Allorecognition

Allorecognition reactions, wherein a colony detects and reacts to a conspecific on the basis of cell-cell contact, are near ubiquitous amongst the clonal marine benthos. These phenomena interest cell biologists as recognition systems, population geneticists by virtue of the substantial allotypic diversity they display, evolutionists in the role such interactions play in mediating the units of selection, immunologists in the oft-repeated hypothesis that these phenomena lie at the root of vertebrate immunity, and ecologists in the coupling of allorecognition to the mechanisms and outcomes of intraspecific competition.

In recent years, my lab has developed the study of allorecognition in the colonial hydroid Hydractinia by generating inbred and congenic lines, using them to identify a chromosomal interval controlling allorecognition, and mapping this interval. Current work includes positional cloning of two allorecognition loci and studies of the mechanism generating the extraordinary polymorphism in this interval.

Colony circulatory design

Colonial animals are typically comprised of repeated units (polyps, zooids, and so on) connected to one another by a system of quasi-vascular canals. These circulatory systems differ in three major respects from the vertebrate circulatory systems. In particular, the vascular canals of colonial animal circulatory systems anastomose rather than dichotomously branch, they often have multiple pumps driving the flow, as opposed to a single heart, and flow is alternately bidirectional.

The colonial animal circulatory system is a microfluidic design that reliably generates an ontogeny. My lab is interested in how ontogeny is coupled to circulatory dynamics in the colonial hydroids Hydractinia and Podocoryna. Understanding of the system is derived from interplay between a modeling effort and high resolution observations of circulation patterns in living animals.

Placozoan biology

The Phylum Placozoa has been known for over a century, but aside from a decade long research program in the 1970's by the German protozoologist Karl Grell and his collaborators, they have received relatively little attention. This is odd in that placozoans are the simplest free-living invertebrate known, comprised of only four cell types.

We have devoted considerable attention in recent years in developing the placozoan Trichoplax adhaerens as a model system. Recent work has established that placozoans are the basal animal phyla, that placozoans have sex and that placozoans are a diverse rather than monotypic phyla. We are a collaborator on the Trichoplax genome project and have a large Trichoplax EST program underway in collaboration with DOE JGI.