Metacrangon karubar, Komai, 2012

Komai, Tomoyuki, 2012, 3468, Zootaxa 3468, pp. 1-77 : 50-54

Metacrangon karubar n. sp.

( Figs 26–28, 43)

Metacrangon sp. — Takeda & Hanamura 1994: 29.

Material examined. Holotype. KARUBAR ( RV Baruna Jaya I ), stn CP 77, Tanimbar Island , Banda Sea, Indonesia, 08°57’S, 131°27’E, 352– 346 m, 3 November 1991, ovigerous female (cl 10.7 mm), MNHN-IU-2009-2103.

Paratypes. Indonesia: KARUBAR ( RV Baruna Jaya I ), stn CP 17, Kai Islands , 05°15’S, 133°01’E, 439–459 m, 24 October 1991, 1 female (cl 10.7 mm), MNHN-IU-2011-5018; stn CC 21 , Kai Islands , 05°14’S, 133°00’E, 688–694 m, 25 October 1991, 2 females (cl 7.0, 8.4 mm), 1 ovigerous female (cl 8.0 mm), MNHN-IU-2009-2104; stn CP 38, Tanimbar Island , 07°40’S, 132°27’E, 620–666 m, 28 October 1991, 1 male (cl 6.0 mm), 3 females (cl 7.4–8.5 mm), 1 ovigerous female (cl 8.5 mm), MNHN-IU-2009-2105; stn CP 39, Tanimbar Island , 07°47’S, 132°26’E, 466–477 m, 28 October 1991, 1 female (cl 10.7 mm), MNHN-IU-2009-2106; stn CC 57 , Tanimbar Island , 08°19’S, 131°53’E, 603–620 m, 31 October 1991, 1 female (cl 7.6 mm), MNHN-IU-2009-2107; stn CP 59, Tanimbar Island, 08°20’S, 132°11’E, 399–405 m, 31 October 1991, 1 female (cl 11.0 mm), MNHN-IU-2009-2108; stn CP 69, Tanimbar Island, 08°42’S, 131°53’E, 356–368 m, 2 November 1991, 1 female (cl 9.1 mm), 1 ovigerous female (cl 11.2 mm), MNHN-IU-2009-2109 . Papua New Guinea. BIOPAPUA, stn CP 3682, Vitu Islands ,

04°38’S, 149°28’E, 515–812 m, 27 September 2010, 1 male (cl 8.2 mm), MNHN-IU-2011-3230; stn CP 3717, Astrolabe Bay , 05°27’S, 145°56’E, 850–946 m, 6 October 2010, 1 female (cl 10.4 mm), MNHN-IU-2011-1797; stn CP 3730, off Mambare Bay , 07°51’S, 148°01’E, 710–750 m, 8 October 2010, 1 male (cl 8.6 mm), MNHN-IU- 2011-0923. Solomon Islands: SALOMON 1, stn CP 1783 , 08°32.8’S, 160°41.7’E, 399–700 m, 29 September 2001, 2 males (cl 7.3, 8.1 mm), 1 female (cl 11.0 mm), MNHN-IU-2011-5056.

Description. Female. Rostrum ( Figs 26A, B, E, 27A) triangular in dorsal view, directed forward, falling short of or extending as far as antennal teeth (less than 0.2 times as long as carapace); tip blunt in dorsal view; dorsal surface shallowly sulcate medially; ventral carina low. Carapace ( Figs 26A, B, E, 27A) widened posteriorly in spawning molt, slightly longer than wide postorbitally; middorsal carina extending nearly to posterodorsal margin, with 2 slightly unequal middorsal teeth; anterior tooth epigastric in position (arising between anterior 0.1 and 0.2 of carapace length), moderately strong, laterally compressed, not reaching base of rostrum, acuminate; posterior tooth smaller than anterior tooth, arising at about 0.70 of carapace length; no denticle present between 2 middorsal teeth; submedian tooth present; antennal tooth directed forward in dorsal view, somewhat ascending in lateral view (angle about 30° against horizontal plane of carapace), acute; postorbital angle rounded; anterolateral margin between antennal and branchiostegal teeth concave, unarmed; branchiostegal tooth moderately strong, directed forward in dorsal view, ascending in similar degree to antennal tooth in lateral view, slightly overreaching dorsolateral distal angle of antennal basicerite; branchiostegal ridge curving, not reaching level of posterior end of hepatic groove; branchial ridge absent.

Abdomen ( Fig. 26C, D) barely sculptured. First to fourth somites rounded dorsally or with trace of middorsal carina on third and fourth somites; fifth somite with blunt middorsal carina. Pleura of anterior three somites rounded; anteroventral angle of fourth pleuron rounded. Sixth somite with weak submedian carinae; posterodorsal margin slightly bilobed; pleuron shallowly depressed; posterolateral process terminating in acute tooth. Telson ( Fig. 26C) with 2 pairs of dorsolateral spines, first pair located at midlength.

