Geographic Variability of Sex-Linked Loci in the Japanese Brown Frog, Rana japonica

Rana japonica has been reported to be of the male heterogametic type in the sex-determining mechanism. In order to detect the sex-linked loci in R. japonica, the linkage relationships between the sex-determining genes and 11 loci controlling eight enzymes and one blood protein were examined in 48 crosses involving 30 males heterozygous at these loci from 10 local populations by using starch-gel electrophoresis. The Ab locus was found to be linked with the sex-determining genes in the Munakata, Yamaguchi, Ochi, Saiki, Saijo, Sahara and Mobara populations, whereas the MDH-B, MPI, Pep-A and Pep-C loci were not linked with the latter in 23 crosses involving 16 heterozygous males from the seven populations. The MPI locus was linked with the sex-determining genes in the Ichinoseki and Toyama populations, whereas the Ab locus was not linked with the latter in 11 crosses involving eight heterozygous males from two populations. In the Akita population, none of the Ab, AAT-B, ADA, α-GDH, LDH-B, ME-A, ME-B and MPI loci was linked with the sex-determining genes in 14 crosses involving six heterozygous males. Thus, it is evident that the locus linked with the sex-determining gene differs with the populations

Reproductive Capacity of Allotriploids between Rana tsushimensis from Tsushima and Rana japonica from Ichinoseki and Hiroshima

Reciprocal allotriploid frogs, (T)TTI, (I)IIT, (T)TTH and (H)HHT, were produced from crossings between Rana tsushimensis from Tsushima, (T)TT, and Rana japonica from Ichinoseki, (I)II, and Hiroshima, (H)HH, by heat-shock treatment of fertilized eggs. Almost all the allotriploids developed normally and became males. In contrast, diploid hybrids between female R. tsushimensis and male R. japonica from Ichinoseki and the reciprocal diploid hybrids between R. japonica from Hiroshima and R. tsushimensis died of underdevelopment at the tadpole stage. However, diploid hybrids between female R. japonica from Ichinoseki and male R. tsushimensis could barely complete metamorphosis, although they died of infirmity within 1∿3 months after metamorphosis. Mature allotriploids were intermediate between the two parental species in external characters. They were more similar to the parental species giving two genomes than to the species giving one genome. A total of 65 mature male allotriploids including two kinds, (H)HHT and (T)TTH, between R. japonica from Hiroshima and R. tsushimensis and one kind, (I)IIT, between female R. japonica from Ichinoseki and male R. tsushimensis were completely sterile. On the other hand, 16 of 44 male allotriploids, (T)TTI, between female R. tsushimensis and male R. japonica from Ichinoseki were fertile. The spermatogenesis in these allotriploids was completely or partially normal. The other 28 male allotriploids, (T)TTI, were sterile. A total of 419 offspring were produced from seven of the above 16 male allotriploids by backcrossing with female R. tsushimensis. They were all diploids and of the R. tsushimensis type in external characters. Most of them (96.9%) were females. They showed the same electrophoretic patterns as those of R. tsushimensis at 14 loci of enzymes and blood proteins. These findings seemed to indicate that some of the male allotriploids reproduce by hybridogenesis, in which the R. japonica genome was eliminated during spermatogenesis

The Differences in Recombination Rate between the Male and Female in Rana nigromaculata and Rana brevipoda

The linkages among six enzyme loci, SORDH, MPI, ENO, HK, Pep-B and LDH-B, situated on chromosome No. 4 were analyzed in order to examine the differences in recombination rates between males and females. Mating experiments were conducted by using heterozygous females or males of Rana brevipoda and Rana nigromaculata, heterozygous females of interspecific hybrids between R. nigromaculata and R. brevipoda and those between Rana plancyi chosenica and R. nigromaculata. The recombination rates among the loci controlling six enzymes located on chromosome No. 4 were found to be large in females when the frogs were pure species, while they became smaller when the frogs were hybrids. The recombination rates were almost zero in males in contrast to females. They had no relation to the existence of the sex-determining genes on the chromosomes of the species used in the present study. The differences in the recombination rates seemed to be attributable to that in the number of chiasmata. When the number of chiasmata became smaller, the recombination rates also became smaller, and in male frogs they seemed to approach zero. Thus, the present study showed that it may be better to use heterozygous males for the purpose of assuming the kinds of genes on specific chromosome. However, it may be better to use heterozygous females in order to clarify the mutual positions of loci on the same chromosome

Differentiation of Rana limnocharis and Two Allied Species Elucidated by Electrophoretic Analyses

The genetic relationships among six populations of Rana limnocharis distributed in Japan and Taiwan, two populations of R. cancrivora distributed in Philippine and Thailand and one population of Platymantis papuensis distributed in New Guinea were examined by electrophoretic analyses of 17 enzymes and two blood proteins extracted from 97 frogs. These enzymes and blood proteins were controlled by genes at 29 loci, where 3.9 alleles produced 4.6 phenotypes on the average. The genetic relationships among the nine populations were examined by estimating the genetic distance according to the method of NEI (1975). The phylogenetic relationships were shown by a dendrogram drawn by the UPGMA clustering method. It was found that Platymantis papuensis first diverged from the others, and then Rana cancrivora and Rana limnocharis were differentiated from each other. In Rana limnocharis, the Iriomote population seems to have first diverged from all the other populations