Fukuyama City Zoo

Because speciation might have been promoted by ancient introgression from an extinct lineage, it is important to detect the existence of 'ghost introgression' in focal taxa and examine its contribution to their diversification. In this study, we examined possible ghost introgression and its contributions to the diversification of ricefishes of the genus Adrianichthys in Lake Poso, an ancient lake on Sulawesi Island, in which some extinctions are known to have occurred. Population-genomic analysis revealed that two extant Adrianichthys species, A. oophorus and A. poptae are reproductively isolated from each other. Comparisons of demographic models demonstrated that introgression from a ghost population, which diverged from the common ancestor of A. oophorus and A. poptae, is essential for reconstructing the demographic history of Adrianichthys. The best model estimated that the divergence of the ghost population greatly predated the divergence between A. oophorus and A. poptae, and that the ghost population secondarily contacted the two extant species within Lake Poso more recently. Genome scans and simulations detected a greatly divergent locus, which cannot be explained without ghost introgression. This locus was also completely segregated between A. oophorus and A. poptae. These findings suggest that variants that came from a ghost population have contributed to the divergence between A. oophorus and A. poptae, but the large time-lag between their divergence and ghost introgression indicates that the contribution of introgression may be restricted.

The Nagoya Daruma pond frog Pelophylax porosus brevipodus is distributed in western Japan and is traditionally divided into two local forms: the Okayama form in the west and the Nagoya form in the east. These two forms are genetically differentiated, but have never been defined taxonomically because their distributions are unclear to date. To complete the distributions and identify the boundary of the two forms, we genetically investigated 16 populations including eight populations located within the unexamined area. We found that the distributional boundary is located within a small area of Hyogo Prefecture where haplotypes of mitochondrial cytochrome b (cytb) and D-loop region corresponding to the two forms co-existed. On the other hand, the polymorphic site of the nuclear gene SOX3 revealed introgression over the boundary into Okayama cytb clade. These results suggest that the two forms were geographically isolated from each other in the past, and secondarily contacted and then accepted one-way introgression. As a next step of the research, taxonomic approach is expected to define the two forms.

水道水中の臭素酸イオン (BrO3-) を既存の告示法よりも高精度かつ迅速・簡便に分析するために, LC/MS/MSによる測定方法を検討し, 臭素酸イオンを高感度に検出でき, さらに水道水中に含まれる他の陰イオンを良好に分離可能な測定条件を確立した。さらに, 本研究で確立した測定条件が全国の水道水に適用できるかどうかを検証するために, 水道事業体等の23機関において水道水に臭素酸イオンを基準値 (0.01 mg L-1) およびその1/10 (0.001 mg L-1) となるように添加した試料を調製し, 各機関で最適化した様々な測定条件で試験を行った。その結果, いずれの機関においても厚生労働省が示している「水道水質検査方法の妥当性評価ガイドライン」の真度, 併行精度および室内精度の目標を満たしたことから, 本分析法は水道水中の臭素酸イオンを基準値の1/10 (0.001 mg L-1) まで高精度に分析可能であると評価した。

Studies on the reproductive endocrinology of koalas have been performed mainly by using blood samples; however, in practice it is difficult to collect blood periodically because koalas are easily stressed. The purposes of the present study were to establish a noninvasive endocrine monitoring technique and to investigate the reproductive physiology of female koalas. Feces were collected from female northern and southern koalas, and progestagen was extracted from lyophilized fecal samples and determined by enzyme immunoassay. In nonpregnant northern and southern koalas, fecal progestagen markedly increased after copulation and remained high for 36.3 +/- 2.5 days and 38.9 +/- 1.4 days (luteal phase, mean +/- SEM), respectively. Mean (+/-SEM) progestagen levels (6.34 +/- 0.49 microg/g) during the luteal phase in northern koalas were significantly higher than in southern koalas (4.19 +/- 0.24 microg/g). Fecal progestagen in parturient northern koalas remained high for 36.2 +/- 1.9 days (gestation period, 34.1 +/- 0.3 days). In northern koalas, the mean levels and profiles of progestagen during pregnancy (6.44 +/- 0.37 microg/g) were consistent with those during nonpregnancy after copulation (6.34 +/- 0.49 microg/g). The duration of behavioral estrus in northern koalas was 13.5 +/- 0.9 days without copulation. In contrast, when estrous females mated, the estrous sign disappeared just after copulation. The mean (+/-SEM) length of the estrous cycle in northern koalas, as determined by behavioral estrus intervals, was 33.5 +/- 2.2 days without the luteal phase and 69.2 +/- 7.6 days with the luteal phase. Fecal progestagen analysis is a helpful and noninvasive tool to monitor ovulatory activity in northern and southern koalas and could help us to understand the reproductive activity of koalas by the combination approach with behavioral estrus.

An experimental study on sperm entry into the micropyle of the medaka egg was carried out in order to analyze the effect of micropylar size on fertilization. The eggs and micropyles of Oryzias latipes were larger than those of Oryzias melastigma. When eggs of O. latipes and O. melastigma were simultaneously inseminated by spermatozoa of O. latipes, O. melastigma or Aplocheilus panchax, O. melastigma spermatozoa rapidly entered the conspecies eggs as well as the large micropyles of O. latipes eggs, while most of the O. latipes and A. panchax spermatozoa failed to rapidly enter the small O. melastigma micropyles. Moreover, when O. latipes eggs with a small or a large vestibule were simultaneously inseminated by O. melastigma spermatozoa, the size of the micropylar vestibules (range of 17-23 μm in diameter) also affected rapid sperm entry into the egg. However, this effect was not recognized when the eggs were inseminated by conspecies spermatozoa. On the other hand, when O. latipes eggs were inseminated by a mixture of O. latipes and O. melastigma spermtozoa or O. latipes and A. panchax spermatozoa, the faster swimming spermatozoa fertilized significantly more frequently than the slower O. latipes spermatozoa. These results suggest that rapid sperm entry into the micropyle is not only affected by differences in the morphology and size of the micropyles, but also might be accelerated by the linear swimming velocity of the spermatozoa.