Stay out of the water: Hatching efficiency and short term survival of an invasive applesnail

Successful reproduction represents a key determinant of an organism’s invasive capacity.  With established reproductive populations in several Gulf Coast states, the freshwater applesnail Pomacea insularum reproduces prolifically and may threaten both natural and agricultural resources.  P. insularum oviposit clutches (often exceeding 1500 eggs) well above the water line, so they fully dry before hatching.  Our experiments examined effects of stress (i.e. water exposure) on clutch hatching efficiency and hatchling survival. We subjected clutches collected from Armand Bayou (Pasadena, TX) to water exposure at two levels of intensity (high, which involved full submergence and low, which presented partial submergence) and three levels of frequency (low: 1 minute or no exposure, medium: 3 hours exposure, high: 24 hours exposure). Clutches exposed to high frequency treatments did not hatch, but variation existed at the medium and low frequency levels.  To test short-term survival (six weeks), we pooled hatchlings hatched under disturbed (i.e. submerged for 3 hours every other day) or undisturbed conditions.  Preliminary analysis suggests no persistent effect of egg stress through hatchling survival, but we continue to investigate this aspect.  Demonstrated reproductive plasticity of P. insularum indicates that the invader may have not yet reached its full invasive potential.