''Gorgonorhynchus repens'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of the proboscis worm in the subclass

Heteronemertea Heteronemertea is a Monophyly, monophyletic order (biology), order of about 500 species of nemertean worms. It contains genus, genera such as ''Lineus'' and ''Cerebratulus'', and includes the largest and most muscular nemerteans. Almost all hete ...

and of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Gorgonorhynchidae. It is to be found on the seabed in shallow water in the Pacific Ocean.

Description

''G. repens'' is orange in color and grows to an unstretched length of about . It is cylindrical in shape with bluntly tapering ends. Proboscis worms are known for their reversible proboscides, but in most species these are unbranched and cylindrical, or may have a sharp, venomous stylet part way to the tip. In a few instances, they are branched but the side branches are short and the proboscis resembles a feather. In the case of ''G. repens'', the proboscis is a densely branching structure giving the impression of a cloud of

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 fluid, serous and muc ...

secretion.

Distribution and habitat

''G. repens'' is native to the Pacific Ocean where it is found in shallow water on the seabed, living on the surface or tunnelling through soft sediment.

Ecology

Proboscis worms in general are

predatory Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

, snaring or spearing their

prey Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not ki ...

. At first, zoologists were unclear precisely how this species fed; the branched proboscis resembles the feeding tentacles of

sea cucumber Sea cucumbers are echinoderms from the class (biology), class Holothuroidea ( ). They are benthic marine animals found on the sea floor worldwide, and the number of known holothuroid species worldwide is about 1,786, with the greatest number be ...

s in the family

Synaptidae Synaptidae is a family of sea cucumbers that have no tube feet, tentacle ampullae, retractor muscles, respiratory trees, or cuvierian tubules. They also lack radial canals of the Sea cucumber#Anatomy, water-vascular system, with only the circumo ...

, which feed by sifting through sediment, and might have the same function; alternatively, the proboscis might function like the cirri in the oral hood of the lion nudibranch (''Melibe leonina'') which feeds by filtering

zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...

out of the water. It is now accepted that the branched proboscis is shot out like a sticky harpoon and snares animals such as

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

s and other worms. It is then reeled in, dragging the prey back to the mouth, where it is swallowed whole. The proboscis is also used defensively if the proboscis worm is stressed.

References

{{Taxonbar, from=Q2023066 Heteronemertea Marine nemerteans Animals described in 1931 Fauna of the Pacific Ocean