PREDATION PATTERNS ON THE GASTROPODS OF THE RED AND CORALLINE CRAG DEPOSITS OF EAST ANGLIA, ENGLAND

It has been suggested that in gastropods, thick shells and ornamentation are adaptations against predators, making them both less easy to inflict damage upon, and also less easy for the predator to handle. Predation is therefore hypothesised as being a critical driving force in the evolution of gastropods and many other groups, by driving the development of new and varied adaptations over time (Vermeij 1977).

Here, a variety of gastropod morphologies from one time slice, in which predation pressure would have been approximately constant, were surveyed in an attempt to ascertain if the varying morphologies seen provided varying resistance to predation. Shells from ten gastropod genera from the Red and Coralline Crag deposits of East Anglia, England (Plio-Pleistocene) were examined for boring, peeling and breakage damage. The environment represented is shallow subtidal sand.

It appears that ornamented forms are less vulnerable to drilling attack, whilst peeling frequency appears correlated with aperture size rather than ornamentation, shape or size. It is suggested that those forms better at withstanding drilling gastropods may be less able to withstand crab attacks. This may be because adaptations against one are detrimental to the prey's chances against another.

In addition to gastropod drill holes and crab damage, well preserved octopus drill holes were found in shells from three genera and possible examples were found in another. These are the first recorded octopod drill holes in fossil gastropods.

Reference:

Vermeij, G. J. (1977) THE MESOZOIC MARINE REVOLUTION: EVIDENCE FROM SNAILS, PREDATORS AND GRAZERS. Paleobiology 3:245-258.