TOMINAGA, Akira and Yasushi KURIHARA (Biological Institute, Faculty of Science, Tohoku University). 1987. Study on the microbial organic decomposition in the tidal flat at river mouth with reference to the occurrence of benthic invertebrate animals. Benthos Research (Bull. Jap. Assoc. benthology), 32 : 1-11.
The microbial activities for decomposition of organic matters in the river mouth were highest in mud of the tidal flat, but low in the brackish reed marsh and bottom mud of the riverbank which was always submerged in the water. The C/N ratio in the tidal flat was lower than those in the riverbank bottom mud and brackish reed marsh, indicating that the quality of sedimentary organic matters in the tidal flat was different from the other places.
Surface of the bottom mud in the tidal flat, on the other hand, is covered sometimes with microalgal mat including Euglena as the dominant species. Therefore, a black box (2.5 x 2.5 x 1.0 m) was installed on a part of the tidal flat in order to avoid the effects of algal mat on the activities of microbial decomposition and benthic animals, and the microbial activities for decomposition of organic matters and the fauna of benthic animals in the darkened condition were compared with the control. No differences were found on the organic matters-decomposing activities between the darkened and control conditions, except for denitrification. In the darkened condition, compared to the control, the denitrification activity was obviously high and the benthic animals including polychaetes were found also in high numbers of individuals. These results indicated that the organic matters-decomposing activities excepting the denitrification were not affected by the benthic animals and microalgal mat and the denitrification activity was enhanced by the presence of polychaetes.

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TANABE, Kazushige (Geological Institute, University of Tokyo). 1988. An attempt for age estimation of bivalves, using shell growth lines. Benthos Research (Bull. Jap. Assoc. Benthology), 32 : 12-17.
Growth lines of different magnitudes are commonly observed in the skeltons of invertebrates. Of these, annual increments may be most important for life history analysis of modern and extinct organisms. They are easily recognized by reading the growth records (= sclerochronology) in marked and recovered individuals. Detailed methods for age and growth rate determinations are described for a venerid bivalve, Phacosoma japonicum (Reeve) inhabiting the coast of the Seto Inland Sea, with remarks on their ecological and paleoecological implications.

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SHIRAYAMA, Yoshihisa (Ocean Research Institute, University of Tokyo) and Reinhardt M. KRISTENSEN (University of Copenhagen). 1988. Taxonomy, ecology and biogeography of Loricifera. Benthos Research (Bull. Jap. Assoc. Benthology), 32 : 18-20.
A new species of the most recently described phylum, Loricifera Kristensen, 1983, was discovered from the red clay collected at ST. 9 of a cruise of RV Hakuho Maru, ORI, UT. The station was situated close to the axis of the Izu-Ogasawara Trench at a depth of 8260 m. The present species was found to belong to the genus Pliciloricus (Pliciloricidae) and is the most closely related to P. profundus Higgins and Kristensen, 1986 in the presence of single pair of P-flosculi, the type of mouth cone and clavoscalids, and the claw-shaped spinoscalids. Unique to the present species is its bulb-like shape of the lorica, the mucous coat of the larval lorica and the 30 sculptured plates in the adult thorax. This is the first record of loriciferans from the Indo-Western Pacific area. In addition, the habitat of the present species is completely different from the other congeneric species. Though the former was discovered from very fine sediment of the hadal depth, all described species so far have been callected exclusively from sublittoral coarse sands off the southeastern coast of the USA. Moreover, in contrast to the interstitial nature of the other species, the present species probably burrows within the sediment. These findings suggest that loriciferans have great ability to adapt to various kinds of habitat and the phylum is distributed ubiquitously throughout marine environments. A cladistic tree was made using the Farris' Wagner method for six species of Pliciloricus collected from Atlantic as well as Pacific. The tree suggested that the dispersions of loricifera between two oceans have occurred at least twice or for two species before.

