My research backgrounds and interests  

Background

The origin of the study of relationships between form and function of organisms can be traced to the work of early naturalists of the 18th and 19th centuries. With Darwin and his development of the concept of adaptation by selection, the function of morphological features became the central pillar in the explanation of the form of organisms as a result of evolution. Subsequent studies on the integration of biological form and function were largely carried out by biologists until the mid-20th century (D’Arcy Thompson being the foremost example). In the second half of the 20th century, the emphasis of biological research shifted toward physiological and biochemical studies. At the same time, the development of palaeobiology (i.e., a biologically-oriented study of fossils, as opposed to traditional palaeontology, which places the emphasis on descriptive morphology outside a functional and, often, evolutionary context, and on fossils as mere tools for biostratigraphic and palaeoenvironmental reconstructions) promoted a renewed interest in the functional morphology of fossil and Recent organisms, this time mostly by palaeobiologists.

Most notable in this context is the conceptual framework of constructional morphology as developed by A. Seilacher. It tells us that the shape of an organism is not the result of function alone, but of the interplay of functional, phylogenetic and constructional/developmental factors. In particular, the range of morphologies that may evolve in a particular group of organisms is restricted by preceding evolutionary “choices” (i.e., the evolution of one among a number of possible but mutually exclusive morphologic adaptations, modes of life, behavioural tracts etc.) that took place during the evolutionary history of the group. This range of possible morphologies is also restricted by the developmental processes and biomaterials available within the group. Thus, the phylogenetic and constructional aspects act most of the time as evolutionary constraints, but occasionally can provide the “building blocks” which may allow the evolution of innovations that radically change the mode of life, morphology and (ultimately) the evolutionary potential of these offshoots, and favour their breakthrough into new ecological and form/function domains.

Before constructional morphology, studies of functional morphology often resulted in “story telling”, i.e., the reconstruction of the immediate evolutionary pressures and processes that led to one particular morphology or species, which rarely has general implications beyond the subject of the study. Constructional morphology, instead, allows the simultaneous examination of larger groups of species or higher taxa with a common phylogenetic background, and reaches more general conclusions (especially the formulation of general principles applicable to all, or most, organisms that undertake a certain evolutionary pathway, e.g., a shift in life habits from hard to soft substrates). It also provides criteria that allow us to recognise instances of parallel evolution within the same group, and often an explanation for this phenomenon, as well as instances of parallel evolution in unrelated groups (and in these cases, often allows us to detect that, and explain why, the resulting adaptations are similar in general traits, but differ in significant details).

The present surge of interest in “evo-devo” (evolutionary developmental biology) and the potential for a similar impact of its recent offshoot, “eco-devo” (ecologic developmental biology, which centres on the ecophenotypic plasticity induced by environmental factors on developmental processes, and hence on morphologic/physiologic/behavioural variability  exhibited by individuals or populations, in spite of their constant genetic makeup) sign a return of biologists to the study of morphology. This return to the origins of biology is made possible by the application of recently developed techniques in genetics and developmental biology that promise an integration between aspects ranging from molecular, genetic and morphogenetic to whole-organism morphology, autecology and community ecology, with the potential of unifying these fields. Constructional morphology, and palaeobiology in general, now stand on the threshold of being able to provide valid contributions to this unification, primarily in providing observations on an evolutionary time-scale not accessible by biological techniques, a broad range of case-histories already studied and suitable for further investigation with new methods, and a record of diversity and evolutionary patterns unrivalled by that presented by Recent organisms alone.

My research

My own research aims at an integration between morphology, development and adaptiveness of invertebrates, viewed in an evolutionary perspective and with special attention to their skeletal parts. Although my work is not restricted to constructional morphology, it derives much of its inspiration from this conceptual framework. I have been working at palaeontological institutions for virtually all my career, but always on themes at the interface between palaeobiology and biology.

My work concentrates mostly on bivalves and gastropods, although I published also on anomuran and brachyuran crabs, barnacles, inarticulate brachiopods, serpulid polychaetes, stomatopod crustaceans and insects. Most of my publications aim at elucidating the function, morphogenesis and evolution of morphological characters and their interplay with the behaviour and autecology of the organism. In my work, usually I deal with these problems by conducting surveys of families or higher taxonomic groups, and often by comparing unrelated taxa which display morphologic and functional convergence (e.g., publ. n. 6, 7, 10, 17, 19, 20, 25, 35, 36, 39, 40, 45, 54, 55, 56, 62). This approach generally proves more fruitful than studying single species outside of their phylogenetic context. The latter type of study, of course, is still appropriate when functional counterparts are not available, or when the adaptations displayed by a single taxon are of special interest or unique nature.

