Use this URL to cite or link to this record in EThOS:
Title: Evolution of the arthropod mandible : a molecular developmental perspective
Author: Coulcher, J. F.
ISNI:       0000 0004 2731 6355
Awarding Body: University College London (University of London)
Current Institution: University College London (University of London)
Date of Award: 2011
Availability of Full Text:
Access from EThOS:
Access from Institution:
The mandible is thought to have evolved once in the ancestor to the mandibulate arthropods; the insects, crustaceans and myriapods. If the mandible is a homologous structure, it suggests that there will be shared developmental genes required to pattern the mandible in different species. As a representative of mandibulate arthropods, the red flour beetle Tribolium castanem was chosen to study genes required to pattern the mandible. This study show that the Tribolium orthologue of cap’n’collar (Tc cnc) patterns the mandible of Tribolium. Loss of Tc cnc function by RNA interference (RNAi) results in a transformation of the mandible to maxillary identity and deletion of the labrum. Analysis of gene expression by in situ hybridisation shows that Tc cnc represses the Tribolium orthologues of the Hox genes proboscipedia (pb) and Deformed (Dfd), which pattern the maxillary appendage. Similar expression patterns of cnc, Dfd and pb homologues in mandibulate arthropods suggests that the functions of these genes are conserved. As the mandible has evolved from a maxilla-like precursor in the ancestor to all mandibulate arthropods, the manner in which Tc cnc differentiates the mandible from a maxilla in Tribolium recapitulates the evolution of the mandible from a maxilla-like precursor. An orthologue of cnc was cloned from the spider Achaearanaea tepidariorum, chosen as an outgroup to the mandibulate arthropods, but no evidence of a developmental role was discovered. Study of the expression of genetic markers for appendage segments shows that the biting edge of the mandible is derived from one endite, and the mandible is divided into a subcoxa and coxa which are also present in the maxillary, labial and leg appendages. There are significant similarities in the expression of genetic markers that presumably indicate serial homology of the subcoxa and coxa of the mandible to the subcoxa and coxa of other appendages.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available