''Ikeda taenioides'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of spoon worm in the family

Ikedidae Ikedidae is a family of spoon worms in the suborder Bonelliida. It is a monotypic family, the only genus being ''Ikeda''. These worms burrow into soft sediment on the seabed. Examination of the original material of '' Ikeda taenoides'' by Ter ...

. It is native to the northern Pacific Ocean where it is found in the subtidal waters around Japan.

Taxonomy

This spoon worm was first described by the Japanese zoologist I. Ikeda in 1904 as ''

Thalassema Thalassema is a genus of spoonworms in the subclass Echiura. Species The World Register of Marine Species includes these species in this genus:- * '' Thalassema antarcticum'' Stephen, 1941 * '' Thalassema arcassonense'' Cuénot, 1902 * '' Thal ...

taenioides'', the type locality being Misaki, Sagami Bay, in

Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island separ ...

, Japan. Examination of the musculature of the body wall led to the observation that the longitudinal muscle layer lay outside both the circular layer and the inner oblique layer, and as this was at odds with all other members of the subclass Echiura, it warranted the creation of a new order. However, examination of the original material by Teruaki Nishikawa in 2002, showed that the longitudinal muscle layer was in fact between the circular layer and the oblique layer, as in all other echurians, throwing the taxonomy of the species into doubt. Nishikawa advocates that the family

be regarded as a

junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...

Echiuridae Echiuridae is a family of spoon worms in the suborder Echiurida. It is a monotypic family, the only genus being ''Echiurus''. These worms burrow into soft sediment on the seabed. Species The World Register of Marine Species recognises the fol ...

Description

''Ikeda taenioides'' is the largest spoon worm in the world, its proboscis being visible protruding from its burrow while the trunk remains hidden. The trunk can be long and the proboscis .

Ecology

''Ikeda taenioides'' lives in soft sediment where it digs itself a burrow, often descending to below the sand surface. The proboscis is protruded through the burrow entrance to feed, and a number of these probosces were observed by researchers in 2011, some eight months after a

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explo ...

had devastated the seabed habitat. The tsunami had destroyed the

seagrass Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the orde ...

beds, the heart urchins and the Venus clams in the community; the researchers thought the spoon worms had survived the turbulent conditions because of the depths of their burrows.

References

{{Taxonbar, from=Q2153915 Echiurans Fauna of the Pacific Ocean Animals described in 1904