Lepeophtheirus gusevi, Moon & Kim, 2012

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 : 205-209

Lepeophtheirus gusevi n. sp.

( Figs. 21-23 )

Lepeophtheirus sp. Gusev, 1951, p. 421, fig. 17.

Material examined. 7¥¥, 2JJ from the skin of Sebastes schlegelii Hilgendorf , at Wando Island in the southern coast of Korea, I.-H. Kim, 10 January 2006. Holotype (¥), allotype (J), and paratypes (5¥¥) have been deposited in the National Institute of Biological Resources , Incheon. Dissected paratypes (1¥, 1J) are retained in the collection of the senior author.

Female. Body ( Fig. 21A ) 6.67 mm long. Cephalothoracic shield subcircular, 3.88× 3.68 mm, with broad membrane on lateral margins; lateral zone with arched ventral rib; shallow posterolateral pit present on dorsal surface. Thoracic zone 1.75 mm wide. Fourth pedigerous somite incompletely divided from genital complex. Genital complex subcircular, 1.93× 1.85 mm, slightly widened distally. Abdomen ( Fig. 21B ) fused with genital complex, nearly as long as wide, divided by lateral constriction into proximal 1/3 and distal 2/3. Caudal rami separated from each other by their width; each ramus 171×146 µm, with 6 setae.

Antennule ( Fig. 21C ) 2-segmented; proximal segment with 25 pinnate and 2 naked setae; distal segment with 13 naked setae and 1 aesthetasc. Antenna ( Fig. 21D ) 3-segmented; first segment with large, distally tapering proximal process; second segment nearly quadrangular, with 1 dorsal and another small, inner distal adhesion pads; third segment forming large, distally strongly bent claw bearing 2 setae. Postantennal process ( Fig. 21E ) bearing 2 papillae each tipped with several setules; another papilla located posterior to postantennal process. Sclerotized process present near base of postantennal process ( Fig. 23E ).

Mandible ( Fig. 21F ) with 12 teeth distally. Maxillule ( Fig. 21G ) consisting of anterior papilla bearing 3 unequal setae and posterior process bearing 2 tines. Maxilla ( Fig. 21H ) 2-segmented; proximal segment (lacertus) unarmed, 750 µm long; distal segment (brachium) with large membrane (flabellum) near middle; calamus about twice as long as canna; canna with 1 claw-like process near middle of inner (convex) margin ( Fig. 21I ). Maxilliped ( Fig. 22A) 3-segmented; first segment (corpus) unarmed but with 2 patches of granules on inner side of distal half; second segment (shaft) short, with 1 distal seta; third segment forming large, sharp claw. Sternal furca ( Fig. 22B) divergent, with spatulate tines.

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; I-1; III,4; endopod 0-1; 6

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

Leg 1 ( Fig. 22C) coxa with branched small outer setule; basis with pinnate outer and inner setae. Proximal exopodal segment bullate, with 1 small outer distal naked seta and row of setules on inner margin; two inner distal spines bifurcating subterminally, with membrane near base. Leg 2 ( Fig. 22E) coxa with large seta on inner posterior margin and small tubercle and setule on ventral surface; basis with small outer seta and 1 inner setule and membrane on inner part of posterior margin. Leg 3 ( Fig. 24G ) exopod with first segment bearing 3 setules on outer margin. Leg 4 ( Fig. 23A ) protopod almost straight, with nearly parallel lateral margins and small outer distal seta; first exopodal segment with very small distal seta (37 µm long); second segment longest among exopodal segments, its distal spine 180 µm long; 3 spines on third exopodal segment 175, 210, 440 µm, respectively, from outer to inner; all spines on exopodal segments accompanied with flabelliform membrane near base ( Fig. 23B ). Leg 5 ( Fig. 23C ) represented by small papilla tipped with 1 seta and plate bearing 3 setae on posterior margin of genital complex.

