Doropygus callosus, Kim & Boxshall, 2020

Kim, Il-Hoi & Boxshall, Geoff A., 2020, Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata), Megataxa 4 (1), pp. 1-6 : 388-391

Doropygus callosus sp. nov.

( Figs. 257 , 258 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21328 ) , paratypes (3 intact ♀♀, MNHN-IU-2014-21329), and dissected paratypes (2 ♀♀, figured) from Eusynstyela floridana (Van Name, 1921) (MNHN-IT-2008-4366 = MNHNS 1/ POL.A/11), Basse-Terre, Guadeloupe, depth 20 m, J. Vacelet coll., 07 April 1981.

Etymology. Thespecific name isfrom the Latin callo (=thick-skinned) and refers to the thick sclerotization of the body.

Descriptionoffemale. Body ( Fig. 257A ) stout, slightly compressed. Bodylength 2.55 mm: prosome 2.10 mm long. Dorsal cephalic shield well-defined. Metasome obscurely 4-segmented, broadening posteriorly. Fourth pedigerous somite strongly expanded to form brood pouch, as long as anterior part of prosome and 1.2 times longer than wide in lateral view, with rounded posterior margin. Freeurosome ( Fig. 257B ) well-sclerotized, 5- segmented: genitalsomitenarrowing posteriorly, 120×240 μm; 4 abdominalsomites 143×202, 102×200, 59×184, and 91×139 μm, respectively. First abdominal somite broaderposteriorly.Anal somite with short posteromedian incision. Caudal ramus ( Fig. 257C ) about 3.2 times longer than wide (194×61 μm) and more than twice as long as anal somite, heavily sclerotized, with rounded swelling proximally on ventral margin: armed with 6 small setae, all less than 0.2 times as long as ramus and shorter than maximum width of ramus.

Rostrum ( Fig. 257D ) small, weak, 103×82 μm, tapering towards rounded apex. Antennule ( Fig. 257E ) relatively slender, about 260 μm long, 9-segmented; armatureformula 2, 16, 6, 2+aesthetasc, 3, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; setae crowded, many densely pinnate. Antenna ( Fig. 257F ) 4-segmented; coxa short; basis 102×47 μm, unarmed; first endopodalsegment 68×44 μm, also unarmed; compounddistalendopodal segment slender, 3.3 times longerthan wide (86×26 μm); armed with 4 setae (1 subdistal and 3 distal) plus strongly curved terminal claw, 50 μm long, 0.58 times as long as segment.

Labrum( Fig.257G )withlarge,smoothposteromedian lobe and setulose posterior margin. Mandible ( Fig. 257H ) with 5 teeth and 2 smallproximal setae on coxal gnathobase; basiswith 1 setaonmedial margin; exopod slender, armedwith 4 large, subequal setae; endopod armed with 4 and 8 setae on first and second segments, respectively; outermost distal seta on second endopodal segment about half as long as adjacent seta. Paragnath ( Fig. 257I ) with distinct outer subdistal lobule and dense setules on medial margin. Maxillule ( Fig. 257J ) armedwith 9 setae on arthrite, 1 on coxal endite, 2 on epipodite, 3 on medial margin of basis, 3 on exopod and 2 on endopod; seta on coxal endite about twice as long as wide. Maxilla ( Fig. 258A ) armedwith 9 setaeonsyncoxa, 3 on basis, and 1, 1, and 3 on first to third endopodal segments, respectively; distal setaon basis 0.8 times as long as middle seta. Maxilliped ( Fig. 258B ) incompletely 2-segmented with 9 setaeonfirst segment and 2 large setae on short second segment.

Leg 1 ( Fig. 258C ) with 3-segmented rami. Outer seta on basis evenly attenuated. Inner distal spine on basis 52 μm long, extending to middle of second endopodal segment, with serrate margins. Legs 2–4 with 3-segmented exopods and 2-segmented endopods ( Fig. 258D, E ), but with compound second endopodal segment bearing trace of suture line as vestige of original segmentation. Outer seta on basis small and naked. Inner coxal seta of leg 4 large, pinnate, only slightly shorter than that of legs 2 and 3. Outer setae on exopods naked; all other setae pinnate. Armature formula for legs 1–4 as in D. corsu sp. nov.

Leg 5( Fig.258F )extendingtomiddleof genital somite: protopod unornamented, but armed with outer margin seta; free exopodal segment elongate, about 4.3 times longer than wide (136×32 μm) with nearly parallel margins; armed distally with 2 unequal setae, and ornamented with 5 rows of minute spinules on dorsomedial surface.

Legs 2 & 3	0-1	1-0	1-1; 1-1; 3, 1, 5	0-1, 1, 2, 5
Leg 4	0-1	1-0	1-1; 1-1; 3, 1, 5	0-1; 1, 2, 4

Male. Unknown.

Remarks. Doropygus callosus sp. nov. shares the possession of a maxillule bearing 3 setae on the exopod and 2 setae on the endopod with D. reductus , D. schellenbergi , and D. corsu sp. nov. It is distinguishable from D. reductus by the possession of a 4-segmented abdomen (cf. 3-segmented abdomen in D. reductus ), 4 setae on the first endopodal segment of the mandible (cf. 2 setaein D. reductus ), 11 setaeon the maxilliped (cf. 9 setae in D. reductus ), and a 3-segmented endopod on leg 1 (cf. 2-segmented in D. reductus ). It can be separated from D. schellenbergi by the possession of short setae on the caudal ramus (according to Illg, 1958, the longest distal caudal seta in D. schellenbergi is more than a third as long as ramus), and 11 setae on the maxilliped (10 or fewer in D. schellenbergi ). Finally, D. callosus sp. nov. can be distinguished from D. corsu sp. nov. by the possession of long, pinnate setae on the antennule (setae short and naked in D. corsu sp. nov.), 8 setae on the second endopodal segment the mandible (9 setae in D. corsu sp. nov.), a thin, evenly attenuating outer seta (seta flagellate distally in D. corsu sp. nov.) on the basis of leg 1, and in having a narrower exopodal segment on leg 5.

Figures

FIGURE 257. Doropygus callosus sp. nov., female. A, habitus right; B, urosome, ventral (caudal rami omitted); C, left caudal ramus, dorsal; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, paragnath; J, maxillule. Scale bars: A, 0.2 mm; B, 0.1 mm; C–F, H, 0.05 mm; G, I, J, 0.02 mm.

FIGURE 258. Doropygus callosus sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 4; F, leg 5. Scale bars: 0.05 mm.