The development of the swimbladder nematode Anguillicola crassus Kuwahara, Niimi et Itagaki, 1974 in the definitive host (eels) was studied under experimental conditions. Small eels, Anguilla anguilla (L.) with body length 8-16 cm were infected by feeding them intermediate host copepods (Cyclops strenuus Fischer) harbouring third-stage larvae of this parasite. These experiments showed that, at 20-22° C, the development from the third-to the fourth-stage larvae lasted approximately three weeks, but some retarding third-stage larvae occurred in the wall of the host’s swimbladder or hyperparasitizing in the cuticle of adult nematodes as late as three months p.i. Young adults developed in the lumen of the swimbladder within approximately one month and noneinbryonated eggs first appeared in females 6-7 weeks p.i. The prepatent period was about three months and the patent period could be estimated to last no more than a month. Females degenerated soon after oviposition. The experiments confirmed that the size of mature A. crassus depends on the body size of its definitive host (eel).
An examination of a sample of European eels, Anguilla anguilla (L.), collected from Lake Bracciano near Rome in 1993, the only known European locality with the occurrence of the introduced swimbladder nematode Anguillicola novaezelandiae Moravec et Taraschewski, 1988, revealed for the first time the presence of two Anguillicola species, A. novaezelandiae and A. crassus. In view of the investigations carried out by current authors in Bracciano Lake in the years 1982-1992, it is apparent that the latter species has been introduced into the lake quite recently, where it quickly became a dominant species. The development of A. novaezelandiae was experimentally studied in the copepod intermediate host, Cyclops strenuus, for the first time. The copepods were infected with nematode second-stage larvae at 21-22°C; fully developed infective third-stage larvae were obtained 13 days p.i. The general morphology of individual larval stages of A. novaezelandiae was similar to that of larvae of the related species Λ. crassus.
The development of the nematode Anguillicola crassus, a swimbladder parasite of eels, was experimentally studied in copepod intermediate hosts Cyclops strenuus and Acanthocyclops vernalis. The copepods, kept at a laboratory temperature of 20-22 °C, were infected with nematode second-stage larvae; the second moult of larvae (the only one in the intermediate host) was observed to start 10 days p,i„ but third-stage larvae liberated from their cuticular sheath were first observed 20 days p.i. These proved to be infective for experimental eels. Free second-stage larvae as well as larvae from copepods were described. The morphology of A. crassus larvae and the mode of their development in the intermediate host were compared with those of other dracunculoid nematodes. From this point of view, Anguillicola members appear to represent an ancient group of dracunculoid nematodes.