Doroixysatlantica sp. nov.

(Figs. 312, 313)

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21365), paratypes (2 intact ♀♀, MNHN-IU-2014- 21366), and dissected paratypes (2 ♀♀, figured) from Morchellium argus (Milne Edwards, 1841), Brest, France, date unknown.

Additionalmaterial. 4 ♀♀ (MNHN-IU-2018-1901) and 2 dissected ♀♀ from M. argus, Dinard, France; 3 ♀♀ (MNHN-IU-2018-1902) from M. argus, Dinard; 2 ♀♀ (MNHN-IU-201801903) from M. argus, Tatihou, France; 1 ♀ (MNHN-IU-2018-1904) and 1 dissected ♀ from unknown host.

Etymology. The Atlantic Ocean, the distributional range of the ascidian host Morchellium argus is taken for the specific name of the new species.

Descriptionoffemale. Body (Fig. 312A) curved ventrally. Bodylength of dissected largest specimen 1.86 mm; prosome 1.51 mm long. Dorsal cephalic shield bearing prominent, claw-likeprocesses (Fig. 312C) at posterolateral corners. Metasome unsegmented, but 4 pedigerous somite boundaries indicated by 3 transverse wrinkles on dorsal surface; fourth pedigerous somite globular, forming brood pouch. Freeurosome (Fig. 312B) stout, 5-segmented: genital and 4 abdominal somites 42×146, 38×133, 46×115, 31×100, and 71×117 μm, respectively. Articulation between third abdominal and anal somites incomplete. Anal somite broadening distally, with broad posteromedian incision. Caudal rami widely divergent; each ramus (Fig. 312D) about 2.5 times longer than wide (79×32 μm), gradually narrowing distally, setulose, with rounded distal margin: armed with 6 setae (1 outer, 1 dorsal, and 4 distal), all setae small, less than half width of ramus at base; outer and dorsal setae positioned at 62 and 68% of ramus length, respectively.

Rostrum(Fig.312E)longerthanwide(82×52μm),with slightly convex lateral margins; tapering towards truncate apex; setulose along distal third. Antennule (Fig. 312F) 133 μm long, 9-segmented; 3 distal segments obscurely defined by indistinct articulations; armature formula 2, 13, 4, 3+aesthetasc, 2, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; all setae naked; aesthetascs small. Antenna (Fig. 312G) stout, 4-segmented; proximal 3 segments unarmed; compound distal endopodal segment 2.5 times longer than wide (42×17 μm) and as long as first endopodal segment: armedwith 6 setae (arranged as 1, 2, and 3) plus stout terminal claw, about half as long as segment.

Labrum (Fig. 312H) denselysetulose posteriorly; posteromedian lobe broad and densely setulose. Mandible (Fig. 312I) withbroadcoxalgnathobasebearing 5 teeth and 1 proximal seta; basiswith 1 seta on medial margin; exopod short, armedwith 5 setae, outermost seta smallest, about one-third as long as adjacent seta; endopod 2- segmentedwith 1 and 5 setaeon firstandsecondsegments, respectively; outer subdistal seta on second endopodal segment much smaller than other 4 setae. Maxillule (Fig. 312J) armed as usual: 9 setae on arthrite, 1 on epipodite, 1 on basis, 4 on exopod and 3 on endopod; endopodal setae equal in length. Maxilla (Fig. 312K) 4-segmented; syncoxa with 4, 2, and 2 setae on first to third endites, respectively; basis with 2 unequal setae plusstrong claw bearing spinules along distal half of concave margin; endopod small, 2- segmented with 1 and 3 setae on first and second segments, respectively. Maxilliped (Fig. 313A) as unsegmented lobe bearing 6 setae.

Legs 1–4 with 3-segmented rami (Figs. 313 B-D); articulation between first and second exopodal segments of leg 1 obscure; endopod of leg 1 strongly directed medially; exopod of legs 2–4 curved medially. Inner coxal seta absent in legs 1–4. Inner distal spine of basis of leg 1 small, 11 μm long.. Armature of endopods of legs 2–4 variable: formula 1, 2, 3 or 0, 2, 3 inleg 2; 1, 2, 2 or 0, 2, 2 in leg 3; and 0, 1, 0 or 0, 2, 0 in leg 4. All setae on legs 2–4 naked and bluntly tipped. Armature formula for legs 1–4 as follows:

Leg 5 (Fig. 313E) represented by 1 setaon outer protopodal lobe and tapering, sclerotized, claw-like exopodal process bearing 1 seta slightly distal to middle of outer margin.

Male. Unknown.

Remarks. The endopod of leg 4 of Doroixysatlantica sp. nov. is 3-segmented and the third endopodal segment is armed with 1 or 2 setae only. These two unique features allow the new species to be differentiated from all of its currently known congeners.