このエントリーをはてなブックマークに追加
ID 50629
file
title alternative
A population of the Japanese giant salamander Andrias japonicus (Amphibia: Caudata) inhabiting a small stream flowing through a wetland upstream of a dam: A study on the population of small individuals and larval growth in the field
creator
IKEDA, Seiji
MUNAKATA, Masaki
SATO, Ken
MIURA, Kou
HASHIZUME, Tsukasa
TOMOTA, Jou
WAKABAYASHI, Natsuki
KUWABARA, Kazushi
OKAWA, Hiroshi
subject
オオサンショウウオ
小型個体群
湿地
ダム
ヒルムシロ
幼生の成長
Andrias japonicus
Potamogeton distinctus
dam lake
Japanese giant salamander
larval growth
population of small individuals
wetland
abstract
広島県廿日市市飯山のダム上流の湿地を流れる小河川に生息するオオサンショウウオAndrias japonicusの個体群について報告する。本産地は標高が775–795mあり,本種の生息地で最も標高の高い部類に入る。飯山貯水池は1932年より水力発電ダム湖として建造され,その上流は約90年間ダムの下流域と隔離されている。水位の低下した2001年以降は長年人の手の加わっていない湿地となっている。2017–2020年ののべ17日間に渡る調査で,0歳から1歳,2歳と考えられる幼生が多数見つかり,全長210mmの幼体や326–680mmの成体,繁殖巣穴も見つかった。これは独立した繁殖個体群として世代交代している証拠でもある。この個体群からは全長700mmを越える個体が見つかっておらず,全長が小さい傾向がある。また,0歳幼生の全長と確認日の関係を見ると,全長46mmで離散した0歳幼生が,6月から8月にかけて急成長して75mmに達し,10月以降はほとんど成長しないで翌春を迎えることを示唆していた。幼生は主にダム湖であった当時の名残の水草,ヒルムシロPotamogeton distinctusの中から見つかる傾向がある点も特異な点である。ダム湖へ直接流入する源流域の小河川で本種が持続的に繁殖している例として本産地と個体群は稀少な存在であると言える。
abstract
Here, we describe a population of the Japanese giant salamander Andrias japonicus inhabiting upstream of the Iinoyama Reservoir in Iinoyama, Hatsukaichi City, Hiroshima Prefecture, Japan. The locality is situated at 775–795 m above the sea level and is one of the highest localities in the habitat of this salamander. The Iinoyama Reservoir was originally built as a hydroelectric dam lake in 1932, and its upstream part has remained isolated for nearly 90 years. Since 2001, when the water level dropped, it has become a wetland, albeit not used by human for many years. In surveys over 17 days during 2017–2020, many zero-, first-, and second-year larvae; a juvenile 210 mm in total length (TL); and adults (326–680 mm in TL) as well as a breeding nest were found, providing evidence that the salamanders in this regions constitute an independent breeding population. No individuals measuring over 700 mm in TL were found in this population, and the overall TL tended to be low. Considering the association between the total length and the date of discovery of zero-year larvae, these larvae likely dispersed when they were about 46 mm and rapidly grew from June to August to reach 75 mm; from October, however, they barely grew until the next spring. Interestingly, the larvae were found in the remnants of the dam lake, near the aquatic plant Potamogeton distinctus. The described locality and population present a rare example of continuous breeding of the Japanese giant salamander in a small stream directly flowing into the dam lake.
journal title
Bulletin of the Hiroshima University Museum
issue
Issue 12
start page
1
end page
18
date of issued
2020-12-25
publisher
広島大学総合博物館
issn
1884-3999
ncid
language
jpn
nii type
Departmental Bulletin Paper
HU type
Departmental Bulletin Papers
DCMI type
text
format
application/pdf
text version
publisher
rights
Copyright (c) 2020 広島大学総合博物館 Hiroshima University Museum
department
Hiroshima University Museum
他の一覧



Last 12 months's access : ? times
Last 12 months's DL: ? times


This month's access: ? times
This month's DL: ? times