2020 年 AA2020 巻 p. AA2020-6-
Temperature is an important environmental factor affecting the larval survival, development and duration of decapod crustaceans. We investigated the effect of temperature on larval performance in six terrestrial hermit crab species (genera Birgus and Coenobita): B. latro, C. brevimanus, C. cavipes, C. purpureus, C. rugosus, and C. violascens. Larvae were cultured at six temperature levels between ~19 and 34 °C. Larvae could not survive to the megalopal stage at temperatures below 20 °C. Megalopae appeared at temperatures above ~22–23 °C, and survival rates to the megalopal stage were high at ~25–31 °C and tended to decline over ~32 °C. Intra- and interspecific variations were found in the developmental pathways to the megalopal stage: 4 zoeal stages in B. latro, 4–8 zoeal stages in C. cavipes and 4 or 5 zoeal stages in the other Coenobita species. The proportions of larvae that completed the shorter developmental pathways tended to increase with increasing temperature in each species. Total zoeal duration tended to decrease with increasing temperature in all species, and C. cavipes, with prolonged developmental pathways, exhibited the longest developmental periods to the megalopal stage. The lower threshold temperature for larval development was estimated to be 16.4–19.3 °C based on the heat summation theory equation. Thus, larvae of coenobitid crabs are not able to develop and survive at low-temperature conditions below 20 °C, exhibiting typical thermal adaptation of subtropical and tropical species.
