The ecology of six species of littoral gastropods. III. Diurnal and seasonal variations in densities and patterns of distribution in three environments

Abstract

The densities and patterns of distribution of the six species of molluscs were determined in the three environments: dry rock surface, "intersection" area, and rock pool, at both midday and midnight low tides during each season. Austrocochlea constricta occurred abundantly within the rock pool area, which was a homogeneous environment at certain times and in certain seasons. The density of Bembicium nanum was inversely related to the presence of water, and this species had a clumped pattern of distribution, except in the rock pool during the winter. Cellana tramoserica occurred in similar densities in all three environments during cool weather, but tended to migrate from the rock surface to the "intersection" environment during hot weather. The densities of Melanerita melanotragus, Montfortula conoidea, and Morula marginalba were greatest in the "intersection" environment, but, because of the generally low densities of these three species on the rock platform, few valid conclusions could be made concerning their abundances and distribution.