A NEW DEEP-WATER SPECIES OF METACRANGON (DECAPODA, CARIDEA, CRANGONIDAE) FROM JAPAN BY TOMOYUKI KOMAI1) Natural History Museum and Institute, Chiba, Chiba 260-8682, Japan ABSTRACT A new species of crangonid shrimp, Metacrangon holthuisi sp. nov., is described and illustrated on the basis of a single male specimen collected in the Sagami Sea, central Japan, at depths of 1039-1300 m. Morphologically, the new species is most similar to M. cornuta Komai & Komatsu, 2009 from off eastern Hokkaido, Japan, and M. spinirostris (Rathbun, 1902) from the Bering Sea and off the Aleutian Islands, but is readily distinguished by the less ascending rostrum distinctly overreaching the distal corneal margins, subequal middorsal spines on the carapace and the short distolateral projections on the first and second segments of the antennular peduncle. RÉSUMÉ Une nouvelle espèce de crevette Crangonidae, Metacrangon holthuisi sp. nov., est décrite et illustrée à partir d’un unique spécimen mâle recueilli dans la mer de Sagami, au centre de l’archipel japonais central, à des profondeurs de 1039-1300 m. Morphologiquement, la nouvelle espèce est très semblable à M. cornuta Komai & Komatsu, 2009 de la côte est de Hokkaido, au Japon, et à M. spinirostris (Rathbun, 1902) de la mer de Béring et des parages des îles Aléoutiennes. Cependant cette nouvelle espèce s’en distingue facilement par son rostre moins ascendant et dépassant les marges distales de la cornée, par les épines médiodorsales de sa carapace qui sont subégales et par les petites projections distolaterales des premier et deuxième segment du pédoncule antennulaire. INTRODUCTION The crangonid genus Metacrangon Zarenkov, 1965 is currently represented by 24 species in the world (De Grave et al., 2009). It is characterized by the 1) e-mail: [email protected] © Koninklijke Brill NV, Leiden, 2010 Studies on Malacostraca: 369-377 370 CRM 014 – Fransen et al. (eds.), LIPKE BIJDELEY HOLTHUIS MEMORIAL VOLUME possession of submedian spines on the carapace, laterally flared pleura of the sixth abdominal somite, the short appendix masculina bearing long spiniform setae, and the lack of an arthrobranch above the base of the third maxilliped (Zarenkov, 1965; Butler, 1980; Christoffersen, 1988; Holthuis, 1993; Kim & Hayashi, 2003). In spite of the wide horizontal and vertical distribution of the genus, many species themselves have rather limited ranges (Komai, 1997; Retamal & Gorny, 2003). Highest species richness is seen in the East Asian region, in which the following 13 taxa have been recorded (Komai, 1995, 1997; Kim, 2005; Komai & Komatsu, 2009): M. cornuta Komai & Komatsu, 2009; M. laevis (Yokoya, 1933); M. longirostris (Yokoya, 1933); M. miyakei Kim, 2005; M. monodon (Birshtein & Vinogradov, 1951); M. nipponensis (Yokoya, 1933); M. ochotensis (Kobjakova, 1955); M. proxima Kim, 2005; M. robusta (Kobjakova, 1935); M. similis Komai, 1997; M. sinensis Fujino & Miyake, 1971; M. trigonorostris (Yokoya, 1933) and M. variabilis asiaticus (Kobjakova, 1955). During the research cruise of TRV “Shin’yo-maru” of the Tokyo University of Marine Science and Technology in October 1996, a deep-water dredging survey was carried out in the Sagami Sea and Izu Islands, central Japan. At the entrance of Tokyo Bay, where traffic is heavy, only one station was sampled, and amongst the collection a single specimen of a previously unknown species of Metacrangon was found. In this paper, a new species, M. holthuisi,is described and illustrated on the basis of this specimen. The holotype remains deposited in the Natural History Museum and In- stitute, Chiba (CBM). The abbreviation cl refers to the postorbital carapace length. For detailed observation of the surface structure on the integument, the specimen (including dissected appendages) was stained with a solution of methylene blue. TAXONOMY Family CRANGONIDAE Haworth, 1825 Genus Metacrangon Zarenkov, 1965 Metacrangon holthuisi sp. nov. (figs. 1, 2) Type material. — Holotype: male (cl 6.0 mm), CBM-ZC 5347, TRV “Shin’yo-maru”, re- ◦ search cruise to Izu Islands 1996, stn 21, west of Sunosaki, Tateyama, Sagami Sea, 34 56.46 N, ◦ 139 33.12 E, 1039-1300 m, 24 October 1996, dredge, coll. T. Komai..