Asterocheres nodulosus, Lee, 2024

Lee, Il-Hoi Kim and Taekjun, 2024, Copepods of the genus Asterocheres Boeck, 1859 (Siphonostomatoida: Asterocheridae) from Korean waters, Journal of Species Research 13 (2), pp. 185-254 : 232-236

publication ID	https://doi.org/ 10.12651/JSR.2024.13.2.185
persistent identifier	https://treatment.plazi.org/id/ED1887CB-FFD1-FFDF-FCF8-B191B254638A
treatment provided by	Felipe
scientific name	Asterocheres nodulosus
status	sp. nov.

Treatment

Asterocheres nodulosus n. sp. ( Figs. 30-32 View Fig View Fig View Fig )

https://zoobank.org/urn:lsid:zoobank.org:act:C3D1431

D-8821-4AE6-AF00-F40D8D5787CE

Type material. Holotype (♀, NIBRIV0000909865 ), intact paratypes (15♀♀, 5♂♂, NIBRIV0000909866 ), and dissected paratypes (1♀, 1♂) from mixed species of sponges, Ulleung Island (approximately 37°32 ʹ 25 ʺ N, 130°50 ʹ 50 ʺ E), depth about 20 m, SCUBA diving, coll. J. Lee. 29 August 2018 GoogleMaps . Holotype and intact paratypes have been deposited in the National Institute of Biological Resources ( NIBR), Incheon, Korea. Dissected paratypes are kept in the collection of I.-H. Kim .

Etymology. The specific name refers to the nodule-like proximal expansion of the medio-distal seta of the third endopodal segment of male leg 2.

Female. Body form ( Fig. 30A View Fig ) as usual for genus. Body length 793 μm in figured and described specimen. Other 4 measured specimens 695, 730, 755, and 840 μm, respectively. Prosome 549 μm long. Cephalothorax wider than long (364 × 436 μm). All prosomal somites with rounded posterolateral corners. Urosome ( Fig. 30B View Fig ) 4-segmented. Fifth pedigerous somite wider than genital double-somite, with spinules on lateral surfaces. Genital double-somite slightly wider than long (108 × 110 μm); genital apertures positioned dorsolaterally at 47% region of double-somite length; postgenital lateral margin bearing 2 groups of spinules consisting of 13 or 14 thin spinules of anterior group and 4 thicker spinules of posterior group ( Fig. 31F View Fig ). Two free abdominal somites 36× 66 and 38 × 58 μm, respectively. Genital double-somite and first free abdominal somite bearing row of minute spinules along posterodorsal margin. Anal somite with row of spinules along posteroventral margin ( Fig. 30C View Fig ). Caudal ramus 1.08 times longer than wide (28× 26 μm), armed with 6 setae and ornamented with few scales on outer and inner margins and row of spinules on posteroventral margin.

Rostrum ( Fig. 30D View Fig ) as tapering ridge between antennules, without defined distal apex. Antennule ( Fig. 30E View Fig ) 320 μm long, 21-segmented; 9th, 18th, 20th, and terminal segments with 7 setae, 2 setae + aesthetasc, 4 setae, and 7 setae, respectively; other segments each with 2 setae. First segment with several spinules on anterior margin; some of setae on anterior segments pinnate; one of setae on 9th and 19th segments with crack-like transverse lines; some of setae on proximal segments truncated and tipped with minute setule. Antenna ( Fig. 30F View Fig ) consisting of coxa, basis, small exopod, and 3-segmented endopod; coxa with several spinules on outer margin; basis with longitudinal row of needle-like minute spinules near outer margin and few spinules on inner margin; first endopodal segment 57 μm long, with setules on outer margin; small second endopodal segment bearing 1 seta; third endopodal segment bearing 2 setae, 1 spinule-like, minute seta; terminal claw spiniform, 54 μm long.

Oral siphon ( Fig. 30G View Fig ) 197 × 65 μm, extending slightly over insertions of maxillipeds. Mandible ( Fig. 30H View Fig ) consisting of coxal stylet and palp; stylet 180 μm long, bearing row of 12 teeth at distal region; palp 1-segment- ed, 56 μm long, tipped with 1 long (159 μm long) and 1 shorter (68 μm long) setae, both setae weakly pinnate; palp plus longer distal seta 1.19 times longer than stylet. Maxillule ( Fig. 30I View Fig ) bilobed; inner lobe about 59 μm long, tipped with 4 large and 1 rudimentary setae (lengths of 4 large setae 83, 85, 75, and 50 μm, respectively, from inner to outer); outer lobe 21 μm long tipped with 4 setae, lengths of these 4 setae 65, 65, 45, and 25 μm, respectively. Maxilla ( Fig. 30J View Fig ) 2-segmented; proximal segment (syncoxa) bearing excretory tube and row of fine spinules at proximal region; distal segment (basis) as long as proximal segment bearing 1 group of setules at distal third and row of minute spinules along distal third. Maxilliped ( Fig. 30K View Fig ) consisting of coxa, basis, and 4-segmented endopod; coxa with 1 small seta subdistally on inner margin and several minute spinules at outer distal corner; basis unarmed but with minute spinules on outer margin; endopodal segments with 2, 1, 1, and 1 setae, respectively. Terminal segment 35 μm long and terminal claw of 61 μm long.

