Asteropontoides parvus, Lee, 2025

Lee, Il-Hoi Kim and Taekjun, 2025, Ten new species of siphonostomatoid copepods (Crustacea) associated with marine invertebrates from Korea, Journal of Species Research 14 (2), pp. 146-181 : 156-160

Asteropontoides parvus n. sp. ( Figs. 7-9 )

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Type material. Holotype (intact ♀, HNIBR IV2396), intact paratypes (1 ♀, 1 ♂, HNIBR IV2397), and dissected paratypes (1 ♀, 1 ♂) from washings of various sponge species, near Beomseom, Seogwipo, Jeju Island (33°13 ʹ 28.7 ʺ N, 126°30 ʹ 46.9 ʺ E), at a depth of 20 m, SCUBA, collected by Tae Won Jung, on 20 July 2022. The holotype and intact paratypes have been deposited in the Honam National Institute of Biological Resources ( HNIBR), Mokpo. The Dissected paratypes are kept in the collection of I.-H. Kim.

Etymology. The name reflects the small body size, derived from the Latin word parv, meaning ’small’.

Female. Body ( Fig. 7A ) narrow. Body length 634 μm in dissected an figured specimen. Prosome 366 μm long, fusiform, consisting of cephalothorax and second to fourth pedigerous somites. Cephalothorax almost as long as wide (264 × 261 μm). Cephalothorax and second and third pedigerous somites with pointed or angular posterolateral corners; fourth pedigerous somite with strongly concave posterior margin and rounded posterolateral corners. Urosome ( Fig. 7B ) 4-segmented. Fifth pedigerous somite 81 μm wide. Genital double-somite 1.30 times longer than wide (95 × 73 μm), consisting of broadened proximal half and narrower distal half, widest at proximal one-fifth; genital apertures positioned dorsally at 36% region of double-somite length. Two free abdominal somites 34 × 43 and 34 × 45 μm, respectively. Anal somite with fine spinules along posteroventral margin ( Fig. 7D ). Caudal ramus ( Fig. 7C, D ) 1.43 times longer than wide (30 × 21 μm), almost rectangular, armed with 6 pinnate setae and ornamented with fine spinules along posteroventral margin.

Rostrum ( Fig. 7E ) longer than wide, beaklike, with point- ed distal apex. Antennule ( Fig. 7F ) slender, 19-segmented, but articulations between second and sixth segments incomplete, recognizable only on one side; first, nineth, eighteenth, and terminal segments with 1 seta, 7 setae, 2 setae + aesthetasc, and 12 setae, respectively; other segments with 2 setae each; aesthetasc on penultimate segment about 60% as long as total segments. Antenna ( Fig. 7G ) slender, consisting of coxa, basis, small exopod, and 3-segmented endopod; coxa short, unarmed; basis unarmed, but ornamented with minute spinules on outer margin; exopodal segment about twice longer than wide (15 × 7 μm), bearing 3 setae; first endopodal segment unarmed, 52 × 13 μm, with 1 longitudinal row of minute spinules; second endopodal segment short, with 1 seta; third endopodal segment slightly longer than wide, with 1 large distal seta (115 μm long), 1 shorter subdistal seta, and 1 row of minute spinules.

Oral siphon ( Fig. 7H ) consisting of expanded proximal quarter and slender distal three quarters, extending between legs 1 and 2. Mandible ( Fig. 7I ) consisting of stylet and 1-segmented palp; stylet thin, articulated at proximal third, 220 μm long, bearing 11 minute teeth at distal region, as arrowed in Fig. 7I ; palp 25 μm long, tipped with 2 unequal, pinnate setae, larger seta 117 μm long. Maxillule ( Fig. 7J ) consisting of 2 slender lobes; outer lobe 38 μm long, with 4 distal setae and setulose outer margin; inner lobe 55 μm long, bearing 1 minute and 3 large distal setae and several setules on inner margin. Maxilla ( Fig. 7K ) 2-segmented; proximal segment unarmed, but bearing 2 longitudinal rows of minute spinules on inner margin; distal segment thin, arched, about 1.4 times longer than proximal segment, bearing 1 seta at proximal 40% region, followed by row of minute spinules along concave margin. Maxilliped ( Fig. 8A ) slender, 5-segmented; armature formula 1, 0, 2, 2, and 1 + claw; second segment 100 μm long; fourth and fifth segments 58 and 33 μm long, respectively; terminal claw 91 μm long, with fine spinules along concave margin.

