Michael F. Land - Animal Eyes

Animal Eyes

Titles

Energy for Animal Life
R. McNeill Alexander

Animal Eyes
M. F. Land, D-E. Nilsson

Animal Locomotion
Andrew A. Biewener

Animal Architecture
Mike Hansell

Animal Osmoregulation
Timothy J. Bradley

Animal Eyes, Second Edition
M. F. Land, D-E. Nilsson

The Oxford Animal Biology Series publishes attractive supplementary textbooks in comparative animal biology for students and professional researchers in the biological sciences, adopting a lively, integrated approach. The series has two distinguishing features: first, book topics address common themes that transcend taxonomy, and are illustrated with examples from throughout the animal kingdom; and second, chapter contents are chosen to match existing and proposed courses and syllabuses, carefully taking into account the depth of coverage required. Further reading sections, consisting mainly of review articles and books, guide the reader into the more detailed research literature. The Series is international in scope, both in terms of the species used as examples and in the references to scientific work.

Second Edition

Michael F. Land
Professor of Neurobiology, University of Sussex, UK

AND
Dan-Eric Nilsson
Professor of Zoology, University of Lund, Sweden

Great Clarendon Street, Oxford OX2 6DP

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Michael F. Land and Dan-Eric Nilsson 2012

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First edition published 2002
Second edition published 2012

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Library of Congress Control Number: 2011944054

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ISBN 9780199581139 (Hbk)
9780199581146 (Pbk)

1 3 5 7 9 10 8 6 4 2

For Rosemary and Maria

The study of animal eyes is cumulative; old knowledge is rarely superseded, but often added to. This is reflected in the way we have approached this new edition. The chapter layout of the first edition worked well, and we have retained it, along with much of the original text. We have concentrated on advances that have been made in the last decade, and on remedying some of the omissions of the first edition. has new material on the head movements of birds and insect larvae. Other chapters have been similarly updated, but not radically changed. And the last line of the original Preface should now read 80 years rather than 60.

The eye to most people means an eye like ours, a single-chambered camera-like structure with a retina in place of the film, or the CCD array. Most know, too, that insects have compound eyes with many lenses, but how many people can answer the question: does the insect see the multitude of images beloved of Hollywood horror films, or a single image similar to our own? We use this example to point out that, even to most biologists, eyes remote from our own are poorly understood and come in only one or two varieties. This hugely underestimates the diversity of eye types: there are at least ten quite distinct ways that eyes form images. Some of these such as pin-holes and lenses are familiar, but others are more exotic. These include concave mirrors, and arrays of lenses, telescopes, and corner reflectors. Some have been known about for centuries (the first demonstration of the inverted image in a mammalian eye was in 1619) but a number are discoveries of the last few decades and have yet to find their way into textbooks of either biology or optics. Some of these eye-types have counterparts in optical technology, but by no means all. Some are still finding applications: for example, the mirror-based optical system of the compound eyes of shrimps and lobsters has recently found a use as the optical basis of wide angle X-ray lenses.

It is our aim in this book to provide a comprehensive account of all known types of eye. We take the diversity of optical mechanisms as a framework, but many other aspects of the structure and function of eyes are also dealt with. Visual ecologythe ways that eyes are specifically adapted to the lifestyles of the animals that bear themis another important theme. As humans we tend to think of vision as a general-purpose sense, supplying us with any kind of information we require. For most other animals this is not so. Predators and prey, for example, have different visual requirements: foxes and rabbits have different eyes and different visual systems, as have dragonflies and mosquitoes. Similarly, a sedentary clam lives in a different world from a flying insect, and the optical requirements are quite different.

addresses these questions, and provides a context in which eyes can be seen as different solutions to problems that are, in many respects, similar.

As well as diversity, we are concerned with the design philosophy of eyes. What are the physical constraints on the way an eye performs its functions, and how are these addressed by the different types of eye? To answer this it is necessary first to have some information about the properties of light that are of importance for vision, and this we provide in , which is devoted to the question What makes a good eye?. This in turn provides a background for assessing the capabilities of the panoply of different eye types, presented in the subsequent five chapters. The ninth and final chapter examines another aspect of the way eyes are used: their movements. Eyes sample the world not only in space but in time, and the movements that they make are as important a part of the process of extracting information as are the optical systems that provide them with spatial resolution.

The book is not aimed at any one readership. It will be of value to undergraduates in Biology and Neuroscience programmes, and to anyone engaged in the study of vision at the post-graduate level. Students and practitioners of ophthalmology and optometry will find it interesting as a background to the study of the human eye, and optical physicists and engineers will find that nature has come up with solutions that they will not have met before.