 0.5 mm. B. 0.1 mm. C-I. 0.05 mm.

Fig. 16. Lepeophtheirus atypicus Lin, Ho and Chen, female. A. leg 2. B. leg 3. C. leg 4. Scales=0.05 mm for all.

Fig. 17. Lepeophtheirus parvulus Shiino, female. A. habitus, dorsal. B. abdomen, ventral. C. antennule. D. antenna, postantennal process, and maxillule. E. maxilla. F. maxilliped. G. sternal furca. H. leg 1. Scales=A. 0.5 mm. B-H. 0.1 mm.