Growth promotion of the juvenile clam, Ruditapes philippinarum, on sugars supplemented to the rearing water

Soft-bodied marine invertebrates are known to have the ability to uptake dissolved organic matter, but actual benefits to growth of these organisms have not been demonstrated. In the present study, the effects of sugars supplemented to the rearing water were tested on juveniles of the clam, Ruditapes philippinarum. Culture water supplemented with glucose at 10 and 100 mg l− 1 significantly promoted soft tissue growth of the clam. In contrast, maltopentaose and pullulan (a polysaccharide composed of maltotriose with average M.W. 105) did not show any promoting effect, suggesting that only low molecular weight sugars can be incorporated through the epidermal pathway and contribute to clam growth. Soaking of adult clams in water supplemented with glucose at 100 mg l− 1 for 24 h resulted in 1.5 times higher quantity of total organic acids in the soft tissues compared with clams soaked in water without glucose, suggesting that the absorbed glucose is easily transformed into organic acids through the glycolysis pathway and makes an energetic contribution to clam growth. Here, we suggest a novel clam rearing method with “sugar supplements”, which can be used to promote clam growth through epidermal uptake.