Weatherfish

Abstract: Habitat preferences and movements of the weatherfish, Misgurnus fossilis, were studied in a drainage channel of the lower River Havel region (Saxony-Anhalt) from July to November 1995 During summer, adult fish preferred dense vegetation patches (eg Elodea canadensis) whereas juveniles preferred the reed zones along the bank lines, characterized by coarse detritus and extremely shallow water depths (<01 m) All size groups totally avoided open substratum without vegetation structures In total, 166 weatherfish ≥ 14 cm were marked individually by injected dyes and their movements were documented by recaptures (recapture rate 29%) Most of the weatherfish showed stationary behaviour or site constancy The majority of fish (701%) were recaptured within ranges of 50 m with reference to the first release point The mean movement distances slightly increased during the search for overwintering habitats in the first weeks of October Weatherfish stocks in drainage channels of the study area are strongly affected by annual machine weeding due to depletion of suitable microhabitats and direct removal of fish Alternative maintenance protocols for drainage channels and ditches are proposed

Abstract: In the loach, or Oriental weatherfish Misgurnus anguillicaudatus (Teleostei: Cobitidae), diploid (2n = 50) and tetraploid individuals (4n = 100) are often sympatric in central China. The evolutionary mechanism of this tetraploidization was analyzed with the observation of meiotic behavior of chromosomes in both the germinal vesicles of mature oocytes and the primary spermatocytes in diploid and tetraploid loaches. Whereas diploid specimens usually showed 25 bivalents in meiotic cells, tetraploid loaches exhibited 0–6 quadrivalents and 38–50 bivalents in both sexes, with the modal number of quadrivalents as three in females and four in males. In the diploid specimens, the two largest metacentric chromosomes bearing nucleolar organizing regions (NORs) identified by chromomycin A3 staining and fluorescence in situ hybridization with a 5.8S + 28S rDNA probe formed one bivalent with terminal association. In the tetraploids, four NOR-bearing chromosomes never formed a quadrivalent, but were organized into two terminally-associated bivalents. These findings suggest an autotetraploid origin of the natural tetraploid loach and subsequent rediploidization of whole genome. The latter process, however, seems still in progress as inferred from the concurrence of up-to several quadrivalents and the majority of bivalents.

Abstract: The introduced range of the European cyprinid, sunbleak Leucaspius delineatus, in England was previously limited to parts of southwest England but has now expanded across Southern England. Natural dispersal mechanisms cannot explain their increased distribution and fish stocking was not a factor. Thus, the accidental movement of either their eggs or larvae via anglers’ nets was believed to be the mechanism by which these fish were accidentally moved between waters over 100 km apart. This dispersal pathway is difficult to regulate, as is the release of unwanted non-native aquarium and pond fish into open waters by the public. This latter pathway has resulted in the recent releases of species including walking catfish Clarias batrachus, Asian weatherfish Misgurnus mizolepis and white catfish Ameiurus catus.

Abstract: Results of previous studies indicate that the medaka, Oryzias latipes, a small aquarium fish found in Japan and neighboring countries, is a suitable animal for use in cancer research. This fish showed a high incidence of liver tumors after a short induction period when kept in water containing diethylnitrosamine. Unscheduled DNA synthesis (UDS) was demonstrated in ganglion cells of the medaka in vivo by autoradiography. For this experiment, part of the bony skull of the medaka was removed surgically, and the living fish was kept in an isotonic solution containing a carcinogen and tritiated thymidine. Its brain was then examined histologically. By this method, UDS was clearly demonstrated over the nuclei of ganglion cells after exposure to a wide variety of chemical carcinogens. The abdominal cavity was opened and treated with carcinogens in the same way as the brain; however, no UDS was detected in liver or intestinal cells. We conducted comparative studies on DNA repair in the brains of 5 species of small fish from widely different families. These 5 species (blond cave fish, Oriental weatherfish, medaka, guppy, and Siamese fighting fish) were exposed to various concentrations of 4-hydroxyaminoquinoline 1-oxide or methyl methanesulfonate. We detected UDS in all 5 species after both treatments, although the extent varied in the different species.