Methods

The methods I generally use in my work can be summarised as:

Study of material in palaeontological and biological collections.

This accounts for most of my work, and I carried it out at a large number of university institutions, museums and private collections in Italy, Germany, Switzerland, Austria, France, Denmark, Sweden, UK, USA, China and Japan. In addition to published scientific results, this work has given me a first-hand experience of curatorial and cataloguing techniques in a broad range of institutional settings.

During my visits to these collections, I take large numbers of conventional and digital photographs of specimens, including material that is not directly related to the present study but that I judge of possible interest for further consideration, or that is related to studies I have already published but that might be worth a continuation at a later date. For this purpose, I have developed portable photographic accessories for taking publication-quality macrophotographs quickly and efficiently (with this equipment, I have been able to take hundreds of publication-quality photographs per day when working at locations expensive to reach, or where access to material is difficult to obtain on a repeated basis). Over the years, this photographic archive has proved to be a fundamental tool in providing me with material and ideas for additional work, often of a type not planned at the time of my visits. It is also proving invaluable to my scientific collaborators and my present PhD student. I am currently carrying out trials with custom-designed, lightweight equipment for high-magnification digital macrophotography in order to further extend the usefulness of future work at museum locations.

Direct observation of the behaviour and autecology of living organisms in the field and in the laboratory.

I carried out this type of study in a few marine biology stations and at several field locations without the support of laboratory facilities. The latter type of work has proved to be a particularly good alternative to laboratory-based work, providing material for many publications at a lower cost and higher flexibility than possible in a laboratory setting. In addition, visits to local fisheries and fish markets have proved a useful tool for collecting material (especially, living specimens to use for laboratory observations) and information on the life habits and distribution of many studied species. To a lesser extent, I carried out also dredging operations from research and commercial vessels (e.g., publ. n. 6, 19, 25).

In preparation for and during this field work, I developed simple field techniques and portable equipment for observation and documentation of results, some of which I described in publications (see especially publ. n. 53). Field photography during this type of work also has proved to be an important tool in providing material for subsequent study and publication. I carried out my field work on Recent invertebrates especially in the Philippines, and to a lesser extent in Italy, Bermuda, China and Japan. Because my work concentrates on morphological specialisations and is best carried out in high-biodiversity areas, it has taken place in temperate-warm to tropical seas (observations on material in collections from cold to temperate-cold waters have shown consistently that these faunas are of far lesser relevance to my type of studies).

In connection with my recently developed interest in terrestrial gastropods, I am testing and developing techniques for growing and breeding these organisms in laboratory settings, with the aim of carrying out future studies on their shell growth and morphogenesis, including aspects of regulation and regeneration of shell geometry.

Inferential techniques applied to both fossil and living organisms.

As outlined in publ. n. 12 and 50, I developed and/or used a variety of indirect, inferential methods in my palaeobiological and biological work.

As I argued in the literature mentioned above, I promote the use of inferential methods also when studying Recent organisms, because this provides an objective verification of these methods by comparing their results with those provided by direct observations on living specimens.

I also used inferential methods, and a comparison of their results with those from direct biological observations, to prove the unsuitability of some inferential methods applied to fossil material in the literature. For instance, I have argued that most of the morphologic criteria proposed and used in the palaeontological literature to infer photosymbiosis in fossil bivalves are not reliable, and are likely to result in a large number of false positive and false negative results. I have arrived to this conclusion this by applying these criteria to Recent bivalves, and by showing that these criteria fail to detect most true instances of photosymbiosis, and at the same time suggest photosymbiosis in several Recent bivalves known not to host photosymbionts (publ. n. 62).

My critical application of inferential techniques to the analysis of function of cuticular terraces in Recent stomatopod crustaceans and mantodean insects (publ. n. 64) is another example of this type of verification of indirect palaeobiological techniques (see also my studies on exoskeletal terraces and related structures in other Recent and fossil organisms, publ. n. 4, 5, 6, 10, 15, 17, 19, 20, 25, 40).

Laboratory experiments on the physical properties of morphologic characters.

