Caligus aesopus Wilson, 1921

Choe, Mi-Kyung & Kim, Il-Hoi, 2010, 1921 and C. spinosus Yamaguti, 1939 (Copepoda: Siphonostomatoida: Caligidae) parasitic on amberjacks (Seriola spp.) from Korea, Zootaxa 2483, pp. 23-34 : 28-32

Caligus aesopus Wilson, 1921

( Figs 4–6 )

Caligus aesopus Wilson, 1921 , p. 72, pl. 3, fig. 8, pl. 4, figs. 11–13; Hewitt 1963, p. 71, text-figs. 4, 5; Kensley & Grindley 1973, p. 74; Fernandez & Villalba 1986, p. 40, figs. 25–49; Lin & Ho 2007, p. 42, figs. 1–3. Caligus spinosus: Shiino 1960 , p. 476, figs. 3, 4 (in part); Pillai 1963, p. 76, fig. 6.

Material examined. 1 female from the gills of Seriola lalandi Valenciennes kept in an aquarium of a seashore fish market in Kangnung, collected by I.-H. Kim, 4 June 2001; 1 female (along with 3 females of Caligus spinosus ) from gills of S. lalandi kept in an aquarium of a seashore fish market in Kangnung, collected by I.- H. Kim, 9 July 2001; 6 females and 4 males from gills of S. lalandi caught with a gill net, off Gosan (33°18΄35ʺN, 126°09΄21ʺE) on Jeju Island, collected by M.-K. Choe, 16 August 2009.

Description of female. Body ( Fig. 4 A) 4.03 mm long. Cephalothoracic shield subcircular, 1.88 × 1.89 mm; lateral zone with T-shaped ventral rib; posterior sinus deep. Fourth pedigerous somite fused with genital complex. Genital complex subtriangular, truncated posteriorly, 1.25 × 1.09 mm, with slightly angular posterolateral corners. Abdomen ( Fig. 4 B) 0.58 × 0.43 mm, 1-segmented, but usually divided by a constriction in the distal third of the lateral margin into a longer anterior part (maximum width 430 μm) and shorter posterior part (maximum width 275 μm). Caudal ramus ( Fig. 4 C) 73 × 83 μm, slightly wider than long, with 6 setae and 1 small dorsal setule.

Antennule ( Fig. 4 D) 2-segmented; proximal segment with 25 pinnate and 2 naked setae; distal segment elongated, 1.3 times longer than proximal segment, with 1 naked subterminal seta on posterior margin and 11 naked setae and 2 aesthetascs on distal margin. Antenna ( Fig. 4 E) 3-segmented; first segment with subcircular proximal process; second segment nearly quadrangular, with 1 adhesion pad; third segment forming long, distally strongly bent claw bearing 2 small setae. Postantennal process ( Fig. 4 F) moderately slender, proximally bearing 1 posterior subsidiary process and 2 papillae each with 5 or 6 setules; another papilla located posterior to postantennal process with 5 setules.

Mandible with 12 teeth distally. Maxillule ( Fig. 4 G) consisting of anterior papilla bearing 3 setae and posterior process bearing fusiform distal tine and smaller medial tine. Maxilla ( Fig. 4 H) 2-segmented; proximal segment (lacertus) unarmed; slender distal segment (brachium) with large subdistal membrane (flabellum) on inner margin; calamus about 1.8 times longer than canna. Maxilliped ( Fig. 4 I) 3-segmented; first segment (corpus) gradually narrowing distally, with small tubercle on myxal area; second segment (shaft) short, with 1 distal seta; third segment indistinctly demarcated from second, forming strongly curved claw with longitudinal surface striations. Sternal furca ( Fig. 4 J) with slender, incurved tines each with sclerotized ventral ridge.

