The geothermally heated water that gushes forth from hydrothermal vents on the sea floor presents an ecological challenge. There’s energy locked in the chemical bonds in the hydrogen sulfide with which the water is laden. But hydrogen sulfide is also extremely toxic to most living things. Pei-Hsuan Chou at Academia Sinica, I-Lan County, Taiwan, and her colleagues explored how the brachyuran crab (Xenograpsus testudinatus, pictured) solves the puzzle to thrive around a shallow-water hydrothermal vent system off the coast of Taiwan. The key, they found, is teamwork. The crab converts sulfide into less toxic thiotaurine in its gills. Next, bacteria that live in the gill cells extract energy from the thiotaurine and detoxify it further. The authors propose that the energy the bacteria extracts is shared with the host crab. The crab is a “holobiont”, the researchers say, a keystone species for an entire ecosystem — in this case, for multiple bacterial species living in and around it. 

Proc. R. Soc. B 290, 20221973 (2023)