Redescription of Argis hozawai (YOKOYA,1939) from Northern Japan (Crustacea, Decapoda,Crangonidae)

Argis hozawai (YOKOYA, 1939),which has been known only by the original description from off Miyagi Prefecture, northern Japan, and the subsequent reports from Korea made by K I M and PARK (1972) and K I M (1976; 1977), is described and illustrated in detail based on specimens recently collected from the Pacific coast of northern Japan. Though A. hozawai closely resembles A. lar ( O W E N , 1839), it is distinguishable from the latter by the presence of a tooth-like tubercle just behind the rostrum, more distinct median carina of the anterior two abdominal somites in the female, and the proportionately stouter palm of the first pereopod. Nectocrangon lar kobjakovi VINOGRADOV, 1 9 5 0 , which was synonymized with A. lar by ZARENKOV (1960),is placed in synonym with A. hozawai. The present material and review of the previous literature on A. lar suggest that A. hozawai is confined to Asian waters. Notes on the biology and coloration of the living animal are also provided. Recent collections made on the Pacific coast of northern Japan, extending from off Miyagi Prefecture, Honshu Mainland, to off eastern Hokkaido in 19871990, have provided two types of crangonids belonging to the genus Argis, which were captured at the depths of 10 to 512 m. These two types were apparently distinguishable by the presence or absence of a tooth-like tubercle just behind the rostrum. Detailed examination of the material proved that the two types were distinct from each other. The type lacking the tubercle belongs to A. lar (OWEN, 1839) without doubt; another type bearing the tubercle agrees in general with the brief original description and figure of Nectocrangon hozawai YOKOYA, 1939 from off Miyagi Prefecture, northern Japan. The latter species has been reported only from Korea by K I M and PARK ( 1 9 7 2 ) and K I M ( 1 9 7 6 ; 1 9 7 7 ) , besides the original description. Both species were of common occurrence in the sublittoral zone of the surveyed area and often were captured sympatrically. Thus it is suggested that the poor previous records of A. hozawai may be due to taxonomic confusion with A. lar. Further, Nectocrangon lar kobjakovi V I N O GRADOV, 1950 from Asian Russian waters, which is also characterized by the presence of a tubercle behind the rotsrum, is strongly suggested to be synonymous with A. hozawai, though the former was placed as a synonym of A. lar by ZARENKOV (1960) . These taxonomic problems led the authors to redescribe A. hozawai and to review the previous literature on A. lar. Some information on the biology of A. hozawai are included in this report. Specimens have been Redescription of A rgis hozawai from Japan 25 deposited at the Laboratory of Marine Zoology, Faculty of Fisheries, Hokkaido University (HUMZ) . Abbreviation CL indicates postorbital carapace length. The terms tooth and spine are defined as follows: tooth = acute or blunt projecting structure lacKing basal suture, thus immovable; spine = acutely projecting structure with distinct basal suture, thus movable. The names of the structures of the carapace follow mainly BUTLER (1980) .