Embryonic development of Amphioctopus fangsiao under elevated temperatures: Implications for resource management and conservation

Abstract

Amphioctopus fangsiao is an important fishery resource in northern coastal China, and this species has been developed for commercial fishing and aquacultural purposes. However, its embryos are vulnerable to ambient temperature, which leads to challenges in resource management and conservation. The present study investigated how high temperatures could affect the embryonic development (e.g., morphology, development time, and viability) of A. fangsiao. The results showed that the embryonic developmental rate was accelerated as the temperature increased. In addition, temperatures higher than the thermal threshold detrimentally affected the morphology and viability of eggs. Embryos maintained at 18, 21, and 24 ℃ successfully hatched at 40, 30, and 24 d after spawning, respectively. However, no embryos hatched at 27 ℃. Elevated temperatures altered the trajectory of normal embryonic development and increased the percentage of eggs with abnormal morphology. Embryos maintained at 24 ℃ failed to undergo the second inversion during embryonic development and remained at the animal pole until stage XVII (15 d). Upon the completion of organogenesis at stage XIX, an elevated temperature, as the external stimulus, could promote the early hatching of embryos with poor physiological features (e.g., small size and large yolk sac). The results indicate that the thermal range for A. fangsiao embryonic development is 18–24 ℃. Our findings on the relationship between embryonic stage and temperature might help fishery managers predict the emergence time of the hatchling population and promote the conservation of this species when establishing related fishery policies.