Legs 1 ( Fig. 31A View Fig ), 2 ( Fig. 31B View Fig ), 3, and 4 ( Fig. 31D View Fig ) with 3-segmented rami. Leg 3 similar to leg 2 except bearing 1 spine and 5 setae on third endopodal segment ( Fig. 31C View Fig ). Intercoxal plate of legs 1-3 with small spinules, but smooth in leg 4. Inner coxal seta of leg 1 small but pinnate, that of leg 4 naked, rudimentary. Out- er seta on basis of leg 1 elongated, that of leg 4 short. Inner distal margin of basis of leg 1 bearing spinules. Armature formula for legs 1-4 same as that of A. processus n. sp.

Leg 5 ( Fig. 30B View Fig ) represented by 1 dorsolateral seta on fifth pedigerous somite and free exopod; exopodal segment ( Fig. 31E View Fig ) 2.14 times longer than wide (47 × 22 μm), bearing spinules on convex inner and outer margins and armed with 3 unequal setae; lengths of these setae 58, 38, and 22 μm, respectively, from outer to inner; longer outermost seta pinnate, other setae naked. Leg 6 ( Fig. 31F View Fig ) represented by 1 pinnate seta and 1 denticle on genital operculum.

Male. Body ( Fig. 32A View Fig ) narrower than that of female. Body length 655 μm. Prosome 430 × 297 μm. Urosome ( Fig. 32B View Fig ) 5-segmented. Fifth pedigerous somite 85 μm wide. Genital somite globular, 91 × 120 μm, bearing spinules on lateral surfaces. Three abdominal somites 22 × 56, 21 × 51, 30 × 50 μm, respectively. Caudal ramus 22 × 23 μm.

Rostrum as in female. Antennule ( Fig. 32C View Fig ) 18-segmented, with weak geniculation between 15th and 16th segments and strong geniculation between 16th and 17th segments; 9th, 13th, 17th, and terminal segments with 7 setae, 2 setae+ aesthetasc, 2 setae + aesthetasc, and 10 setae, respectively; other segment with 2 setae each; first segment with setules and spinules on anterior margin. Antenna as in female.

Oral siphon, mandible, maxillule, maxilla as in female. Maxilliped ( Fig. 32D View Fig ) with beak-like proximal process on inner margin of basis.

Legs 1 and 4 as in female. Endopods of legs 2 and 3 different from those of female. Third endopodal segment of leg 2 ( Fig. 32E View Fig ) with mediodistal seta bearing nodule-like proximal expansion and outer distal seta reduced in size. Third endopodal segment of leg 3 ( Fig. 32F View Fig ) with hook-like, curved outer distal process and 2 small denticles medial to outer distal process.

Exopodal segment of leg 5 ( Fig. 32G View Fig ) 2.17 times longer than wide (26 × 12 μm), shaped and ornamented as that of female, bearing 2 pinnate distal setae and 1 naked mediodistal seta; lengths of these setae 43, 34, and 21μm long, respectively, from outer to inner. Leg 6 ( Fig. 32H View Fig ) consisting of 2 unequal setae on spinulose outer distal region of genital operculum.

Remarks. Asterocheres nodulosus n. sp. appears to be most similar to three congeners: A. fici n. sp., sharing 14 same character states in 17 characters with the new species, and A. aesthetes and A. horridus each sharing 13 same character states in 17 characters with the new species (see Table 2). These three species are distinguished from the new species by the following features:

Asterocheres aesthetes has caudal rami of the female which are wider than long and a 2-segmented mandibular palp. Asterocheres fici n. sp. has the terminal claw of the female antenna which is distinctly longer than the first endopodal segment and the exopodal segment of female leg 5 which is 2.83 times longer than wide. Asterocheres horridus has a longer oral siphon which extends to leg 1, a 2-segmented mandibular palp, and the exopodal segment of female leg 5 which is 2.90 times longer than wide ( Kim, 2016).

The distinctiveness of the above three species and A. nodulosus n. sp. can be confirmed by their different forms of legs 2 and 3 of the male, as follows: (1) in the third endopod of male leg 2, the outer distal process is expanded with a small tubercle in A. aesthetes , thinned in A. horridus , and slightly curved in A. fici n. sp. and A. nodulosus n. sp.; (2) in the third endopodal segment of male leg 3, the outer distal process is slightly curved in A. aesthetes , A. fici n. sp., and A. nodulosus n. sp., but not modified in A. horridus ; (3) the outer distal seta of the third endopodal segment of male leg 3 is minimized in A. fici n. sp. and A. nodulosus n. sp. but normal in A. aesthetes and A. horridus ; and finally, the presence of a nodule-like proximal expansion on the inner distal seta of the third endopodal segment of male leg 2 is a unique feature of A. nodulosus n. sp., which is easily observable under the microscope without dissection.