SPATIAL DISTRIBUTION OF NUCULA PROXIMA SAY PROTOBRANCHIA): AN EXPERIMENTAL APPROACH

¹ Department of Earth and Space Sciences, State University of New York, Stony Brook, New York 11790

The spatial patterns of populations of Nucula proxima were studied in the laboratory using x-radiography, and in the field using a multiple-coloring device.

Trays with sediment and varying population densities of N. proxima were x-rayed under different temperature and elapsed time conditions. Almost all experiments were shown to exhibit random patterns. The two exceptions were aggregated distributions which were probably due to inhomogeneities in the experimental environment.

The field samples showed Nucula proxima to be randomly distributed, with a tendency towards aggregation in some cases. Juveniles were distributed essentially the same as the adults.

It is argued that the lack of defense mechanisms, the instability of the substrate, the small "reach" of the feeding organ, and the lack of advantage of territoriality to a mobile deposit-feeder all contribute to the observed random patterns of Nucula proxima.

It is concluded that x-ray studies of infaunal invertebrates done in concert with field studies is an excellent means of distinguishing the factor of environmental heterogeneity from negative or positive interactions between individuals caused by territoriality or gregariousness.