Research Program
Current research in my lab is focused on evolutionary innovations as viewed from the standpoint of an interplay between developmental constraints and opportunities. Gastropod molluscs provide a rich source of subject material in which to address questions about the evolutionary diversification of body plan. My students and I study these questions by examining comparative patterns of development; an approach that acknowledges the pivotal role of development in the process of evolutionary change in morphology. This research program has grown out of my broad interests in the functional morphology, neurobiology, and development of marine invertebrates.

Ongoing research in my lab is focused on three major problems.
 
1)  Evolution of derived feeding structures in gastropods. A major theme for the adaptive radiation of gastropods, particularly caenogastropods, is the diversification and specialization of adult feeding structures.  How have the various adult innovations been generated within a life history that includes a larva that feeds on microalgae?  Early results of comparative developmental studies suggest that evolution of the adult foregut in predatory gastropods involved dramatic developmental novelties that are invisible in the adult stage.
2)  Gastropod torsion. Torsion is seen as the defining characteristic of gastropod molluscs and is described as a rotation between two major body compartments, the head-foot and visceropallium. This hypothesized rotation was one of the earliest specific proposals for evolutionary change via developmental modification (Garstang, 1929).  However, the torsion hypothesis assumes that: (a) evolutionary history can be read from developmental sequences, and (b) basal gastropod clades are more likely to preserve the ancestral developmental sequence for gastropods than derived clades. Contemporary research in evolutionary developmental biology has eroded the validity of both these assumptions. My approach to reconstructing the essential components of the gastropod body plan and the evolutionary emergence of those novelties is to search for aspects of developmental organization that are expressed by representatives of all gastropod clades, even if only transiently. These comparative studies focus on the morphogenesis of the shell-anchored retractor muscles, the mantle cavity, and the visceral nerve connective. Initial results suggest that profound asymmetry between the left and right sides of the originally symmetrical mantle cavity may be the essential innovation of the gastropod body plan.
3)  Larval nervous systems.  For organisms with a complex life cycle, a larval stage is the first functional product of embryogenesis.  The nervous system of these free-living organisms has been the subject of much recent interest. Relevant questions include: What is the circuitry of the larval nervous system and what behaviours does it control? Is the larval nervous system involved in sensory and integrative processes involved in induction of settlement and metamorphosis or are these processes controlled by later formed components of the post-metamorphic nervous system? Does the larval nervous system help to organize formation of the definitive, post-metamorphic nervous system? Might aspects of the larval nervous system be informative phylogenetic characters?
 

Research in my lab is supported by the Natural Sciences and Engineering Research Council and by a New Opportunities grant from the Canada Foundation for Innovation.
 
 

Veliger larva (echinospira type) of Marsenina stearnsii. Larval metamorphosis in this species is induced by the compound ascidian, Trididemnum sp., which is the prey of the post-metamorphic snail.