Development of Betta splendens embryos and larvae reveals variation in pigmentation patterns.

Vertebrate pigmentation provides an ideal system for studying the intersections between evolution, genetics, and developmental biology. Teleost fish, with their accessible developmental stages and intense and diverse colours produced by chromatophores, are an ideal group for study. We set out to test whether Betta splendens is a good model organism for studying the evolution and development of diverse pigmentation.

Who came first--larvae or adults? origins of bilaterian metazoan larvae.

There is a classic controversy in zoology over whether the common ancestor of living bilaterian phyla was a benthic animal with a bilaterian body plan, or was a pelagic larva-like animal similar to what we see today in the primary larvae of indirect-developing bilaterians. We examine the current larva-like adult hypothesis, and present an alternate model for the evolution of complex life histories by intercalation of larval features into the ontogeny of an ancestral direct-developing bilaterian. This gradual accumulation of larval features results in a developmental regulatory program that produces a larva distinct in body plan from the adult.

Regulatory punctuated equilibrium and convergence in the evolution of developmental pathways in direct-developing sea urchins.

We made hybrid crosses between closely and distantly related sea urchin species to test two hypotheses about the evolution of gene regulatory systems in the evolution of ontogenetic pathways and larval form. The first hypothesis is that gene regulatory systems governing development evolve in a punctuational manner during periods of rapid morphological evolution but are relatively stable over long periods of slow morphological evolution. We compared hybrids between direct and indirect developers from closely and distantly related families.

Patterns of gene expression in the developing adult sea urchin central nervous system reveal multiple domains and deep-seated neural pentamery.

The adult sea urchin central nervous system (CNS) is composed of five radial nerve cords connected to a circular nerve ring. Although much is known about the molecular mechanisms underlying the development and function of the nervous systems of many invertebrate and vertebrate species, virtually nothing is known about these processes in echinoderms. We have isolated a set of clones from a size-selected cDNA library prepared from the nervous system of the sea urchin Heliocidaris erythrogramma for use as probes.