Vita Malacologica 13: 1-25 20 December 2015 Gastropod skeletal defences: land, freshwater, and sea compared Geerat J. VERMEIJ Dept. of Earth and Planetary Sciences, University of California at Davis One Shields Avenue, Davis, CA 95616, U.S.A. email:
[email protected] Key words: Mollusca, Gastropoda, predation, antipredatory defence ABSTRACT like oxygen and carbon dioxide diffuse into and out of living bodies much more readily in air than in water. As a result, Predation is a primary agency of natural selection affect - resistance to locomotion (through friction drag and pressure ing the evolution of skeletal form in gastropods. The nature of drag) is high, gas exchange between the body and its sur - antipredatory defence depends on how predators attack their roundings is slow, heat loss and gain are rapid, and gravita - prey as well as on the types and quantities of resources that tional forces acting on the body are small in water (Denny, are available to the potential victims. Here I review the five 1993; Vermeij & Grosberg, 2010). On the other hand, precipi - main methods of predation on shell-bearing gastropods (swal - tation of an external mineralized skeleton is energetically lowing prey whole, apertural entry, drilling, shell breakage, more favourable in water (especially seawater) than in air. and partial consumption) and 31 categories of shell and oper - Given this mix of different challenges and opportunities cular defence that are effective at one or more of the three for specialization in defence that life in water and life in air stages of predation (detection, pursuit, and subjugation). provide, it is surprising how little attention has been paid to These categories are evaluated for marine Palaeozoic, marine comparisons of defences on land, in freshwater, and in the Late Mesozoic to Recent, freshwater, and terrestrial environ - sea.