INTERRENAL FUNCTION AND SERUM CORTISOL LEVELS DURING THE MIGRATORY CYCLE OF STURGEONS.

Abstract

Histophysiology of interrenal gland and cortisol blood levels in Russian sturgeon (Acipenser gueldenstaedti Br.), stellate sturgeon (Acipenser stellatus Pall.), and beluga ( Huso huso L.) were studied. Cortisol levels (ng/ml) in serum were measured by enzyme-linked immunosorbent assay (ELISA). The interrenal function of Russian sturgeon females at the early previtellogenesis (Caspian Sea, salinity 5.17.4 o/m) is moderately activated. With many large vacuoles (cholesterol) in the gland tissue. The degree of vacuolization is variable. In some cells of the interrenal bodies many picnotic nuclei are present. Average nucleus volume of activated interrenal cells is 155.5f1.5 pm3 in females and 158.5 f2.9 pm3 in males. Cortisol concentrations are 22.2f3.7 ng/ml (June), 22% 5.1 ng/ml (Oct.) in females at this state and are 53.M7.4 in males (Oct.). At the beginning of the anadromous migration to the Volga River cortisol levels are significantly higher in comparison to those fish at: 109.8+11.7 (p<O.OOl) in the winter form females of Russian sturgeon (vitellogenic period), 126.5f39.1 in males (spermatogenic period). Functional activity of interrenal gland was significantly higher then during the sea period. The nucleus volumes were 170.1f1.8 pm3 (p<O.OOl) in females, and 172.4 f1.8 vm3 (p<O.OOI) in males. Interrenal tissue of these fish was characterized by strong vacuolization, hyperemia and cytolysis. During sexual maturation cortisol levels decreased in the spring form females of sturgeon. In females with germinal vesicle in the oocyte centre serum cortisol level was 1 1 1.8k16.6. In the females with germinal vesicle migrated to oocyte periphery cortisol concentration was 72.5f5.0 (p<0.05). Serum cortisol levels in females of stellate sturgeon during early previtellogenesis (Caspian sea) are similar at June and October ( 12 31 ng/ml), and significantly elevated at the beginning of anadromous migration in April (1 70.2 f 28.5). A similar tendency was observed in the beluga. Higher serum cortisol level were found in female captured from river (165.4 ng/ml) compared to females captured at sea ( 7.1 18.9 ng/ml) was occurred, Serum cortisol levels in all investigated species at same state of gonads are similar. Our results show an active role of interrenal gland and its main hormone in sturgeons (cortisol) in the migratory impulse, sexual maturation and osmoregulation.