The Influencing Factors Of Crayfish (Procambarus Clakii) Predation On Snail (Oncomelania Hupensis)

The biological control of the snail hosts of the trematodes that cause human schistosomiasis appears to be a promising method for achieve sustainable reductions in the transmission of the parasites. The present paper studied about, under laboratory conditions, the affective elementes of crayfish (Procambarus clakii) predation on snail Oncomelania hupensis, the intermediate host of Schistosoma japonicum. Its ability of predation and the possibility of being a biocontrol factor of the snail are discussed. The experiments includes, 1) the affection on predation by the sex, different body size and various starvation level of crayfish, different body size of snail and the existence of food available for crayfish to test whether the body condition of the predator and the prey might influence the crayfish predation. The experiment was conducted according to factorial randomly group design; 2) the influence of the shell in crayfish predation. Both adult and juvenile snails were tested separately. There were four levels in this experiment, which were snail with intact shell, snail without spire, snail without body whorl, and snail without entire shell; 3) predatory behaviors of crayfish on snail were described. The results show: the body size of crayfish, the existence of optional food for crayfish and the body size of snails significantly influenced the crayfish predation, while the sex and the starvation level of crayfish not obviously; the shells of snails play an impedimentary role in crayfish predation; the crayfish treat adult and juvenile snails differently.