Legs 1-4 ( Fig. 8B- F ) with 3-segmented rami. Outer seta on basis naked in leg 1 but pinnate in legs 2-4. Inner distal element on basis of leg 1 as thin, naked seta. Second endopodal segment of legs 1-4 with monocuspid outer distal corner. Second exopodal segment of leg 1 with nipple-shaped outer proximal process, concave, setulose outer margin, and serrate outer distal corner ( Fig. 8C ). Second endopodal segment of legs 1-4 with 2 inner setae. Legs 3 and 4 with slender rami. Distal margin of intercoxal plate smooth in legs 1-3, but spinulose in leg 4. Armature formula for legs 1-4 as follows:

Coxa Basis Exopod Endopod Leg 1 0-1 1-1 I-1; I-1; III, 2, 2 0-1; 0-2; 1, 2, 3 Leg 2 0-1 1-0 I-1; I-1; III, I, 4 0-1; 0-2; 1, 2, 3 Leg 3 0-1 1-0 I-1; I-1; III, I, 3 0-1; 0-2; 1, I, 3 Leg 4 0-1 1-0 I-1; I-1; III, I, 3 0-1; 0-2; 1, I, 2

Leg 5 ( Fig. 8G ) consisting of short protopod and elongate exopod; protopod completed fused with somite, bearing 1 pinnated dorsodistal seta; exopodal segment 5.73 times longer than wide (63 × 11 μm), gradually broadened distally, armed distally with 3 pinnated setae, spinules on outer margin, and patch of several spinules on distal margin. Leg 6 ( Fig. 8H ) represented by 1 pinnate seta and 1 spinule on genital operculum.

Male. Body ( Fig. 9A ) resembling that of female. Body length 620 μm. Prosome 409 μm long, Anterior part of cephalothorax tapering anteriorly. Urosome ( Fig. 9B ) 5-segmented. Fifth pedigerous somite 77 μm wide, bearing spinules on ventrodistal margin ( Fig. 9D ). Genital somite quadrate, 62 × 77 μm, with scattered spinules on lateral surfaces. Three abdominal somites 41 × 53, 36× 48, and 28 × 51 μm, respectively. Caudal ramus 1.32 times longer than wide (29 × 22 μm).

Rostrum and antenna as in female. Antennule ( Fig. 9C ) 18-segmented; first, nineth, seventeenth, and terminal segments with 1 seta, 7 setae, 2 setae + aesthetasc, and 12 setae, respectively; other segments each bearing 2 setae; terminal segment characteristically attenuated distally; nineth segment inflated ventrodistally.

Antenna, oral siphon, mandible, maxillule, maxilla, maxilliped, and legs 1-4 as in female. Leg 5 ( Fig. 9D ) consisting of 1 pinnate lateral seta on fifth pedigerous somite and free exopod; exopodal segment ovoid, 20 × 13 μm, with 3 naked setae and several spinules on distal margin.

Remarks. The genus Asteropontoides comprises four acknowledged species: A. attenuatus (Thompson & Scott A., 1903) , A. elephatinus Johnson, 1998 , A. nicobaricus ( Sewell, 1949) , and A. acutirostris Kim, 2016 . The ratios of length to width of the female caudal ramus in these species are 2.5 for A. attenuatus , 0.48 for A. elephantinus , 0.8 for A. nicobaricus , and 2.37 for A. acutirostris . The female antennule is 18-segmented in A. attenuatus and A. nicobaricus , 15-segmented in A. elephantinus , and 20-segmented in A. acutirostris . With a caudal ramus that is 1.43 times longer than wide in the female and a 19-segmented female antennule, A. parvus n. sp. is easily distinguishable from the four congeners. The unique possession by A. parvus n. sp. of a digitiform outer proximal process and a serrate outer distal corner on the second exopodal segment of leg 1 is unprecedented in Asteropontoides , further distinguishing A. parvus n. sp.

Figures

Fig. 7. Asteropontoides parvus n. sp., female.A, habitus, dorsal; B, urosome, dorsal; C, left caudal ramus, dorsal; D, left caudal ramus, ventral; E, rostrum; F, antennule; G, antenna; H, oral siphon; I, mandible; J, maxillule; K, maxilla. Scale bars: A, 0.1 mm; B, H, 0.05 mm; C-G, I-K, 0.02mm.

Fig. 8. Asteropontoides parvus n. sp., female.A, maxilliped; B, leg 1; C, exopod of leg 1; D, leg 2; E, leg 3; F, leg 4; G, leg 5; H, right genital aperture, dorsal. Scale bars: 0.02mm.

Fig. 9. Asteropontoides parvus n. sp., male.A, habitus, dorsal; B, urosome, ventral; C, antennule; D, leg 5. Scale bars:A, 0.1 mm; B, C, 0.05mm; D, 0.02mm.