Male. Body ( Fig. 23D ) 3.55 mm long. Cephalic shield 2.33× 2.03 mm, resembling that of female. Genital complex fused with fourth pedigerous somite and abdomen, but discernible by lateral constrictions, 630×570 µm. Abdomen ( Fig. 23E ) 280×330 µm, gradually widened distally. Caudal ramus 115×145 µm.

Antennule armed with 29 setae on proximal segment; distal segment armed as in female. Antenna ( Fig. 23F ) with large adhesion pads on first and second segments; second segment strongly expanded proximally; third segment bearing 2 setae and 2 strong claws, one of latter with subsidiary claw. Second segment with 3 adhesion pads; third segment with 2 inner proximal setae and forming strongly curved, large claw ( Fig. 23F ). Postantennal process more slender than that of female.

A F D C B G E

Mandible and maxilla as in female. Maxillule ( Fig. 23G ) with 3 tines on posterior process. Maxilliped ( Fig. 23H ) with 1 small process subdistally on inner margin. Sternal furca as in female.

Legs 1-4 as in female. Leg 5 represented by 4 setae on lateral process ( Fig. 23E ). Leg 6 represented by 3 setae on posterior process of genital complex ( Fig. 23E ).

Etymology. The specific name gusevi is derived from the former Russian researcher A. V. Gusev who first report- ed this species as Lepeophtheirus sp.

Remarks. Gusev (1951) discovered only a single female of this species from Sebastes taczanowskii Steindachner in the Siberian coast and recorded it as Lepeophtheirus sp. His illustrations for the habitus, caudal rami, sternal furca, posterior tines of maxilla, and leg 5 are generally similar to those of our specimens.

Lepeophtheirus gusevi n. sp. bears the following key characters: 1) the exopod of leg 4 is 3-segmented, with armature formula I-0; I-0; III; 2) the maxillule of female bears 2 distal tines; 3) the female abdomen is single-segmented and slightly wider than long; and 4) the tines of the sternal furca are spatulate, with truncate distal margin. The above characters of L. gusevi are shared by five congerners, L. hummi Pearse, 1952 , L. longicaudus Cressey, 1966 , L. paralichthydis Yamaguti and Yamasu, 1960 , L. spatha Dojiri and Brantley, 1991 , and L. uluus (Lewis, 1964) . These congeners may be distinguished from L. gusevi by their features as follows.

In L. hummi and L. spatha , the tines of the female sternal furca greatly expanded distally, almost ax-like, and the terminal segment of the male antenna is simple, forming a claw. In L. longicaudus , the caudal ramus is elongated, about four times as long as wide, and the postantennary process is unusual in shape. In L. paralichthydis the caudal ramus is very small and wider than long, the abdomen is tapering, and the proximal process of the female antenna and the tines of the maxillule are spatulate. In L. uluus leg 5 of the female is elongated, extending much beyond the caudal ramus.

Figures

Fig. 21. Lepeophtheirus gusevi n. sp., female. A. habitus, dorsal. B. abdomen, dorsal. C. antennule. D. antenna. E. postantennal process. F. mandible. G. maxillule. H, I. maxilla. Scales=A. 1 mm. B, D, E, G, H. 0.2 mm. C, F, I. 0.1 mm.

Fig. 23. Lepeophtheirus gusevi n. sp., female. A. leg 4. B. juction between second and third exopodal segment of leg 4. C. leg 5. Male. D. habitus, dorsal. E. genital somite and abdomen, dorsal. F. antenna. G. maxillule. H. maxilliped. Scales=A, C, E. 0.2 mm. B, F-H. 0.1 mm. D. 0.5 mm.

Fig. 24. Anuretes quadrilaterus Shiino, female. A. habitus, dorsal. B. abdomen, ventral. C. antenna, postantennal process, and maxillule. D. maxilla. E. maxilliped. F. sternal furca. G. leg 1. H. distal part of leg 1. Scales=A. 1 mm. B, D, F-H. 0.1 mm. C, E. 0.2 mm.