| Popis: |
Eighty-four specimens of the maruta-type of anadromous cyprinid Tribolodon brandtii collected from six rivers in the Tohoku and Kanto Districts between 1952 through 2012 included one individual with hooked vertebral column and 18 individuals with fused centrums. These abnormal individuals were all collected from three rivers in the 1960s, and specimens from the other three rivers collected in other times were all normal ones. The individual with hooked vertebral column looked abnormal in appearance, too. The individuals with fused centrums, on the other hand, looked normal and had the same morphological characteristics with the other individuals with normal vertebrae collected at the same time except for number of vertebrae and snout length. The adjusted number of vertebrae of the individuals with fused centrums by their number of neural spines was indifferent from those of the normal individuals. The corrected number of abdominal and caudal vertebrae, however, was more and less than those of the normal individuals, respectively. Length/height (%) of non-fused caudal centrum of the individuals with fused centrums was larger than those of the normal individuals. The individuals with fused centrums would have recovered their normal body shape by the vertebral alteration mentioned above through their daily swimming life in their growth. |
