Effects of illumination on early life development and digestive enzyme activities in common pandora Pagellus erythrinus L. larvae

The activities of main digestive enzyme (proteases, amylase and lipase) and animal husbandry (mainly growth and survival) were studied in common pandora Pagellus erythrinus larvae until 30 days after hatching (DAH). Three different illumination levels (10, 30 and 100 lx) were compared in triplicate and green water technique was carried out. At the end of the experiment, illumination did not affect neither survival nor growth except 10 lx treatment. Similarly, specific growth rate (SGR) was different in 10 lx treatment (p < 0.05), although no differences were found in group 30 and 100 lx treatments (p > 0.05). In all groups, trypsin and chymotrypsin specific activities were firstly detected on day 3 related with mouth opening and slightly increased until 20 and 25 DAH respectively, and after this date specific activities of those decreased. Although, there was a significant difference between 10 lx treatment and other experimental groups (p < 0.05), no differences were found in other treatments (p > 0.05). Pepsin was firstly detected on day 25 related with stomach formation and sharp increase was observed until 30 DAH and then slight decrease was measured from this date and no differences were found between all groups. Amylase was firstly determined on day 2 and increased to day 5. After this date, slight decreases were measured in all groups and continued until end of experiments. The highest specific activity of amylase was determined in 30 lx treatment and no significant differences were found between groups (p > 0.05). Lipase was firstly detected on day 4 and increased to day 10. Then, activity of lipase decreased until day 15 and increased again until 25 DAH. Slight decreases were found in all groups until day 30 and continued to end of experiments. No significant differences were detected among groups (p > 0.05).

Finally, the significant improvement in survival, larval development and specific enzyme activities of larvae were determined in 30 lx treated group. It is thought that this phenomenon is related to optimal keeping conditions provided by the medium illumination level for Pagellus erythrinus larvae.