This review compiles information on the taxonomy, identification, geographical distribution, life cycles, host ranges, occurrence, development and growth in both intermediate and final hosts, pathogenicity, and control measures of AnguilUcola crassus and A. globiceps, swimbladder nematodes of farmed and wild populations of two species of eels, Anguilla japonica and A. anguilla, in East Asia. Anguillicola crassus is distributed in Japan, Korea, Taiwan, and China, while A. globiceps is reported only in Japan and China. These nematodes use cyclopoid copepods as intermediate hosts. Known intermediate hosts are Eucyclops serrulatus (Japan) and Therirwcyclops hyalinus (Korea) for A. crassus, and Mesocyclops leuckarti, T. hyalinus, T. taihokuensis, E. serrulatus, Acanthocyclops viridis, and Cyclops slrenuus (China) for A. globiceps. Anguillicola crassus shows a seasonal occurrence in T. hyalinus with high prevalence in summer, Paratenic hosts are yet unknown in East Asia. Anguillicola crassus is relatively common in farmed and wild populations of Anguilla japonica in East Asia, but A. globiceps is usually found in wild populations of A. japonica in Japan and China. In culture ponds, A. crassus is more prevalent and abundant in A. anguilla than in A. japonica. Although A. globiceps induces only the thickening of the host’s swimbladder wall, A. crassus gives severe pathological effects in A. anguilla and heavy infection leads to host mortality. Prevalence of A. crassus in A. japonica cultured in Japan and Korea is relatively low in winter, whereas prevalence of A. globiceps in wild populations of A. japonica from Japan is high in winter.
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 nematode Rhabdochona anguillae Spaul, 1927, a specific intestinal parasite of the European eel, Anguilla anguilla (L.), is redescribed and illustrated from specimens collected from eels of the Sousa River, northern Portugal (prevalence 20%, intensity 2-13). The species is characterized by the presence of 14 anterior teeth in the prostom, small non-bifurcate deirids, absence of lateral preanal papillae, by the length (0.460-0.660 and 0.130-0.150 mm) and the shape of spicules, fairly large (0.041-0.054 x 0.025-0.030 mm) mature eggs without filaments, and by the bluntly pointed to rounded tip of the tail. Its morphological features are discussed in relation to other congeneric species. This nematode has hitherto been recorded only from eels in southern Europe (Portugal, Spain, Bulgaria).