This is a natural extension of direct observation of living organisms but, unlike the latter, some of these techniques can be applied directly also in palaeobiology. My studies on the properties of terrace sculptures in the context of burrowing (publ. n. 4, 41) are such an example. Experiments on the biomechanical properties of skeletal material in the context of functional analysis, on the other hand, can be performed only on freshly collected Recent material (e.g., publ. n. 31).

Computer modelling of growth, morphogenesis and skeletal construction.

The use of theoretical shell morphology in most of the literature in this field is restricted to reproducing shell coiling and studying the distribution of the geometries of biological coiled shells in a theoretical morphospace of all possible coiled geometries. My interest in this field, instead, is more closely related to functional morphology and morphogenesis. In particular, I have analysed the constraints imposed by shell growth and function in bivalves on the range of shell geometries available to these organisms (publ. 21), comparable constraints on certain gastropods that grow by highly specialised mechanisms (publ. 37), the more general biological constraints on shells that grow by marginal accretion in molluscs and brachiopods (publ. n. 20, 32) and the relationships between theoretical shell morphology and functional morphology (publ. n. 42). For these studies, I have developed algorithms and software which have been the subjects of separate publications (publ. n. 18, 29, 30, 38). Currently I am writing text and software for a multi-author book on the computer modelling of biological growth and form I am editing for Elsevier.

My computer-modelling of sculpture and colour patterns is discussed below.

An unrelated field in which my proficiency in programming has been useful, coupled with my experience in photography and hand-drawing, is the development of algorithms to process digital photographs of palaeontological and biological specimens into the visual equivalent of hand-drawings (publication n. 47, 53). The software I wrote to implement these algorithms has enabled me to prepare in a short time hundreds of “hand-drawings” I published in several chapters of my functional morphology book (edited book n. 1). I have estimated (publication n. 47, 53) that the manual drawing of these illustrations would have required hundreds of man-hours by skilled technicians.

Themes

Aside from the methods discussed above, my research can be viewed also in terms of general themes. In particular, the subjects of several of my publications can be grouped into three general themes, which are discussed below. These themes, however, do not exhaust my areas of interest, which include also shell-biomechanics (e.g., publ. n. 31, 36, 46), symbiosis and parasitism (publ. n. 9, 44, 45, 49, 55, 56, 57), adaptations to endolithic habits (publ. n. 39, 49, 55, 56, 60) and extreme morphologic adaptations resulting from secondary sessile habits (publ. n. 7, 11, 43, 46, 54, 57, 58, 61).

Outside of functional morphology and computer programming, I have published on taxonomy (see below), and also occasional papers on palaeoecology (publ. no. 16) and on the use of fossils in the reconstruction of sedimentological processes (publ. n. 2).

Burrowing mechanisms and burrowing sculptures

A large part of my publications deals with the behavioural mechanisms used by aquatic invertebrates to burrow in soft sediments. Some of these studies concentrate on the relationships between burrowing mechanisms and the presence of specialised sculpture-patterns that aid the burrowing process. Initially I dealt with terrace-patterns in bivalves and decapod crustaceans, which had been already the focus of interest by other researchers, but I realised quickly that terrace sculptures are a special case of more general, and more morphologically varied, burrowing sculptures (i.e., relief-patterns that aid the burrowing process in a variety of direct ways) (publ. n. 4, 5, 6, 10, 15, 19, 25). In subsequent work, the application of criteria derived from these studies to fossil organisms allowed me to detect, for instance, that the burrowing mechanisms and behaviour of Palaeozoic lingulid versus obolid brachiopods were radically different (publ. n. 20). I also studied terrace-patterns that are not functioning as burrowing sculptures, and instead are adaptive in different contexts (publ. n. 17). This latter interest has brought me recently to study the frictional terraces present on the raptorial appendages of predatory stomatopods crustaceans and mantodean insects (publ. n. 65). These terraces are functional in increasing friction between prey and appendage, and therefore decrease the risk that a prey will succeed in breaking free, but the terraces in these two groups function in quite different ways, and this results in distinctive morphological differences.

