Notodelphyopsis deplanata Kim & Boxshall 2020, sp. nov.

Notodelphyopsis deplanata sp. nov.

(Figs. 58, 59)

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21233), from Ascidia ornata Monniot F. & Monniot C., 2001 (MNHN-IT-2008-1160 = MNHN P5/ASC.A/299), CRRFCRCHO 148, Caminguin I., Bohol Sea, the Philippines (9°15.38’N, 124°39.12’E), west side of White Island, offshore sand cay, depth 18 m, 19 April 1997.

Etymology. The species name is from the Latin deplanat (= flattened), alluding to its flattened body form.

Descriptionoffemale. Body (Fig. 58A) broad, dorsoventrally depressed. Bodylength 1.21 mm; greatest width 0.59 mm across third pedigerous somite. Prosome with parallel lateral margins; prosomites well-sclerotized, ornamented with minute setules on dorsal and lateral surfaces. Cephalosome extended posterolaterally, with strongly concave posterodorsal margin and pointed posterolateral corners. First pedigerous somite overlapped by cephalosome, not visible in dorsal view. Second and third pedigerous somites as wide as cephalosome, with well-developed epimera. Brood pouch incorporating fifthpedigerous somite, 580×580 μm, sub-circular, as long as wide and equal in width to second and third pedigerous somites. Freeurosome (Fig. 58B) very small, 4-segmented, comprising genital double-somite and 3 freeabdominal somites, narrowing distally; each somite much wider than long; anal somite much narrower than second freeabdominal somite. Caudal ramus (Fig. 58B) short, as long as wide (31×31 μm); armed with 6 setae, 4 distal and 2 subdistal.

Rostrum (Fig. 58C) small, highly sclerotized, triangular, with angular apex. Antennule (Fig. 58D) slender and shorter than cephalosome; 9-segmented with armature formula 3, 16, 6, 4, 4, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; setae generally long; 2 setae on third segment and 1 setaon fourth segment pinnate, all other setae naked; aesthetascs thin, each confluent at basewith adjacent seta. Antenna (Fig. 58E) consisting of coxa, basis and 2-segmented endopod; coxa short and unarmed; basis with 2 large pinnate setae of equal length at outer distal corner representing exopod; first endopodal segment with 1 thin setaon inner margin; compound distal endopodal segment slender, about 6 times longer than wide, ornamented with row of spinules on outer margin; armed with terminal claw plus 11 setae (arranged as 1, 1, 3, 1, 2, and 3), one of subdistal setae pinnate and 3 distal setae blunt at tip; terminal claw about one-thirdaslongas segment.

Labrum lost. Mandible (Fig. 58F) with 4 pointedteeth and 1smallsetaoncoxalgnathobase; basiswith1 relatively large seta and few setules on medial margin; exopod 2-segmented and armed with 1 and 4 setae on first and second segments, repectively; distal outer seta broadened proximally and longerthan other 4 setae; endopod with 2 (short pinnate and long naked) and 7 pinnate setae on firstandsecondsegments, respectively. Maxillule (Fig. 58G) with 9 setae (2 small and 7 larger) on arthrite, 1 on coxal endite, 2 on epipodite, and 3 (2 small proximal and 1 larger distal) on medial margin of basis; exopod with 4 setae distally; endopodindistinctly 2-segmented with 2 small medial margin setae on first segment and 3 long setae on small second segment. Maxilla (Fig. 59A) 5-segmented; armedwith 9 setae (arranged as 3, 1, 2, and 3) on syncoxa, 3 on basis, and 0, 1, and 3 on first to third endopodal segments, respectively. Maxilliped (Fig. 59B) 3-segmented with 9, 0, and 2 setae on first to third segments, respectively; second segment with long setules on medial margin and irregular, membranous fringe on outer margin.

Legs 1–4 with 3-segmented rami (Fig. 59 C–E). Inner seta on coxa pinnate but small in legs 3 and 4. Outer seta on basis of leg 1 small and naked, but pinnate in legs 2–4. Inner distal spine on basis of leg 1 smooth, shorter than first endopodal segment. Outer margin of first exopodal segment spinulose in leg 1, but setulose in legs 2–4. Third exopodal segment of leg 1 directed outwards. Proximal spine on third exopodal segment of leg 1 smaller than other spines on same segment. Third exopodal segment of leg 4 with 3 spines and 4 setae (not 5 setae). Second endopodal segment of leg 4 with only 1 seta (not 2 setae). Armature formula for legs 1–4 as follows:

Leg 5 (Fig. 58B) represented by 2 digitiform processes, each tipped with 1 naked seta; seta on inner (exopodal) process much longer than outer basal seta.

Male. Unknown.

Remarks. Notodelphyopsis deplanata sp. nov. has a broad, dorsoventrally depressed body, and short caudal rami.In addition, itcarries 7 setaeon thesecond endopodal segment of the mandible and has reduced setation on the third exopodal and second endopodal segments of leg 4. Within the genus Notodelphyopsis, these features are unique to the new species and serve to differentiate it from all congeneric species.