世界最小の爬虫類か、新種のカメレオン発見　マダガスカル

【パリＡＦＰ＝時事】マダガスカル北部で世界最小の爬虫（はちゅう）類とみられるカメレオンが発見された。発表した科学者らは、森林破壊がこの種の存続を脅かしていると警告している。（写真はマダガスカルで発見された世界最小の爬虫（はちゅう）類とみられる新種のカメレオン「Brookesia　nana」）
　ドイツのバイエルン州動物標本収集研究所の爬虫両生類学学芸員のフランク・グラフ氏は「マダガスカル北部の山で発見した」とＡＦＰに語った。発見された超小型のカメレオンは、「Ｂｒｏｏｋｅｓｉａ　ｎａｎａ」と命名された。
　ドイツとマダガスカルの科学者らは２０１２年の共同調査で、雌１体と雄１体の２体を捕獲したが、成体であると確認されたのはずっと後になってからだとグラフ氏は説明した。「雌は体内に卵があり、雄は大きな生殖器を持つことが分かり、成体であることが明らかになった」と同氏は述べた。
　雄の生殖器が体の大きさの２０％近くを占め、非常に大きかったと、グラフ氏らは英科学誌ネイチャー系のオンライン科学誌「サイエンティフィック・リポーツ」に発表した。
　雄は頭部から胴までが１３・５ミリとピーナツほどの大きさで、尾は９ミリ。雌は頭部から尾の先端までが２９ミリだった。グラフ氏は「この種がなぜこれほど小さいのか、まだ説明がついていない」と述べた。この種はこれまでにこの２体しか見つかっていない。
　科学者らにとって明白なのは、この小型の爬虫類が絶滅の危機にひんしている可能性が高いということだ。グラフ氏は「生息地の破壊は、マダガスカルの両生類と爬虫類にとって最大の脅威だ」と指摘する。マダガスカルでは２０世紀半ば以降、森林面積の約４５％が失われている。
　マダガスカルは世界で最も貧困率の高い国の一つで、自然保護や天然資源の管理のためのリソースが不足している。【翻訳編集ＡＦＰＢＢＮｅｗｓ】

〔ＡＦＰ＝時事〕（2021/02/09-14:04）

Scientists have identified Earth's smallest known reptile, warning at the same time that sustained destruction of forests in northern Madagascar threatens its survival.
Tiny enough to perch comfortably on a fingertip, the ultra-compact chameleon -- dubbed Brookesia nana -- has the same proportions and world-weary expression as its larger cousins around the world.
We discovered it in the mountains of northern of Madagascar, Frank Glaw, curator of herpetology at the Bavarian State Collection of Zoology, told AFP in an interview.
A joint expedition in 2012 of German and Malagasy scientists did not know whether the two specimens collected -- one female and one male -- were adults until much later, he explained.
We found out that the female had eggs in her body, and that the male had large genitals, so it was clear that they were adults.
Exceptionally large genitals, it turned out, accounting for nearly 20 percent of its body size, Glaw and colleagues reported in the journal Scientific Reports.
The male's body -- about the size of a peanut -- was 13.5 millimetres long (half an inch), with the tail adding another nine millimetres.
By contrast, the female measured 29 mm from its nose to the tip of its tail.
The pair remain the only specimens of the species ever found.
Islands connected long ago to neighbouring continents are known for miniaturised versions of animals that crossed ephemeral land bridges, a phenomenon known as island dwarfism.
There are numerous extremely miniaturised vertebrates in Madagascar, including the smallest primates and some of the smallest frogs in the world, said co-author Andolalao Rakotoarison of the University of Antananarivo in Madagascar.
But the island effect does not apply to B. nana, which lives exclusively in mountainous regions some 1,300 metres (4,200 feet) above sea level, the researchers concluded.
- 'Biodiversity hotspot' -
We have no good explanation as to why this species is so small, said Glaw.
What scientists do know is that the diminutive reptiles are likely teetering on the edge of extinction, even if the International Union for the Conservation for Nature (IUCN) -- keepers of the Red List of threatened species -- has yet to do an assessment.
Habitat destruction is the biggest threat to the amphibians and reptiles of Madagascar, said Glaw.
Maybe in the future it will be climate change, but for now it is deforestation.
Since the mid-20th century, Madagascar has lost about 45 percent of its forest cover.
B. nana and another mini-chameleon discovered by Glaw and his colleagues on a small island off the coast of Madagascar are especially vulnerable because their range is so small.
Brookesia micra lives on less than two square kilometres, Glaw explained.
One big catastrophic event -- a forest fire -- and the population might be lost very quickly.
Madagascar in a global biodiversity hotspot, accounting for five percent of the world's unique plant and animal species.
The island nation has one of the highest rates of poverty in the world, and lacks resources for conservation and natural resource management.