Meeting Abstract
Siphonophores are pelagic colonial hydrozoans that are composed of genetically identical zooids that are considered to be homologous to solitary individuals. The zooids are produced asexually, and remain physiologically integrated and attached to one another. Within the colony, each zooid is functionally specialized to a particular task, for example: feeding, swimming, defence, and reproduction. In mature colonies, new zooids bud from two distinct growth zones with the youngest zooids closest to the growth zone and the oldest furthest away. We use a comparative approach to look at the mRNA expression in different zooid types at different developmental stages both within a single siphonophore species, and also between different species, to assess sets of genes that are involved in specifying zooid identity, and to determine whether there is molecular evidence for homeotic transformations in zooid identity. Here we describe preliminary results suggesting key differences between different zooid types, and discuss methods to analyze gene expression within a phylogenetic context, overcoming issues of non-independence of the data due to phylogenetic relatedness.
