鸦片鱼的做法大全:神奇的气体！（甲烷）一条奇异的生物链

发布时间：2011年10月8日

MOST biological molecules—and hence, most living organisms—are ultimately the result of photosynthesis. Most, but not all. Some creatures are part of food chains that begin with methane gas which seeps from the Earth’s interior in particular places, frequently at the bottom of the sea. Bacteria living in these seeps process the methane into complex molecules, and worms and clams feast on the bacteria. It now seems, though, that such methane-based food chains may stretch farther up the tree of life than mere invertebrates—and may have done so for millions of years.

Recently, as they report in Marine Ecology Progress Series, Tina Treude of the IFM-GEOMAR marine-research institute in Kiel, Germany, and her colleagues sent a remotely operated vehicle called Cherokee to investigate a seep known as the North Alex mud volcano, which is located in the Mediterranean, to the north of the Nile delta. Cherokee, which was equipped with a digital camera and a flashgun, started transmitting images of golden and dark-brown objects, 50-70mm across, that were scattered among the worms and clams (see photograph). The researchers quickly realised that these were sharks’ eggs. Moreover, on closer examination they were able to see yolks, indicating that the embryos inside the eggs were alive and developing.

They do not know which species the eggs belong to, but Dr Treude speculates they are from the deepwater catshark, which is known to produce egg capsules of this size, colour and shape. And the North Alex volcano is not alone. She has found that another site, the Concepción methane seep area, off the coast of Chile, is littered with thousands of large, black egg capsules of the sort often laid by skates and rays—fish that are, to all intents and purposes, flattened sharks.

In light of these discoveries her colleague Steffen Kiel, at the University of Göttingen, turned his attention to a fossilised methane seep in the American state of Washington. The rocks in this seep, which are 35m years old, were already known to contain lots of mussels and worm tubes, similar to those found in a modern seep. Lo and behold! when Dr Kiel looked more closely, these rocks, too, contained fossil shark eggs.

Methane seeps, then, look as if they act as nurseries for sharks—and may have done so for a long time. Presumably (though this has still to be proved) the hatchling sharks are eating the worms and perhaps, if their teeth are up to the necessary crunching, the clams. Instead of being powered by the sun, then, some young sharks seem to run on fossil fuel.