Caligus amblygenitalis Pillai, 1961

Lee, Jimin, Chang, Cheon Young & Kim, Il-Hoi, 2022, Symbiotic copepods (Cyclopoida and Siphonostomatoida) collected by light trap from Korea, ZooKeys 1115, pp. 1-71 : 1

Caligus amblygenitalis Pillai, 1961

Figs 30 , 31 , 32

Caligus amblygenigtalis Pillai, 1961: 98, figs 8, 10; Ho and Lin, 2003: 56, figs 1, 2. Caligus longipedis : Ho and Lin, 2001: 188, fig. 9 (male only).

Material examined.

Two ♀♀, 5 ♂♂ (MABIK CR00250989-CR00250995), Site 7, 21 Nov. 2019; 1 ♂, Site 11, 10 Jun. 2019.

Description.

Female. Body (Fig. 30A ) 3.06 mm long. Cephalothoracic shield 1.66 × 1.52 mm. Lunules distinct. Thoracic zone of cephalothorax distinctly extending beyond posterior ends of lateral zones. Genital complex longer than wide (619 × 479 μm), nearly rectangular, not clearly articulated from fourth pedigerous somite. Abdomen one-segmented, longer than wide (540 × 330 μm). Caudal ramus (Fig. 30B ) 2.09 × longer than wide (167 × 80 μm), with three large and three small setae; one of small setae located on ventral surface of ramus.

Antennule (Fig. 30C ) two-segmented; proximal segment 220 μm long, armed with 29 setae, two dorsal setae naked; distal segment 123 μm long, armed with 12 naked setae and two aesthetascs. Antenna (Fig. 30D ) three-segmented; first segment with narrow, pointed process; second segment unarmed, with adhesion pad on anterior surface; third segment bearing curved distal claw and one small seta on convex margin. Postantennary process (Fig. 30D ) bluntly tipped, with two papillae each bearing unbranched setule; another setule-bearing papilla on sternum posterior to process.

Mandible with 12 teeth on distal blade. Maxillule (Fig. 30D ) comprising anterior papilla bearing three setae and bluntly tipped posterior process. Post-maxillular process (indicated by arrowhead in Fig. 30D ) present postero-medial to maxillule. Maxilla (Fig. 30E ) two-segmented; proximal segment unarmed; distal segment slender, bearing hyaline membrane at distal 38% region of segment and distally with short canna and long calamus; distal half of inner margin of distal segment with fine spinules. Maxilliped (Fig. 30F ) slender, consisting of two segments and terminal claw; proximal segment proximally with sclerotized process; distal segment less than half length of proximal segment, unarmed; terminal claw short, proximally with one small seta. Sternal furca (Fig. 31A ) with widely divergent, narrow tines.

Leg 1 (Fig. 30G ) consisting of coxa, basis, two-segmented exopod and rudimentary endopod; basis with two setae (one outer and one medio-distal) and large patch of spinules on ventral surface; proximal exopodal segment with one small subdistal seta on outer margin; distal exopodal segment with three large, pinnate setae on medial margin, and four small, naked setal elements on distal margin, outer spines 1-3 each with accessory process. Leg 2 (Fig. 31B ) as usual for the genus; armature formula I-1; I-1; II, I, 5 for exopod, 0-1; 0-2; 6 for endopod. Leg 3 as Fig. 31C, D . Leg 4 (Fig. 31E ) consisting of protopod and two-segmented exopod; protopod with one small seta subdistally; proximal and distal segments of exopod armed with one and three spines, respectively. Leg 5 (Fig. 31F ) represented by two papillae; outer and inner papillae tipped with one and two small setae, respectively.

Male. Body (Fig. 32A ) 2.56 mm long. Urosome (Fig. 32B ) indistinctly four-segmented. Fifth pedigerous somite (first urosomal somite) not clearly demarcated from genital complex. Genital complex rhomboidal, 424 × 323 μm. Abdomen indistinctly two-segmented; proximal somite 95 × 195 μm; distal somite 1.63 × longer than wide (273 × 168 μm). Caudal ramus (Fig. 32C ) straight backwards, 2.39 × longer than wide (136 × 57 μm).

Antennule (Fig. 32D ) armed as in female; proximal segment 172 μm long; distal segment elongated, 184 μm long, longer than proximal segment. Antenna (Fig. 32E ) three-segmented; first segment with one corrugated pad; second segment with several corrugated pads; short third segment with one claw-like process, one leaf-like plate and one seta. Postantennary process acutely pointed, larger than that of female. Maxilliped (Fig. 32F ) with blunt protrusion tipped with corrugated pad on inner margin. Sternal furca (Fig. 31G ) with more slender tines than in female.

Leg 1 (Fig. 32H ) different from that of female in absence of spinules on basis, elongate first exopodal segment, and the lack of an accessory process on outer distal spine 1 (Fig. 32I ). Legs 2-4 as in female. Leg 5 (Fig. 32J ) as in female. Leg 6 (Fig. 32J ) represented by two small setae on genital operculum.

Remarks.

Caligus amblygenitalis was originally described by Pillai (1961) on the basis of a single female specimen from India. Subsequently, Ho and Lin (2003) redescribed this species based on a single female from Taiwan. Previously, Ho and Lin (2001) recorded one female and one male of C. longipedis Bassett-Smith, 1898 from Taiwan. However, when Venmathi Maran et al. (2009) redescribed the latter species based on females and males from Penang, Malaysia, they found that the female and the male of Ho and Lin (2001) were not conspecific. A comparison of our Korean material with the above records indicates that the male of Ho and Lin (2001) is not C. longipedis but C. amblygenitalis . Our female specimens collected by a light trap from Korea are identifiable as young adults, since they are ~ 3.0 mm long, compared to 4.14 mm long in the female of Ho and Lin (2003), and the female genital complex is immature. Caligus amblygenitalis is new to the Korean fauna. Both C. amblygenitalis and C. longipedis belong to the " C. macarovi -group" defined by Boxshall (2018).

Figures

Figure 30. Caligus amblygenitalis Shiino, 1961, female A habitus, dorsal B caudal ramus, dorsal C antennule D antenna, postantennary process, maxillule, and post-maxillular process (indicated by arrowhead) E maxilla F maxilliped G leg 1. Scale bars: 0.5 mm (A); 0.1 mm (B, D-F); 0.05 mm (C, G).

Figure 31. Caligus amblygenitalis Shiino, 1961, female A sternal furca B leg 2 C leg 3 D first exopodal segment of leg 3 E leg 4 F right genital area. Scale bars: 0.1 mm (A-C, E); 0.05 mm (D, F).

Figure 32. Caligus amblygenitalis Shiino, 1961, male A habitus, dorsal B urosome, dorsal C caudal ramus, ventral D antennule E antenna F maxilliped G sternal furca H leg 1 I distal region of leg 1 exopod J legs 5 and 6. Scale bars: 0.5 mm (A); 0.1 mm (B, F); 0.05 mm (C-E, G, H, J); 0.02 mm (I).