著者

白石 哲

出版者

九州大学

雑誌

九州大學農學部學藝雜誌 (ISSN:03686264)

巻号頁・発行日

vol.21, no.1, pp.97-109, 1964-02

被引用文献数

1

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Through the collection and rearing of the Japanese harvest mouse occurs in Kyushu, the author has noticed that neither the relation between head and body length (HB) and tail length (T) nor the coloration of pellage does accord with the hitherto theory of some previous investigators. Until the present, the harvest mouse occurs in Kyushu Micromys japonicus japonicus, has been said to have a tail shorter than head and body length, while the one in Honshu, M. j. hondonis, have a tail longer than head and body length, As one of other characteristics to distinguish these two subspecies, it has been said that M. j. japonicus has belly hairs suffused with slate at their bases, while M. j. hondonis has pure white belly hairs from their roots. This time the author has reexamined statistically six external characters of. M. j. japonicus, that is, body weight (BW), head and body length (HB), tail length (T), ear length (E), hind foot length (HF) and tail coefficient (TC). At the same time, comparison between M. j. japonicus and M. j. hondonis has been made statistically, too. The following is the summary of the present study. 1) The materials consist of adult harvest mice collected in the suburbs of Fukuoka and Kurume City, which involve both sexes of individuals. Not only collected mice in the field, but also reared ones under artificial conditions were made the object of the statistical examination.2) Aging was done by body weight, that is, males that have body weight over 6.5 grams and females over 6.0 grams were regarded as adults. The histological investigation of genital organs supported this aging by body weight (Tables. 1-3). 3) Actually, being only a few specimens obtained by the author himself, external measurements concerning individuals in Honshu have been gathered from the data of the previous investigators (Table. 4). 4) The statistical examination was carried out using t-test under the level of significance 1% (Tables. 10, 11). 5) The significant difference between males and females was found only in body weight of M. j. japonicus under artificial rearing. 6) The significant differences between the individuals under natural and artificial conditions, which occur in Kyushu, are recognized in tail length and tail ratio in males, while in head and body length, tail length and tail ratio in females. So far as the result shows, the harvest mice under artificial conditions can be said to have longer tails than wild ones. 7) Between the males in Kyushu and Honshu, differences are significant in tail and ear length. Even in mice in Kyushu, those which have tha tails as long as or longer than head and body length, occupy a greater parts of materials, that is, 95.6% in males and 94.0% in females. Whether tail is longer or shorter than head and body length can not be made one of subspecific characteristics between M. j. japonicus and M. j. hondonis, as it used to be done. Between the two subspecies of females, significant differences are recognized in four external characters, that is, head and body length, tail, ear and hind foot length. From the above fact, females in Honshu can be distinguished in their size from the ones occur in Kyushu. 8) As the result of comparison of M. j. japonicus under artificial conditions with M. j. hondonis, difference is found significantly only in ear length in both sexes. 9) The author has collected mice in the field which have white belly hairs from their roots even in Kyushu. Besides the above mention, reared mice have come to show bellies pure white from hair roots under artificial conditions. The difference in coloration of belly hairs can not be made one of subspecific characteristics, though the reason of change of coloration under rearing conditions is obscure. 10) Concerning the reexamination of one more subspecies in Japan, M. j. aokii, which occurs in Tsushima islands, the author expects the arrival of another opportunity when more available data come to his hand.筆者は九州産カヤネズミの採集や飼育を行なつているうちに,外部形質における本州産カヤネズミとの主な相違点とされている頭胴長と尾長の関係,毛色が必ずしも従来の説に従わぬことに気づいた.そこで外部形質(体重,頭胴長,尾長,耳長,後足長,尾率)の大きさ,毛色について統計学的に吟味した.また本州産カヤネズミの測定値とも比較吟味したので,以下にその結果を報告する. 1) 材料は福岡県福岡市と久留米市郊外で採集された野生の雌雄個体群および室内で飼育した雌雄個体群である.このうち体重を指標として成体と思われるものを選び出し統計処理の対象とした(第1~3表). 2) 本州産のものについては,筆者自身の採集によるものは極めて少ないので,既往の文献から資料を集めた(第4表). 3) 有意差の検定はt検定法(危険率1%以下)によつて行なつた. 4) 雌雄差は室内飼育した九州産カヤネズミの体重にのみ見られた. 5) 九州産カヤネズミの野生個体群と室内で餌育した個体群の間では,雄に関しては尾長と尾率に,雌に関しては尾長,尾率,頭胴長に有意差をみとめた.原因は不明であるが室内で飼育したものは尾が長くなることがわかつた. 6) 九州産野生雄と本州産雄の間では,尾長と耳長に有意差をみとめた.しかし,九州産の個体でも尾が頭胴長に等しい長さか,より長いものが絶対的に多い(雄では95.6%,雌では94.0%).尾が頭胴長よりも長いか,短いかということを,ホンシュウカヤネズミとシコクカヤネズミの亜種的特徴の1つにするのは妥当でないと考える.雌同志では頭胴長,尾長,耳長,後足長に有意差をみとめた.本州産のものが九州産の個体よりも大型だといえる. 7) 九州産飼育個体群と本州産のものとの比較を行なつたところ,有意差は雌雄とも耳長にのみみとめられた. 8) 本州産カヤネズミの腹部の毛は基部まで純白,本州産および四国産のものの毛は基部が石板色とされている.しかし,九州産野生個体にも腹部純白のものが採集され,飼育した場合にはほとんどすべてが純白の腹毛を有するようになる.腹部の毛色の相違は亜種的特徴として決定的なものではないと考える. 9) 対馬産カヤネズミとの比較考察は今後の資料の蓄積を待つて行ないたい.