instigator worm using its body to strike its con-specific. This contact is usually interpreted as aggressive, as both worms withdraw to their respective tubes afterwards, and is likely a way for the worms to maintain their feeding territory. In this respect, it seems that size matters, as bigger worms are able to maintain a larger area than their smaller conspecifics. The worms hardly leave their tubes, and when they did, it was mostly in response to habitat disturbance. One other possibility for worm migration is the decrease in food availability in the worm’s general area. Habitat Paralvinella sulfincola are mostly found on the chimneys that form near the Juan de Fuca Ridge on the Northwestern Pacific. Chimney formation happens in two main phases. In the first phase, hot seawater that is intensely saturated with calcium sulfate emerges from the seafloor and deposits anhydrite minerals into a porous, chimney-like structure. In the second phase, sulfide minerals replace the initial anhydrite minerals as the chimney gets thicker. P. sulfincola starts to colonize the chimney during this second phase and it contributes to the chimney’s chemical environment by forming a marcasite crust on the chimney as the worms build their tubes. It is thought that the elemental sulfur found in the worms’ tube mucus react with the sulfides present to form this marcasite material. The temperatures generated on and surrounding the hydrothermal vent limit the kinds of species that can live on it: the surrounding water nears freezing temperatures, but the vent itself is a source of extreme heat. As a result, the species living on the vents must be able to tolerate a wide range of temperatures. P. sulfincola is among the most eurythermal of the marine invertebrates, with the worm remaining active at a range of . It is also able to survive up to temperatures as high as . Activity in this species seems to decrease as temperature increases. One theory for this is that food is more abundant in warmer temperatures, and so the worm does not need to forage much and can remain stationary. See also Pompeii worm References External links Photo gallery at NOAA Pacific Marine Environmental Laboratory Terebellida Thermophiles Animals living on hydrothermal vents