Experimentally induced infections of European eel <i>Anguilla anguilla</i> with <i>Anguillicola crassus</i> (Nematoda, Dracunculoidea) and subsequent migration of larvae

Migration patterns of third-stage Anguillicola crassus larvae, and pathogenesis of the lesions induced by third-stage larvae, was investigated in European eel Anguilla anguilla L. Young elvers (1g) were fed infected Paracyclops fimbriatus (Copepoda). Eel samples were collected and examined histologically at varying intervals during 6 mo post-infection period. Third-stage larvae (L-III) migrated directly through the intestinal wall and body cavity to the swimbladder within 17h post-infection. L-IV larvae were detected 3 mo post-infection, and immature adults were detected within 4 mo post-infection. The parasites occasionally showed aberrant migration paths. Pathological effects caused by the parasite were less severe after experimentally induced infections than those detected in some natural infections

Hydrocephalus in burbot (Lota lota L.) larvae

During an experiment aimed at elucidating the nutritional requirements of burbot (Lota lota L.) larvae, the latter displayed a dorsal swelling of the cranium. Histological examination revealed dilated brain ventricles (hydrocephalus internus). Bacterial culture of the content of the swelling was negative. Slightly elevated copper concentrations were found in the culture water resulting in an increased larval body copper content. This is the first reported case of hydrocephalus in burbot larvae

Spatio-temporal analysis of fish behaviour: lessons learnt to stimulate fish passage

Obstacles like weirs, watermills and locks are barriers for migratory fish. The fact that specific fish species cannot reach their optimal spawning habitat can have severe consequences for the survival of these species. While numerous fish passage types have been designed to solve this problem, these are sometimes not efficient. More insight into fish behavior is needed to improve fish pass efficiency, and acoustic telemetry allows such detailed observation of spatio-temporal migration patterns. We present novel findings on fish behavior at anthropogenic structures based on acoustic telemetry. The impact of several constructions like sluices, weirs, pumping stations and small-scale hydropower plants will be assessed and potential solutions to enhance fish migration at these structures will be discussed. This approach will identify crucial information needs for effective fish passage management and reveal a range of opportunities for fish passage research

Indications for a recent Holarctic expansion of pike based on a preliminary study of mtDNA variation

An extremely limited haplotypic diversity within populations and a strikingly low divergence between European and Canadian haplotypes were found in pike Esox lucius. Certain haplotypes were associated with a particular geographical region in Europe: a widespread European and a restricted Hungarian–Norwegian type. The low haplotypic intraspecific divergence suggests a late Pleistocene expansion from an ancestral population

An improved method for artificial infection of the European eel, <i>Anguilla anguilla</i>, with <i>Anguillicola crassus</i> (Nematoda, Dracunculoidea)

A standardized method was developed for artificially infecting the European eel with Anguillicola crassus, a parasitical swim bladder nematode. For this purpose, an intermediate host, Paracyclops fimbriatus, and a paratenic host, Cyprinus carpio, were used. Parasite prevalence in the artificially infected eels was very high, although there was a large variation in the number of worms per eel. Compared to other methods of artificial infection described in the literature, this method appears to be more efficient ad reliable; there were also more infectious larvae that were recovered and the mortality rate of eels under treatment was lower

Development of nine polymorphic microsatellite loci in the spined loach, Cobitis taenia, and cross-species amplification in the related species C. elongatoides, C. taurica and C. tanaitica

Nine polymorphic microsatellite loci were developed for the spined loach, Cobitis taenia (Teleostei: Cobitidae). The loci were validated using 50 individuals from a population in Belgium. Moderate to high levels of polymorphism were detected (two to 11 alleles). In addition, most markers amplified successfully in three closely related taxa that are known to hybridize with C. taenia: C. elongatoides, C. taurica and C. tanaitica. Some of the loci are most likely diagnostic among species. These markers will be valuable for the study of the historical and contemporary interactions within C. taenia and the Cobitis species complex.status: publishe