Chemical conditioning of the environment by the freshwater pulmonate snails ( Biomphalaria glabrata ) and its effect on growth and natality rates

The effects of heterotypically conditioned media on the growth and natality rates of Biomphalaria glabrata have been studied under conditions which prevented the assay snails from being stimulated by tactile and visual signals from other snails. It was demonstrated that increasing the density of snails producing the conditioned medium up to a critical threshold resulted in enhancement of growth and natality rates. Further increases in density beyond the optimum level caused a reduction in growth and natality rates. Possible explanations for these effects, which were caused by chemical conditioning, are discussed.