Slugs and snails are part of the great Phylum Mollusca, a group that contains creatures as different as the fast-moving squid of the oceans and the sedentary clams, cockles and mussels. The largest group, however, are the gastropods, animals originally with a single foot and, arguably, a single coiled shell.
They are the only group of molluscs to have representatives living on land as well as in the sea and freshwaters. Slugs and Snails is about those gastropods that made that transition to a terrestrial existence, the slugs and snails that live on land. With a few exceptions, they have attracted less attention than their aquatic relatives, but the more we know about them, the more extraordinary they appear.
For creatures living on land they are bizarre. Snails carry round with them a huge weight of shell. Both snails and slugs move slowly relative to potential enemies and most are not well camouflaged. Their wet bodies are at the mercy of dry weather and their movement is apparently very wasteful of energy and water. Despite this, they are found from the tundra through to deserts, and on all continents apart from Antarctica. They have reached the most remote oceanic islands and undergone amazing evolutionary radiations there. As pests, they are remarkably tenacious and hard to control. They have evolved to span a huge range of size. Through all this, they have retained a set of shapes and structures very similar to those of their marine relatives and ancestors. Furthermore it is evident that the emergence onto land happened not once, but several times, originating in different groups of aquatic snails.
In this long-anticipated New Naturalist volume, Robert Cameron introduces us to this remarkable group of gastropods, telling us the stories of the snail familiar to all British and many other readers, the garden snail, and of the giant African snail, introduced into many tropical countries, as well as providing a comprehensive natural history of slugs and snails of the British Isles specifically. Snails can be and have been used to explore important ideas in evolutionary biology, in biogeography and in ecology, and Cameron draws out these explorations, looking specifically at the role of evolution in determining how our understanding of snails has developed.
Editors' Preface vii
Author's Foreword and Acknowledgements viii
Prologe: Two Unlikely Conquerors and One Tall Story xiii
1. Snails on Land: Structure, Evolution and Classification 1
2. Shells: Variations on a Spiral Theme 38
3. Why Be a Slug? 82
4. Variation Within Species 107
5. Staying Alive 142
6. Sex and Reproduction 186
7. Life Cycles, Longevity and Population Biology 221
8. Habitats and Microhabitats 252
9. Diversity, Distribution, Dispersal and the Origin of Snail Species 296
10. Snails and the Past 330
11. Invasions, Extinctions and Conservation 371
12. Pests and Snail-borne Diseases 405
13. The Uses of Slugs and Snails: Practical, Symbolic, Poetic and Recreational 426
Appendix: Checklists and Identification Guides for the Land Slug and Snail Fauna of Britain and Parts of Europe 467
Species Index 489
General Index 497
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