Ontogeny of immunoreactive somatolactin, prolactin and growth hormone secretory cells in the developing pituitary gland of Cichlasoma dimerus (Teleostei, Perciformes)

Prolactin, growth hormone and somatolactin constitute a hormone family beca use they are structurally related and are secreted by acidophilic cells of different regions of the adenohypohyisis. In this work, we report the ontog eny of ir-prolactin, ir-growth hormone and ir-somatolactin cells in the dev eloping pituitary gland of the cichlid fish Cichlasoma dimerus (Teleostei; Perciformes). Antisera raised against fish pituitary hormones were used. In this species hatching occurs 54 hs after fertilization and the three diffe rent: cell types were recognized two days later. The neurohypophysis was re cognized on day 14 after hatching and in later stages it began to show the characteristic deep interdigitations of the adults, On day 42 (juvenile sta ge) the distribution of ir-PRL, ir-GPI and ir-SL showed the pattern describ ed for adults of this species. The ir-SL cells were not PAS-positive in lar vae as they are in adults. This would suggest the presence of a nonglycosil ated form of somatolactin in early stages of development which may coexist in adults with a glycosilated form. The appearence of these hormones so ear ly in development suggest their importance in the survival of fish larvae b ut further studies focused on the ontogeny of hypothalamic factors that reg ulate their synthesis and secretion must be performed.