Stable isotopes of carbon and nitrogen as indicators of food source of the gastropods Bellamya aeruginosa
【摘要】：Suspension feeding behavior of B. aeruginosa was observed in detail visually. Food sources for snails were estimated using stable carbon and nitrogen isotope ratios in the field. δ15N mass balance estimates indicated that B. aeruginosa obtained only 19.9% of its diets from deposit in Meihu Reservoir. But the proportion of deposit was 57.7% and 77.3% in Campus pond and Tingxia Reservoir, respectively. These results suggested that B. aeruginosa can utilize the suspension organic matter in the field, but the proportion of food consumed by snail depended on the availability of suitable food in the ambient. A three month feeding experiments were also conducted to confirm whether snails assimilate five types of diets. The stable carbon isotope ratios of hepatopancreas of B. aeruginosa fed green alga (-30.0‰), deposit (-30.1‰) or mixtures (-29.9‰ for algal mixture, -30.2‰ for mixture of alga and deposit) were closer to that of diet at the end of the experiment. These revealed that snails were able to assimilate suspension algae under laboratory conditions. However, the snails that were fed toxic M. aeruginosa showed δ13C values (-32.2‰) similar to the starveling animals (-32.4‰) and lower than the control animals (-31.0‰) after three months experiment. These findings suggest that B. aeruginosa is a facultative suspension feeder and can exhibit feeding selectivity in some extent.