Deep ocean fish swimming among giant tube worms (Riftia pachyptila) by a hydrothermal vent. Many deep ocean fish are new, previously unknown, species. The tube worms are marine invertebrates that are a key part of the ecosystem of deep ocean hydrothermal vents. They can tolerate high temperatures, and obtain nutrients from the water by symbiosis with bacteria living in their bodies. The white tubes are made of chitin. The red structures, called plumes, contain haemoglobin that combines with the hydrogen sulphide and transfers it to the bacteria. The bacteria then convert the inorganic chemicals to organic molecules that are used by the tube worms. Photographed on the East Pacific Rise.