Asterocheres horridus, 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 : 407-412

publication ID	https://doi.org/ 10.12651/JSR.2016.5.3.393
persistent identifier	https://treatment.plazi.org/id/96353C58-E76A-FFB0-FC8E-FB32FEE3F928
treatment provided by	Felipe
scientific name	Asterocheres horridus
status	sp. nov.

Treatment

Asterocheres horridus View in CoL n. sp. ( Figs. 10-12 View Fig View Fig View Fig )

Material examined. 23$$, 8♂♂ from a sponge genus Poecillastra , off Mumseom in Seogwipo (approximately 33°12′35″N, 126°34′10″E), Jeju Island, in the depth of 45 m, 03 October 2013, collected by S.H. Kim. Holotype ($, NIBRIV0000680732 ), allotype (♂, NIBRIV000068 0787), and paratypes (20$$, 6♂♂, NIBRIV00006807 88) have been deposited in NIBR, Incheon, Korea. Dissected paratypes (2$$, 1♂) are retained in the collection of the author. GoogleMaps

Female. Body ( Fig. 10A View Fig ) small and moderately broad. Length of dissected and described paratype 621 μm (other 3 measured specimens 615, 646, and 669 μm long, respectively). Prosome oval, 434 μm long. Cephalothorax wider than long, 282 × 332 μm, with angular posterolateral corners. Second and third pedigerous somites with narrow marginal membrane along lateral margins. Urosome ( Fig. 10B View Fig ) 4segmented. All urosomal somites heavily ornamented with spinules and scales on all surfaces ( Fig. 10B, C View Fig ). Fifth pedigerous somite 77 μm wide, with row of fine spinules along posterodorsal margin. Genital doublesomite as long as wide, 88 × 88 μm, with lateral, postgenital protrusion bearing about 1012 spinules (56 longer anterior and 56 shorter posterior spinules) ( Fig. 11H View Fig ); genital area located dorsolaterally slightly anterior to halfway of lateral margin of doublesomite. Two abdominal somites 23 × 46 and 26 × 44 μm, respectively. Anal region distinct. Caudal ramus almost rectangular, 23 × 20 μm, 1.15 times as long as wide, and armed with 6 plumose setae.

Rostrum ( Fig. 10D View Fig ) small, indistinct, and abruptly narrowing in middle, with obscure posterior apex. Antennule ( Fig. 10E View Fig ) 343 μm long and 21-segmented; armature formula 2, 2, 2, 2, 2 / 2, 2, 2, 7, 2 / 2, 2, 2, 2, 2 / 2, 2, 2 + aesthetasc, 2, 3, and 7 + aesthetasc; about half of setae on proximal segments plumose, some of them truncate and tipped with 2 or 3 fine spinules. Antenna ( Fig. 10F View Fig ) with short, unarmed coxa. Basis about 55 μm long, with 2 longitudinal rows of needlelike spinules near base of exopod. Exopod small 12 × 5 μm, armed with 1 proximal and 2 unequal, distal setae. Endopod 3 segmented; first segment 57 μm long, with spinules and setules; second segment short, with 1 seta distally; terminal segment armed with 2 setae and 1 spiniform claw of 60 μm long.

Oral siphon ( Fig. 10G View Fig ) narrow, 254 μm long, 55 μm wide at widest proximal region, and extending to intercoxal plate of legs 1. Mandibular stylet ( Fig. 10H View Fig ) slender, 177 μm long, with about 10 fine teeth distally. Mandibular palp ( Fig. 10I View Fig ) 2segmented; proximal segment setulose, 38 μm long; distal segment about 1/3 as long as proximal segment, 12 μm long, with 2 unequal apical setae of 138 and 74 μm long, respectively. Combined length of palp and longer seta 188 μm, slightly longer than stylet. Maxillule ( Fig. 10J View Fig ) bilobed; inner lobe 70 × 18 μm, setulose, widest at proximal third, and distally armed with 5 setae (including minute one), 3 of which being elongate, equal in length, 169 μm long, about 2.4 times as long as inner lobe; small outer lobe 20 × 6.5 μm and armed with 4 setae distally, all of them being distinct, longest one of them 92 μm long. Maxilla ( Fig. 11A View Fig ) consisting of syncoxa and basis; syncoxa with transparent tube of maxillary gland proximally; basis narrow and clawlike, with 1 linguiform extension proximally, 1 minute seta at proximal third, and spinules along distal 2/5. Maxilliped ( Fig. 11B View Fig ) 6segmented; syncoxa with 1 thin, inner distal seta and outer distal patch of setules; basis with 1 minute seta at proximal 0.44 region of inner margin, row of spinules on inner margin distal to inner seta, and several spinules near middle of outer margin; endopod 4segmented and armed with 2, 1, 1, and 1 + claw, respectively; terminal claw 68 μm long, more than twice as long as terminal segment.

Legs 14 ( Fig. 11 View Fig CF) with 3segmented, spinulose rami; outer distal corner of second endopodal segment bicuspid. Inner seta on coxa of legs 13 plumose, that of leg 4 rudimentary and naked. Intercoxal plate of legs 14 with thick setules on lateral sides. Outer margin of first and second exopodal segment of leg 1 setulose but that of legs 2-4 spinulose. Outer spine of first exopodal segment of leg 1 large, 35 μm long. Terminal spine on leg 3 endopod 44 μm long, that of leg 4 59 μm long. Armature formula for legs 14 as in A. lilljeborgi .

