Marine beauties display their all

The ocean was the cradle where multicellular animals first evolved more than 600 million years ago. Among the most primitive are sessile organisms (such as sponges and corals), which are anchored to the seabed and make their living by filtering out floating microorganisms and detritus from passing currents. They have no equivalents on land. They are colonial structures, built up from simple elements or modules, each with a distinctive form. These modules fit together to provide open structures that optimise the mutually incompatible requirements of capturing nutrients and withstanding the forces of waves, currents and tides.

Seaweeds have adopted similar structures. The simplicity of the building blocks gives these structures great flexibility, and their responsiveness to environmental forces results in a chaotic diversity of branched and fan-like forms so that even animals and plants are indistinguishable to the casual observer. Indeed, the taxonomic specialist is often forced to identify the organisms by a microscopic analysis of the individual modules. The plasticity of their overall form arises from an intricate interplay of external physical forces and the internal regulatory processes. The purpose of this book, edited and largely written by Jaap Kaandorp and Janet Kubler, is to provide "an overview of how simulation models can provide insights into the growth and form of seaweeds, sponges, corals and other marine sessile organisms".

The classic text On Growth and Form was published by D'Arcy Thompson in 1917. This elegant volume with its lucid text, close analysis and broad scope is still accessible to a wide audience and provides a yardstick against which to judge the potential appeal of Kaandorp and Kubler's book. More recent treatments, such as Life's Other Secret : The New Mathematics of the Living World by Ian Stewart (1998) and The Self-made Tapestry by Philip Ball (1999), have extended the scope and breadth of Thompson's treatise, and have produced beautiful books, but they have wisely steered clear of the complexities of form presented by colonial organisms.

In Kaandorp and Kubler's book, the physical environment encompassing these organisms is briefly but succinctly covered in a dozen pages or so. This rapid-fire initiation is followed by a fascinating series of case studies on individual species, which will provide the main interest for the more general reader. Here the beauty of the organisms is amply displayed. However, it is more difficult to appreciate the algorithmic component of this beauty because the remaining two-thirds of the book is directed towards the specialist and is less accessible.

There are severe problems in describing these intricate structures quantitatively. Nearly a quarter of the book is devoted to statistical and computational methods, sometimes taking their information from the three-dimensional computational tomography scans that are more often encountered in medical diagnoses. Another major section deals with the computer-simulation techniques used to unravel the processes controlling the overall forms observed. This is the most fascinating and tantalising section. The mathematical detail is too shallow for a modeller from another discipline adequately to grasp the issues involved and yet too abstruse for the non-specialist to follow.

Because the models themselves have to attempt to simulate interactions between the environment and the organisms in three dimensions, they require substantial computing power. So it is not feasible, for instance, to provide examples on CD to allow the reader to observe the action of the simulations. This is frustrating given the considerable promise implied in the book's title. There are nonetheless useful but short sections on the difficult experimental procedures required to validate the models (since these organisms are generally very slow growing) and on applications to the study of Antarctic sponges and of environmental information encapsulated in coral skeletons.

Although this book is the outcome of a scientific workshop, the contributions of the other authors (comprising about one-third of the book) have been interwoven so that the text as a whole has coherence and balance. It is beautifully, if sometimes eccentrically, illustrated with photographs, drawings and computer simulations. It provides a clear and much-needed summary of the state of the art in this difficult but important area of biological simulation that will appeal to the specialist. Thompson would certainly be amazed that such substantial progress could be made in understanding such chaotic and apparently intractable structures. If you find the book in a library, you should take the opportunity to browse. But despite its reasonable price and attractive layout, I do not think it has the accessibility and scope to appeal to a wide audience.

Michael Whitfield is honorary visiting professor in marine science, University of Plymouth.