Sterility induced by heat stress on the invasive apple snail Pomacea canaliculata is reversible but even short exposures cause long reproductive delays in females

Abstract

Pomacea canaliculata is an invasive South American apple snail with multiple impacts and high costs, especially in subtropical and tropical areas. However, experimental cohorts experience negative demographic effects at 30ºC and complete sterility at 35ºC. We aimed to understand the underlying mechanisms and to explore if exposure to 35º could be used for mass production of sterile P. canaliculata as safe agents for inundative control of aquatic weeds. Therefore, we tried to estimate the minimum exposure time required to induce sterility, whether it affects both sexes equally and if it is reversible or not. Experimental females and males were separately exposed to 35ºC for zero (control), one, two, three and five months, after which were maintained at 25ºC. They were coupled with consort snails of the opposite sex reared at 25ºC. The results indicate that exposure to 35ºC strongly delayed the onset of reproduction in females, and to a lesser degree in males and that sterility is reversible after a return to 25ºC. This clearly indicates that exposure to 35º cannot be used for the mass production of sterile P. canaliculata for safe biocontrol of aquatic weeds. Although fecundity and viability of egg masses were mostly unaffected by exposure to 35ºC, even a one-month exposure to 35ºC doubles the age at which females produce viable egg masses, hence increasing generation time and reducing population growth rate. Heatwaves increasing in frequency, duration and intensity due to climatic change, may have unexpected demographic consequences for both invasive and vulnerable apple snails.