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ITO, Syoichi (Ryotsu High School, Sado), Koji IKEHARA (Japan Sea Regional Fisheries Research Laboratory) and Yoshiharu HONMA (Sado Marine Bialogical Station, Niigata University). 1988. Caprellids (Crustacea : Amphipoda) attached to the floating seaweeds on the Sea of Japan. Benthos Research (Bull. Jap. Assoc. Benthology), 32 : 30-36.
Extensive survey of floating seaweeds (Sargassum spp.) has been carried out offshore area along the coast of the Sea of Japan from June 1981 to June 1986. Caprellidae was one of the most dominant taxa among the invertebrate fauna attached to the floating seaweeds, and was found in all floating seaweed samples collected from 84 sampling stations distributed from the end of western coast of Honshu to Sado Island, Niigata. Twelve species of caprellids were identified among the specimens collected. Caprella penantis and C. danilevskii were the dominant species both in numerical abundance and wide range of occurrence, and next was C. decipiens as the third rank. The occurrence of other species concentrated in the floating algae occurred in Toyama Bay and Sado Strait. This fact suggests that a part of the floating seaweeds found in offshore of Hokuriku District consists of those transported long distance by the Tsushima Current from the northern Kyushu, while a part of them derived from the seaweed zone of adjacent coastal area such as Toyama and Niigata region.

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TAKEUCHI, Ichiro and Reijiro HIRANO (Department of Fisheries, Faculty of Agriculture, University of Tokyo). 1988. A preliminary report on the life-history of Caprella danilevskii Czerniavski (Crustacea, Amphipoda) reared in the laboratory Benthos Research (Bull. Jap. Assoc. Benthology), 32 : 37-41.
Caprella danilevskii Czerniavski was successfully reared two generations under laboratory conditions. This report presents an outline of the life cycle. Animals were maintained in pairs or four individuals in petri dishes (5.7 cm in diameter and 5.6 cm in depth) containing filtered seawater at 20°C. Colony of Cylindrotheca closterium (Ehrenberg) Reimann et Lewin was supplied as a source of food, and the red alga Gelidium amansii (Lamouroux) Lamouroux was given as a site of attachment for caprellids.
Juveniles, 1.5 mm in body length, released from brood pouch were prescribed as the instar I. Following instars were decided by affirmation of molts. They molted successively at 2.5-6.5 days intervals. Body length of males increased exponentially, and that of female represented a sigmoid curve. Body length of instar VII was 6.5 mm in male and 5.5 mm in female, and that of X was 10.9 mm in male and 7.0 mm in female. Average life span was 46.5 days in male (n=15) and 46.0 days in female (n=8). At the age of 20.8 days, females reached instar VII and produced first eggs, and juveniles were released 5.1 days later. Females reproduced eggs 5.4 times successively at about 5 days intervals, and the total number of offspring was 69.4 individuals per female.

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AOKI, Masakazu (Amakusa Marine Biological Laboratory, Kyushu University), 1988. Factors affecting population fluctuations of caprellid amphipods inhabiting a Sargassum patens bed (Preliminary report). Benthos Research (Bull. Jap. Assoc. Benthology), 32 : 42-49.
Factors affecting the population fluctuations of caprellid amphipods inhabiting Sargassum patens bed were analysed. S. patens began to grow in August and the height and volume reached maximums in April. Increase of caprellids correlated with the growth of the seaweed and the population size reached a maximum in March. The seaweed population began to decline in May and continued to be washed away until July, but caprellid populations showed a drastic decrease in March, ahead of the decline of the seaweed bed. Sudden increase of predation pressure by wrasses in March was considered to be an important factor responsible for drastic decrease of caprellids. Results of a cage experiment indicated the large effect of the predation pressure on caprellid populations. In summer, there was no substratum in the field for caprellids, and caprellid populations were limited to the shorter and shrub-like Sargassum bed on the rocky coast in Aka-iwa, about 400m north of the S. patens bed. Source populations are apparently maintained in such areas during summer and then drift into the S. patens bed in autumn.

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