A study on the ecology of Aplexa hypnorum.

Abstract

This is a report on the adaptations of the snail Aplexa hypnorum to the variable conditions found in temporary ponds. Resistance to freezing variable water depths and dessication were observed on the adults, eggs and juveniles of the species. This is no more than an observational study. The facts presented here were derived from on site observations and crude laboratory methods. The aquatic snail Aplexa hypnorum appears to survive in the egg or juvenile form during period when constant water cover is questionable in a temporary pond. The adult can not withstand desiccation. They appear to migrate to the deepest parts of the drying pools, laying eggs before death occurs due to desiccation. The eggs are able to develop under condition which are too dry for the adults and actually will hatch within a short time if enough moisture is provided. The eggs appear to have a tremendous resistance to desiccation and develop whenever they are remoistened. Keeping in mind the fact that Aplexa adults concentrate into the lowest areas of the pool to lay their eggs, (or escape desiccation), the chances that these low areas will become moist enough for development to occur several times in a season appears quite good. Aplexa is able to take advantage of the short periods of moisture that characterize a temporary pond from July to March, and continue its development. It is interesting to note that Cheatum states that Aplexa hypnorum this very snail is the northern hemispheres most northern snail, living at 74 lat. with average temperatures of 10 F. The ability of this snail to turn development on and off must aid its survival in these areas.