Doroixys obesa, 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 : 486

Doroixys obesa sp. nov.

( Figs. 322 , 323 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21373 ) from Polyclinum isipingense Sluiter, 1898 (MNHN-IT-2008-XXX = MNHN A1/POL.B/108), ATIMOVATAE TR07, Madagascar (25°01 Ń, 47°00 É), depth 12-16 m, MNHN coll., 01 May 2010 .

Etymology. The specific name refers to the obese body form of the female.

	Coxa	Basis	Exopod	Endopod
Leg 1	0-0	1-I	I-1; 1-1; 3, 1, 3	0-1; 0-1; 1, 2, 3
Leg 2	0-0	1-0	1-0; 1-0; 3, 1, 5	0-0; 0-0; 0, 2, 3
Leg 3	0-0	1-0	1-0; 1-0; 3, 1, 5	0-0; 0-0; 0, 2, 1
Leg 4	0-0	1-0	1-0; 1-0; 3, 1, 4	0-0; 1, 2, 0

Descriptionoffemale. Body ( Fig. 322A ) stout, ventrally curved; bodylength 1.01 mm. Prosome 808 μm long: dorsal cephalic shield expanded ventrolaterally, with small, paired, dorsally curved horn-likeprocesses ( Fig. 322D ) posterolaterally. Freeurosome ( Fig. 19B ) 5-segmented. Caudalramus ( Fig. 322C ) about 3.2 times longer than wide (89×28 μm) and about twice as long as anal somite, with almost parallel lateral margins and rounded distal margin, ornamented with many scattered setules: armedwith 6 setae (outer lateral, dorsal, and 4 distal) outer lateral and dorsal setae positioned in same plane at 60% length of ramus; all caudal setae small, less than half width of ramus at base.

Rostrum ( Fig. 322E ) large, 95×53 μm, proximal third with parallel lateral margins, distal two-thirds tapering towards blunt apex. Antennule ( Fig. 322F ) stout, strongly tapering, 9-segmented, but articulation between seventh and eighth segments incomplete; armature formula 2, 13, 5, 2+aesthetasc, 2, 3, 2, 2, and 7; all setae naked. Antenna ( Fig. 322G ) stout, 3-segmented, comprisingunarmed coxa and basis and unsegmented endopod; endopod about 2.5 times longer than wide (42×17 μm) and about 0.8 times as long as basis: armedwith 1 middle and 2 distalsetae plus terminal claw, half as long as endopod.

Labrum ( Fig. 322H ) simple, with narrow setulose posterior margin. Mandible ( Fig. 322I ) with broadened coxal gnathobase bearing 5 teeth and 1 seta; basis with 1 seta: exopod 2-segmented; first segment armed with 2 equal, large setae; secondsegment with 2 equal, distal setae and 1 small outer seta (about half as long as larger setae): endopod with 1 and 5 setaeon first and second segments, respectively; all setae short, subequal in length. Maxillule ( Fig. 322J ) armedwith 9 setaeon arthrite, 2 unequal setae on epipodite, 1 on basis, 4 on exopod, and 3 on endopod; coxal endite absent. Maxilla ( Fig. 323A ) 4-segmented; syncoxa bearing 4, 2, and 2 setae on first to third endites, respectively; basis with smooth claw plus 1 seta; endopod small, lacking setaon first segment, with 3 setae on second segment. Maxilliped ( Fig. 323B ) lobate, armedwith 6 subequal setae.

Legs 1–3 ( Fig. 323 C-E) with 3-segmented rami. Leg 4 ( Fig. 323F ) with 3-segmented exopod and 2- segmented endopod; second endopodal segment of leg 4 elongate, about 4.2 times longer than wide (54×13 μm), 3.5 times longer than first endopodal segment. Inner coxal seta absent on all swimming legs. Inner distal spine of basis of leg 1 small, 12 μm long. Second exopodal segment of leg 1 bearing outer seta (instead of spine). All setae on swimming legs naked, except feebly pinnate (or spinulose) setae on third exopodal segment of leg 3. Leg 4 asymmetical: outer setae on exopod of left leg 4 slender (as on leg 3), but setae on right leg 4 broad and spiniform ( Fig. 323F ). Armature formula for legs 1–4 as follows:

Leg 5 ( Fig. 322B ) represented by 2 tapering, pointed posteroventral processes on surface of somite; outer process smaller; inner exopodal process larger, armed with 1 small seta on outer margin.

Male. Unknown.

Remarks. This is the first species of Doroixys to be characterised by the possession of a 3-segmented antenna, comprising coxa, basis, and an unsegmented endopod, although additional new species sharing the same kind of 3-segmented antenna are described below. Doroixys obesa sp. nov. is unique within the genus in the absence of a seta on the first endopodal segment of the maxilla. Other unusual features include the endopod of the mandible is armed with 6 equal, short setae (1 on first and 5 on second segment, respectively) rather than setae of dissimilar lengths, and the maxillule bears 2 setae on the epipodite rather than the typical single seta. These features are sufficient to distinguish the new species from its congeners.

Figures

FIGURE 19. Notodelphys tenera Thorell, 1859, female. A, habitus, right; B, anal somite and caudal rami, dorsal; C, rostrum; D, antenna; E, mandible; F, maxillule; G, maxilla; H, maxilliped; I, leg 5. Scale bars: A, 0.5 mm; B, C, 0.1 mm; D–I, 0.05 mm.

FIGURE 322. Doroixys obesa sp. nov., female. A, habitus, right; B, leg 5 and urosome, ventral; C, left caudal ramus, dorsal; D, posterolateral process of cephalic shield; E, rostrum; F, antennule; G, antenna; H, labrum; I, mandible; J, maxillule. Scale bars: A, 0.1 mm; B, D, 0.05 mm; C, E–J, 0.02 mm.

FIGURE 323. Doroixys obesa sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 3; F, leg 4. Scale bars: 0.02 mm.