Showing papers in "Publications of the Seto Marine Biological Laboratory in 1990"

Naupliar Development of Hansenocaris furcifera Ito (Crustacea : Maxillopoda : Facetotecta) from Tanabe Bay, Japan

Abstract: Five naupliar stages of Hansenocarisfurcifera Ito, 1989, the first of which is Nauplius y Type IX sensu Ito, are described in detail, based upon specimens originally collected in Tanabe Bay on the Pacific coast of Honshu, Japan, and reared in the laboratory. The naupliar sequence was determined by connecting partial series of exuviae of separately cultured individuals. The five naupliar stages, which are planktotrophic, are all metanauplii with a pair of setiform maxillular rudiments, and no orthonauplius stage was found. The surface structure of the first naupliar stage was studied by SEM. In front of the first antennae lies a pair of small protuberances with central pores, which are identified as the termini of the head gland instead of frontal filaments. Most of the body surface has a very fine, mesh-like texture, but the dorsocaudal organ and at least part of the window do not. The dorsal plates are deliniated by prominent, chitinous ridges about I Jlm high. Some new terminology is introduced to describe the developmental changes of the plates. Remarkable alterations in the Elongate and Intercalary plates are noticed through naupliar development. The setal ornamentation of the antennule changes through the first four naupliar stages, but that of the antenna and mandible remains unchanged. Hansenocaris furcifera Ito, 1989, was described from Tanabe Bay on the Pacific coast of Honshu, Japan, on the basis of five individuals at the cypris y stage, all raised from nauplii in the laboratory (Ito, 1989a). It has already been noted that Nauplius y Type IX, provisionally described by Ito (1987c), is a naupliar stage of this species. In the present paper, the five naupliar stages preceding the cypris y stage are described. The nauplii of H. furcifera seemed planktotrophic, so I tried to feed them with lsochrysis sp., Nannochloropsis sp. and Nitz(chia sp. in earlier, preliminary cultures. However, adding such algae to the cultures was unsuccessful because the animals readily accumulated organic debris on their setae and other parts of the body, which made microscopic observation of the animals and their exuviae very difficult. Moreover, such the debris apparently disturbed their continuous swimming acitivity and, in the worst cases, they did not molt and finally died in spite of repeated changes of culture dishes and medium. Hence, I did not feed the larvae used for the present study, but treated them in the same manner as lecithotrophic nauplii (Ito & Takenaka, 1988; Ito, in press). I have not yet succeeded in raising a first-stage nauplius of H. furcifera into its cypris y stage in the laboratory, although cypris y larvae of many species with lecithotrophic naupliar stages have already been obtained in this fashion from early naupliar larvae (Ito, 1984, 1986b, 1989b, Ito & Takenaka, 1988). The longest sequence Publ. Seto Mar. Biol. Lab., 34(4/6), 201-224, 1990. (Article 9)

Pelagic Amphipods, Infraorder Physosomata (Crustacea : Amphipoda : Hyperiidea) from the CSK International Zooplankton Collection (western North Pacific), with the Description of Four New Species of Scina

Abstract: Physosomata were poorly represented in the CSK (Cooperative Study of the Kuroshio and Adjacent Regions) collections as samples were restricted to the upper 150m and most Physosomata are deep-water species. Nineteen species were identified, all belong to the family Scinidae and, except for Acanthoscina birsteini, the genus Scina. The collection is remarkable in that four of the species are new to science and another ten are new records for the western North Pacific. An annotated list of species is given, the new species are described and a newly constructed key to the world species of Scina is provided. This study concerns the hyperiid amphipods of the infraorder Physosomata collected by the CSK (Cooperative Study of the Kuroshio and Adjacent Regions) during 1965-74. The general area surveyed in the western North Pacific ranged from the Timor, Arafura and South China Sea to just east of .Japan. Further details concerning the CSK International Zooplankton Collection are given by Chuang (1977), Kubota (1984), Motoda (1980) and Yamazi (1971). Previous records of Physosomata from the western North Pacific are given by Bulycheva (1955), Vinogradov (1957) and Yoo (1971). In all, 35 species in 12 genera representing all 7 families have been recorded from this general area. In the CSK collections Physosomata were rare probably because the collections were restricted to the upper 150m and most Physosomata are deep-water species (Vinogradov, 1957). Of the 2, 749 plankton samples, containing hyperiid am phi pods, examined, only 169 contained Physosomata resulting in 202 specimens. All belong to the family Scinidae. I have determined 19 species; Acanthoscina birsteini and 18 species of Scina including 4 species new to science. Apart from the new species the following are new records for the general area surveyed, Acanthoscina birsteini, Scina damasi, S. excisa, S. inermis, S. marginata, S. nana, S. oedicarpus, S. similis, S. stenopus and S. tullbergi. Of the four new species that I describe here three are small (2.0 mm or less) but appear to be fully developed specimens with clear, distinctive features. The discovery of these new species of 2.0 mm or less is not surprising as some species of Scina attain Publ. Seto Mar. Biol., 34(4/6), 167-200, 1990. (Article 8)

Two New Species of the Genus Melita (Crustacea : Amphipoda) from Shallow Waters of the Seto Inland Sea of Japan

Abstract: Two new species of gammaridean amphipods of the genus Melita, M. hoshinoi and M. quadridentata, are described from shallow waters of the Seto Inland Sea of Japan. Melita hoshinoi is unique within the genus in having two basofacial spines on the peduncle of uropod 1. Melita quadri­ dentata is characterized by markedly setose pereopods 6-7 and uropod 3. The two new species are clearly distinguishable from other congeners also by the shapes of male gnathopod 1 and female coxa 6. A biarticulate outer ramus of the uropod 3, which is usually regarded as an important characteristic of the genus Abludomelita (sensu Karaman, 1981) that distinguishes it from the genus Melita, is rec­ ognized in the two new species. The present paper deals with two new species of the genus Melita Leach (Gam­ maridea, Melitidae) from the Seto Inland Sea of Japan. Although the materials of these two new species used for the present study were obtained only from a small area around the Mukaishima Marine Biological Station, they are not rare species. Actually they are very abundant there and have repeatedly been collected. The two new species markedly differ from other species of Melita previously reported from the same region (Yamato, 1987, 1988) in the morphology of the male gnathopod 1 and the female coxa 6, and the biarticulate uropod 3 which will be discussed from a taxonomic point of view. The new species seem to differ from the previously report­ ed species also in the habitat because they have so far been found in subtidal sedi­ ments, while the latter species are known to occur in intertidal and brackish-water areas. The figures of appendages are depicted from two specimens, which are the holotype and the allotype. The figures from subsidiary specimens are denoted after the dash, like "m2" and "f2". Type specimens will be deposited in the National Science Museum, Tokyo, after the completion of this study. Abbreviations used in the figures. R., right; L., left; A, antenna; CX, coxa; E, epimeral plate; G, gnathopod; H, head; IP, inner plate; LL, lower lip; MD, mandible; MX, maxilla; MXP, maxil­ liped; OP, outer plate; PL, pleopod; PLS, pleosomite; PR, pereopod; T, telson; U, uropod; UL, upper lip; URS, urosomite; f, female; i, inner surface; o, outer surface.