ParaHox gene expression in larval and postlarval development of the polychaete Nereis virens (Annelida, Lophotrochozoa).

Background: Transcription factors that encode ANTP-class homeobox genes play crucial roles in determining the body plan organization and specification of different organs and tissues in bilaterian animals. The three-gene ParaHox family descends from an ancestral gene cluster that existed before the evolution of the Bilateria. All three ParaHox genes are reported from deuterostomes and lophotrochozoans, but not to date from any ecdysozoan taxa, and there is evidence that the ParaHox genes, like the related Hox genes, were ancestrally a single chromosomal cluster.

The abdominal-B-like gene expression during larval development of Nereis virens (polychaeta).

We have studied the posterior Hox gene Nvi-Post1 expression in the early development of the polychaete Nereis virens. This is the first evidence of the posterior group Hox genes expression during the larval development of a Lophotrochozoan. The expression begins in the trochophore hyposphere at the prospective sites of larval parapodia.