Enteropsis obtusa, Kim & Boxshall, 2021

Enteropsis obtusa sp. nov.

( Fig. 181 View FIG )

Type material. Holotype ♀ (MNHN-IU-2014-21584), 5 ♀♀ paratypes (MNHN-IU-2014-21585), and 1 ♀ paratype (dissected, MNHN-IU-2014-17399) from aẚstaplẚa cçrçlla Monniot F., 1974 (MNHN-IT-2008-3694 = MNHN A3 About MNHN / DIS/35 View Materials ); Guadeloupe, Baille Argent face Nord, Stn 83-20, depth 1-3 m, Monniot coll., 04 April 1983.

Etymology. The name of the new species is derived from the Latin çbtus (=blunt), referring to the blunt posterior end of body.

Description of female. Body ( Fig. 181A, B View FIG ) eruciform, stout, indistinctly 6-segmented, consisting of cephalosome, first to fourth pedigerous somites, and genitoabdomen. Mean body length 1.0 mm ( 0.78-1.17 mm, n=7); dissected specimen 1.17 mm; maximum width 393 μm (across third pedigerous somite). Cephalosome ( Fig. 181C View FIG ) narrowing anteriorly, with rounded anterior margin; first to fourth pedigerous somites lacking dorsal tergites. Genitoabdomen wider than long; anal prominence (indicated by arrowhead in Fig. 181B View FIG ) small; genital apertures positioned subdistally on same plane as anal prominence. Caudal rami and caudal setae absent.

Rostrum absent, but sclerotized longitudinal sculpture present in rostral area ( Fig. 181C View FIG ). Antennule ( Fig. 181D View FIG ) 55 μm long, narrowing distally, 3-segmented; first segment unarmed; second segment with 1 seta on posterior mar- gin; third segment slightly shorter than second, armed with 7 setae. Antenna ( Fig. 181E View FIG ) 67 μm long, unarmed, consisting of spinulose basal segment and spinulose distal claw; claw 34 μm long, curved, as long as basal segment, with acutely pointed tip.

Labrum ( Fig. 181F View FIG ) spinulose, with convex posterior margin, 1 broad, triangular, tongue-like medial process and 2 densely spinulose setiform processes, 1 either side of medial process. Mandible absent. Maxillule ( Fig. 181G View FIG ) distally bilobed; longer inner lobe tipped with 2 spinulose setae and densely covered with setules in distal half of lobe; shorter outer lobe tipped with 2 equal, spinulose setae. Maxilla ( Fig. 181H View FIG ) massive, 2-segmented; proximal segment with strongly protruding medial margin and 1 blunt tubercle near apex of medial protrusion; distal segment terminating in strong claw, with 1 small seta proximally on posterolateral surface and patch of fine granular ornamentation near base of seta. Maxilliped absent.

Leg 1 ( Fig. 181I View FIG ) biramous with 2-segmented protopod; protopod spinulose on anterior surface. Rami rudimentary; exopod as conical claw, embedded in transparent covering; endopod wider than long, truncate. Legs 2-4 same as leg 1 in form and structure. Leg 5 absent. Leg 6 not visible in genital aperture.

Male. Unknown.

Remarks. bnterçpsẚs çbtusa sp. nov. can be clearly defined by its characteristic labrum which bears a broad, linguiform median process plus a pair of slender, setiform processes laterally. The caudal rami are absent in b. çbtusa sp. nov., as in four congeneric species ( b. abbçttẚ, b. fusẚfçrmẚs, b. mẚnçr, and b. elçngata sp. nov.). However, in b. çbtusa sp. nov. the antennule is 3-segmented, in contrast to the 1-segmented condition in these congeners, and the inner and outer lobes of the maxillule are each tipped with 2 distinct, basally articulating setae, compared to the armature of the inner and outer lobes each bearing 2 setae and 2 cusps in b. abbçttẚ, 0 and 2 setae in b. fusẚfçrmẚs, 2 and 0 setae in b. mẚnçr, and 2 setae and 1 cusp in b. elçngata sp. nov. The new species can be characterised by the combination of the armature of the labrum, the lack of caudal rami, the 3-segmented antennule, and the 2 setaebearing lobes of the maxillule.