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application/pdf, The known distributional range of the Japanese crayfish, Cambaroides japonicus（ De Haan, 1841（）Crustacea, Decapoda, Cambaridae） is restricted to north part of Japan including Hokkaido, Aomori and northern parts of Akita and Iwate Prefectures. Recently a new population of this species was discovered from natural habitat in Tamozawa, Nikko, Tochigi Prefecture, Centaral Honshu, Japan. Present study examined origin of the Nikko population based on the composition of symbiotic crayfish worms（ Annelida, Clitellata, Branchiobdellida） as well as the crayfish morphologies （rostrum, telson and annulus ventralis）. Three species of crayfish worms, Cirrdrilus cirratus Pierantni, 1905, C. inukaii （Yamaguchi, 1934）, and C. ezensis（ Yamaguchi, 1934） were detected from the Nikko crayfishes, all of which are known to endemic to Hokkaido. Morphological characteristics in the crayfishe corresponded to those in Hokkaido population. Some documents and old archives （ca. 1900） in the Archivs and Mausolea Department, Imperial Household Agency, Japan suggest that many individuals of C. japonicus had been transported to the Nikko Tamozawa Imperial Villa from Hokkaido, and they were used as foods for the royal family. A map in an old archive indicates that there was an aquarium near the kitchen of the Imperial Villa. Consequently, it is highly probable that the present Nikko population of C. japonicus is derived from introduced individuals for foods from Hokkaido., 弘前大学教育学部紀要. 101, 2009, p.31-40

Molting and breeding entail major energetic costs for female crustaceans. However, females of some hermit crabs perform a molt immediately prior to copulation (prenuptial molt). The evolutionary significance of the prenuptial molt was examined in Pagurus hermit crabs, and two hypotheses were tested: (1) prenuptial molt might enhance the success of the present clutch by cleaning the pleopods of females and thereby preventing eggs from being dislodged from the pleopods, and (2) prenuptial molt might function for growth and increase future fecundity at the cost of energetic expenditure on the present brood. Although these hypotheses are not mutually exclusive, our results rejected the former hypothesis and supported the latter hypothesis. All four Pagurus species examined showed significant negative relationships between prenuptial molting and continuity of breeding; i.e., they showed high molting frequency after they had a long rest period from breeding. Females of P. minutus increased their size through the prenuptial molt, and showed a decreased clutch size due to the molt. The number of dislodged eggs increased if females molted in P. minutus. These results suggest that hermit crabs undergoing a prenuptial molt might not gain any clear immediate advantage of enhanced survival of eggs in the present clutch, and that the prenuptial molt would mainly contribute to growth.

An investigation was conducted to evaluate the annual variation in potential predation impact (PPI) on larval and juvenile Pseudopleuronectes yokohamae by Crangon uritai in Hakodate Bay using predator–prey size relationships. Laboratory experiments were designed to estimate the favorable prey size of C. uritai through back-calculation of body length (BL) of P. yokohamae from sagittal otolith diameter observed in the stomachs of C. uritai. The most favorable prey–predator size ratio (BL of P. yokohamae–total length (TL) of C. uritai) class was 0.15–0.19, and ranged from 0.12–0.31. There was a significant positive correlation between the BL increase of P. yokohamae and the bottom water temperature in the field, such that BLs stagnated during the cold year of 1999 from April to June, and increased during the warm year of 2002. In contrast, no significant correlation was found between the TL increase of C. uritai and the bottom water temperature. Moreover, there were no significant differences in the mean TL of C. uritai between months (April–June) or years (1998–2002). Variation of PPI depended on the relationships between the growth rates of P. yokohamae and bottom water temperature. Therefore, the warm year of 2002 resulted in higher potential predation impact (PPI ≥ 20), and it was at least 20 days shorter than that of the cold year of 1999. These results suggest that increased bottom water temperature in the nursery area was one of the most important factors for cumulative predation loss.

The response of the shore crab Gaetice depressus to predation risk stimuli of either the octopus Octopus vulgaris or crushed conspecifics was examined at two different time phases in the activity rhythm (active and inactive period) by laboratory experiments. When octopus chemical stimuli were introduced to the experimental aquarium, the crab activity decreased in the active period (night) but not in the inactive period (daytime). When the chemical stimuli of crushed G. depressus were introduced, the activity of the crabs increased in the inactive period although the stimuli decreased the activity in the active period. This indicates that G. depressus adjust their anti-predator response according to a combination of the type of predation risk and also the activity rhythm.

東京海洋大学修士学位論文 平成25年度(2013) 海洋生命科学 第1807号, 指導教員: 延東真, 全文公表年月日: 2014-09-29

東京海洋大学修士学位論文 平成25年度(2013) 海洋生命科学 第1735号, 指導教員: 竹内俊郎, 全文公表年月日: 2014-07-25

東京海洋大学修士学位論文 平成22年度(2010) 海洋環境保全学 第1166号, 指導教員: 石丸隆, 全文公表年月日: 2012-10-05

東京海洋大学修士学位論文 平成19年度(2007) 海洋環境保全学, 指導教員: 石丸隆, 全文公表年月日: 2008-05-29

We investigated how the physiological characteristics and synaptic activities of nonspiking giant interneurons (NGIs), which integrate sensory inputs in the brain and send synaptic outputs to oculomotor neurons innervating eyestalk muscles, changed after unilateral ablation of the statocyst in order to clarify neuronal mechanisms underlying the central compensation process in crayfish. The input resistance and membrane time constant in recovered animals that restored the original symmetrical eyestalk posture 2 weeks after operation were significantly greater than those immediately after operation on the operated side whereas in non-recovered animals only the membrane time constant showed a significant increase. On the intact side, both recovered and non-recovered animals showed no difference. The frequency of synaptic activity showed a complex pattern of change on both sides depending on the polarity of the synaptic potential. The synaptic activity returned to the bilaterally symmetrical level in recovered animals while bilateral asymmetry remained in non-recovered ones. These results suggest that the central compensation of eyestalk posture following unilateral impairment of the statocyst is subserved by not only changes in the physiological characteristics of the NGI membrane but also the activity of neuronal circuits presynaptic to NGIs.

東京水産大学博士学位論文 平成14年度(2002) 論文博士 乙第74号, 全文公表年月日: 2008-03-31

本人による語句の追加・修正あり, 校友会誌. 29, 1938, p.13-19

application/pdf, Article, 動物学雑誌. 41(484), 1929, p.105-106