''Ochetostoma erythrogrammon'' 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

Thalassematidae Thalassematidae is a family of spoonworms in the suborder Echiurida. Genera The World Register of Marine Species The World Register of Marine Species (WoRMS) is a taxonomic database that aims to provide an authoritative and comprehensive lis ...

. It is found in shallow water in the Atlantic Ocean, the Mediterranean Sea, and the Indian and Pacific Oceans, burrowing in soft sediment.

Description

Like other echiurians, ''O. erythrogrammon'' is very mobile and flexible. It consists of a sausage-shaped trunk up to in length, with reddish longitudinal grooves and a violet-coloured posterior. This is attached to a gutter-like proboscis, a third to three quarters the length of the body, green on its dorsal surface and yellowish on its ventral surface.

Distribution and habitat

The fauna and geography of the Maldive and Laccadive archipelagoes V1P2 Plate VI

''Ochetostoma erythrogrammon'' occurs in the Atlantic Ocean, the Mediterranean Sea, and the Indian and Pacific Oceans. Its typical habitat is beaches of muddy sand where it lives in a burrow it digs in the

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...

. Countries from which this spoon worm has been reported in the Indo-Pacific region include Somalia, Mauritius, Malaysia, Indonesia, Vietnam, Hong Kong and Japan. It is also known from the Red Sea, the Mediterranean Sea, South Africa, Bermuda, Bahamas, Venezuela and Brazil.

Ecology

This spoon worm tunnels into the soft sediment and creates a burrow in which it lives. Digging is performed mostly by the basal region of the proboscis, with the trunk playing little part in the process. The burrow is U-shaped, having a horizontal section wide and some long, with a vertical or oblique section about long at either end. The

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...

can be extended through an entrance just wide while the other end of the tube is plugged with mud or sand. Feeding takes place shortly after the tide retreats while the sediment is still wet. The proboscis is extended like a scoop, first scraping up the sediment and

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

close to the burrow entrance and ingesting it, and then extending with the tip moving progressively farther away. The proboscis becomes thinner and narrower as it lengthens and may reach in length. The dorsal surface of the proboscis is pressed against the wet sediment, and sand and debris particles are coated with

mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...

and moved by

cilia The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...

along the grooved, ventral surface to the mouth. Large particles are discarded. The worm can turn round in its burrow and search for food through what was the rear entrance of the burrow. If disturbed the proboscis rapidly retreats into the burrow. A number of other organisms live inside the burrow as commensals. These include various species of polyclad flatworms, scale worms,

bivalve molluscs Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

, gastropod molluscs, pea crabs, snapping shrimps and

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

s; several associates can share the burrow with the spoon worm simultaneously.

References

{{Taxonbar, from=Q2228222 Echiurans Fauna of the Atlantic Ocean Fauna of the Indian Ocean Fauna of the Mediterranean Sea Fauna of the Pacific Ocean Animals described in 1828 Taxa named by Friedrich Sigismund Leuckart Taxa named by Eduard Rüppell