How sea anemones living on deep-sea hydrothermal vents avoid metal poisoning

Life near deep-sea hydrothermal vents can be pretty metal — literally.

In addition to crushing pressures, total darkness and scorching temperatures, poisonous plumes belch from beneath the Earth’s surface. Exhaust from these underwater chimneys contains particles of heavy metals like iron and manganese, which become toxic at high concentrations. But many animals cozy up next to these vents and form thriving communities, seemingly able to withstand the dangerous metals around them.

Now, researchers have a hint of how one creature survives this hard-core environment. The sea anemone Alvinactis idsseensis has a surprising abundance of genes geared toward producing proteins that move metals into a cellular area where they can’t cause harm, researchers report October 20 in Science Advances.

Many organisms have a few of these MTP genes for normal metal metabolism. For instance, a related sea anemone that lives in shallow waters has one MTP gene. In comparison, A. idsseensis has 13 MTP genes, marine biologist Haibin Zhang and colleagues found.

The Edmond and Kairei vent fields in the southwest Indian Ocean are home to this abundant, unassuming sea anemone. A. idsseensis “is the dominant species living in these vent fields, and preys on blind shrimps as food,” says Zhang, of the Chinese Academy of Sciences’ Institute of Deep-Sea Science and Engineering in Sanya. “But how these anemones adapt to the vent’s extreme conditions is not well understood.”

The researchers discovered the anemone’s secrets when they analyzed the genome of one of the tentacled invertebrates, collected from the Edmond vent field by the human-occupied vehicle Shenhaiyongshi in 2019. Genetically engineering two of the sea anemone’s most active MTP genes into yeast protected the yeast from toxic levels of iron and manganese, the most common metals in the vent environment.

The proliferation of MTP genes is a metal detoxification strategy also found in plants. The mustard plant Arabidopsis halleri, for example, thrives in soils rich with zinc and has more MTP genes than its relatives, which can’t withstand too much metal.

Zhang thinks the new finding is evidence of “convergent evolution” between anemones and plants, where similar environmental pressures lead to the development of the same solution in distantly related organisms.

“I do believe that they actually found a good convergence, or at least a similar strategy to detoxify metals,” says Felipe Klein Ricachenevsky, a plant physiologist at the Federal University of Rio Grande do Sul in Porto Alegre, Brazil, who was not involved with the study.

How exactly the anemone MTP genes work to prevent metal poisoning remains to be seen. In plants, MTPs sequester metals into large cellular compartments, or organelles, called vacuoles (SN: 6/4/19). But animal cells don’t have those kinds of vacuoles. “Which organelle is doing that in those animals?” Ricachenevsky asks. “I think that will be very interesting to address in the future.”