SITE SELECTION BY A SMALL DRILLING PREDATOR - WHY DOES THE GASTROPOD HAUSTRUM-BAILEYANUM DRILL OVER MUSCLE-TISSUE OF THE ABALONE HALIOTIS-RUBRA

Abstract

The muricid gastropod Haustrum baileyanum bores holes through the shell of the abalone Haliotis rubra to feed on the underlying tissue. Analysis of the borehole positions on shells of H. rubra showed that they were significantly concentrated in the area where the abalone muscle is attached. This is in sharp contrast to other drilling predators of molluscs. The whelks did not change their choice of drilling site in response to experimental removal of the shell surface, or to changes in shell thickness. They may use shell ridges and possibly the morphology of the abalone shell to determine where to drill. The behaviour of the prey appears unlikely to affect the drilling position, and shell rep..