Yasushi Yokohata

A brief review of the biology on moles in Japan

ABSTRACT There are six species of moles, Euroscaptor mizura, Mogera uchidai, M. tokudae, M. echigo, M. imaizumii and M. wogura, in Talpidae in Japan, and the diverse talpid fauna has been interested in for a long time. Aspects on the taxonomy, morphology, ecology and conservation of them were reviewed briefly.

Effects of environmental radiation on testes and spermatogenesis in wild large Japanese field mice (Apodemus speciosus) from Fukushima.

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident that occurred after the Great East Japan Earthquake in March 2011 released large quantities of radionuclides to the environment. The long-term effects of radioactive cesium (Cs) on biota are of particular concern. We investigated the accumulation of radioactive Cs derived from the FDNPP accident, and chronic effects of environmental radionuclides on male reproduction, in the large Japanese field mouse (Apodemus speciosus). In 2013 and 2014, wild mice were captured at 2 sites in Fukushima Prefecture and at 2 control sites that were distant from Fukushima. Although the median concentrations of 134Cs and 137Cs in the mice from Fukushima exceeded 4,000 Bq/kg, there were no significant differences in the apoptotic cell frequencies or the frequencies of morphologically abnormal sperm among the capture sites. Thus, we conclude that radiation did not cause substantial male subfertility in Fukushima during 2013 and 2014, and radionuclide pollution levels in the study sites would not be detrimental to spermatogenesis of the wild mice in Fukushima.

Classification of the spermatogenic cycle, seasonal changes of seminiferous tubule morphology and estimation of the breeding season of the large Japanese field mouse (Apodemus speciosus) in Toyama and Aomori prefectures, Japan

The large Japanese field mouse, Apodemus speciosus, is a potential indicator of environmental stress, but this function has not been confirmed by histological studies. Since environmental stress affects the reproductive function of mice, we determined the reproductive characteristics of this species at two locations: Toyama (36°35ʹN, 137°24ʹE) and Aomori (40°35ʹN, 140°57ʹE). Mice were captured during May–November (n=119) and July–November (n=146) at these locations, respectively. We classified the breeding season from the numbers of pregnant females and young, in addition to the spermatogenic cycle and seasonal changes in seminiferous tubule morphology of males. Testicular weight was measured, and seminiferous tubule morphology was examined histologically. Fourteen stages were found in the seminiferous epithelium cycle based on acrosome formation and spermatid head morphology. At both locations, the breeding season peaked from late summer to early autumn and possibly in spring. Spermatogenic activity was classified into 4 periods from June to November: resting around June and October–November; resumptive around July; active around August; and degenerative around September. During the resting period, the seminiferous tubules consisted of Sertoli cells, spermatogonia and spermatocytes. Spermatogenesis began during the resumptive period, and spermatids were observed. During the active period, active spermatogenesis and a broad lumen were observed. During the degenerative period, spermatogenesis ended, and Sertoli cells, spermatogonia, spermatocytes and degenerating exfoliated round spermatids were observed. This study provides scientific information about the testicular histopathological evaluations of the large Japanese field mouse for its use as an index species of environmental pollution.

Isolation and characterization of 25 polymorphic microsatellites of the large Japanese wood mouse (Apodemus speciosus)

The large Japanese wood mouse (Apodemus speciosus) is common, but endemic to Japan, and its population structure was affected by habitat fragmentation because of urbanization. It suggested that the species might be one of the important models for the conservation of ecosystems and biodiversity affected by humans, including the effect of radioactive discharge caused by nuclear power plant accidents at Fukushima. We developed and characterized 25 novel polymorphic microsatellite markers from the next-generation sequencing data in an effort to provide an effective tool for genetic studies on this species. In 8 individuals from Aomori, Japan, the number of alleles and expected heterozygosities ranged from 5 to 13 and from 0.795 to 0.991, respectively, suggesting the availability of these markers for genetic studies in this species.

