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Journal of Fish Biology 81(3)

Home Forums Ichthyology Journal of Fish Biology 81(3)

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    Matt
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    First cytogenetic studies of the genus Heptapterus (Actinopterygii, Siluriformes): karyotype differentiation and review of cytogenetic data on the Heptapteridae family

    The Neotropical fish Heptapterus mustelinus, collected in the Pindorama stream of the upper Paraná River basin (Brazil), was studied cytogenetically, verifying 54 chromosomes (26m + 18m + 4st + 6a). This diploid number has not been reported among the Heptapteridae that have been studied to date. Unlike most species of the family, there were multiple Ag-nucleolar organizer regions (NOR) and heterochromatin present in the centromeric region of most of the chromosomes of the complement, being Chromomycin A3 (CMA3+)/4′,6-diamidino-2-phenylindole (DAPI) in nine chromosomal pairs, besides the one that coincides with the Ag-NORs. The data presented in this work reveal a different path in the karyotypic evolution of H. mustelinus when compared to the others Heptapteridae genera.

    Aspects of the biology of Galaxias maculatus
    The biology of three landlocked and a riverine population of Galaxias maculatus were examined in western Victoria, Australia. All systems supported reproducing populations of these fish, including Lake Corangamite which had salinities that on occasion reached 82. Spawning sites in Lake Corangamite were located in adjacent tributaries and not in the main lake as was the case for other populations. The smallest fish were found in the fresh water Lake Purrumbete and the largest in the hypersaline Lake Corangamite. The size at which 50% of the population attained sexual maturity varied across sites, with fish maturing at a smaller size in Lake Purrumbete, followed by the Merri River, Lake Bullen Merri and Lake Corangamite. Condition was higher in the freshwater Lake Purrumbete and there was no relationship between condition and temperature, conductivity, turbidity and pH; but there was a positive relationship between condition and dissolved oxygen. Length frequency analysis suggested that the majority of fishes live for a year.

     
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