| Summary: | 碩士 === 靜宜大學 === 生態學研究所 === 98 === Larval release migration is an important event in the life history of land crabs. During the migration, ovigerous females are apt to expose themselves to extreme environments and the risk of predation. The aim of this study is to investigate the evaporative water loss through the changes of haemolymph osmolarity during larval release migration of two ovigerous crabs, Gecarcoidea lalandii and Metasesarma aubryi, in Hengchun Peninsula, Taiwan. The results showed that in G. lalandii at Hsiangchiaowan, the haemolymph osmolarity of ovigerous females (886 ± 10.4 mOsm kg-1, n = 64) and spawned females provided with fresh water for two days in laboratory (772 ± 7.4 mOsm kg-1, n = 18) were significantly different. As for M. aubryi, the haemolymph osmolarities of ovigerous females both at Hsiangchiaowan (737 ± 9.9 mOsm kg-1, n = 71) and seashore near Gangkou River (783 ± 21.6 mOsm kg-1, n = 15) were significantly higher than spawned females provided with fresh water for two days in laboratory (655 ± 6.5 mOsm kg-1, n = 23). Both in G. lalandii and M. aubryi, the smaller ovigerous females had higher haemolymph osmolarities than the larger ones. However, body sizes showed low statistical correlation with haemolymph osmolarities. Environmental factors such as ambient temperature, relative humidity and air flow velocity during larval release period had little influence on haemolymph osmolarity of ovigerous females. When dehydrated, the smaller crabs lost more water than the larger conspecifics; the smaller M. aubryi suffered from more water loss than the larger G. lalandii. The data of measurements and desiccation experiments in laboratory indicated that the ovigerous females both species at Hsiangchiaowan may not experience severe water loss during larval release migration, which coincided with the field observation.
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