A new species of poecilosclerid sponge (Porifera) from bathyal methane seeps in the Gulf of Mexico

A new species of poecilosclerid sponge from methane seeps on the Louisiana Slope, Gulf of Mexico, USA is described. This thickly encrusting sponge grows around vestimentiferan tubes and has a very patchy distribution. The skeletal structure and the spicule set match those characterizing the genus Ectyomyxilla. The new species, Ectyomyxilla methanophila sp. nov., is distinguished from the remaining species in the genus by the structure of its ectosomal skeleton, where small acanthostyles are never present, and by its choanosomal skeleton, which is barely reticulate and has echinated main tracts. The small size of the choanocyte chambers suggests occurrence of nutritional benefits derived from association with chemoautotrophic symbiotic bacteria. However, the presence of oscules, ostioles, aquiferous canals and choanocyte chambers indicates that this sponge also relies partly on filtration for its nutrition. This is the first record of the genus Ectyomyxilla in the northern hemisphere, and the first non-carnivorous demosponge known to exploit methane-rich marine environments.