Clonal nature of gynogenetically induced progeny of triploid (diploid × tetraploid) loach,Misgurnus anguillicaudatus (pisces: cobitididae)

Abstract

In the loach Misgurnus anguillicaudatus, triploid fish, which had been produced by hybridizations between normal diploid females and natural tetraploid males, laid mature hexaploid (triploid egg nucleus + triploid polar body nucleus) eggs of large size as well as diploid (haploid egg nucleus + haploid polar body nucleus) eggs of small size. Gynogenetic triploidy was artificially induced by activating the large eggs with UV-irradiated spermatozoa. Gynogenetic hexaploidy was also generated by blocking the polar body release with pressure shock after induction of gynogenesis. Unexpected mosaics and pentaploid gynogens were infrequently observed in these crosses. Most triploid and all hexaploid gynogens from each triploid female demonstrated absolutely identical DNA fingerprints, suggesting clonal nature among the mature large eggs of each female. However, a small number of triploid gynogens were aclonal with slightly different DNA fingerprints. These results indicate that triploid loach generate viable large eggs which are genetically identical or highly similar to the somatic cells. J. Exp. Zool. 278:412–421, 1997. © 1997 Wiley-Liss, Inc.