Lampbrush Chromosomes of Rana nigromaculata, R. brevipoda, R. plancyi chosenica, R. p. fukienensis and their Reciprocal Hybrids
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Landmarks and chiasmata of lampbrush chromosomes were observed in the oocytes of female Rana nigromaculata, (N) NN, R. brevipoda, (B) BB, R. plancyi chosenica, (C) CC, and R. p. fukienensis, (F) FF, and in those of 12 kinds of hybrids produced from these species and subspecies. The lampbrush chromosomes of the three species and one subspecies are not always parallel to their mitotic chromosomes in morphological characters. The lampbrush chromosomes of Rana plancyi chosenica are peculiar in extreme scarcity of landmarks and remarkably differ from the conspecific R. p. fukienensis at nearly the same degree as the other two species. (N) NN, (B) BB, (C) CC and (F) FF had all 13 bivalents in each of 50 oocytes and were 38.5,38.7,42.5 and 38.2,respectively, in the mean number of chiasmata of the 13 bivalents. When compared with the parental species and subspecies, all the 12 kinds of hybrids among them were fewer in the number of oocytes having 13 bivalents as well as in the mean number of chiasmata found in the 13 pairs of homologous chromosomes. These fewer numbers in bivalents and chiasmata are attributable to the differences between the lampbrush chromosomes of the two parental species or subspecies. On the other hand, the difference between reciprocal hybrids in the number of oocytes having 13 bivalents and the mean number of chiasmata in the 13 pairs of homologous chromosomes seems to be attributable to a difference in cytoplasm between the two parental species or subspecies.
Scientific report of the Laboratory for Amphibian Biology
Institute for Amphibian Biology, Hiroshima University