Metacrangon holthuisi Komai, 2010

Komai, Tomoyuki, 2012, 3468, Zootaxa 3468, pp. 1-77 : 55

Metacrangon holthuisi Komai, 2010

( Fig. 41)

Metacrangon holthuisi Komai, 2010: 370 , figs 1, 2 [type locality: Sagami Sea, off Sunosaki, Tateyama, 1039–1300 m]; Komai 2011: 286, fig. 1C; De Grave & Fransen 2011: 457 (list).

Material examined. Holotype: male (cl 6.0 mm), RV Shin’yo-maru, 1996 cruise, stn 21, off Sunosaki, Tateyama, Sagami Sea, 34°56.46’N, 139°33.12’E, 1039–1300 m, 24 October 1996, dredge, CBM-ZC 5347.

Non-type : RV Tansei-maru, KT 07-31, stn L-2’-1000, Sagami Sea, S of Jogashima, 35°02.78’N, 139°33.27’E to 35°03.04’N, 139°33.74’E, 633–716 m, 28 November 2007, beam trawl, 2 males (cl 4.0, 4.4 mm), 2 females (cl 3.7, 4.0 mm), CBM-ZC 10092 .

Diagnosis. Male. Rostrum narrow triangular with acute tip in dorsal view, slightly ascending (angle about 25° against horizontal plane of carapace), overreaching antennal teeth by half-length (0.3 times as long as carapace); ventral carina low. Carapace with subequal, similarly ascending middorsal teeth; anterior middorsal tooth arising at about 0.2 of carapace length; posterior tooth arising at 0.6 of carapace length; submedian teeth present; postorbital lobe slightly produced; antennal tooth ascending in similar degree of rostrum, acuminate; branchiostegal tooth strong, directed slightly laterally in dorsal view, ascending in similar degree to rostrum in lateral view. First and second abdominal somites rounded dorsally, third and fourth somites each with weakly delimited middorsal carina, fifth somite with broad, better delimited middorsal carina. First to third abdominal pleura rounded marginally. Sixth abdominal somite with distinct submedian carinae. Telson with 2 pairs of dorsolateral spines. Eye approximately as long as wide. Antennular peduncle slightly falling short of distal margin of antennal scale; first segment with short, blunt distolateral process; stylocerite reaching midlength of first segment; second segment widened distally, with prominent, blunt distolateral process. Antennal scale about 0.6 times as long as carapace, 2.9–3.0 times longer than wide; lateral margin concave; distolateral tooth distinctly overreaching lamella. Third maxilliped with ultimate segment 7.0 times longer than wide. First pereopod with palm 3.5 times longer than wide.

Only young female specimens available, generally similar to male specimens except for proportionally shorter outer antennular flagellum consisting of 5 or 6 articles.

Description. See Komai (2010).

Coloration. Entirely brownish, darker on carapace; cornea black, reflective (Komai 2011).

Size. Largest male cl 6.0 mm; known largest female cl 4.0 mm.

Distribution. Known only from the Sagami Sea, central Japan ( Fig. 41); 633–1300 m.

Remarks. As discussed by Komai (2010), Metacrangon holthuisi is most similar to M. cornuta and M. spinirostris . The length of the rostrum is clarified to vary individually in M. holthuisi , and thus this character is not reliable in distinguishing M. holthuisi from the latter two species. Nevertheless, the subequal and similarly ascending middorsal teeth on the carapace and blunt distolateral processes on the first and second segments of the antennular peduncle immediately distinguish M. holthuisi from M. cornuta and M. spinirostris . In addition, the rostrum ascends less in M. holthuisi than in the latter two species.