The effects of constant and oscillating temperature on embryonic development and early larval morphology in longfin yellowtail (Seriola rivoliana Valenciennes)

Constant and oscillating egg incubation temperatures on embryonic development and early larval morphology were studied in longfin yellowtail (Seriola rivolianaValenciennes). We investigated the effects of constant temperatures from 16 to 32 degrees C on embryo development and larval morphology at hatch, and whether oscillating temperature during embryogenesis could lead to larval morphological variations. After hatching, larval morphology and development during yolk sac (YS) utilization were examined in larvae at constant temperatures and larvae at 25 degrees C that had oscillating temperature during egg incubation. Hatching rates were > 75%, only decreasing to similar to 50% at 30 degrees C. At constant temperatures, the largest larvae occurred at 22 and 24 degrees C. The oscillating temperature did not affect the timing of embryo development but resulted in larger and smaller larvae with a smaller and bigger YS, respectively, with a similar hatching time. Therefore, a growth response occurred in embryos during a window of development before hatching, depending on the adaptive response to temperature (spawn-specific). After hatching, most of the YS was absorbed within 24 hr in all treatments, and the growth of the larval head was a priority with an optimal development at 26 degrees C. There was compensatory growth in smaller larvae resulting in similar sizes after YS utilization, but larvae showed variations in body structure that could be important in further aquaculture research.

Automated summary

The study found that constant and oscillating egg incubation temperatures in longfin yellowtail have significant effects on embryonic development and larval morphology, leading to different growth responses in larval structure. Prior to hatching, embryos exhibit growth responses to temperature during a specific developmental window, influencing larval size and morphology.