Physiology of Finfish and Shellfish (2+1)

5.2.9. Chromaffin tissue

Chromaffin cells (adrenaline producing) are generally dispersed in the head kidney near the post cardinal vein and exhibit considerable variation in their distribution in teleosts. These cells are rounded in appearance with slightly basophilic cytoplasm and may show typical chromaffin reaction also. The chromaffin cells may occur singly or in groups in different locations in the head kidney. They may be

1. Embedded in the vein wall or
2. Associated with the inter-renal tissue or
3. Dispersed in the inter-renal tissue and the vein walls
4. Present in the ovary of teleosts.

Studies show that 2 hormones, adrenaline and non adrenaline are present in the head kidney as well as plasma of teleosts, but vary in their concentration in different species. Fish treated with adrenaline immediately become hyperglycaemic (Very high blood sugar). Chromaffin cells of teleosts contain dihydroxyphenylanaline (dopa) and 5-hydroxytryptamine (serotonin). Extracts from the chromaffin tissue stimulate the sympathetic nervous system of another fish. The hormones produced by the chromaffin cells are epinephrine and nor-epinephrine performs functions comparable to the adrenal medulla of mammals. It concentrates pigment granules in melanophores and controls blood pressure. Hence, chromaffin tissue of teleosts may be considered homologous to the adrenal medulla of mammals. Chromaffin tissue is reported to be present in the ovary of several freshwater teleosts like L. rohita, Catla, Mrigala, Puntius spp, Channa spp, Notopterus inside the ovarial folds along the lamellae.