Swima
Swima is a genus of polychaete worm that lives in the deep ocean. This deep ocean pelagic (free-swimming) annelid has modified bioluminescent gills that can be cast off from an individual. These discarded gills somewhat resemble green "bombs" that remain illuminated for several seconds after they have been discarded. It is thought that this is a defensive mechanism rather than reproductive, as it is seen in both mature and juvenile individuals. Animals of the genus "Swima" are closely related to the recently discovered genus "Teuthidodrilus", another pelagic cirratuliform of the bathyal zone. Discovery. The first specimens of the  genus "Swima" were discovered in the deep trenches of Monterey Bay, off the coast of California. Taxonomy. There are currently three species recognised within the "Swima": Anatomy and physiology. Animals of the "Swima" are characterized by a thick gelatinous sheath, transparent body, simple nuchal organs, a single medial subulate branchia, and four pair of small segmental branchiae modified as elliptical, bioluminescent sacs. Etymology. The genus name, "Swima", is derived from the Latin, referring to the animal's ability to swim.