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Abstract

Nematode pharyngeal glands have historically been associated with feeding as well as cuticle moulting, although little is understood of the molecular biology underlying these processes. By utilising two evolutionary divergent nematode species with differing diets and feeding traits we are elucidating the roles of the pharyngeal gland cells and their function in feeding, diet and other cellular processes. The model organisms C. elegans and P. pacificus provide an apt system with which to analyse the pharyngeal glands, as while both nematode species contain several pharyngeal gland cells, C. elegans is predominantly a bacterial feeder, whereas P. pacificus is capable of predating other nematode species in addition to its bacterial feeding habits. Accordingly, gland cells display an evolutionary divergence in both quantity and morphology between species. The pharynx of C. elegans contains five pharyngeal gland cells, a large dorsal gland (g1D) exiting at the mouth opening, two ventral glands (g1V) emptying into the median bulb and two ventral glands (g2) exiting into the terminal bulb. The pharynx of P. pacificus contains three gland cells, lacking the g2 glands, and additionally the g1D is morphologically distinct as the gland duct exits through the predatory dorsal tooth used to eviscerate other nematodes before feeding. Furthermore, substantial divergence in the function of pharyngeal glands between these two nematode species has been predicted. The dorsal gland in the bacterial feeding nematode C. elegans is stimulated through inputs from the isthmus while the dorsal gland in the bacterial and predatory feeder, P. pacificus receives inputs from the corpus. This dramatic shift in regulation may indicate an alteration in gland cell regulation towards additional predatory functions. Cell ablation experiments removing g1D cells however reveal much functional conservation as animals become starved due to a bacterial plug blocking the pharynx in both species. Therefore, we have begun generating the transcriptome of the pharyngeal gland cells using mRNA tagging followed by RNA-seq with which we will pursue the genetic candidates behind gland cell function and the expanded diet evident in P. pacificus.