Asterocheres quadridens, 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 : 420-423

Asterocheres quadridens n. sp. ( Figs. 19 , 20 )

Material examined. Two $$ from washings of intertidal invertebrates, at Seogwipo (33°14′20″N, 126°33′ 33″E) in Jeju Island , 17 September 2005. Holotype ($, legs 5 detached, NIBRIV0000681226 ) has been deposit­ ed in NIBR, Incheon, Korea. Dissected paratype (1$) is retained in the collection of the author.

Female. Body ( Fig. 19A ) broad and 941 μm long. Prosome expanded laterally. Cephalothorax 220 × 586 μm, much wider than long, with angular posterolateral corners and rounded anterior and lateral margins. Second and third pedigerous somites 105 × 468 and 109 × 423 μm, respectively, with blunt posterolateral corners. Third pedigerous somite 275 μm wide, with deeply concave posterior margin. Urosome ( Fig. 19B ) 4­segmented. Fifth pedigerous somite 157 μm wide. Dorsal and ventral surfaces of genital double­somite and abdominal somites ornamented with scales. Genital double­somite 140 × 155 μm, with 1 prominent dentiform process at distal fifth of lateral margin and about 12, rather thick setules on lateral margin near genital aperture; genital aperture located dorsolaterally slightly posterior to halfway of lateral margin. First and second abdominal somites 38 × 98 and 53 × 94 μm, respectively. Anal somite with ser­ rate membrane on inner side of ventrodistal margin ( Fig. 19C ). Caudal ramus ( Fig. 19C ) wider than long, 28 × 39 μm (length/width ratio 0.72: 1), characteristically armed with 7 setae including 1 naked, large whip­like seta on ventral surface (indicated by arrowhead in Fig. 19C ), and ornamented with 2 large, transparent, leaf­like lamellae on ventrodistal margin. Largest inner median distal seta (seta V) distinctly expanded proximally. Innermost distal seta (seta VI) markedly reduced, spinule­like.

Rostrum short, much wider than long, with rounded posterior margin. Antennule ( Fig. 19D ) 374 μm long and 20­segmented; armature formula 1, 2, 2, 2, 2 / 2, 2, 2, 6, 2 / 2, 2, 2, 2, 2 / 2, 2, 2 + aesthetasc, 2, and 12; one of setae on terminal segment inserted on proximal part of terminal seta. One of 2 setae on third and fifth segments minute, setule­like. One of 2 setae on second to fourth segments truncate and tipped with setule. Antenna ( Fig. 19E ) with short, unarmed coxa. Basis unarmed but spinulose in distal half. Exopod small, 7 × 5 μm, armed with 1 lateral and 2 distal setae. Endopod 3-segmented; first segment 75 × 17 μm, unarmed but spinulose; short second segment with 1 distal seta; distal segment with 2 setae and slender, spiniform terminal claw of 97 μm long.

Oral siphon 395 μm long, slender, and extending beyond intercoxal plate of legs 1 but not reaching leg 2. Mandible consisting of stylet and palp. Stylet ( Fig. 19F ) slender, 384 μm long, consisting of broader proximal 1/3 and thread­like distal 2/3, with 4 broad teeth or tooth­like processes distally ( Fig. 19G ). Palp ( Fig. 19F, H ) 2­ segmented; proximal segment 40 μm long; distal segment 15 μm long, tipped with 2 unequal setae of 193 and 54 μm long, respectively. Combined length of palp and longer distal seta distinctly shorter than stylet. Maxillule ( Fig. 20A ) bilobed. Inner lobe 88 × 28 μm with row setules laterally and 5 naked distal setae, including 1 minute seta; remaining 4 setae 287, 280, 158, and 75 μm long, respectively. Small outer lobe 28 × 8 μm and armed with 3 naked setae of 87, 75, and 35 μm long, respectively. Maxilla ( Fig. 20B ) slender, consisting of unarmed syncoxa and claw like basis bearing 1 minute seta at proximal fourth, transverse row of setules near middle, and row of fine spinules along distal 2/3 of concave margin. Maxilliped ( Fig. 20C ) 6­segmented; syncoxa with 1 inner seta distally; basis with 1 minute seta at 0.6 region of inner margin and few spinules on outer margin; endopod armed with 2, 1, 1, and 1 setae on first to terminal segment, respectively; terminal segment 48 μm long; terminal claw 110 μm long, more than twice as long as terminal segment, with fine spinules along concave margin.

Legs 1­4 with 3­segmented rami, with armature formula as in preceding species. Inner seta on coxa well­developed and plumose in legs 1­3, but rudimentary in leg 4 ( Fig. 20G ). Inner distal corner of leg 1 basis projected and tapered ( Fig. 20D ). Second endopodal segment of legs 1­4 with bicuspid outer distal corner ( Fig. 20 D­G). Distal spine on third endopodal segment of legs 3 and 4 slightly shorter than segment ( Fig. 20F, G ).

Leg 5 consisting of 1 naked dorsolateral seta on fifth pedigerous somite and free exopod; exopod ( Fig. 20H ) elongate, 109 × 24 μm (length/width ratio 4.54: 1), gradually narrowing distally, with spinules along both margins and 2 distal and 1 subdistal setae of subequal lengths, all of these setae shorter than exopod segment. Leg 6 represented by 2 minute setae on genital operculum ( Fig. 19B ).

Male. Unknown.

Etymology. This specific name quadridens is from Latin words quadr (= four) and dens (= tooth), alluding to the presence of the four distal teeth on the mandibular stylet.

Remarks. Asterocheres quadridens n. sp. is very similar to A. genodon Stock, 1966 which was recorded from the Indian Ocean and Red Sea ( Stock, 1966a; 1966b). It was redescribed by Kim (2010), based on the specimens from Madagascar, and Bandera and Conradi (2013) re­examined type specimens. Asterocheres quadridens n. sp. and A. genodon share several features that are unusual for Asterocheres , as follows: (1) the caudal ramus has a ventral seta ( A. dysideae Humes, 1996 also has a ventral seta on the caudal ramus); (2) the mandibular stylet consists of broader proximal third and thin distal two­thirds, with four distal teeth (or tooth­like processes); (3) the genital double­somite in the female with tooth­like process on the lateral margin posterior to the genital aperture; and (4) the exopod of leg 5 is elongate. Nevertheless, they are different species, because, according to Kim (2010), in A. genodon (1) the caudal ramus is longer than wide (vs. wider than long in A. quadridens n. sp.), with outer margin longer than inner margin(vs. both margins similar in length); (2) the antennule is 21­segmented (vs. 20-segmented) and its first segment is armed with 2 setae (vs. 1 seta); (3) the outer lobe of the maxillule is armed with 4 setae (vs. 3 setae); (4) the inner distal corner of the basis of leg 1 is rounded (vs. tapered); and (5) the exopod of leg 5 is 3.77 times as long as wide (vs. 4.54 times) and armed with 3 unequal setae (vs. 3 subequal setae).

Figures

Fig. 19. Asterocheres quadridens n. sp., female. A, habitus, dorsal; B, urosome, dorsal; C, right caudal ramus, ventral; D, antennule; E, antenna; F, mandible; G, distal part of mandibular stylet; H, mandibular palp. Scale bars: A, 0.1 mm; B, D­F, 0.05mm; C, H, 0.02mm; G, 0.01 mm.

Fig. 20. Asterocheres quadridens n. sp., female.A, maxillule; B, maxilla; C, maxilliped; D, leg 1; E, leg 2; F, third endopodal segment of leg 3; G, leg 4; H, leg 5 exopod. Scale bars: 0.05 mm.