Newly-found sea spiders survive on methane-fed microbial coats

Scientists have discovered three new species of sea spiders (genus Sericosura) in the deep Pacific Ocean that survive by grazing on methane-eating microbes living on their translucent exoskeletons. Unlike typical sea spiders that hunt prey by piercing and sucking fluids, these spiders lack hunting tools and instead farm bacteria that convert methane leaking from the seafloor into sugars and fats. This symbiotic relationship allows the spiders to obtain nutrition directly from their microbial coats, effectively turning them into living ecosystems. This unique feeding strategy is the first of its kind observed in sea spiders and highlights a novel adaptation to the extreme, sunless environment of methane seeps. These tiny, nearly transparent spiders—about 1 centimeter long—are found in localized populations off the U.S. West Coast and Alaska. Their reproductive behavior is also unusual: females release hundreds of eggs from their kneecaps, which males carry in sac-like bundles on their limbs, passing methane-consuming bacteria to their offspring to ensure an immediate food source.