Pharynx or oesophagus? A comparative review of the terminology and homology of the nematode feeding organ

The digestive tract of nematodes is divided into several regions with distinct functions. The anterior region contains a muscular-glandular feeding organ that has traditionally been designated either as the oesophagus or as the pharynx. This review examines the historical origin of this dual terminology and evaluates it in the light of anatomical definitions and comparative morphology. The evidence indicates that the coexistence of both terms is largely the result of historical convention rather than anatomical interpretation. The nematode feeding organ shares with the pharynx of other ecdysozoans, particularly cycloneuralians, its position, specialized musculature, glandular organization and role in food ingestion, whereas the oesophagus, when present, is consistently a short conduit connecting the pharynx to the intestine. These observations support the recognition of the nematode feeding organ as a pharynx and the abandonment of the term oesophagus in favour of terminology that is more consistent with current concepts of homology and comparative anatomy.