Asterocheres cuspis, Kim, 2016

Kim, Il-Hoi, 2016, Siphonostomatoid copepods (Crustacea) mainly associated with marine invertebrates from Korean waters, Journal of Species Research 5 (3), pp. 393-442 : 412-416

publication ID	https://doi.org/ 10.12651/JSR.2016.5.3.393
persistent identifier	https://treatment.plazi.org/id/96353C58-E777-FFB4-FF59-F92FFBBDFA66
treatment provided by	Felipe
scientific name	Asterocheres cuspis
status	sp. nov.

Treatment

Asterocheres cuspis View in CoL n. sp. ( Figs. 13-15 View Fig View Fig View Fig )

Material examined. One $, 1♂ from a sponge of the genus Myxilla , off Nogok (37°12′02″N, 129°20′38″E) in Samcheok on the eastern coast of Korea, 22 December 2005. Holotype ($, NIBRIV0000723569 dissected and mounted on a glass slide) has been deposited in NIBR, Incheon, Korea. Dissected paratypes (1♂) is retained in the collection of the author. GoogleMaps

Female. Body ( Fig. 13A View Fig ) tapering distally, 1.00 mm long. Prosome 704 μm long, with greatest width of 530 μm. Cephalothorax expanded, spherical, with rounded anterior and lateral margins. Third pedigerous somite (second metasomite) with nippleshaped posterolateral corners. Fourth pedigerous somite tapering laterally, with nippleshaped lateral apices. Urosome ( Fig. 13B View Fig ) 4segmented. Fifth pedigerous somite 138 μm wide. Genital doublesomite 117 × 133 μm, with broader anterior half bearing rounded lateral margins and narrower, weakly tapering posterior half; lateral margin near genital area with about 15 spinules, several posterior ones of which being longer than anterior ones. First and second abdominal somites 60 × 72 and 50 × 63 μm, respectively. Anal somite with spinules along posteroventral margin. Genital doublesomite and abdominal somites covered by scales on dorsal and ventral surfaces. Caudal ramus ( Fig. 13C View Fig ) 31 × 30 μm, nearly as long as wide, with spinules along posterior margin, longer outer margin and shorter inner margin, and armed with 6 setae; inner dorsal seta naked, other 5 setae plumose.

Rostrum absent. Antennule ( Fig. 13D View Fig ) 442 μm long and 20segmented; armature formula 2, 2, 2, 2, 2 / 2, 2, 2, 7, 2 / 2, 2, 2, 2, 2 / 2, 2, 2 + aesthetasc, 2, and 11; first segment with several minute spinules on anterior margin and armed with 2 unequal, plumose setae; terminal segment with indistinct transverse line as rudiment of articulation. Antenna ( Fig. 13E View Fig ) with short, umarmed coxa; basis 100 μm long, with longitudinal row of minute pectens along distal 3/5 of basis. Exopod 17 × 7 μm, 2.43 times as long as wide, narrow proximally, with 1 small lateral and 2 unequal distal setae. Endopod 3segmented; first segment 75 μm long, unarmed, but ornamented with fine spinules along outer margin; short second segment with 1 blunt seta distally. Terminal segment with 2 distal setae and terminated by claw of 70 μm long.

Oral cone ( Fig. 13F View Fig ) evenly tapering, 188 × 100 μm, extending to base of maxilliped. Mandible ( Fig. 13G View Fig ) consisting of stylet and palp. Stylet 170 μm long, distally bifurcated, with finely denticulated tips. Palp indistinctly 2-segmented; first segment 55 μm long; second segment 28 μm long, with 2 unequal setae distally, longer one of them 165 μm long and shorter one 55 μm long; palp, together with longer seta, distinctly longer than stylet. Maxillule ( Fig. 13H View Fig ) bilobed. Inner lobe 74 × 29 μm, about 2.6 times as long as outer lobe and armed distally with 5 larger setae: 1 minute seta, 1 mediumsized seta (53 μm long), and 3 larger, setules-tipped setae of equal length (about 83 μm long). Outer lobe 29 × 10 μm, with 4 setae distally (108, 104, 67, and 30 μm long, respectively). Maxilla ( Fig. 13I View Fig ) 2segmented; syncoxa with transparent tube and row of spinules proximally; basis represented by claw bearing minute spinules in distal region. Maxilliped ( Fig. 14A View Fig ) 6segmented. Syncoxa with 1 small, subdistal seta, 1 small, pointed process at inner distal corner, and row of fine spinules on outer distal and inner proximal regions. Basis 122 × 38 μm, with few spinules on outer margin. Endopod 4segmented and armed with 2, 1, 1, and 1 setae, on first to fourth segments, respectively; terminal claw 80 μm long.

