Chelipygus bulbosus, 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 : 403-406

Chelipygus bulbosus gen. et sp. nov.

( Figs. 267 , 268 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21337 ) , paratypes (2 intact ♀♀, MNHN-IU-2014-21338), anddissectedparatype (♀, figured) from Molgula amesophleba (Codreanu & Mack-Fira, 1956) , Etang de Leucate on Mediterranean coast of France, Clanzig coll., 1985.

Etymology. The specific name refers to the bulbous prosome of the new species.

Descriptionoffemale. Body ( Fig. 267A ) slightly compressed: bodylength 3.40 mm. Prosome 2.45 mm long, consisting of small cephalosome with well defined cephalic shield and strongly inflated, unsegmented metasome. Metasome bulbous, gradually broadening posteriorly; entire metasome forming brood pouch. Free urosome ( Fig. 267B ) 5-segmented, cylindrical, gradually narrowing distally: genital and 4 abdominal somites 158×406, 297×358, 273×320, 176×273, and 158×230 μm, respectively. Anal somite with deep posteromedian incision. Caudal ramus ( Fig. 267C ) evenly tapering distally, 3.9 times longer than wide (293×75 μm) and 1.85 timeslongerthan anal somite: armedwith 2 naked setae (outer proximal and dorsal) and 4 distal spines; outer proximal and dorsal setae short (less than half width width of ramus at base), located at 29 and 63% of ramus length, respectively; 4 distal spines ( Fig. 267D ) small, conical, largest 15 μm and smallest 11 μm long.

Rostrum ( Fig. 267E ) 158×198 μm, consistingof broad, steeply tapering proximal third, weakly tapering in distal two-thirds towards blunt apex. Antennule ( Fig. 267F ) 303 μm long, 9-segmented; first and second segments markedly broader than more distal segments; armatureformula 3, 16, 6, 4+aesthetasc, 4, 2+aesthetasc, 2, 2+aesthetasc, 7+aesthetasc; first segment ornamented with proximal patch of minute spinules on anterior surface; 2 large pinnate setaeon first segment, all other setae naked and much smaller. Antenna ( Fig. 267G ) 4- segmented; coxa unarmed; basis 98×53 μm, with 1 small seta distally; first endopodal segment 76×55 μm, with 1 smallseta subdistally; compounddistalendopodal segment 88×35 μm, armedwith 8 smallsetae (arranged as 1, 3, 1, and 3) plusterminal claw about 60 μm long, 0.68 times as long as segment.

Labrum ( Fig. 267H ) with large, semicircular posteromedianlobe. Mandible ( Fig. 267I ) with 5 teeth and 1 small seta on coxal gnathobase, distalmost tooth acutely pointed; basis with 1 seta subdistally on medial margin; exopod with 5 setae, 2 distal setae shorter than proximal 3; endopod indistinctly articulated from basis, armed with 4 and 9 setae on first and second segments, respectively; 2 distal setae on second segment distinctly longer than other setae. Paragnath ( Fig. 268A ) with scattered spinules on apex and dense setules on medial margin. Maxillule ( Fig. 267J ) with 9 setaeon arthrite, 1 broad, blunt seta on coxal endite, 2 unequal setae on epipodite, 3 subequal setae on medial margin of basis, 4 setae on exopod (outer seta distinctly larger than medial 3), and 2 setae on endopod; endopod much smaller than exopod. Maxilla ( Fig. 268B ) armedwith 9 setaeon syncoxa (arranged as 3, 1, 2, and 3), 3 on basis, and 1, 1, and 4 on first to third endopodal segments, respectively; distal setaon basis about half as long as middle seta; 2 of 4 setae on third endopodal segment small and naked. Maxilliped ( Fig. 268C ) incompletely 2-segmented; first segment with 9 setae medially; short second segment with 2 setae apically.

Legs 1–4 with 3-segmented rami ( Fig. 268 D-F). Inner coxal seta of legs 1–4 large, extending to distal tip of endopod. Outer seta on basis of leg 1 broad, sclerotized, and tipped with thin flagellum ( Fig. 268D inset). Inner distal spine on basis of leg 1 short, 45 μm long, not reaching distal border of first endopodal segment. Outer setae on exopod of leg 1 and all setae on third exopodal segment of legs 2–4 naked and shorter than inner setae on exopod. Inner and distal setae on third endopodal segment of legs 2–4 also naked and shorter than inner setae on endopod. Armature formula for legs 1–4 as follows:

	Coxa Basis Exopod			Endopod
Leg 1	0-1	1-I	I-1; I-1; III, I, 4	0-1; 0-1; 1, 2, 3
Legs 2 & 30-1		1-0	1-1; 1-1; 3, 1, 5	0-1; 0-2; 1, 2, 3
Leg 4	0-1	1-0	1-1; 1-1; 2, 1, 5	0-1; 0-1; 1, 2, 2

Leg 5 ( Fig. 268G ) protopod wider than long, not articulated with somite, with small seta on outer margin and row of small spinules distally; free exopodal segment about 3.2 times longer than wide (136×42 μm), armed distally with slender spine (33 μm long) and thin seta (66 μm long), ornamented with 3 rows of minute spinules on dorsomedial surface.

Male. Unknown.

Remarks. The 3-segmented condition of the endopods of legs 2–4 seems to be the most prominent feature separating the type species from its two congeners, C. catalai and C. dinardensis gen. etsp. nov. described below, both of which have 2-segmented endopods. The presence of 4 setae on the third endopodal segment of the maxilla is another distinguishing feature of C. bulbosus gen. et sp. nov., since the other two species both have only 3 setae on this segment.

Figures

FIGURE 267. Chelipygus bulbosus gen. et sp. nov., female. A, habitus, right; B, urosome, ventral; C, right caudal ramus, ventral; D, distal tip of caudal ramus; E, rostrum; F, antennule; G, antenna; H, labrum; I, mandible; J, maxillule. Scale bars: A, 0.5 mm; B, 0.2 mm; C, E–J, 0.05 mm; D, 0.02 mm.

FIGURE 268. Chelipygus bulbosus gen. et sp. nov., female. A, paragnath; B, maxilla; C, maxilliped; D, leg 1, with inset showing outer basal seta; E, leg 2; F, leg 4; G, leg 5. Scale bars: A, 0.02 mm; B, C, G, 0.05 mm; D–F, 0.1 mm.