In addition to organisms that bear burrowing sculptures, I studied the burrowing behaviour and morphological characters related to burrowing and infaunal life in a variety of other organisms (publ. n. 22, 25, 26, 33, 34, 40), especially gastropods. The inferential criteria I derived from these studies have allowed me to reconstruct the life habits of fossil gastropods, especially Strombidae (publ. n. 35, 39)

Twisted bivalves

One of my general interests lies with organisms that have evolved from hard-bottom into soft-bottom forms. In the bivalves, in particular, this phenomenon has resulted in the secondary return to soft bottoms (which were the original environment in which early bivalves evolved and diversified). In most cases, these secondary soft-bottom dwellers could not return to active motility, which had been lost in the hard-bottom environment, or could develop only a limited motility. As a consequence, they developed a broad range of morphological adaptations to sessile or semi-sessile life on or within soft sediments. One of the adaptive morphologies that have evolved multiple times, and in which I have been especially interested, is a shell geometry in which the commissure-plane is twisted into a three-dimensional structure. The distinctiveness of this geometry, and the availability of Recent twisted species in at least three families, has allowed me to develop criteria to assess the life habits in fossil twisted bivalves (publ. n. 3, 13, 14, 27, 36)

Morphogenesis of shell geometry and shell colour pattern

These phenomena in molluscs are another of my major areas of interest. At a time when little work had been carried out on the biochemical basis of divaricate patterns, I used simple computer models to study the geometric properties and growth of these patterns, in connection with their hypothesised burrowing function, in linguliform brachiopods (publ. n. 20). The conclusions are still valid (although models that better incorporate biochemical processes are now available), since my discussion made few assumptions on the exact nature of the underlying morphogenetic program.

Later on, my interest in programming has allowed me also to model two- and (slightly) three-dimensional colour patterns in cypraeid gastropods as the result of reaction-diffusion systems (publ. n. 48, 51). All previous studies of colour-patterns in mollusc shells have dealt with one-dimensional activity patterns of the mantle-edge, recorded in time as a two-dimensional colour pattern on the external shell surface. My studies showed that, in adult cypraeid gastropods, the external shell-surface is periodically covered by a two-dimensional mantle surface that remains stationary with respect to the shell while secreting its colour pattern as a thin three-dimensional layer on top of the outer surface of the shell. In several cypraeids, the visible pattern does not seem to result from a non-uniform distribution of pigment within the shell material (as is the case in other molluscs), but, at least in part, from a non-uniform thickness of this added layer of pigmented shell material. In several respects, the colour patterns in this gastropod family are unlike any others in mollusc shells, and more similar to those displayed by vertebrate skins and fur-coats. In addition, I showed that fine relief on the original shell surface (including normal growth lines and abnormal relief caused by shell-breakage and repair) becomes a morphogenetic cue in determining the location of individual colour spots and stripes of the colour-pattern subsequently deposited on these surfaces.

More recently, I have undertaken two broad projects dealing with aspects of the function and morphogenesis of gastropod shells. In one of these, together with a collaborator, I studied synchronised sculpture (i.e., relief-patterns in which individual ribs or varices are placed at fixed reciprocal position on successive whorls; publ. n. 65). In the second, still under way, I am reviewing the distribution, function and associated morphogenetic processes of determinate growth-patterns in gastropods. This growth-pattern occurs in several families (including a few in which it has previously passed undetected), and can be detected from morphological shell-features. Often it is associated with extreme morphological specialisations of the aperture (e.g., in strombid gastropods: publ. n. 35), and frequently with extended “count-down” morphogenetic processes. In both projects, it has become apparent that morphologic features located on the last shell-whorl are sensed by soft tissues, and the resulting tactile feedback is used as a morphogenetic contact-guidance to place subsequent morphological features of the shell at their optimal reciprocal positions. These studies substantially broaden the documented occurrence of contact-guidance in the morphogenesis of skeletal systems, and show that contact-guidance is common in gastropods. Together with my studies of burrowing sculptures (publ. 25, 34, 40), they also show that gastropod shells are more amenable to functional interpretation than previously thought, and at least as useful as the skeletons in other, better studied groups (e.g., the bivalves) in providing information on life habits and behaviour.

Other interests

For a while, I concentrated on Ediacara-type organisms, which in my opinion still are not understood in terms of functional morphology and affinities. In publ. 69, I showed that features of the Early Cambrian genus Protolyellia, previously regarded as genuine, are actually a combination of true anatomical features and taphonomic effects, which caused morphologic features originally located in different regions of the organism to be juxtaposed in fossils. An examination of the Early Cambrian Spatangopsis (publ. 72) likewise reveals morphological features distinct from those of Recent organisms.

Scientific photography has been a useful tool for my research work throughout my career. A large part of this site is devoted to technical aspects of photography, and I also wrote a book on digital photography applied to science and scientific publishing (publ. 70) and a paper on equipment used in focus stacking (publ. 71). More information on my books is available here.


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