Effects of submergence on embryonic survival and developmental rate of the Florida applesnail, Pomacea Paludosa: implications for egg predation and marsh management
Aerial deposition of egg clutches by the aquatic Florida applesnai! is believed to have evolved in response to aquatic egg predators. Adaptation to aerial conditions might, however. have rendered embryos intolerant of submergence, a potential occurrence in natural and managed marshes, rivers. and lakes. In this study, eggs were submerged in water for various durations in the laboratory to assess their ability to survive flooding; and clutches of known ages were submerged for several days in the field to determine if aquatic predators might decrease survival below levels expected to occur due to flooding alone. Submergence of clutches slowed embryonic development and increased mortality. Embryos that were within a few days of hatching at the time of submergence were not strongly affected. When younger embryos were submerged. none hatched; and most died in early stages of growth. Submergence of clutches in the field increased mortality above that in laboratory submergence, but factors other than predation. such as loss of adhesion and entanglement with floating debris, accounted for the losses. There was no evidence that aquatic predators were a significant factor in embryonic mortality. In managed wetlands that hold populations of Pomacea paludosa, flooding should occur slowly during the reproductive season (March through October), particularly in the first few months when clutch production is high, to avoid loss of as much as 2 wk of clutch production.