Caligus elongatus Nordmann, 1832

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 : 176

Caligus elongatus Nordmann, 1832

( Figs. 1 , 2 ) Caligus elongatus Nordmann, 1832, p. 24 ; Parker, 1969,

p. 1014, figs. 1-4; Hewitt, 1971, p. 163, figs. 73-78;

Kabata, 1979, p. 179, figs. 549-558.

Material examined. 2¥¥, from the skin of Lepidotrigla sp. , Samcheonpo, in the southern coast of Korea, I.- H. Kim, 20 October 2011 .

Female. Body ( Fig. 1A ) 5.62 mm long. Cephalothoracic shield subcircular, 3.23× 2.88 mm. Lateral zone with thin, slightly undulated ventral rib; shallow posterolateral pit present on dorsal surface. Thoracic zone extending beyond posterior end of lateral zone. Fourth pedigerous somite incompletely divided from genital complex. Genital complex subcircular, 1.50× 1.73 mm, wider than long. Abdomen ( Fig. 1B ) rather well defined from genital complex, 577×615 µm, and proximally narrowed. Caudal ramus 208×200 µm, with 6 setae.

Antennule ( Fig. 1C ) 2-segmented; proximal segment 406 µm long, with 27 pinnate and 2 naked setae; distal segment 252 µm long, with 11 naked setae and 2 aesthetascs. Antenna ( Fig. 1D ) 3-segmented; first segment with slender, tapering proximal process; second segment nearly quadrangular, with 1 dorsal adhesion pad; third segment forming large, distally strongly bent claw bearing 2 setae. Postantennal process ( Fig. 1E ) bearing 2 papillae each tipped with 2 or 4 setules; another papilla locat- ed posterior to postantennal process, bearing 4 setules.

Mandible ( Fig. 1F ) with 12 teeth distally. Maxillule ( Fig. 1G ) consisting of anterior papilla bearing 3 unequal setae and posterior process bearing 1 simple tine. Maxilla ( Fig. 1H ) 2-segmented; proximal segment (lacertus) unarmed; distal segment (brachium) with small membrane (flabellum) in distal 1/3 of margin; calamus less than twice as long as canna. Maxilliped ( Fig. 1I ) 3-segmented; first segment (corpus) unarmed but with 1 small, indistinct process on medial (myxal) margin; second segment (shaft) with 1 vestigial subdistal seta; third segment forming large, sharp claw bearing 1 seta at base. Sternal furca ( Fig. 1J ) narrow, with tapering, slightly divergernt tines bearing narrow lateral flanges and pointed 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. 2A ) coxa with branched small outer setule; basis with pinnate outer and inner setae. Proximal exopodal segment slightly bullate, with 1 small outer distal naked seta and row of setules on inner margin; 3 distal spines of distal segment 77, 68, and 38 µm, respectively, from outer (anterior) to inner, second and third spines bifurcate; innermost distal seta(seta IV) much longer than distal spines, weakly pinnate along outer margin but flanged with membrane along inner margin ( Fig. 2B ). Leg 2 ( Fig. 2C ) coxa with large seta on inner posterior margin 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. 2D ) exopod with first segment bearing large outer spine. Leg 4 ( Fig. 2E ) protopod slightly bullate in middle, with small outer distal seta. Exopod 2-segmented; proximal segment with 1 distal seta (83 µm long); distal segment longer than proximal segment, with 1 spine (77 µm) on outer margin and 3 spines on distal margin (78, 114, 325 µm, respectively, from outer to inner; all spines on exopodal segments accompanied with flabelliform membrane at base. Leg 5 represented by small papilla tipped by 1 seta and another neaby papilla bearing 2 setae on posterior margin of genital complex.

Male. Unknown in Korea.

Distribution and hosts. Most regions of the world’s oceans; parasitic on more than 80 species of fish ( Kabata, 1979).

Remarks. Major morphological characters of the present specimens, such as the exopod of leg 4 which is 2-segmented, with the armatures of 1 and 4 spines respectively on the proximal and distal segments, with the innermost distal spine of them being more than twice as long as nearby spine and the innermost terminal seta (fourth element) on the distal exopodal segment of leg 4 has a membrane along the inner margin, belong to C. elongatus . However, there are some characters in our specimens deviate from previous descriptions of C. elongatus ( Parker, 1969; Kabata, 1979): the abdomen is not distinctly longer than its width; the tines of sternal furca bears lateral flanges; the third distal spine of the distal exopodal segment of leg 1 is distinctly smaller than the second spine. We consider these differences to be less important than the former major similarities. Although C. elongatus has been recorded from most part of the world ( Parker, 1969; Kabata, 1979), it has so far not been reported from the Far Eastern region.

Figures

Fig. 1. Caligus elongatus Nordmann, female. A. habitus, dorsal. B. abdomen, ventral. C. antennule. D. antenna. E. postantennary process. F. mandible. G. maxillule. H. maxilla. I. maxilliped. J. sternal furca. Scales=A. 1 mm. B. 0.2 mm. C-J. 0.1 mm.

Fig. 2. Caligus elongatus Nordmann, female. A. leg 1. B. distal part of exopod of leg 1. C. leg 2. D. leg 3. E. leg 4. Scales=0.1 mm for all.