Comparative Ultrastructures of the Fertilized Egg Envelopes in Nothobranchius guentheri and Nothobranchius patrizii, Nothobranchiidae, Teleostei

Fish eggs are surrounded by an acellular structure, egg envelope. It plays a role in diffusive exchanges of gases such as carbon dioxide and oxygen, selective transport of materials into the egg, protections for physical damage (Donovan & Hart, 1986) and from chemicals and pathogens, and polyspermy prevention (Harvey et al., 1983; Cameron & Hunter, 1984). In teleost, the fine structure of the fertilized egg envelope differ according to the physiochemical characteristics of the water environment (Lönning, 1972). These ultrastructures have related with environmental factors (Stehr & Hawkes, 1979), and type of spawning place (Ivankov & Kurdyayeva, 1973). Also, the structure of the egg envelope differ according to species as well as by family (Deung et al., 1999; Kim et al., 2002). Even eggs of the same species have been reported to have different shapes depending on their geographical distribution (Brummett & Dumont, 1981). The Guentheri killifish (Nothobranchius guentheri) belong to Nothobranchiidae also known as the redtail notho. These species live in water holes, streams, and marshes in Africa (Huber, 1996). The food are mosquito larvae and plankton. During the dry season when the temporary pools of water the fish inhabit dry up and the adult fish perish, specially adapted