Leg 5 bimerous; protopod with 1 dorsolateral seta; exopod ( Fig. 11G View Fig ) 44 × 16 μm, 2.75 times as long as wide, heavily spiniferous on all surfaces, and armed with 3 (2 distal and 1 subdistal) plumose setae. Leg 6 represented by 2 small setae in genital aperture ( Fig. 11H View Fig ).

Male. Body ( Fig. 12A View Fig ) 547 μm long and narrower than that of female. Prosome 385 μm long. Cephalothorax 265 × 274 μm. Urosome ( Fig. 12B View Fig ) 5segmented. Fifth pedigerous somite 70 μm wide. Genital somite nearly circular, 75 × 95 μm, with spinules (or scales) on all surfaces. Three abdominal somites spinulose along posteroventral and posterodorsal margins, 13 × 42, 10 × 39, and 21× 39 μm, respectively. Caudal ramus 18 × 18 μm, as long as wide.

Rostrum as in female. Antennule ( Fig. 12C View Fig ) 18segmented; armature formula 2, 2, 2, 2, 2 / 2, 2, 2, 8, 2 / 2, 2, 2 + aesthetasc, 2, 2 / 3, 2 + aesthetasc, and 12. One of 2 setae on first to fourth and sixth segments blunt and tipped with 2-4 fine spinules. Thirteenth segment characteristically with 1 small aesthetasc. Penultimate segment with beaklike anterodistal process. One of seta on terminal segment inserted on proximal part of terminal seta. Antenna as in female.

Oral siphon, mandible, maxillule, and maxilla as in female. Maxilliped ( Fig. 12D View Fig ) with beaklike inner proximal process; inner seta on this segment minute and inserted on conical process.

Legs 14 as in female, except for narrowed and curved outer and outer distal processes of third endopodal segment of legs 2 and 3 ( Fig. 12E View Fig ).

Leg 5 exopod ( Fig. 12F View Fig ) 29 × 10 μm. Leg 6 represented by 2 unequal setae on genital operculum ( Fig. 12B View Fig ).

Etymology. The specific name horridus is from the Latin horrid, meaning prickly, and alluding to the densely spinulescovered body surface.

Remarks. Asterocheres horridus n. sp. displays two outstanding features. First, the thirteenth segment of the male antennule has an aesthetasc. Second, three of five setae on the inner lobe of the maxillule are equally elongate, more than twice as long as the lobe.

The first outstanding feature of the new species is shared by four congeners: A. spinosus Kim and Min, 2013 ; A. urabensis Kim, 2004 ; A. walteri Kim, 2004 ; and A. boecki sensu Giesbrecht (1899) . Of these A. boecki sensu Giesbrecht is particularly noticeable, because, according to the illustration of Giesbrecht (1899), the genital doublesomite in the female of his specimen has an inflated area on the lateral margins posterior to genital area, as in the new species. But Stock (1960) already treated A. boecki sensu Giesbrecht (1899) as nonconspecific with A. boecki (Brady, 1880) and gave a new name A. complexus Stock, 1960 for it. Recently, Bandera and Conradi (2014) reexamined the type specimens of A. complexus . In their illustration of the mandible, the stylet has five relatively large teeth, a condition quite different from that of A. horridus n. sp. Other three species are easily differentiated from A. horridus n. sp., because A. spinosus has a caudal ramus which is distinctly longer than wide (1.88 time as long as wide in the female, according to Kim and Min, 2013), A. urabensis has an elongate exopod of leg 5, which is 3.65 times as long as wide in the female ( Kim, 2004), and A. walteri has four enlarged setae on the outer lobe of the maxillule ( Kim, 2004).

The second outstanding feature is shared by A. genodon Stock, 1966 (See Kim 2010), A. stimulans Giesbrecht, 1897 (See Giesbrecht, 1899), and probably A. boecki (Brady, 1880) . As differences from A. horridus n. sp., A. genodon has a caudal ramus bearing a ventral seta, as mentioned by Kim (2010) and Bandera and Conradi (2013), A. boecki has a prominent rostrum bearing round ed distal apex and a tapering exopod of leg 5 in the female, according to the illustrations of G.O. Sars (1914). Asterocheres stimulans is difficult to be compared with A. horridus n. sp. because of its incomplete description. Giesbrecht (1899) illustrated some morphological features for the female and male of A. stimulans , but Bandera and Huys (2008) explains that the male A. stimulans of Giesbrecht (1899) is in reality the male of A. mucronipes which is the type species of the genus Stockmyzon Bandera and Huys, 2008 they established. The morphological informations of A. stimulans given by Giesbrecht (1899) are only of the habitus, urosome, antennule, maxillule, maxilla, and maxilliped of the female. Of these, only the maxilliped seems to reveal characteristic feature usable to differentiate it from A. horridus n. sp. In this appendage of A. stimulans the inner margin of basis (second segment) is smooth, without any seta or spinules (a seta and a row of spinules present in A. horridus n. sp.), and the terminal claw is much longer and more slender than that of A. horridus n. sp., about three times as long as terminal segment (less than 2.5 times in A. horridus n. sp.).