Qualitative changes in carboxylesterase-2 phenotypes of tetraploid loaches (Misgurnus fossilis L.)

We have shown in our previous work that in the tetraploid loach Misgurnus fossilis carboxylesterase-2 (E-2) phenotypes of embryos and early larvae are controlled by the alleles of the Est-2 locus. In the present work it has been established that the somatic tissues of many adult fish homozygous for one of the Est-2 alleles, unlike the tissues of embryos and larvae, reveal an additional fraction of E-2 with electrophoretic mobility corresponding to that of the second allozyme. The activity of this additional fraction of E-2 varies with the tissue and depends on the age of fish and maintenance conditions. Phenotypes of the same individual homozygous for one of the Est-2 alleles can be manifested as homozygous or heterozygous according to the activity of the additional E-2 fraction. The results obtained are consistent with the assumption that in the tetraploid species Misgurnus fossilis there are two E-2 loci with common alleles of identical electrophoretic mobility.