Document Type : Primary Research paper
The purpose of this study was to evaluate the alkaline phosphatase activity in haemocytes and midgut gland of the penaeid shrimp Artemesia longinaris in relationship with different doses of vitamin D3 in feedand to estimate its potential use as biomarker for nutritional stress. A nine-week trial was carried out with juvenile shrimp in aquaria. Animals were fed semipurified feeds with increasing levels of vitamin D3 (0; 0.2; 0.375; 0.75 and 1 mg vitamin D3 kg-1 feed). Treatments without vitamin D revealed the significantly highest protein content in haemocytes (P<0.05), as the lowest values were recorded on 0.2 and 1 mg vitamin D kg-1 treatments. The analysis of protein content of midgut glands revealed a maximum content for diets containing 0.2 and 0.75 mg Vitamin D kg-1. The optimum pH value for alkaline phosphatase in midgut gland was 9.5. The results show the occurrence of alkaline phosphatase activity in the tissues of shrimp A. longinaris, describing higher enzymatic activity values in haemocytes than in midgut glands. The highest enzyme activity in haemocytes was observed for shrimp fed without vitamin D (1.235 abs min-1 mg protein-1), however, in midgut gland, the activity varied from 0.141 to 0.297 abs min-1 mg protein-1, with the highest values on 0 and 1 mg vitamin D kg-1. Histological analysis of the midgut gland confirmed a good health of the shrimp fed 0.375 and 0.750 mg vitamin D kg-1 and were used as optimal values for determining enzymatic activity. Shrimp fed diets lacking of vitamin D or 1 mg kg-1 showed signs of malnourishment. The results indicate that alkaline phosphatase activity in A. longinaris was influenced by dietary vitamin D and may be used as a biomonitor of nutritional stress.