Legs 14 with 3segmented rami. Second endopodal segment of legs 14 with bicuspid outer distal corner ( Fig. 14 View Fig BE). Legs 13 with inner setae on coxa ( Fig. 14B, C View Fig ), but leg 4 lacking this seta ( Fig. 14E View Fig ). Intercoxal plate of leg 1 with spinules on both sides of distal margin, but that of legs 24 unornamented. Inner distal corner of basis of legs 14 with spinules. Leg 3 different from leg 2 in armature of third endopodal segment ( Fig. 14C, D View Fig ). Leg 4 without inner seta on coxa, otherwise, armature formula for legs 14 as typical for genus.

Leg 5 represented by dorsolateral seta on fifth pedigerous somite and free exopod; exopod ( Fig. 14F View Fig ) suboval, 49 × 29 μm, 1.69 times as long as wide, heavily spinulose on both dorsal and ventral margins, and armed with 2 distal setae (58 and 48 μm long, respectively) and 1 ventral seta (34 μm long). Leg 6 represented by 2 unequal setae in genital aperture ( Fig. 14G View Fig ).

Male. Body ( Fig. 15A View Fig ) similar in shape to that of female, 830 μm long. Cephalothorax 346 × 377 μm. Urosome ( Fig. 15B View Fig ) 5segmented. Fifth pedigerous somite 113 μm wide. Genital somite 128 × 183 μm, wider than long, with several spinules on lateral margin. Three abdominal somites equal in length, 35 × 72, 35 × 58, and 35 × 50 μm, respectively. Caudal ramus 25 × 27 μm, slightly wider than long.

Rostrum absent as in female. Antennule 410 μm long, 17segmented, and geniculate between antepenultimate and penultimate segments; armature formula 2, 2, 2, 2, 2 / 2, 2, 2, 7, 2 / 2, 4, 2, 2, 2 / 1 + aesthetasc, and 11; one of setae on nineth segment truncated and bifurcated at tip; twelfth segment slightly swollen. Antenna as in female.

Oral cone, mandible, maxillule, maxilla as in female. Maxilliped( Fig. 15D View Fig ) shaped as that of female, but inner distal seta on syncoxa mounted on prominent, papillalike swelling; basis without any process on inner margin.

Leg 1 as in female. Legs 2 and 3 different from those of female in having slightly enlarged and curved distal process on third exopodal segment ( Fig. 15E, F View Fig ). Leg 4 as in female.

Leg 5 exopod 33 × 17 μm, 1.94 times as long as wide; two distal setae spinulose, 60 and 37 μm long, respectively; ventral seta 28 μm long and distally plumose. Leg 6 represented by 2 equal setae on genital operculum ( Fig. 15B View Fig ).

Etymology. The scientific name is taken from cuspis (Latin, meaning a point), alluding to the pointed distal process on the syncoxa of the maxilliped.

Remarks. Asterocheres cuspis n. sp. has a unique feature that allows it to differentiate from all congeners: the possession of a small cusp at inner distal corner of the syncoxa of the maxilliped in both sexes. No species in Asterocheres has been reported to have this cusp.

The new species can be compared with congeners in different ways. It has, as a combination of three diagnostic features, 2segmented mandibular palp, no inner seta on the coxa of leg 4, and a relatively short oral cone extending only to the base of the maxilliped. Thus, species having 1segmented mandibular palp or an inner seta on the coxa of leg 4 or a longer oral cone (or siphon) which is extended beyond the base of the maxilliped are exclud ed from a comparion with the new species. After this screening, 17 species are remained. The caudal ramus of A. cuspis n. sp. is slightly longer than wide. Thus the species having a caudal ramus which is distinctly longer than wide (more than 1.2 times as long as wide) or distinctly shorter than wide (less than 0.9 times as long as wide) can be further excluded from the comparison with the new species. There are three finally remaining species: A. dysideae Humes, 1996 , A. honkongensis Malt, 1991 , and A. nudicoxus Kim, 2010 . Differences of these three species from A. cuspis n. sp. are follows:

In A. dysideae recorded from the Moluccas, the caudal ramus has a ventral seta, the prosome and oral cone are very broad, and the caudal ramus has a large pointed hyaline posteroventral process ( Humes, 1996).

In A. hongkongensis recorded from Hong Kong, the body is small (0.50 mm long in the female), the antennule of the female is 19segmented with an aesthetasc on the penultimate segment, and the exopod of leg 5 is extending beyond the level of the genital aperture ( Malt, 1991).

In A. nudicoxus known from Madagascar, the oral cone is very broad, the exopod of leg 5 is elongate, more than 6 times as long as wide in the female, the posteroventral margins of the genital doublesomite and abdominal somites are crenate ( Kim, 2010)