Chronic Starvation-Induced Alterations in Biochemical Parameters and Hypothalamic-Pituitary-Testicular Axis in the Mozambique Tilapia Oreochromis mossambicus (Cichlidae)

Abstract

Although fish are often exposed to food restrictions in natural or aquafarming conditions, the relationship between altered energy status and the reproduction is not well understood. The aim of the present investigation was to elucidate the effect of chronic food-deprivation on energy status and reproductive axis in male Mozambique tilapia Oreochromis mossambicus. The controls received food ad libitum, whereas the fish in the starvation group were deprived of food for 21 days. The liver showed significantly higher levels of gluconeogenesis and triglycerides, whereas the levels of blood glucose and total protein content in the liver were significantly lower in starved fish compared to controls. Furthermore, the mean numbers of different spermatogenic cells, such as spermatogonia-A, primary spermatocytes, secondary spermatocytes, early spermatids, and late spermatids were significantly lower, but the number of spermatogonia-B did not show a significant difference compared to controls. In starved fish, there was a significant increase in germ cell apoptosis at different stages of development concomitant with faintly immunoreactive androgen receptors in the Sertoli cells of the testis compared with controls. In addition, the percent areas of gonadotropin-releasing hormone—immunoreactive fibres and luteinizing hormone—immunoreactive content—in the proximal pars distalis part of the pituitary gland were significantly lower in starved fish compared with controls. Collectively, these results suggest that decreased energy status negatively affects the gonadotropin-releasing hormone—luteinizing hormone – testicular axis, leading to inhibition of spermatogenesis before entry of germ cells into meiosis through increased apoptosis and decreased expression of androgen receptors in the testis of the Mozambique tilapia.