[in Japanese]

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The present paper deals with the breeding ecology of two dogielinotid amhipods on the five sandy-beaches in southern Hokkaido. Japan. Haustorioides japonicus and H. munsterhjelmi are semelparity species. The peaks of egg-laying in H. japonicus population on the Omori-beach. Hakodate were observed four or five times in a breeding season, and these peaks synchronized with the semi-lunar cycle. In the first half of breeding season, the large size females occupied the majority in the latter half. The number of eggs per brood in both species is positively, correlated to the female body length. Mean fecundity ranges from 70 to 87 eggs in the first generation of H. japonicus, and the ranges from 84 to 106 eggs in H. munsterhjelmi. Dogielinotid amhipods seems to be productive comparing with other gammarid families.

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This paper deals with the development and growth of two dogielinotid amphipods in southern Hokkaido, Japan. The early developmental stages of Haustorioides japonicus and H. munsterhjelmi were observed, and five clearly defined stages were regognized within the brood pouch of female by morphological characteristics. The characteristics of juveniles just after hatching were observed in detail, and compared with those of adult specimens. From these observation, it was clear that these juveniles could be identified immediatory to the species level. Loss of embryos in brood pouch was about 18-41% just before hatching, and 37-56% just before releace from the brood pouch of H. japonicus. High mortality during early development were observed between stage III and stage IV, and between stage V and stage VI.

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Three types of the life cycle of the atyid shrimp Neocaridina denticulata were observed in the Sugow River, Japan. A short generation cohort (type I) showed high growth at the high water temperatures occurring after hatching in early June ; many ovigerous females were observed subsequently in early and middle August and they died. A long generation cohort (type II) hatched in mid July and large females incubated eggs during late August and late September but they grew little at low water temperature from November to the following March and ovigerous females appeared again in May. Hatching of another long generation cohort (type III) occurred in late August ; growth recommenced after the months which of low water temperature ; and females incubated eggs during early June and early August. The population were consisted of two groups which took the same cyclic change of generation types, I→III→II→I→III→II→I→(continued), with time lag of a year each other. Growth equations over the life cycle for types I→III, including seasonal variation, ate described. The influence of mest size selection, by sweep nets, on sample size frequency distributions in also discussed.

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Individual density and reproduction of Cambaroides japonicus in a stream, the southernmost habitat of this species, Oodate City, Akita Prefecture, were studied from 1981 to 1989. Decrease of the animal density was caused by shallow depth indicating water volume of the habitat. The relationship between carapace length (X, mm) and number of eggs attached to pleopods (Y) was Y=-50.69+4.704X. In the stream, spawning season is March and April. Hatching is caused in June and July. An adult female spawns one time in a year.

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Sexual dimorphism of Palaemon pacificus and P. serrifer were investigated during 1987 to 1989 in Tateyama Bay, Chiba Prefecture. It was found that both the rostral length and the number of segments of the inner branch of the bifurcated outer flagellum were larger in males than in females. The difference between male and female appeared nearly the size of the minimual ovigerous female. Difference between male and female on both the rostrum and the inner branch of the bifurcated outer flagellum appeared with maturing.

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Observation upon the feeding habit of Eriphia smithii were made from May to September in 1988 at rocky shore near Banda Marine Station of Tokyo University of Fisheries in Chiba Prefecture. Observations were recorded, forty eight in total. Most foraged organisms for food were Polyplacophora and Patellacea (52.1%). Predation on Brachyura and Pelecypoda were observed seven (16.7%) and six (12.5%) times respectively. The other animal groups as food were observed less than four times.

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The breeding of the xanthid crab, Leptodius exaratus (H. MILNE EDWARDS) was investigated. Secondary maturation signs appeared in abdominal size in females. Ovigerous females occurred from June to September and its peak was observed in August. The females may spawn one or two times in a breeding season.

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The giant spider crab, Macrocheira kaenpferi, Takaashigani (Japanese name) is the largest of all living Arthropoda. The leg span of a large adult male is 4 meters. This crab is found along the Pacific coast of Japan, from Kamaishi to Kyusyu districts at depths ranging from 50 to 400 meters. Studies on both spawning and the early larvae forms of the crab were reported before. We have now succeeded in rearing this crab from, the megalopa stage to the juvenile stage. This short report is dealt with these result and some other observations.

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Oviposition, release of larvae and molting were investigated for individual Gaetice depressus (DE HAAN) crabs reared throughout the year in the laboratory. Oviposition and larvae release occurred from April to October or November. Molting occurred throughout nearly the entire year, although few crabs molted in winter. Most of the crabs molted shortly after the breeding season. The length of oviposition season and the number of ovipositions varied among individual females, and were not correlated with body size but affected by molting. The period between larvae release and the next oviposition was longer when molting occurred within that interval. The start of oviposition at the beginning of the breeding season tended to be affected by the preceding molting. Rearing of females isolated from males showed that females of this species can store sperm and then fertilize 3 broods of eggs. Stored sperm is considered to be retained through molting.

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