Frequent Occurrence of Partial Albinism in Lesser Japanese Moles (Mogera imaizumii) on Kinkazan Island, Miyagi Prefecture, Northeastern Japan

Abstract. Forty lesser Japanese moles (Mogera imaizumii) were trapped on Kinkazan Island, which is a small island (959 ha) located 1 km off Honshu in northern Japan. Of these, 36 moles (90%) showed some degree of partial albinism of the fur, ranging from only small tufts of cream-colored hairs on their basal forefoot to multiple large interconnected patches spread around the whole body. Most tufts, spots and patches were cream-colored, but some tufts and spots on the lower abdomen were light brown. This coloration is attributable to staining by a secretion from skin glands that are distributed ventrally, with a higher density in the lower abdomen. The high frequency of partial albinism may be attributable to a lack of predators in this insular ecosystem or to low genetic diversity in the population, although it is difficult to know which of these two is more important.

Mixed Distribution of Mogera imaizumii and Mogera wogura in the Tedori Alluvial Fan in Ishikawa Prefecture, Japan

Abstract. Distributions of the lesser Japanese mole (Mogera imaizumii) and the larger Japanese mole (Mogera wogura) were researched in the Kanazawa Plain of Ishikawa Prefecture, Japan, from 2001 to 2002, based on the different diameters of their tunnels. M. imaizumii and M. wogura were found at 63 and 65 different sites, respectively. M. imaizumii is excluded from most areas colonized by M. wogura, but the two species were found together in the Tedori Alluvial Fan. At this location, the tunnels of M. imaizumii were found in areas with harder soil at a depth of 0–20 cm, whereas those of M. wogura were found in areas with softer soil at the same depth. This is the first observed case of a mixed distribution of these two species of Japanese moles on a plain in a large geomorphological structure, such as an alluvial fan. This phenomenon may be attributable to the sediment characteristics in an alluvial fan, where various sediments with different diameters, from crude stone to fine clay, are distributed in a complex mosaic pattern.

The preface of “Evolutionary biology and phylogeny of the Talpidae”

The symposium “Evolutionary biology and phylogeny of the Talpidae” was held on the 3rd of August as part of the IX International Mammalogical Congress (IMC9) in Sapporo, Japan, 31 July–5 August 2005, and attracted about 50 individuals interested in the family Talpidae and other subterranean mammals. After a brief introduction by Dr. Y. Yokohata, Dr. S. Kawada highlighted his recent studies on the karyological and morphological aspects of the lesser-known Asian mole species, and forwarded several taxonomic problems yet to be addressed. Dr. A. Loy followed this presentation by discussing the origin and evolutionary history of Western European fossorial moles of the genus Talpa based on her and her collaborators’ studies of their morphology, karyology, and molecular phylogeny, in the context of historical glaciations of the region. Mr. A. Shinohara’s presentation incorporated mitochondrial and genomic nucleotide data from a wide range of Eurasian and North American species, and reviewed our current understanding of the molecular phylogenetic relationships among the family Talpidae. Finally, Dr. K. L. Campbell presented his studies on the physiological and molecular evolution of hemoglobin oxygen affinity within the family Talpidae. The latter two presentations largely focused on the evolution of semi-fossorial (shrew-moles), strictly fossorial (moles) and semiaquatic (desmans and star-nosed moles) species from primitive terrestrial forms (shrew-like moles). Our understanding of the biology of the Talpidae still has many unanswered questions, especially pertaining to their taxonomic classification, phylogenetic relationships, evolution, and behavior, thus further studies are needed. Following the presentations, Drs. Campbell and Kawada lead a group discussion focused on how best to proceed with such future studies on this fascinating group of mammals, with many insightful comments from the audience. It was our hope that this symposium would encourage future collaborations, facilitate the exchange of information among researchers, and attract new researchers in the study of talpid mammals. Based on the kind remarks of several participants, it is our pleasure to say “Mission accomplished”! This symposium was accompanied by three poster presentations. Dr. N. Sagara presented his new research topic, ‘Myco-talpology’, which is the science pertaining to the ecological relationships between mushrooms and moles. Dr. Y. Yokohata communicated his and his student’s research on lesser Japanese moles. The first poster examined the social relationships between individual moles in captivity, while the second documented and compared the diet of an isolated insular population (Kinkasan Island) of moles inhabiting a ‘turf’ habitat altered by high populations of sika deer with those in natural ‘forest’ environments. In this proceeding, the following four reviews are included.