Bacterial feeding nematodes including Zeldia punctata (Rhabditida: Nematoda), and Caenorhabditis elegans differ profoundly in feeding adaptations and specifically in the rhabdions (cuticular thickenings), and associated cells lining in the buccal capsule. We are carrying out a range of tests to determine what rhabdions are evolutionarly homologous between the two species. Reconstruction of the buccal capsule and procorpus (pharynx) with transmission electron microscopy indicates that the lining of the buccal capsule of Z. punctata includes four sets of muscular radial cells ma, mb, mc, md in contrast the same region in C. elegans which has two sets of epithelial radial cells (
e1,
e3) and two sets of radial muscle cells (
m1,
m2). In Z. punctata ma is a set of three radial muscle cells each with 2 nuclei. In C. elegans
m1 has the identical arrangement. Similarly, in Z. punctata mb is a set of 3 muscle cells each with one nucleus, similar to
m1 in C. elegans. These findings could contradict all previous hypotheses of homology, and suggest instead that ma and mb in Z. punctata are homologous respectively with
m1 and
m2 in C. elegans. Ongoing additional tests of homology include comparative cell lineages and screening mutants to recognize genes involved in buccal capsule expression.