The impact of light intensity and photoperiod on ontogeny of digestive enzymes activity of Persian sturgeon (Acipenser persicus Borodin, 1897)

In the present study the impact of different photoperiod and light intensity on digestive enzymes activity (pepsin, trypsin, chymotrypsin, lipase, amylase and alkaline phosphatase) of Persian sturgeon (Acipenser persicus) from hatching until complete absorption of yolk sac were monitored. The newly hatched Persian sturgeon larvae with average weight and length of 19.23 ± 0.08 mg and 11.35 ± 0.03 mm respectively were treated with 3 photoperiods (24L, 12L, 24D) and 3 light intensities (50, 150 and 300 lux). The light intensity for 24D was 0-10 lux. The larvae in different treatments were cultured under similar experimental conditions (pH, temperature, water flow and feeding rate). The results demonstrated significantly higher activity of pepsin and trypsin at 9 days post hatch (dph) in treatment 2 (12L-150 lux light intensity) and in treatment 5 (24L-150 lux light intensity) compared to control respectively. The alkaline phosphatase was higher in treatment 2 whereas amylase and chymotrypsin exhibited higher activity under 12L-300 lux, however showed no significant difference with control. In conclusion the results of this study indicated that light is an important physical factors in ontogeny of Persian sturgeon digestive system during early larval stages. Moreover most of the enzymes showed higher activity under 12L and 150 and 300 lux light intensity.