BROWNE, W.E.; PATEL, N.H.; MARTINDALE, M.Q.; Kewalo Marine Lab, University of Hawaii; HHMI, University of California, Berkeley; Kewalo Marine Lab, University of Hawaii: Developmental Expression of lab and ems in the head and CNS of Parhyale hawaiensis

The arthropod head is a complex multimeric structure. At the level of molecular patterning in Drosophila it appears that a relatively small number of transcription factors play a major role in specification of the supraesophageal ganglion. From anterior to posterior in the crustacean, Parhyale, the supraesophageal ganglion can be subdivided into protocerebral, deutocerebral, and tritocerebral neuromeres. Here we present expression patterns associated with Parhyale orthologs of labial (lab) and emptyspiracles (ems). The Hox gene lab is expressed in the IC segment during insect development. In Parhyale, Ph lab is expressed pregastrulation in a single row of cells corresponding to the primordium of the second antennal (AN2) segment (homologous to the insect intercalary (IC) segment). During formation of the Parhyale germband, Ph lab expression includes all ectodermal cells contributing to the AN2 segment. Later expression of Ph lab is restricted medially to the tritocerebrum and to lateral and posterior regions of the stomodeum. In Drosophila the head gap gene ems is expressed in an early broad domain in both the AN and IC segments and plays a role in specifying structures on these segments. In Parhyale there is no analogous broad ems domain in the head. Parhyale ems is first detected in small, bilateral, domains after germband formation. Once the germband is complete and appendage buds begin to appear anteriorly, Ph ems is detected in bilateral reiterated sets of ventral ectodermal cells along the A-P axis. Early expression of Ph ems is inconsistent with a role as a �head gap gene� as Ph ems expression in the anterior head occurs after the head lobes appear. Current experiments seek to explore the function of lab and ems genes in Parhyale.