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The highly variable male color morphs of the guppy (Poecilia reticulata) have been studied for more than 80 years, and the guppy was one of the first vertebrates in which sex-linked inheritance of color loci was demonstrated (Winge, 1927). More recently, the guppy has become a model organism for studying behavioral traits such as courtship and mate choice (Evans et al., 2003; Magurran and Henderson, 2003), as well as for understanding ecogeographic adaptation (Endler, 1991, 1995; Reznick, 1997). Guppies are live-bearers, who retain their fertilized eggs within the follicle throughout gestation (Turner, 1940; Lambert, 1970). The synchronously growing diplotene oocytes store nutrients in oil droplets and yolk, before their maturation and fertilization. This developmental program is termed lecithotrophic, and it contrasts matrotrophic programs where nutrients are provided by means of the maternal circulation throughout gestation. Matrotrophy and lecithotrophy can contribute simultaneously to embryonic nutrition in other species of poeciliid fish (Reznick et al., 2002). In guppies, the interface between the embryonic yolk portal system and the maternal follicle allows for efficient gas exchange and waste disposal, whilematernal food provisioning does not seem to be required after fertilization (Turner, 1940; Thibault and Schultz, 1978). Unfortunately, studying the early development of live bearers is more complicated than that of oviparous species, due to the inaccessibility of developing embryos for experimental manipulation. Therefore, despite a wealth of classic genetic studies on the male color polymorphism found in guppies, knowledge of both the ontogeny and the molecular mechanisms underlying this polymorphism is virtually nonexistent.In vertebrates, trunk neural crest cells (NCCs), which become precursors of pigment cells, most likely start their migratory pathways at neurula and tail bud stages (Jacobson, 1991)
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