Abstract: The food consumption rate and absorption efficiency for different foods of the sea cucumber, Apostichopus japonicus Selenka, were examined in laboratory experiments. Four types of food were provided:‘ sediment’, ‘ sediment and suspended particles’, ‘ sediment and seaweed’ and‘ seaweed’. The consumption rate did not vary between seasons, with the exception of summer, when A. japonicus did not feed at all. However, there was a variation in consumption rate among different food types; daily consumption rate per dry body-weight varied from 0.61to 1.50g/g-body-weight for sediment-based foods(‘ sediment’ and‘ sediment and suspended particles’);and from 0.10 to 0.30g/g-body-weight for seaweed-based foods(‘ sediment and seaweed’ and‘ seaweed’). The consumption rate tended to decrease with increasing total organic carbon(TOC), total nitrogen(TN), and total phosphorus(TP)content in foods. The absorption efficiency(AE)varied precisely among food types. In contrast, the AE varied between seasons only in sediment-based foods. The AE for dry-weight, TOC, TN and TP varied from-3.6 to 56.1%, 18.3 to 51.8%, 16.5 to 56.2%and5.6 to 68.4%, respectively, and tended to rise with increasing TOC, TN and TP content in the food.

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Abstract: Paracerceis sculpta(Holmes, 1904)[Crustacea: Isopoda: Sphaeromatidae]has been introduced into many localities in the world and its distribution has spread steadily. From July, 2000 to October, 2001, 809 individuals of this species were collected from an artificial sandy beach in Osaka Bay, central Japan. Descriptions of the morphological characters of both sexes are given based on the specimens. Comparison of these specimens with specimens previously identified as Paracerceis japonica Nunomura, 1988 collected in 1986 from Uwajima in Ehime Prefecture revealed synonymy of the two species, indicating that the occurrence in Osaka Bay is the second record of Paracerceis sculpta from Japan. The species was collected throughout most of the study period, and the abundance increased during the study period. Large males having elongate uropods, non-ovigerous females and juveniles were collected, with body lengths ranging from 1.3 mm to 10.3 mm. Paracerceis sculpta was probably introduced into Osaka Bay by ship-fouling in 1998, however, the donor area cannot be determined because ships arrive frequently in Osaka Bay from many ports around the world where P. sculpta occurs.

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A bstract: The species composition of two species in genus calyptogena, C. soyoae and C. okutanii, was examined in three areas in Sagami Bay. Species were identified based on shell morphology. The dominant species in cold-seepage sites Off Hatsushima Island(OHI)and at the Okinoyama Bank(OB)was C. okutanii(74.4 and 60.5%, respectively). However, most Colyptogena at the Sagami Knoll(SK)were C. soyoae(90.7%) .The proportion of these two Calytogena species differed significantly among the three seepage sites. Given that most ecological studies of Calypogena have been conducted at the OHI cold-seepage site, these results suggest that most of the ecological information on Calyptogena in Sagami Bay is derived not from C. soyae but from C. okutanii.

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Abstract: Midori River estuary faces Ariake Bay, and has the largest sandy tidal flat(approximately 2, 100 ha)in Japan. We investigated the spatial distribution of particle size composition of the sediment, microphytobenthos on the surface sediment and macrobenthic animals at the stations set along a cross transect line in Midori River estuary. The Chl-a concentrations of the surface sediment that reflected the biomass of the microphytobenthos ranged between 19.3 and 113 mg/m2 at the stations on the tidal flat, and tended to decrease from the upper part to the lower part of the tidal flat and the offshore area. However, 92.0%of the total biomass of the macrobenthic animals collected at the sampling stations on the tidal flat was concentrated at the stations on the middle to lower part of the tidal flat. The highest biomass reached 3, 760g WW/m2, mainly due to the occurrence of dense patches of two suspension feeding bivalves, Ruditapes philippinarum and Mactra veneriformis. These two bivalves alone occupied 93.2%of the biomass of all the benthic animals collected at all sampling stations. The consumption of the primarily produced organic matter estimated from the secondary production of only a single species of Ruditapes apparently exceeded the potential primary production at the same place. The results of this study suggest that the re-suspension of primarily produced organic particles by the microphytobenthos on“ the upper part” of the tidal flat and its lateral transportation to“ the middle to lower part” of the tidal flat is essential to sustain the high secondary production of the suspension feeding benthic bivalves on the middle to lower part of this tidal flat.

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