"Ogasawarajijimi" butterfly native to the Ogasawara Islands – the specimen for breeding were all dead

 Recently NHK News On-line reported the following:

小笠原諸島固有のチョウ「オガサワラシジミ」繁殖用個体全滅

2020年8月27日 23時20分

小笠原諸島でしか生息が確認されておらず、絶滅の危険性が極めて高いチョウ「オガサワラシジミ」について、環境省と東京都は繁殖を続けてきましたが、27日までに繁殖用の個体がすべて死んだと発表しました。野生でもおととし以来、生息が確認されておらず、環境省は「種の保存にとって非常に危機的な状況だ」としています。

「オガサワラシジミ」は、小笠原諸島でしか生息が確認されていない固有種のチョウで、国の天然記念物に指定されています。

外来種の影響などで急激に数が減ったため、平成12年には環境省が絶滅危惧種に指定しました。

種の保存に向けて東京都が15年前に繁殖させる取り組みを始め、環境省も都から個体を譲り受けて去年10月から繁殖を続けていましたが、今月25日までにすべての成虫と幼虫が死んだということです。

環境省は、近親交配によって有害な遺伝子が蓄積され、オスの精子の量が極端に減ったことが原因の一つではないかとしています。

「オガサワラシジミ」は、野生でも、おととし6月、小笠原諸島の母島で見つかったのを最後に生息が確認されておらず、仮に絶滅すれば、日本固有のチョウとしては初めてになります。

環境省は、「種の保存にとって非常に危機的な状況だ。小笠原諸島でモニタリングを継続し、生息が確認されれば速やかに保護して保全に取り組む」としています。

Translation

About the butterfly "Ogasawarajijimi" which had been confirmed to have lived only in the Ogasawara Islands and was having a very high risk of extinction, the Ministry of the Environment and the Tokyo Metropolitan Government continued to breed them. It was announced on the 27th that all the specimen for bleeding were dead. No habitat had been confirmed in the wild starting from two years ago, and the Ministry of the Environment said that they were "in a very critical situation for species conservation."

"Ogasawaraishijimi" was a native species of butterfly that had been confirmed only to live in the Ogasawara Islands and was designated as a natural memorial item of the country.

Since its number had decreased sharply due to the influence of alien species, the Ministry of Environment designated it as an endangered species in 2000.

The Tokyo Metropolitan Government began efforts to breed this species 15 years ago for species conservation, and the Ministry of the Environment had inherited from the Tokyo Metropolitan the specimen and continued to breed them from last October, but by the 25th of this month, all adults and larvae were dead.

The Ministry of the Environment argued that one of the causes was that the harmful gene had accumulated by inbreeding, and the amount of sperm in male was seriously reduced.

About "Ogasawaraishijimi", even in the wild, having found it on the Hahajima Retto of the Ogasawara Islands in June two years ago could not confirm that it was their last habitat; and if it became extinct, it could be the first butterfly native to Japan to do so.

According to the Ministry of the Environment, “the conservation of the species is in a very critical situation. We will continue our monitoring in the Ogasawara Islands, and if their habitat is confirmed, we will promptly protect and work on conservation”.

              So, it seems that the Japanese is keen to preserve the species.