No.155 研究課題 / Project
秋川上流域におけるナガレタゴガエルの生命表の作成、及び、水位と流下行動の相関関係についてThe population age structure and the effect of water level on migratory behaviour of Rana sakuraii in the upper basin of Akigawa River| 一般研究 General Research |
No.155 |
|---|---|
| 代表研究者 Principal Investigator |
三輪 時男 Tokio Miwa |
| 所属（採択当時） Affiliation |
元、東京農工大学大学院 農学研究科 研究生 Former Tokyo University of Agriculture and Technology, Graduate School of Agricultural Science, research student |
| 研究内容要約 Research Summary |
1991年度より秋川上流域においてナガレタゴガエルの生態調査を継続し、2003年度までに８万匹以上を捕獲・リリースしてきた。本研究では、2002・2003年度のデータを中心にナガレタゴガエルの詳細な［平均体長；年令と体長；性成熟年令；寿命；平均産卵数；♀の年令と産卵数＆卵径；幼生の全長；個体群の年齢構成の割合］等についてまとめた。体長は、♂で平均46㎜（±3SD:40－52㎜、；♀で平均54㎜（±3SD：46－62㎜）。幼生は、最大成長時に平均28－30㎜になり、変態完了時の体長約８㎜；1年目の冬眠期頃には体長21－30mmになる。２年目には雄雌ともに一部が性成熟し冬眠明けには繁殖活動に参加し、３年目には皆、性成熟し繁殖活動に参加する。［雄・雌］の平均体長(㎜)は、３年目の冬眠期前後（＝３才）で［45.2・52.5］；４才［47.5・54.7］；５才［49.6・57.6］；６才［52.6・60.8］。成体は２－６才で構成され、［約15％が２才；約55％が３才；約20％が４才；約８％が５才；約1％が６才］。産卵数（蔵卵数）は130～250個、平均175－180個。卵径は、2.75－3.35㎜、平均3.15㎜；早熟の２才雌では、2.75－2.85㎜で３㎜を超えることない；一般♀(３－６才)では3.00－3.35㎜で年令によって大きくは変わらない。一方、約半年近くも水中下生活するナガレタゴガエルにとっては、水温の変化と共に、本降りの降雨や融雪増水による水位上昇は、移動行動誘発の重要な要因と推測された。 By fiscal 2003, we had captured and released more than 80,000 mountain stream frogs (Rana sakuraii) in our ecological survey of the frog conducted in the upper reaches of the Akigawa River since 1991. In this study we summarized data on the stream brown frog [mean body length; relationship between age and body length; reproductive maturation age; longevity; mean number of eggs; relationship between females’ age and the number and diameter of eggs; full length of larvae; and age composition] based on surveys conducted in fiscal 2002 and 2003. Mean body length was 46 mm (±3SD：40-52 mm) in males, and 54 mm (±3SD：46-62 mm) in females. Larvae reached 28-30 mm on average at the maximum growth point. They were approximately 8 mm long after metamorphosis, and grew to 21-30 mm during hibernation in the first year. In the second year, some males and females became reproductively mature, and started reproductive activities after hibernation. In the third year, all of them became reproductively mature enough to participate in reproductive activities. Mean body lengths (mm) of males and females were respectively 45.2 and 52.5 at the age of three (=around hibernation in the third year), 47.5 and 54.7 at the age of four, 49.6 and 57.6 at the age of five, and 52.6 and 60.8 at the age of six. Adults consisted of two- to six-year-old frogs, and age composition was as follows: about 15% were two-year-old fogs, about 55% were three-year-old frogs, about 20% were four-year-old frogs, about 9% were five-year-old frogs, and about 1% were six-year-old frogs. The number of spawned eggs (fecundity) was 130-250, averaging 175-180. Egg diameter was 2.75-3.35 mm, averaging 3.15 mm. Eggs spawned from premature two-year-old females were 2.75-2.85 in diameter, always smaller than 3 mm, while eggs from mature females (three to six years old) were 3.00-3.35 mm, showing no differences attributable to age. Water level rise due to heavy rain and melting snow as well as water temperature fluctuation were believed to be important factors that induced migratory behavior in stream brown frogs, which live in water for about half a year. |
| 共同研究者 Collaborators |
- |
| 研究全文 Full Text |
全文をダウンロード Download (Japanese Only) |