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

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

Leg 1 ( Fig. 5 A) coxa with branched outer setule; basis with pinnate outer seta, smaller inner plumose seta, and on ventral surface small dentiform inner process and patch of numerous minute spinules. Proximal exopodal segment elongate, with 1 small outer distal seta and row of setules on inner margin; distal segment with digitiform process on distal margin; three distal spines each accompanied by flabelliform membrane; two inner distal spines bifurcating at about their midlength and distal naked seta distinctly longer than spines ( Fig. 5 B); endopod flexible, relatively long and tipped with 2 small processes. Leg 2 ( Fig. 5 C) coxa with large seta on inner posterior margin, 1 patch of spinules and 1 setule on ventral surface; basis with small outer seta, 1 inner setule, and membrane on inner part of posterior margin. First endopodal segment expanded posterolaterally, with setules on proximal part and spinules on distal part of outer margin; anterior margin of basis and outer margin of first exopodal segment with broad membrane (not illustrated in Fig. 5 C). Leg 3 ( Fig. 5 D) protopod (apron) with adhesion pads on outer surface, broad membrane on posterior margin, longitudinal patch of spinules on mid-ventral surface, and patch of 11–14 large spinules (these spinules usually truncated) on inner ventral surface; spine on first exopodal segment ( Fig. 5 E) enlarged and strongly curved; distal endopodal segment partially subdivided. Leg 4 ( Fig. 5 F) protopod expanded, 456 × 197 μm, with small outer distal seta; spines on first and second exopodal segments 112 and 97 μm, respectively; three spines on terminal segment 97, 115, and 147 μm from outer to inner; all spines on exopodal segments accompanied with flabelliform membrane near base. Leg 5 ( Fig. 4 B) represented by 1 and 3 small setae on posterolateral margin of genital complex.

Male. Body ( Fig. 6 A) 2.34 mm long. Cephalic shield resembling that of female. Genital complex ( Fig. 6 B) fused with abdomen to form fusiform genito-abdomen of 761 × 433 μm (1.76:1, excluding caudal rami), leaving incomplete suture line between them, distinctly wider than fourth pedigerous somite. Caudal ramus 86 × 85 μm, with setules on inner margin.

Antennule armed as in female, but distal segment 1.6 times longer than proximal segment. Antenna ( Fig. 6 C) 3-segmented as in female; first segment with 1 adhesion pad; second segment with 3 adhesion pads; third segment with 2 inner proximal setae and forming strongly curved, large claw. Postantennal process ( Fig. 6 D) more slender than that of female.

Mandible, maxilla, and sternal furca as in female. Maxillule ( Fig. 6 E) with adhesion pad on ventral surface of posterior process. Maxilliped ( Fig. 6 F) with 1 ventral (posterior) and 4 small inner tubercles on first segment; claw with small denticles on distal part.

Legs 1–5 as in female. Leg 6 ( Fig. 6 G) represented by 2 small setae on each posterolateral corner of genital complex.

Hosts and distribution. “ Seriola peruana ” in Juan Fernandez, Chile; S. grandis in New Zealand; S. dumerili in Taiwan; S. lalandi in Japan, Korea, South Africa and Chile; and Sphyraena obtusata Cuvier in India.

Figures

FIGURE 4. Caligus aesopus Wilson, 1921, female. A, habitus, dorsal; B, abdomen, ventral; C, caudal ramus, ventral; D, antennule; E, antenna; F, postantennal process; G, maxillule; H, maxilla; I, maxilliped; J, sternal furca. Scale bars: 0.5 mm for A; 0.1 mm for B, D, E, H, and I; 0.05 mm for C, F, G, and J.

FIGURE 5. Caligus aesopus Wilson, 1921, female. A, leg 1; B, distal part of leg 1; C, leg 2; D, leg 3; E, first exopodal segment of leg 3; F, leg 4. Scale bars: 0.1 mm for A and C – F; 0.05 mm for B.

FIGURE 6. Caligus aesopus Wilson, 1921, male. A, habitus, dorsal; B, urosome, ventral; C, antenna; D, postantennal process; E, maxillule; F, maxilliped; G, legs 5 and 6. Scale bars: 0.5 mm for A; 0.2 mm for B; 0.05 mm for C – G.