Gonadal morphogenesis in the South American toad Rhinella Arenarum (Anura, Bufonidae) unveils an extremely delayed rate of sex differentiation.

Among anurans, Bufonids are recognized for their retarded sex differentiation. However, few studies have addressed gonadal morphogenesis in this family. Here, we analyzed the early gonadogenesis in laboratory-reared Rhinella arenarum.

Integrative study of the reproductive biology and growth of Acestrorhynchus pantaneiro Menezes, 1992 (Characiformes, Acestrorhynchidae).

We studied the reproductive strategy, sexual system and growth of dientudo paraguayo Acestrorhynchus pantaneiro. After 2 years of monitoring in shallow areas of a floodplain lake from the lower Paraná basin (Argentina), it was evidenced that water temperature modulated gonadal maturation, but it was the river water level the synchronising stimulus that triggered spawning. This species exhibited a single annual breeding period from October to January, with most spawning activity in November.

Ivermectin: A multilevel approach to evaluate effects in Prochilodus lineatus (Valenciennes, 1836) (Characiformes, Prochilodontidae), an inland fishery species.

Ivermectin (IVM) is one of the most widely used antiparasitics worldwide. It is a potent and effective drug for treatment and prevention of internal and external parasitic infections of livestock and humans. IVM is excreted unchanged in manure of treated animals.

Effects of waterborne exposure to 17β-estradiol and 4-tert-octylphenol on early life stages of the South American cichlid fish Cichlasoma dimerus.

Estrogenic chemicals are often detected in the aquatic environment and can negatively affect animal development and reproduction. In teleost fishes, the hormonal regulation during a critical period of larval development has a strong influence on gonadal sex differentiation; thus this process may be affected by the exposure to environmental estrogens. In this study, we first assessed the lethal acute toxicity of the natural estrogen 17β-estradiol (E2) and the weaker estrogen mimics 4-tert-octylphenol (OP) and 4-nonylphenol (NP) on larval stages of the South American cichlid fish Cichlasoma dimerus.

Effect of the organochlorine pesticide endosulfan on GnRH and gonadotrope cell populations in fish larvae.

Endocrine-disrupting chemicals can influence the hypothalamus-pituitary-gonad axis and possibly affect reproduction in vertebrates. We analyzed the effect of 30-day endosulfan (ES) exposure in sexually undifferentiated larvae of the cichlid fish Cichlasoma dimerus. The number, area, mean cytoplasmic and nuclear diameter, and mean cytoplasmic optical density of gonadotropin-releasing hormone (GnRH) I, II, and III immunoreactive (ir-) neurons and β follicle-stimulating hormone (βFSH) ir-cells were measured.