Researchers led by Occidental College professor Shana Goffredi have discovered three new species of sea spiders that consume methane at deep-sea vents off the Southern California coast, revealing a previously unknown ecological relationship where these tiny, translucent creatures cultivate methane-oxidizing bacteria on their exoskeletons as a food source.
Methane seeps are remarkable deep-sea ecosystems where fluids rich in methane and hydrogen sulfide escape through fissures in the ocean floor, typically at depths between 600 and 5,000 feet, though they can occur from as shallow as 15 meters to depths exceeding 7,800 meters.12 These cold seeps (sometimes called cold vents) create unique habitats that support specialized communities of organisms through chemosynthesis rather than photosynthesis.3 Unlike hydrothermal vents which release heat and energy, methane seeps primarily trap energy within the seafloor, with over 80% of methane being oxidized before reaching the sediment surface.4
The ecological importance of methane seeps extends far beyond their immediate vicinity. These ecosystems play a crucial role in global climate regulation by consuming approximately 90% of the released methane, preventing this potent greenhouse gas (25 times more powerful than carbon dioxide) from entering the atmosphere.5 Methane seeps form biological hotspots of diversity, hosting extensive mussel and clam beds and creating prime fishing habitats.5 While they share some higher taxa with hydrothermal vents, they have distinct species compositions, with connectivity between these ecosystems facilitated by sedimented vents that share characteristics of both environments—particularly along the active continental margins of the Pacific Ocean.67
The three newly discovered methane-consuming sea spiders belong to the genus Sericosura in the family Ammotheidae and appear to live exclusively at methane seeps along the eastern Pacific coast1. These tiny creatures, measuring only about a centimeter long with translucent bodies, were collected from specific locations including the Del Mar seep near San Diego and the Palos Verdes seep off Los Angeles County2. Their discovery was a "happy accident" according to Goffredi, as the research team initially set out to explore methane seep ecosystems rather than identify new species2.
What makes these findings particularly significant is the specialized symbiotic relationship these spiders have developed with methane-oxidizing bacteria. The research team observed methane gas molecules moving from outside the spiders onto their exoskeletons and then into their tissues2. Similar bacterial communities were also identified in egg sacs carried by male sea spiders, suggesting that these microbes are transmitted between generations3. Researchers hypothesize that at least 11 other previously identified sea spider species in the same genus, all found exclusively at methane seeps, likely consume methane through similar mechanisms24. The species remain unnamed, though Goffredi hopes their eventual names will reflect their "methane-loving" nature2.
In the deep ocean's methane-rich environments, diverse symbiotic relationships between marine animals and chemosynthetic bacteria have evolved to harness energy from chemical compounds rather than sunlight. These relationships take various forms, with bacteria positioned either externally (ectosymbionts) or internally (endosymbionts) within their hosts. The vent shrimp Rimicaris, for example, harbors specialized bacteria in its gill chambers that convert chemicals from vent fluids into nutrients, potentially supplying the shrimp with organic carbon.12 Similarly, yeti crabs (Kiwa tyleri) cultivate chemosynthetic bacteria on the setae covering their bodies, deliberately waving their arms near hydrothermal vents to feed these microbes before consuming them directly off their claws—essentially farming their own food.3
Other remarkable examples include tube worms that acquire chemosynthetic bacteria as larvae and maintain this relationship throughout their 200+ year lifespan, with the bacteria converting sulfides into energy for their hosts.3 More recently discovered are Laminatubus and Bispira worms that host Methylococcaceae bacteria on their respiratory plumes, gradually digesting these methane-harvesting microbes to indirectly obtain carbon and energy from methane seeps.4 These symbiotic relationships demonstrate the incredible adaptability of life in extreme environments, where organisms from seven different phyla have developed specialized partnerships with bacteria to survive in the absence of sunlight.2