Eye ( Fig. 26E) relatively slender for genus, 1.5–1.7 times longer than wide; cornea as wide as eyestalk, its width about 0.1 of carapace length; eyestalk with dorsodistal protrusion nearly reaching distal corneal margin, bearing rounded dorsal tubercle.

Antennular peduncle ( Figs 26E, 27A) relatively slender, reaching midlength of antennal scale. First segment with prominent, blunt distolateral process directed dorsolaterally; stylocerite terminating in elongate, slender, acute spine, reaching tip of distolateral process of first segment, lateral margin gently convex. Second segment with prominent, blunt distolateral process. Outer flagellum subequal in length to peduncle, overreaching distal margin of lamella of antennal scale by 0.3–0.4 length, consisting of 10–13 articles.

Antenna ( Figs 26E, 27A) having basicerite with dorsolateral distal angle produced in acute or subacute tooth, ventrodistal tooth slender, acute. Antennal scale about 0.5 times as long as carapace and 2.2–2.3 times longer than wide; lateral margin nearly straight; distolateral tooth moderately narrow, slightly falling short of distal margin of rounded distal lamella.

Third maxilliped relatively slender; ultimate segment gradually tapering distally in distal half, about 6.8 times longer than wide; penultimate segment 3.3–3.4 times longer than wide ( Fig. 27B).

First pereopod ( Fig. 27C, D) with palm 3.3–3.5 times longer than wide, not markedly widened proximally or distally, lateral and mesial margins nearly straight; carpus with tiny distolateral tooth; merus with 1 moderately large dorsodistal tooth, ventral margin sinuous, sharply crested. Second and third pereopods typical of genus (not illustrated); third pereopod reaching distal margin of antennal scale by tip of dactylus. Fourth pereopod ( Fig. 27E) relatively slender, slightly falling short of distal margin of antennal scale; dactylus ( Fig. 27F) spatulate with distinctly convex dorsal and straight ventral margins, about 5.0 times longer than broad. Fifth pereopod ( Fig. 27G) with dactylus subspatulate, about 0.8 times as long as propodus, shorter than that of fourth pereopod ( Fig. 27H); merus-ischium combined about 0.7 times as long as that of fourth pereopod.

Uropodal exopod with acute posterolateral tooth; spinule present mesial to posterolateral tooth ( Fig. 27I).

Eggs 1.5 x 1.3 mm; not counted.

Males. Carapace ( Fig. 28A) with middorsal teeth larger than in females, subequal in size. Outer antennular flagellum ( Fig. 28B) longer than peduncle, consisting of 15–18 articles (articles as wide as or slightly wider than long except for first article).

Coloration. In life (based on color slide). Carapace light brown. First and second abdominal somites white, third to sixth somites brown, telson and uropods again white. Pereopods generally white, but palm of first pereopod light brown.

Size. Males cl 6.0– 8.5 mm; females cl 7.0– 11.2 mm, ovigerous females cl 8.0– 11.2 mm.

Distribution. Known from the eastern part of the Banda Sea, Indonesia, Papua New Guinea and the Solomon Islands ( Fig. 43); 352– 945 m.

Remarks. In the epigastric anterior middorsal tooth and the absence of distinct middorsal carina on the second to fourth abdominal somites, this new species morphologically resembles M. munita and M. richardsoni . It differs from M. munita in the following features (cf. Butler 1980): the carapace is more depressed in M. karubar than in M. munita ; the rostrum is triangular with an acute or blunt tip in M. karubar , whereas subtrapezoidal with a rounded distal margin in M. munita ; and the stylocerite reaches the distolateral process of the first segment of the antennular peduncle in M. karubar , rather than far falling short of it in M. munita . From M. richardsoni , M. karubar n. sp. is distinguished by the following morphological differences (cf. Komai & Ahyong 2011): the rostrum is shorter in M. karubar than in M. richardsoni (slightly falling short of or reaching the antennal teeth versus distinctly overreaching them) with a more narrowly rounded tip; the posterior middorsal tooth on the carapace arises at about 0.7 length of the carapace in M. karubar , rather than slightly posterior to the midlength in M. richardsoni ; and the lateral margin of the antennal scale is nearly straight in M. karubar , whereas concave in M. richardsoni . Furthermore, when spawning molts of females are compared, the body is less stout in M. karubar than in M. richardsoni .

Takeda & Hanamura (1994) reported an unidentified species of Metacrangon from the Flores Sea, Indonesia. They clearly mentioned the similarity of their specimen to M. munita . There is little doubt that the specimen reported by Takeda & Hanamura represents M. karubar , although the specimen could not be located in the collection of NSMT.

Etymology. Named after the Indonesian-French KARUBAR Expedition, which collected most specimens of this new species.