Chelipygus dinardensis, 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 : 406-409

Chelipygus dinardensis gen. et sp. nov.

( Figs. 269 , 270 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21339 ) anddissectedparatype (♀, figured) from Molgula bleizi (Lacaze-Duthiers, 1877) (MNHN-IT-2008-5425 = MNHNS 3/ MOL.A/206), La Rance, Dinard, France, Monniot coll., 1982.

Additionalmaterial. 2 ♀♀ (MNHN-IU-2018-1876) from M. bleizi, Morgat ; 1 ♀ (MNHN-IU-2018-1877) and 1 dissected ♀ from M. bleizi, Morgat ; 1 ♀ (MNHN-IU-2018-1878) from M. complanata Alder & Hancock, 1870 , Carteret; 1 ♀ (MNHN-IU-2018-1879) from M. citrina Alder & Hancock, 1848, Dinard; 1 ♀ (dissected) from M. complanata , Saint-Vaast-La-Hougue. France.

Etymology. The name of the type locality, Dinard on the Atlantic coast of France, is the basis for the specific name of the new species.

Descriptionoffemale. Body ( Fig. 269A ) strongly compressed laterally: bodylength 3.26 mm. Prosome consistingof small cephalosome with well developed dorsalshieldandunsegmented,dorsallyinflatedmetasome. Metasome not divided, lacking any trace of suture lines or constrictions, entire metasome forming brood pouch. Dorsal inflation of metasome variable according to reproductive status of individual female, 2.01×1.72 mm in lateral view in strongly inflated specimen ( Fig. 269A ). Freeurosome ( Fig. 269B ) short, 5-segmented. Genital somite characteristically with large, robust posteroventral protuberance (indicated by arrowhead in Fig. 269B ) with rounded tip in middle of distal margin. Caudal ramus ( Fig. 269C ) graduallynarrowing distally, 3.8 times longerthan wide (179×47 μm) and about 1.3 timeslongerthan anal somite: armedwith 2 setae (outer proximal and dorsal) and 4 small distal spines; outer proximal and dorsal setae positioned at 35 and 70% of ramus length, respectively, about half as long as width of ramus at base; distal spines conical, atmost 15μmlong, bluntly tipped.Spermatophore ( Fig. 270A ) detached from female elliptical, 91×45 μm.

Rostrum ( Fig. 269D ) subtriangular, 108×103 μm, slightly longerthan wide, with gently tapering proximal three quarters and tapering more steeply in distal quarter. Antennule ( Fig. 269E ) 274 μmlong, 8-segmented; first and second segments much broader than distal segments; armatureformula 3, 17, 9+aesthetasc, 3, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; 2 large setae on first segment pinnate, all other setae naked. Antenna ( Fig. 269F ) stout, 4-segmented; coxa unarmed; basis 75×55 μm, unarmed; first endopodal segment 64×54 μm, with small seta subdistally on medial side; compound distal endopodal segment markedly narrower than proximal segments, graduallynarrowing distally, about 2.1 times longerthanwide (73×35 μm); armedwith 9 setae (arranged as 1, 3, 2, and 3) plusterminal claw about 65 μm long, only slightly shorter than segment.

Labrum ( Fig. 269G ) with setulose posterior margin and large, setulose posteromedian lobe. Mandible ( Fig. 269H ) with 5 teeth and 2 small setae on gnathobase: basiswith 1 setaat mediodistal corner; exopod with 5 setae; 3 proximal setae equally large; fourth seta shorter, (half length of proximal setae), distalmost seta vestigial (arrowhead in Fig. 269H ); endopod 2-segmented, incompletely articulated from basis; first segment with 4 setae on medial margin; second segment distinctly narrowerthan first, armedwith 9 setae. Maxillule ( Fig. 269I ) with 9 setae on arthrite, 1 broad, blunt seta on coxal endite, 2 unequal setae on epipodite, 3 setae on medial margin of basis (proximal seta slightly shorter than distal 2), 4 setae on exopod (3 equally long medial and 1 longer outer), and 2 setaeon endopod. Maxilla ( Fig. 270B ) armedwith 9 setaeonsyncoxa (arranged as 3, 1, 2, and 3), 3 setae on basis (distal seta 0.7 times length of middle seta), and 1, 1, and 3 setae, respectively, on first to third endopodal segments. Maxilliped ( Fig. 270C ) incompletely 2-segmented, articulation present on only one surface; armed with 9 setae on first and 2 setae on short second segment.

Leg 1 ( Fig. 270D ) with 3-segmented rami. Outer seta on basis naked, thinner (flagellate) in distal third. Inner distal spine on basis 42 μm long, spinulose, extending to distal border of first endopodal segment. Legs 2–4 with 3-segmented exopods and 2-segmented endopods ( Fig. 270E, F ); exopods slightly longerthan endopods. Inner seta on coxa relatively longer than in leg 1. Outer and distal setae on exopods naked. Distalsetae on endopods naked and shortened. Armature formula for legs 1–4 as follows:

	Coxa	Basis	Exopod	Endopod
Leg 1	0-0	1-I	I-1; I-1; II, 2, 3	0-1; 0-1; 1, 2, 2
Leg 2	0-0	1-0	1-1; 1-1; 3, 1, 4	0-1; 0-1; 1, 2, 3
Leg 3	0-0	1-0	1-1; 1-1; 2, 1, 4	0-1; 0-1; 1, 2, 3
Leg 4	0-0	0-0	1-1; 1-1; 2, 1, 3	0-0; 0, 2, 1

	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, 1, 2, 5
Leg 4	0-1	1-0	1-1; 1-1; 2, 1, 5	0-1; 1, 2, 4

Leg 5 ( Fig. 270G ) protopod indistinctly articulated from somite, broad, with seta on outer margin and row of spinules on distal border; free exopodal segment about 1.9 times longerthanwide (98×52 μm), gradually narrowing distally, with slightly irregular margins; armed distally with small, spiniform medial seta (18 μm long) and longer outer seta (47 μm long); ornamented with 3 rows of spinules on dorsomedial surface.

Male. Unknown.

Remarks. The large ventrodistal protuberance on the genital somite seems to be the most distinctive feature of Chelipygus dinardensis gen. et sp. nov. It is unique and serves to differentiate it not only from its congeners but also from species of closely related genera. The small size of the distalmost seta on the apex of the mandibular exopod is also a characteristic feature, distinguishing C. dinardensis gen. et sp. nov. from both of its congeneric species.

Figures

FIGURE 269. Chelipygus dinardensis gen. et sp. nov., female. A, habitus, right; B, urosome, right, showing posteroventral protuberance (arrowhead); C, right caudal ramus, lateral view with inset showing detail of armature at tip; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible showing vestigial seta on exopod (arrowhead); I, maxillule. Scale bars: A, 0.5 mm; B, 0.1 mm; C–I, 0.05 mm.

FIGURE 270. Chelipygus dinardensis gen. et sp. nov., female. A, spermatophore; B, maxilla; C, maxilliped; D, leg 1; E, leg 2; F, leg 4; G, leg 5. Scale bars: 0.05 mm.