Botryllophilus norvegicus Schellenberg 1921

Botryllophilus norvegicus Schellenberg, 1921

(Figs. 39-41)

Material examined. 1 ♀ (MNHN-IU-2014-17369, dissected and figured) in mçlycarpa pẚgmentata (Herdman, 1906) (MNHN-IT-2008-6635 = MNHN S1 / POL.B/405); Boiboiwaga Island, Papua New Guinea, OCDN 5782 - T (10°12.26’S, 150°44.75’E), depth 20 m, CRRF coll., 27 May 2008; 1 ♀ (MNHN-IU-2018-1961) in mçlycarpa sp., Mediterranean coast of Israel; 1 ♀ (MNHN-IU-2018-1962) in aendrçdça sp., Grand Rivière, Atlantic coast of Canada.

Supplementary description based on female from Papua New Guinea. Body (Fig. 39A) T-shaped in lateral view, 4.05 mm long in dissected specimen. Broader anterior part of body unsegmented, extremely swollen posterodorsally. Narrower posterior part of body (Fig. 39B) consisting of genital and 4 abdominal somites; genital somite 464×709 μm, with broad tubercle in middle of dorsal surface; genital apertures positioned dorsally. Four abdominal somites gradually narrowing posteriorly. Caudal ramus (Fig. 39C) 267×127 μm, armed with 4 straight, blunt claws and 2 small setae; claws unequal in length, longest claw 152 μm, and second longest claw 70 μm long.

Rostrum absent. Antennule (Fig. 39D) 4-segmented with indistinct articulation between last 2 segments; armature formula 12, 3, 4, and 8; 7 setae on first segment very large, exceeding length of antennule. Antenna consisting of coxa, basis, and 1-segmented endopod; endopod armed with 5 rod-shaped spines on right antenna, but with 5 slender setae on left antenna (Fig. 39E) (2 on inner margin and 3 on distal margin).

Labrum (Fig. 39F) with broad posteromedial lobe and 4 patches of minute spinules along medial surface. Mandible with broadened coxal gnathobase (Fig. 39G) bearing bifurcate distal tooth and 5 small, blunt denticles on medial margin; palp (Fig. 39H) armed with 8 setae arranged as 3, 1, and 4. Maxillule (Fig. 39I) with precoxal arthrite bearing 7 setae including 1 minute seta; palp with 2 setae on medial margin and 3 setae on outer margin of basis region, 1 seta on epipodite; endopod fused with basis, armed with 3 setae on distal margin. Maxilla (Fig. 40A) obscurely segmented, with 11 setae (including 4 small and naked). Maxilliped (Fig. 40B) robust, 4-segmented; syncoxa as long as wide, with protruded outer margin, 2 minute setae on proximal inner margin, and patch of minute spinules at subdistal inner margin; basis with 2 minute inner distal setae; first endopodal segment shorter than wide, unarmed; second endopodal segment with 1 minute seta near middle; terminal claw small, about half as long as second endopodal segment.

Legs 1-4 (Figs. 40-G, 41 A-C) with 1-segmented exopods and 2-segmented endopods; coxa lacking inner seta; basis with small outer seta. Exopod of right leg 1 (Fig. 40C) with 1 inner subdistal seta, in addition to 6 spines. First endopodal segment of right and left leg 1 bearing setulose tubercle on anteromedial surface. Numbers of spines (Roman numerals) and setae (Arabic numerals) on rami of legs 1-4 as follows:

Leg 5 (Fig. 40H) elongate, gradually narrowing distally, with dorsolaterally curved distal part and blunt tip: armed with 4 setae; largest subdistal seta as long as proximal width of leg, other 3 setae minute. Leg 6 represented by 2 small spinules and 1 spiniform process on genital operculum.

Male. Unknown.

Remarks. Bçtryllçphẚlus nçrvegẚcus is known to be widely distributed in the North Atlantic and Arctic Oceans (Dudley & Illg, 1991). In the present study its known distribution is extended to include the Mediterranean Sea and the tropical West Pacific. Ooishi (1996) redescribed this species based on a single female collected in Scotland and mentioned that this species is distinguishable from other “ type A” species of the genus primarily by the humpshaped body and the presence of 5 spines on the antenna. Additional remarkable diagnostic features of this species are as follows: the caudal rami bear straight, rod-shaped claws, leg 5 is curved dorsolaterally, and the antennule bears extremely large setae on the first segment.

It is noticeable that B. nçrvegẚcus displays variation in the setation pattern of the antenna and of the exopods of right leg 1 and right leg 4, as follows: (1) the right antenna is always armed with 5 spines, but left antenna may be armed with 5 spines as in Ooishi’s (1996) specimen and our specimen from the Atlantic coast of Canada, or may be armed with 5 setae as in 2 specimens each collected in Papua New Guinea and off the Mediterranean coast of Israel; (2) the exopod of the right leg 4 may be armed with 6 spines as in Ooishi’s specimen and our specimen from the Atlantic coast of Canada, or it may be armed with 7 spines as in our specimens from Papua New Guinea and off the Mediterranean coast of Israel; and (3) the exopod of right leg 1 may be armed with 6 spines plus 1 seta, as in Ooishi’s specimen and all of our specimens, but Dudley & Illg (1991) figured the exopod as bearing 7 spines (Dudley & Illg, 1991: Fig. 27). The material available for study was limited so the exact nature of this variation cannot yet be determined.