Botryllophilus coniorhynchus Kim & Boxshall 2021, sp. nov.

Botryllophilus coniorhynchus sp. nov.

(Figs. 60-62)

Type material. Holotype ♀ (MNHN-IU-2018-1973), 3 ♀♀ paratypes (intact, MNHN-IU-2018-1974), and 2 ♀♀ paratypes (dissected, MNHN-IU-2014-17376) from Aplẚdẚum falklandẚcum Millar, 1960 (MNHN-IT-2008-386 = MNHN A1 / APL.B/532); Antarctic, Terre Adélie, CEAMARC cruise, RV “Aurore Australis”, Stn 18EV479 (66º10’S, 139º41’E), depth 402-437 m, IPEV-AAD-MNHN coll., 15 January 2008.

Etymology. The name of the new species is derived from the Greek cçnẚ (= a cone) and rhynch (= a snout), and refers to the conical rostrum.

Description of female. Body (Fig. 60A, B) asymmetrical, 1.15 mm long. Anterior part of body comprising cephalosome to fifth pedigerous somite, 0.73 mm long, invariably slightly curved to right side, unsegmented but with 4 weak constrictions dorsally and laterally; lateral margins parallel. Body width 0.33 mm across middle of anterior part. Posterior part of body (Fig. 60C) consisting of genital and 4 abdominal somites. Genital apertures positioned dorsally on genital somite. Caudal ramus (Fig. 60D) armed with 4 claws and 1 seta; 1 outer distal claw bluntly tipped, other claw not articulated with ramus.

Rostrum (Fig. 61A) distinct, conical, longer than wide (57×42 μm). Antennule (Fig. 60E) short, about 115 μm long, strongly tapering, with markedly broadened first and second segments; terminal segment subdivided on posterior side; armature formula 9 (3 large and 6 small), 5 (2 large and 3 small), 2 (1 large and 1 small), and 12. Left antenna (Fig. 60F) apparently 5-segmented, consisting of coxa, basis, and 3-segmented endopod; proximal 3 segments unarmed; second endopodal segment (fourth segment) 46×18 μm, with 2 bluntly tipped setae on inner margin; third endopodal segment 17×16 μm, with 4 (2 shorter inner and 2 longer outer) bluntly tipped setae on distal margin. Right antenna similar in size and segmentation to left antenna; 2 setae on second endopodal segment and 2 inner distal setae on third endopodal segment slightly longer than those of left antenna and distally spinulose (Fig. 60G); 2 outer distal setae distinctly shorter than those of left antenna.

Labrum (Fig. 60H) with large, semicircular posteromedian lobe. Mandible (Fig. 60I) with 1 bifurcate tooth and 2 shorter teeth on coxal gnathobase; palp with 2 lobes in middle of inner margin, armed with 9 setae arranged as 3, 2, 2, and 2. Maxillule (Fig. 61B) consisting of precoxa and palp; precoxa with 5 distinct setae on arthrite; palp 3-segmented, consisting of coxa, basis, and endopod; coxa unarmed (lacking seta of epipodite); basis with 2 setae on medial margin, 3 setae on outer margin, and setulose distal lobe; endopod articulated from basis, armed with 3 setae on distal margin. Maxilla (Fig. 61C) indistinctly 3-segmented and armed with 2, 4, and 3 setae on first to third segments, respectively. Maxilliped (Fig. 62A) 4-segmented; syncoxa large, with 1 small seta proximally on inner margin and patch of spinules subdistally on inner side; basis with 2 small isolated setae; short first endopodal segment unarmed; second endopodal segment with 2 small setules and 1 pointed inner distal process; terminal claw small, about half as long as second endopodal segment.

Legs 1-4 (Figs. 61 D-G, 62B-E) biramous, with 1-segmented exopods and 2-segmented endopods; coxa unarmed; basis with 1 seta on outer margin. Basis of legs 1-3 with 1 prominent, spiniform process at inner distal corner and 2 to 4 spinules on distal margin near base of endopod; basis of leg 4 with 2 patches of several spinules at each inner distal corner and on distal margin. Spines on exopods of right legs 1-3 elongate. Exopods of right legs 1 and 2 armed with 1 seta (outer proximal element) and 5 spines. Numbers of spines (Roman numerals) and setae (Arabic numerals) on right and left legs 1-4 as follows:

Leg 5 (Fig. 62F) positioned dorsolaterally on fifth pedigerous somite, evenly tapering, 2.4 times longer than wide (140×58 μm), with 1 small seta proximally and 2 small plus 1 larger seta distally; larger distal seta longer than leg (exopodal) segment. Leg 6 (Fig. 62G) represented by 1 spinule and 2 spinule-like processes on genital operculum; 9 small denticle-like elements on surface adjacent to leg 6.

Male. Unknown.

Remarks. Three outstanding features serve to characterize BK cçnẚçrhynchus sp. nov. as follows: (1) the exopods of right legs 1 and 2 each carry 1 seta in addition to spines; (2) the combination of armature elements on right legs 1-4 is 6-6-6-4, and (3) the endopod of the antenna is apparently 3-segmented, the segmentation has not been recorded previously in Bçtryllçphẚlus and, as it appears incomplete, it may represent a distinct fold in the cuticle rather than a true articulation. The combination of armature elements on the exopods of left legs 1-4 (5-5-5-4) also is unusual, known previously only in B. banyulensẚs.