''Osedax japonicus'' is a species of

bathypelagic The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The bathypelagic ...

polychaete tube worm that lives at great depths on the seabed and is able to sustain itself on the bones of a dead whale. It was first described in 2006 from a sunken

sperm whale The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the genus ''Physeter'' and one of three extant species in the sperm whale famil ...

carcase near Kyushu, Japan.

Discovery

Scientists from the Monterey Bay Aquarium Research Institute using the submarine ROV ''Tiburon'' first discovered worms of the genus '' Osedax'' in Monterey Bay, California, in February 2002. The worms were found living on the bones of a decaying

gray whale The gray whale (''Eschrichtius robustus''), also known as the grey whale,Britannica Micro.: v. IV, p. 693. gray back whale, Pacific gray whale, Korean gray whale, or California gray whale, is a baleen whale that migrates between feeding and bree ...

in the Monterey Canyon, at a depth of . The discovery caused great excitement among marine biologists, and since then other species of worms of the same genus have been discovered on whale carcases lying in deep water in other parts of the world. ''Osedax japonicus'' was first described in 2006 from a

carcase that fell to the seabed off

Kyushu is the third-largest island of Japan's five main islands and the most southerly of the four largest islands ( i.e. excluding Okinawa). In the past, it has been known as , and . The historical regional name referred to Kyushu and its surroun ...

, Japan, settling at a depth of . Numerous female tube worms were observed but no males were seen.

Description

An adult worm has a ringlike crown of feathery plumes which are involved in respiration, a trunk and a rooting structure which contains

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

bacteria. It has no digestive system nor a segmental structure as do most worms.

Behaviour

When a whale dies, its carcass falls to the seabed. Here it provides a feast for many deep-sea creatures. Worms such as ''Osedax japonicus'' make use of the bones when only the

skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

remains. The worms produce a branching network of "roots" that house

bacteria, which enable the worms to utilise the bones' nutrient content. The reproduction of ''Osedax japonicus'' has been studied. Female worms reach maturity at about six weeks. They secrete mucus to form a tube that surrounds their trunk. Male worms are minute by comparison with the females and they take up residence inside the tubes. The females spawn eggs and retain them in the mucus where they are fertilised by the males. Here they develop for a time before they swim out of the mucus as trochophore larvae. The larvae are then planktonic and can live for at least ten days in the open sea. It seems that if they settle on a suitable vertebrate bone they will develop into female worms but if mature females are already present on the bone, they will develop into males. The vast majority will fail to find any sunken bone.

References

{{Taxonbar, from=Q3155476 Canalipalpata Taxa named by Yoshihiro Fujiwara Taxa named by Masaru Kawato Animals described in 2006