Enterocola quadrisetus Kim & Boxshall 2021, sp. nov.

Overview & Synopsis

Enterocola quadrisetus sp. nov. (Figs. 134, 135) Type material. Holotype ♀ (MNHN-IU-2014-21546), 3 ♀♀ paratypes (MNHN-IU-2014-21547), and 1 ♀ paratype (dissected, MNHN-IU-2014-17397) from aẚdemnum sp.; Tulear, Madagascar, depth 15 m. Etymology. The name of the new species refers to the presence of only 4 setae on the female antenna. Description of female. Body (Fig. 134 A-C) small, eruciform, curved dorsally, narrowing from anterior to posterior, consisting of cephalosome, 5-segmented trunk, and unsegmented genitoabdomen. Body length of dissected largest specimen 535 μm; maximum width 192 μm (across cephalosome). Cephalosome 125 μm long, much wider than long. First pedigerous somite bearing simple dorsal tergite; second to fourth pedigerous somites each bearing pair of large dorsolateral tergal folds. Second and third pedigerous somites each bearing 1 tubercle in middle of dorsal surface, large on second pedigerous somite and smaller on third (Fig. 134A). Pedigerous somites lacking ventral interpodal protrusions. Genitoabdomen short, flexible, unsegmented, but with 2 or 3 wrinkles on ventral surface (Fig. 134D); anal prominence distinct. Caudal rami unarmed, incompletely articulated from genitoabdomen, about 3.2 times longer than wide (73×23 μm) with parallel lateral margins and rounded distal margin. Rostrum absent. Antennule (Fig. 134E) unsegmented, about 1.5 times longer than wide (37×25 μm), with in- flated, convex posterior margin and nearly straight anterior margin; armed distally with 6 small setae (2 anterodistal setae setule-like). Antenna (Fig. 134F) indistinctly 2-segmented, 2.2 times longer than wide; proximal segment unarmed; distal segment 50×34 μm, slightly shorter than proximal segment, and ornamented with minute spinules; armed with 4 setae, lengths of setae I-IV (medial to distal) 13, 14, 21, and 23 μm, respectively; 2 lateral setae origi- nating close to each other. Labrum (Fig. 134G) with sclerotized, angularly protruded lateral margins; palp inflated, bulbous, and spinulose. Mandible (Fig. 134G) spinulose, tapering, distinctly narrower than labral palp. Maxillule consisting of precoxa and palp; precoxa (Fig. 134I) with trilobate distal margin, 1 tubercle subdistally, and endite bearing thin, spinulose seta and about 15 thin setules; palp (Fig. 134H) with 5 spines on distal margin plus setiform process on lateral margin. Maxilla (Fig. 134J) 2-segmented; proximal segment with mediodistal endite bearing distally spinulose, bifurcate process; distal segment (Fig. 134K) bluntly tipped, subdistally with 1 stout spine bearing numerous spinules on medial surface and 1 small seta proximally on posterior surface. Maxilliped absent. Legs 1-4 biramous with incompletely 2-segmented protopods and 1-segmented rami (Fig. 135A, B); protopods unarmed. Exopods of legs 1, 2, and 4 tipped with small cusp; exopod of leg 3 attenuated distally (Fig. 135B). Endopods 45×20, 35×24, 30×30, and 38×36 μm, respectively, in legs 1-4. Lengths of laterodistal and mediodistal setae on endopods 39 and 33, 35 and 32, 40 and 34, and 33 and 25 μm, respectively, in legs 1-4. Leg 5 (Fig. 135C) lamellate, unarmed, wider than long (82×145 μm). Leg 6 (Fig. 135D) probably represented by 2 small cusps in genital operculum. Male. Unknown. Remarks. The antenna of female bnterçcçla is typically armed with 6 setae, rarely with 5 setae. bnterçcçla quad- rẚsetus sp. nov. is the only known species in the genus having only 4 setae on the antenna, which allows the new species to be easily distinguished from all of its congeners. The possession of a dorsal tubercle on the second and third pedigerous somites is another unusual feature of the new species.