New Zealand Mud Snail

In the New Zealand mud snail’s native habitats, it is vulnerable to infection by the trematode Microphallus sp.. The potential biological control method that is currently underway at the University of California, Santa Barbara, is the use of the trematode parasite Microphallus sp.. This parasite lives and reproduces in the intestines of ducks and reproduce sexually, with eggs being released through the feces and then consumed by the New Zealand Mud Snail. Inside the snail, eggs hatch and the larvae reproduce asexually result in thousands of cysts forming inside the snail. This trematode uses the snail as only an intermediate host, with the ultimate goal of reaching the intestine of a local water fowl. Snails are infected by the larval stages of the parasite, which multiply asexually and castrate the snail—completely stopping reproduction. Encysted snails also undergo behavioral modification, increasing the chances that the snail will forage near the water’s surface in the morning, the time of day that water fowls hunt (Levri 1998).  

The combined effects of parasitic castration and predation may reduce snail densities to tolerable levels. The efficacy of this host-parasite interaction in reducing snail population size, and safety of biological control, must be determined before the costs and benefits of biocontrol can be evaluated.

In 2011, a Sea Grant funded project (Principal Investigators: Tom Dudley and Ryan Hechinger) worked on developing potential biocontrol agents for the New Zealand Mud Snail. We proposed that Classical Biological Control (biocontrol), the introduction of natural enemies from the native region of the pest to suppress the abundance of invasive pest species, is a potentially appropriate means of achieving this goal, and possibly the only effective means of doing so.

This research will provide the information basis regarding efficacy and safety of the intended NZMS biocontrol agent.