Dissertation Gabriela Silva Campos

AUTHOR: Gabriella Silva Campos

TITLE: Population percentage of ovarian follicles and ovarian morphometric characterization as a new tool for evaluating the effect of photoperiod in danio rerio, associated with biochemical characterization on oxidative stress and ros

ADVISOR: Profa. Dra. Mônica Rodrigues Ferreira Machado and Prof. Dr. Benner Geraldo Alves

DEFENSE DATE: 04/29/2021

ABSTRACT

The photoperiod has been cited as one of the main factors that control reproduction in teleost fish. It is already known that the increase in photoperiod promotes the induction of the reproductive process, but most studies evaluate this induction using gonadosomatic index and follicular type count in fragments of ovaries. Therefore, the objective of this work was to determine if the photoperiod 12 Light: 12 Dark or 14 Light: 10 Dark, influenced the follicular population, follicle morphometry and biochemical indices in zebrafish (Danio rerio). Twenty-four females were used, divided into two photoperiods 12 light: 12 dark and 14 light: 10 dark. For histology, 12 ovaries from 6 females from each photoperiod were used, and for the determination of reactive oxygen species (ROS) the same number of ovaries. For histology, the ovaries were embedded in historesin, cut with a 3 μm thick ultramicrotome and stained with toluidine blue. After this procedure, the follicular development phases were counted to determine the follicular population and both oocyte and follicle morphometry. . To determine the activation of oxidative stress, biochemical analyzes were then performed to determine nitric oxide (NO), reactive species to thiobarbituric acid (TBARS), hydrogen peroxide (H2O2), ROS, peroxide dismutase (SOD), catalase (CAT), total proteins and acetylcholinesterase and butyrylcholinesterase. We conclude that photoperiod can indeed influence some follicular and oocyte structures such as area, thickness of the vitelline envelope and follicular cells. In addition to demonstrating that the 12:12 photoperiod can alter biochemical indices, such as NO, TBARS, H2O2, ROS, SOD and CAT, in addition to decreasing the concentration of total proteins and increasing the activation of acetylcholinesterase. However, it was not able to influence the population percentage, making it possible to determine the follicular population.

Keywords: zebrafish, follicular population, melatonin.