話飲徒然草〜Tokyo Meanderings

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2008年06月28日

ヤゴ痛恨の共食い　A Painful Case of Nymph Cannibalism

(2)

カテゴリ：アクアリウム・ガーデニング

ピンセットで触れてみると、案の定、死んでいます。
どうやら脱皮直後に共食いの被害にあったようなのです。

水槽から出して裏返してみると、体の右下の部分を食いちぎられているのがわかります。（右側にあるのは抜け殻）脱皮直後の個体は体が柔らかく、共食いの対象になりやすいのです。
しかし、今回の共食いは、まさに人災、私のミスでした。

というのも、一昨日、水換えをしたのに（水換えは総じて脱皮を促します）、昨晩、ワインを飲みすぎてエサをやらないまま寝てしまったのです。
水換えで刺激を受けたヤゴは思惑通り脱皮しましたが、まさにそのタイミングで、腹ペコの他のヤゴに喰われてしまった…。

それにしてもこのタイミングでの共食いは痛すぎです。これで水槽の中のヤゴは、終齢段階の３匹になってしまいました。ガックシです。

ひまわりもガックシ。

＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊＊

This morning, I went to feed the nymphs, but something seemed off. I noticed an exuvia—one of the smaller nymphs had just molted—but the nymph itself was lying in a strange posture and wasn’t moving. When I gently touched it with tweezers, I realized it was dead.

It seems that it became a victim of cannibalism right after molting.

When I removed it from the tank and turned it over, I could see that the lower right part of its body had been bitten off (the exuvia is to the right in the photo). Newly molted nymphs are soft-bodied and particularly vulnerable to cannibalism.

In this case, though, it was basically a man-made disaster—my fault.

The day before yesterday, I had changed the water (which generally stimulates molting), but last night I drank too much wine and went to bed without feeding them. The nymph, stimulated by the water change, molted as expected, but at that exact moment, a hungry tank mate ate it…

Cannibalism at this timing is especially painful. With this loss, only three final-instar nymphs remain in the tank. What a blow.

Even the sunflower seems disappointed.

The remaining nymphs are expected to emerge as dragonflies by mid-next week. I hope to get all three safely through to emergence—and if possible, I’d love to capture the moment on camera at least once.

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