Observations on the Embryonic Development of Freshwater Pulmonate Snail Lymnaea Acuminata (lamarck, 1822) (gastropoda: Mollusca)

Molluscs have played important role in strengthening our knowledge of fundamental processes in developmental biology, with the common pond snail Lymnaea stagnalis contributing greatly to this body of literature for nearly a century (Gatenby, 1919; Sturtevant, 1923; Canton and Sloof, 1977). The morphological, morphometric and behavioral aspects of development of L. stagnalis have been well documented (Cumin, 1972; Morill, 1982; Marois, 1989; Mescheryakov, 1990; Marois and Croll, 1991; Voronezhskaya et al., 1999; Nagy and Elekes, 2000). The freshwater snails of family Lymnaeidae develop through what corresponds to trochophore and veliger stages within transparent egg capsules (Morill, 1982; Mescheryakov, 1990). These capsules while conveniently permitting observations of growing embryos, acts as diffusion barrier and prevent passage of large molecules. The fluid in the eggs capsules has been reported to fulfil nutritional requirements of the embryos. Molluscs are model experimental animals because of simplicity in organization of various organ systems. They have been used as model animals in various types of studies in many laboratories all over the world (Canton and Sloof, 1977; Browder, 1980; Victor and Balamban, 2001). They are also animals of choice in studying embryonic development. A number of research workers preferred molluscs over other animal groups for embryological experimentation (DeWitt, 1954; Barraud, 1957; Bayne, 1968; Suliman et al., 1987; Cumming, 1993; Rondelaud and Dreyfuss, 1996; Naoaki and Yamakawa, 1999; Okusu, 2002).