Inter-individual variation in the diet within a group of Japanese macaques and its relationship with social structure investigated by stable isotope and DNA analyses.

We investigated individual variation in diet in relation to age-sex class and kin relationship in 28 of 40 members of a small group of wild Japanese macaques (Macaca fuscata). We used stable isotope ratios from hair as an index of individual dietary profiles, genetic relatedness as an index of kin relationship, and mitochondrial DNA (mtDNA) haplotype as a marker of being an immigrant or native member of the group. The range of carbon and nitrogen stable isotope ratios from hair of individual macaques (δ13C: -24.1‰ to -22.6‰, δ15N:3.8-5.5‰), which reflected their diet over a period of ~ 6 months, implied small individual variation in diet. The results of PERMANOVA implied that there were no significant effects of age class, sex, or mtDNA haplotype on hair stable isotope ratios between individuals, or on the variation in individual diet. However, the isotope values of males with mtDNA haplotypes that differed from those of the native females appeared to differ from those of other group members, which implies that immigrant males might have had a different diet profile from that of native group members. Furthermore, there was a weak correlation trend between genetic relatedness and differences in stable isotope ratios between pairs of individuals. Differences in stable isotope values were more marked in pairs with a more distant genetic relationship. This implies that within the group, closely related kin tended to forage together to avoid competing for food. However, this effect might have been weak because the size of the group was small relative to the size of the food patches, thereby reducing competition.

Heat shock factor 1 protects germ cell proliferation during early ovarian differentiation in medaka.

The heat shock response is important for the viability of all living organisms. It involves the induction of heat shock proteins whose expression is mainly regulated by heat shock factor 1 (HSF1). Medaka (Oryzias latipes) is a teleost fish with an XX/XY sex determination system. High water temperature (HT) inhibits the female-type proliferation of germ cells and induces the masculinisation of XX medaka in some cases during gonadal sex differentiation. Here, we investigated the roles of HSF1 on the proliferation of germ cells using HSF1 knockout medaka. Loss of HSF1 function under HT completely inhibited the female-type proliferation of germ cells, induced the expression of the anti-Mullerian hormone receptor type 2 (amhr2) and apoptosis-related genes, and suppressed that of the dead end (dnd) and heat shock protein-related genes. Moreover, the loss of HSF1 and AMHR2 function under HT recovered female-type proliferation in germ cells, while loss of HSF1 function under HT induced gonadal somatic cell apoptosis during early sex differentiation. These results strongly suggest that HSF1 under the HT protects the female-type proliferation of germ cells by inhibiting amhr2 expression in gonadal somatic cells. These findings provide new insights into the molecular mechanisms underlying environmental sex determination.