Temperature effects on early development and biochemical dynamics of a marine fish, Inimicus japonicus

A study was undertaken to evaluate the development and metabolic substrates (carbohydrate, protein, lipid and fatty acids) dynamics during the embryonic and yolk-sac larval stages of the devil stinger, Inimicus japonicus, at different water temperatures (18, 21, 24, 27 and 30 °C). The hatching time was significantly shortened when the temperature increased (P < 0.05). Only 14.5% of embryos hatched at 30 °C, while the hatching rate was 92.5% at 24 °C. Larvae incubated at 21 °C displayed the greatest survival at mouth-opened larva stage (96.5%), but the rate dropped sharply when the temperature surpassed 24 °C (P < 0.05). The full length and yolk-sac volume of newly hatched larva at 18 °C and 30 °C were significantly smaller than those at 21, 24 and 27 °C. Larva at 21 °C always had the largest full length during early development. The advent of mouth-opened larvae was closely related to temperature, so were the full length and yolk volume of the mouth-opened larva. As the incubation temperature declined, the mouth-opened larva obtained longer full length and less yolk remain. Lipid was, to a large extent (47.0% of the initial amount), a fuel for development when the embryo was incubated at 18 °C. The depletion of protein in the embryo was significantly higher at 30 °C (67.6%) than that at 21 °C (31.3%). Consumption of carbohydrate was observed only in embryo at 18 °C. During the development of yolk-sac larva, a lower incubation temperature induced more protein anabolism and less lipid consumption. In I. japonicus, polar lipids (PL) constituted the principal class of lipid in eggs (74.0% of the total lipid); and it was the most consumed portion during embryogenesis in all treatments. The lipid composition in mouth-opened larva was affected by the incubation temperature. The storage triglycerides (TG) tended to comprise a higher proportion in larva incubated at 30 °C than in those at lower temperatures. The PL proportions in larva at 18 °C and 30 °C were lower than those in larvae at 21 °C, 24 °C and 27 °C. Low concentrations of polyunsaturated fatty acid (PUFA) in embryos and larvae were correlated with increased temperatures; this indicated that the rapid development at higher temperatures was at the cost of more PUFA loss. It is concluded that 21–24 °C is an appropriate range for incubation of I. japonicus eggs and larvae and that 24 °C is optimal in terms of shortening the endogenous nutritional stage and improving metabolic efficiency.

► Temperature affects early development and nutrient dynamics of Inimicus japonicus.
► Highest hatching rate and survival of mouth-opened larva occurr at 21 °C and 24 °C.
► Mouth-opened larva at lower temperature has longer length and less yolk reserve.
► Embryogenesis consumes more lipid at 18 °C while uses more protein at 30 °C.
► PUFA contents in embryo and larva decrease with increasing temperature.