Abstract
The aim of this study is to demonstrate the growth-promoting effect of alginate hydrolysates (AHs) on the Manila clam Ruditapes philippinarum, and to verify the physiological change occurring within a living R. philippinarum stimulated by AHs. We show that growth of clams was dramatically promoted by supplementing a diet of the diatom Chaetoceros neogracile with AHs at 4 mg/mL. Furthermore, metabolomics indicates that each state of starvation, food satiation, and sexual maturation have a characteristic pattern. In the groups given AHs in addition to C. neogracile in particular, excess carbohydrate was actively utilized for the development of reproductive tissue. In contrast, it appeared that clams in the groups given C. neogracile only were actively growing, utilizing their adequate carbohydrate resources. Meanwhile, the unfed groups have slowed growth because of the lack of an energy source. Hence, supplementation of AHs in addition to the algal diet may be an inexpensive way to shorten the rearing period of R. philippinarum. Moreover, metabolomics can evaluate the growth condition of R. philippinarum in a comprehensive way, and this approach is crucially important for not only the development of a mass culture method but also for the conservation of the clam resource in the field.
Highlights
The aim of this study is to demonstrate the growth-promoting effect of alginate hydrolysates (AHs) on the Manila clam Ruditapes philippinarum, and to verify the physiological change occurring within a living R. philippinarum stimulated by AHs
Growth of clams was dramatically promoted by supplementing a diet of C. neogracile with AHs at 4 mg/mL (Fig. 1)
The mode in unfed clams was more than 15.0 mm but less than 15.5 mm (Fig. 2A) and in the groups given AHs in addition to C. neogracile was more than 17.5 mm but less than 18.0 mm (Fig. 2C)
Summary
The aim of this study is to demonstrate the growth-promoting effect of alginate hydrolysates (AHs) on the Manila clam Ruditapes philippinarum, and to verify the physiological change occurring within a living R. philippinarum stimulated by AHs. Metabolomics can evaluate the growth condition of R. philippinarum in a comprehensive way, and this approach is crucially important for the development of a mass culture method and for the conservation of the clam resource in the field. Suspension-feeding bivalves are considered “keystone” species in freshwater and coastal marine environments[1] These filter-feeders can exert “top-down” grazer control on phytoplankton and reduce turbidity[2]. Suspension-feeding bivalves assume “bottom-up” control through biodeposition and promotion of nutrient removal, and stabilization of phytoplankton growth dynamics through the moderation of ammonia cycling in the water column[1]; these species play a uniquely important role in the ecosystem. The development of a growth-promoting factor, a mass-culture method for production of the clam, and clarification of its growth mechanisms would have important implications for clam culture, and would contribute to the conservation of the clam resource in the field and a stable market supply
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