Distribution of Onchidium damelii Semper (Gastropoda, Onchidiidae)

Abstract

The pulmonate gastropod Onchidium damelii Semper has a widespread tropical Indo-Pacific intertidal distribution. The present study examines some environmental factors in relation to the local distribution and density of the species in a tropical mangrove region. Tidal regime, flora l zonation, substrate particle size and organic content, and temperature relationships were investigated. O. damelii shows habitat preference rather than a zonal (tidal pattern) distribution within the mangroves; population density is associated with substrate particle size and organic content. Considerable differences in size of individuals were noted between populations, probably related to available organic matter and feeding time. Animal temperatures were correlated with substrate temperatures and do not appear to influence distribution patterns.