Marine and freshwater habitats of remote oceanic islands contain neritid
gastropods that live in drastically different environments yet are very closely related.
This study examined pH change and its effect on the physiology of both freshwater and
marine gastropods of the family Neritidae. Because freshwater stream neritids have a life
cycle that includes a marine stage of development, we expected that they would have a
higher tolerance to pH change compared to marine neritids. To understand more about
specific factors influencing distributions of different life history stages of neritid snails,
new natural history information was compiled. Egg capsules were morphotyped for the
freshwater neritids and two metapopulations of freshwaters neritids were found on
different parts of the island. Additionally, we tested the hypothesis that embryonic
viability in freshwater neritid snails would be greater than that of marine neritid snails
when reared in acidic conditions. Results indicated the opposite of what we had
predicted; freshwater neritids survival rate was 0% while marine neritids survival rate
was 100% when reared in acidic conditions. Furthermore, we found that the calcareous
egg capsule of marine neritids serves as a type of protective buffer to stressful pH
conditions