SOME FACTORS AFFECTING VERTICAL DISTRIBUTION AND RESISTANCE TO DESICCATION IN THE LIMPET, ACMAEA TESTUDINALIS (MÜLLER)

¹ Department of Zoology, University of Maine, Orono, Maine 04473

1. This study examined tolerance of desiccation in the limpet, A. testudinalis, collected from two intertidal habitats, vertical rock faces and tide pools, and one subtidal area on Schoodic Peninsula, Hancock County, Maine.

2. The results of two laboratory desiccation experiments showed that subtidal limpets and those from vertical rock faces were more tolerant of desiccation than those from tide pools.

3. Greater tolerance of desiccation was related to the size of the organisms. Mean shell sizes of subtidal limpets and those from vertical rock faces were significantly larger than those of limpets from tide pools.

4. Shell shapes of limpets from the three habitat groups did not differ significantly, which showed that differences in tolerance of desiccation were not related to differences in shell shape.

5. Limpets from vertical rock faces showed a slightly greater tolerance of desiccation than those from the subtidal area.

6. The size distribution of limpets on Schoodic Peninsula suggests either that larvae of this species may settle in tide pools and migrate outward to exposed intertidal and subtidal habitats as they mature, or that population density in each habitat determines the rate and limits of growth of the resident limpets.

7. This species tolerated more desiccation than it would be required to withstand in its natural habitat. Desiccation must act with other factors in determining the upper limit of the distribution of this species.