Ovarian follicle structure of Zebrafish (Danio rerio Hamilton) after poly(2-ethyl-2-oxazoline) exposure.

Poly(2-oxazoline)s have been widely known for their biomedical applications. They mimic natural systems and are generally used as liposomes, drug and gene delivery modules and also as pseudopeptides. In this study, effects of different doses (10 and 50 mg/L) of poly(2-ethyl-2-oxazoline) on ovarian follicle ultrastructure of zebrafish were investigated with light and electron microscopy. After five days of administation, ovary tissues were disected and routine histological processes were done. Severe structural deformation at zona radiata, follicular epithelium and outer granulosa cell structure were observed. Edema at follicular epithelium, zona radiata and vitelline envelope stuructures were detected. Dose dependent increase in the number of immature oocytes were seen. Briefly, it was demonstrated that poly(2-ethyl-2-oxazoline) exposure affected oogenesis and caused apoptosis in zebrafish.

Egg surface structure of the freshwater toadfish Thalassophryne amazonica (Teleostei: Batrachoididae) with information on its distribution and natural habitat

The egg surface structure of Thalassophryne amazonica, a freshwater toadfish from the Amazon basin is described. Eggs of this species show a remarkable, highly unusual system of parallel ridges and intermittent grooves that originate at the equator of the egg and lead to the micropylar pit, at which they end in a spiralling pattern. A similar egg surface structure has so far been described only from a group of Asian anabantoid percomorphs, obviously not closely related to Thalassophryne. This egg surface pattern may enhance fertilization success by guiding sperm to the micropyle. We review museum records for T. amazonica, present an updated map of its occurrence in the Amazon basin, and provide information on its habitat.

A estrutura da superfície do ovo de Thalassophryne amazonica um batracoidídeo de água doce da bacia amazônica é descrita. Os ovos dessa espécie apresentam um sistema notável e incomum de cristas paralelas e canais intermitentes, que se originam na porção equatorial do ovo e vão até a micrópila onde terminam em um padrão espiralado. Uma estrutura superficial de ovo semelhante foi até agora descrita apenas para um grupo de anabantóideos asiáticos, obviamente não relacionado a Thalassophryne. Esse padrão de superfície de ovo talvez aumente o sucesso da fertilização ao guiar o espermatozóide até à micrópila. Nós revisamos os registros de T. amazonica em museus, apresentamos um mapa atualizado de sua ocorrência na bacia Amazônica e fornecemos informações sobre seu habitat.