Lepeophtheirus parvulus Shiino, 1952

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 : 199

Lepeophtheirus parvulus Shiino, 1952

( Figs. 17 , 18 )

Lepeophtheirus parvulus Shiino, 1952, p. 105 , fig. 12.

Material examined. 4¥¥, 2JJ from Sebastiscus marmoratus (Cuvier and Valenciennes) , at Donggwi, Jeju Island, M.-K. Choe, 2 August 2009 ; 1¥, 1J from S. marmoratus , at Aeweol in Jeju Island, M.-K. Choe, 30 September 2009 .

Female. Body ( Fig. 17A ) 3.88 mm long. Cephalothoracic shield subcircular, 2.27× 2.17 mm; lateral zone with simple, curved ventral rib; posterolateral pit present on dorsal surface. Thoracic zone extending over posterior end of lateral zone. Genital complex nearly circular, 1.15 × 1.25 mm. Abdomen 1-segmented, wider than long, and 233×287 µm. Caudal rami slightly convergent; each ramus 108×94 µm, 1.15 times as long as wide, with 6 setae, including small subdistal one on outer margin.

Antennule ( Fig. 17C ) 381 µm long and 2-segmented; proximal segment occupying 73% length of antennules, with 28 pinnate; distal segment with 12 naked setae and 2 aesthetascs. Antenna 3-segmented ( Fig. 17D ); first segment with proximal process; second segment nearly quadrangular, with 1 adhesion pad; third segment forming large, distally strongly bent claw bearing 2 small setae. Postantennal process bearing 2 papillae each tipped with 4 or 5 setules ( Fig. 17D ); another papilla located posterior to postantennal process also tipped with 5 setules.

Mandible with 12 teeth distally. Maxillule consisting of anterior papilla bearing 3 unequal setae and posterior process bearing ramified tine ( Fig. 17D ). Maxilla ( Fig. 17E ) 2-segmented; proximal segment (lacertus) unarmed; distal segment (brachium) curved in middle; flabellum located near middle of inner margin and divided into proximal and distal parts; calamus and canna very long, the former about twice as long as the latter. Maxilliped ( Fig. 17F ) 3-segmented; first segment (corpus) with slightly uneven inner margin; second segment (shaft) short, with 1 distal seta; third segment forming curved claw and longer than second segment. Sternal furca ( Fig. 17G ) with slightly divergent tines; each tine weakly tapering, 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; I-1; III,4; endopod 0-1; 6

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

Leg 1 ( Fig. 17H ) basis with pinnate outer and inner setae. Proximal exopodal segment expanded, widest in proximal one-third, with 1 small outer distal seta and row of setules on inner margin; distal segment with 2 flabelliform membrane on distal margin; two inner distal spines bifurcating distally; distal seta pinnate; endopod flexible and tipped with 2 small processes. Leg 2 ( Fig. 18A ) coxa with large seta on inner posterior margin and 1 small setule on ventral surface; basis with small outer seta and 1 inner setule and membrane on inner part of posterior margin; first endopodal segment with setulose membrane on outer margin; outer spines on exopod large, with membranous flanges on margins). Leg 3 ( Fig. 18B ) exopod 3- segmented; first exopodal segment with 3 setules on outer margin and large distal spine. Leg 4 ( Fig. 18C ) protopod narrow, with small outer distal seta; 3-segmented exopod slender; its first segment with 1 minute setule on outer margin and 1 small distal seta (22 µm long); second segment longest among segments, with distal seta of 88 µm long; 3 spines on third segment 96, 177, and 273 µm long, respectively, from outer to inner; innermost one longer than segment. Leg 5 represented by papilla tipped by 1 seta and plate bearing 3 setae on posterolateral margin of genital complex.

Male. Body ( Fig. 18D ) 2.30 mm long. Cephalic shield resembling that of female, 1.35× 1.34 mm. Urosome ( Fig. 18E ) small. Genital complex 370×342 µm. Abdomen 1- segmented and 121×175 µm, gradually broadened distally. Caudal ramus 113×83 µm, 1.36 times as long as wide.

Antennule similar to that of female. Antenna ( Fig. 18F ) 3-segmented; first segment with 1 large adhesion pad; second segment greatly expanded proximally, with several adhesion pads; third segment with 2 inner proximal setae and forming strong claw bearing 2 subsidiary claws. Postantennal process with fewer setules on papillae.

Mandible and maxilla as in female. Maxillule ( Fig. 18G ) with 1 additional, hyaline, aesthetasc-like process on inner side. Maxilliped ( Fig. 18H ) with 1 small process subdistally on ventral margin and 2 patches of granules on inner distal side. Sternal furca as in female.

Legs 1-4 as in female. Leg 5 represented by 4 small setae on lateral process of genital complex ( Fig. 18E ). Leg 6 represented by 3 small setae on each posterior process on genital flap ( Fig. 18E ).

Distribution and host. Only from Sebastiscus marmoratus (Cuvier and Valenciennes) in Japan ( Shiino, 1952) and Korea (present study).

Remarks. This is the second record for Lepeophtheirus parvulus . The distinguishing features of this species may be as follows: 1) the distal segment of maxilla has a curvature in the middle; 2) the tines of sterna furca are blunt at tip; 3) leg 1 is stout, with two mid-terminal spines being bifurcate at tip; 4) the first exopodal segment of leg 3 bears 3 setules; and 5) the plate of leg 5 extends over posterior margin of genital complex.

Figures

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.

Fig. 18. Lepeophtheirus parvulus Shiino, female, A. leg 2. B. leg 3. C. leg 4. Male. D. habitus, dorsal. E. genital somite and abdomen, dorsal. F. antenna. G. maxillule. H. maxilliped. Scales=A-C, E-H. 0.1 mm. D. 0.5 mm.