Seasonal morphophysiological changes during the reproductive cycle of tripletail (Lobotes surinamensis BLOCH 1970) (Perciformes: Lobotidae) in natural environment

Author(s)

Kainã Rocha Cabrera Fagundes

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2019-05-24

Examining board members

Renata Guimarães Moreira Whitton; Maria Ines Borella; Gisele Akemi Oda; Elizabeth Romagosa

• Advisor: Renata Guimarães Moreira Whitton; Renato Massaaki Honji

Abstract

The present study aimed to study the morphology and reproductive physiology of Lobotes surinamensis in a natural environment, gathering information that allows applied works in the production and conservation of this species. Adult males and females were collected in the Baía da Ilha Grande, Rio de Janeiro during the spring (October-November-December), summer (January-February-March), autumn (April- May-June) and winter (July-August-September). Plasma profiles of gonadal steroids, 17β-estradiol (E2), 17-hydroxyprogesterone (17-OHP) and 11-ketotestosterone (11-KT) were analyzed in females, and the concentration of testosterone (T) and 11-KT in males. Histological analyzes of the gonads were performed as a tool for morphological evaluation, which was corroborated with the physiological data, during the reproductive cycle. The genetic expression of fshβ and lhβ and the relative fecundity by the number of developed oocytes were also analyzed. During spring and summer, the females had the ovaries developed and capable of spawning, with vitellogenic and developed oocytes, and a well evident radiata zone. In autumn and winter, females were preparing for the reproductive period, with a predominance of nest of oogonia and perinucleolar oocytes in general. The plasma concentration of E2 remained higher in females during the spring in relation to summer and autumn/winter. The annual profile of this steroid in L. surinamensis females may be related to the degree of development of the ovarian follicle observed in histology. The plasma concentration of 11-KT was inversely of that observed for E2, with a low concentration in the spring and a tendency to increase in winter/autumn, corroborating the role of 11-KT in the primary oocyte growth. The plasma concentration of 17-OHP in the females did not present significant differences between the seasons, suggesting that this is not the active progestogen in teleosts, but the precursor of the final maturation inducing steroid (MIS). In spring and summer, lhβ presented higher gene expression than in the autumn/winter period in females, while fshβ remained with constant expression levels during all seasons. In males, the histological analysis of the testicles showed that in the spring and summer, the sperm ducts were filled with spermatozoa, evidencing the period of spermiation, whereas in the autumn/winter period there was a predominance of cysts of spermatogonia and cells in different stages of. development, which corresponds to an initial maturation stage, that is, the preparation for the reproductive period. The plasma concentration of T in males remained stable throughout the seasons, whereas the plasma concentration of 11-KT was higher in the spring when compared to the autumn/winter period. In spring and summer, the expression of lhβ was higher than in the autumn/winter period, while similarly to females, fshβ expression levels did not change over the seasons. The analysis of the expression of these gonadotropin genes, associated with the concentration of gonadal steroids and gonadal morphology, made it evident that the peak of the reproductive period of L. surinamensis occurs in the spring, extending until the summer (AU)

• FAPESP's process: 17/10971-4 - Morpho-physiological characterization of reproductive cycle of prejereba (Lobotes surinamensis) (Perciformes: Lobotidae) in natural environment
• Grantee: Kainã Rocha Cabrera Fagundes
• Support Opportunities: Scholarships in Brazil - Master