Abstract
The morphology of the head, mouth, and oesophagus in four species of the nematode family Cucullanidae Cobbold, 1864, has been studied in detail. The species examined are: Cucullanus cirratus Müller, 1777 and C. heterochrous Rudolphi, 1802 from the west coast of Norway, C. minutus Rudolphi, 1819 from Scotland, and Dacnitis truttae (Fabricius, 1794) from east Norway; the first three are from marine fish, the last from a freshwater fish.
In the Cucullanus species, transverse cuticular structures projecting into the muscle mass from the pseudobuccal capsule are described, illustrated, and named. Such projections are absent in Dacnitis, but the pseudobuccal cuticular lining forms thickened plates separated by narrow grooves which form a characteristic pattern. The morphology of the pseudobuccal capsule and its associated cuticular structures may be used as taxonomic characters at the species level, possibly also at genus and higher levels. A new definition of Dacnitis is proposed. The functional significance of the head, mouth, and oesophagus is discussed.
A note on fixing and clearing media is included.
