Effects of prey size on predatory behaviour of leech ( Whitmania pigra ) feeding on snails ( Cipangopaludina cathayensis )

Abstract

Rapid development of medicine has led to increased use of leech (Whitmania pigra). The suitable feeding technology is the key factor for successful breeding leeches. However, there is little information available to concern the effect of prey size on predatory behaviour of the leeches. In this study, we conducted predation trials by two sizes of W. pigra preying on three sizes of snails (Cipangopaludina cathayensis), and then analysed predation rate, feeding rate, searching time and handling time. Our results demonstrated that there were higher predation rate of small-size W. pigra preying on small-size snails compared with medium or large ones, and the predation rates gradually decreased with prolongation of the predation time. In addition, the small-size W. pigra had higher feeding rates than larger size among three treatments. However, snail sizes did no have significant effects on the feeding rates of the leeches. Furthermore, we found that it took longer time of small-size leeches to search snails than large-size leeches, while the handling time of two sizes of W. pigra increased with the snail size. This study suggests that farmers should take smaller amount and more frequent feeding approach for leech larva in the artificial breeding processes. On the other hand, adult leeches should be provided with enough feeding in one time. Due to the size-specific feeding characteristics of the leeches, we suggest that leeches should be raised based on size.