- 著者
- Tetsuya Sanda Tomohito Shimizu Shigeki Dan Katsuyuki Hamasaki
- 出版者
- Carcinological Society of Japan
- 雑誌
- Crustacean Research (ISSN:02873478)
- 巻号頁・発行日
- vol.51, pp.129-135, 2022-11-09 (Released:2022-11-09)
- 参考文献数
- 23
Temperature is one of the most important environmental factors affecting the geographic distribution of ectotherms. We evaluated the low- and high-temperature tolerance limits of juveniles of two mud crab species, Scylla paramamosain and Scylla serrata, which are distributed in temperate and subtropical/tropical areas in Japan, respectively. Experiments were performed twice for S. paramamosain and four times for S. serrata using laboratory-raised juveniles. The juveniles were stocked in small containers, and the temperature was reduced or raised by 1°C every 24 h. The critical low or high temperatures (CLT or CHT) were estimated as the temperatures at which 50% of test juveniles ceased walking behaviour or died. The estimated CLT values for walking and survival were summarised as 8.4±0.7°C (mean±standard deviation) and 6.4±0.9°C in S. paramamosain and 9.6±0.6°C and 7.4±0.4°C in S. serrata, respectively. The CHT for walking could not be estimated, as almost all surviving juveniles exhibited walking behaviour, whereas the estimated CHT values for survival were summarised as 39.0±0.4°C in S. paramamosain and 39.1±0.6°C in S. serrata. Thus, interspecific variation in low-temperature adaptation was evident, and S. paramamosain are adapted to the lower-temperature environment.
- 著者
- Tetsuya Sanda Tomohito Shimizu Shigeki Dan Katsuyuki Hamasaki
- 出版者
- Carcinological Society of Japan
- 雑誌
- Crustacean Research (ISSN:02873478)
- 巻号頁・発行日
- vol.50, pp.87-93, 2021-07-03 (Released:2021-07-03)
- 参考文献数
- 21
- 被引用文献数
- 2
Cannibalism is considered a major cause of mortality among juveniles in nursery cultures of the mud crab Scylla serrata. Size grading is recommended as an effective measure to mitigate cannibalistic behavior; however, little is known about how body size differences influence cannibalistic episodes between juvenile individuals. We conducted one-to-one match experiments using hatchery-raised juveniles with carapace width between 12.5 and 33.3 mm. Two crabs were placed in an experimental arena for 24 h, and survival and pereiopod loss were subsequently observed. Large crabs always preyed on small crabs, and the probability of cannibalistic behavior significantly increased with the increasing relative size difference [RSD=1−(size of small crab)/(size of large crab)]. The loss of chelipeds and walking legs in the surviving small crabs amounted to 25% and 38%, respectively, and the proportion of lost walking legs increased with the increasing RSD, indicating the stronger aggressive behavior of larger crabs. This study suggests that maintaining size differences below the RSD threshold (0.34) at which 50% of the small crabs are cannibalized by large crabs would be an effective strategy to contain the occurrence of cannibalism in mud crab nursery cultures.