Bulletin of the Hiroshima University Museum Issue 12
2020-12-25 発行

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個体群 : 小型個体群と野外における幼生の成長に関する考察

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
IKEDA, Seiji
MUNAKATA, Masaki
SATO, Ken
MIURA, Kou
HASHIZUME, Tsukasa
TOMOTA, Jou
WAKABAYASHI, Natsuki
KUWABARA, Kazushi
OKAWA, Hiroshi
file
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.
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
rights
Copyright (c) 2020 広島大学総合博物館 Hiroshima University Museum