INVESTIGADORES
SOMOZA Gustavo Manuel
congresos y reuniones científicas
Título:
Implications of xenoestrogens on the physiology of the neotropical fish, Cnesterodon decemmaculatus. Reproduction and sex differentiation.
Autor/es:
GUSTAVO M. SOMOZA
Lugar:
Santos
Reunión:
Congreso; 12th SETAC Latin America Biennial Meeting.; 2017
Institución organizadora:
SETAC-LA
Resumen:
It is known that teleost fish have a hormone-dependent sexual dimorphism and the process of sex differentiation is also dependent on steroid hormones. In this context, they can be used as model organisms to study the adverse effects of steroid derived anthropogenic chemicals. Nevertheless several fish model species are being used to study these effects, because of the diversity of fish species, there is a need to look for local models. Wastewaters are important sources of estrogenic compounds like the natural estradiol (E2) and 17α-ethynylestradiol (EE2), and they have been reported in surface waters of Brazil and Argentina, in some case at high concentrations. Therefore, it is important to look for potential effects of these substances on the physiology of local species. Under this conceptual framework a series of studies were conducted with the Ten spotted live-bearer, Cnesterodon decemmaculatus, a Poecilid fish (the same family of Gambusia, Xiphophorus, and Poecilia spp.), widely distributed in Argentina, Chile, Uruguay and the South of Brazil. This is a gonochoric, sexually dimorphic, and ovoviviparous species. Females are larger than males, and the male anal fin is modified into a gonopodium.First, the responses of the gonopodium morphology and the gonadal and liver histology were assessed in adult males long-term exposed to sublethal concentrations of EE2. Two experiments were conducted exposing fish to concentrations of EE2 ranging from 20 to 200 ng/L during 8, 12 and 16 weeks. Intersex gonads (testis-ova) were observed after 8 and 16 weeks in fish exposed to 200 ng EE2/L and 100 ng EE2/L, respectively. Oocytes? development from testis germ cells and replacement of the efferent duct periodic acid-Schiff?positive secretion surrounding spermatozeugmata by parenchymal tissue and duct structure alterations were the major observed changes in the gonads. However, no response was observed in the gonopodium morphology. Liver histology was also altered, showing increasing steatosis, single-cell necrosis to generalized necrosis, and disruption of acinar organization from 100 ng EE2/L to 200 ng EE2/L. Also, in order to know the effects of xenoestrogens on the sex differentiation process, a series of studies were conducted to characterize the morphology of secondary sexual characteristics and gonads using sexually undifferentiated fish. The exposure of sexually undifferentiated fries to EE2 was also evaluated on mortality, sex ratio and the occurrence of pigmentation in the perianal area. This pigmentation presented a clear relationship with water borne EE2. An occurrence frequency of 0, 38, 85 and 100% was observed in fish exposed to 0, 20, 100 y 200 ng/L of EE2 respectively. The percentage of phenotypic males decreased from 49 (control) to