EFFECTS OF PROLACTIN, CORTICOTROPHIN AND CORTISOL ON THE ADENOHYPOPHYSIS AND INTERRENAL GLAND OF ANADROMOUS THREESPINE STICKLEBACKS, GASTEROSTEUS ACULEATUS L. FORM TRACHURUS, IN WINTER AND SUMMER

Abstract

SUMMARY: In 'winter' anadromous threespine sticklebacks (Gasterosteus aculeatus L. form trachurus), corticotrophin (ACTH) injections significantly decreased the size of epsilon-cells (corticotrophs), alpha-acidophils (somatotrophs) (with an apparent increase in the degree of degranulation) and dorsal basophils (thyrotrophs) (with an apparent increase in granulation). Corticotrophin was also found to increase interrenal nuclear size, to decrease body length and to cause the development of a green skin coloration typical of summer fish. Cortisol injections significantly decreased the size of thyrotrophs and increased the size of periodic acid—Schiff's reagent (PAS)-negative cells of the pars intermedia. Prolactin injections significantly decreased the size of the thyrotrophs and caused the development of a green skin coloration though to a lesser extent than ACTH injections. In 'summer' sticklebacks which received fewer injections than winter fish (four compared with ten) ACTH significantly decreased the size of corticotrophs and PAS-negative cells of the pars intermedia whereas cortisol produced no significant effect on any of the cells studied.