''Synaptula recta'', sometimes known as the gut-like sea cucumber, 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 ...

sea cucumber Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothuria ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

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 water-vascular system, with only the circumoral ring present. S ...

in the phylum

Echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea ...

ata. It occurs in shallow water in the tropical Indo-Pacific region.

Description

''Synaptula recta'' is an elongated sea cucumber growing to a maximum length of about . The mouth is at the anterior end and is surrounded by thirteen feeding tentacles. The colour is variable but it is often a deep colour, ranging from dark reddish-purple to a fairly bright red, olive or a pattern of longitudinal lilac stripes on a pale background. The calcareous

spicules Spicules are any of various small needle-like anatomical structures occurring in organisms Spicule may also refer to: *Spicule (sponge), small skeletal elements of sea sponges *Spicule (nematode), reproductive structures found in male nematodes ( ...

in the

cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

consist of anchors with knobbed ends and curved bodies. The tips of these spicules project through the cuticle and help give traction during locomotion which is performed by

peristalsis Peristalsis ( , ) is a radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. Peristalsis is progression of coordinated contraction of involuntary circular muscles, which ...

, synaptids having no

tube feet Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on britt ...

Distribution and habitat

''Synaptula recta'' is native to the tropical western Indo-Pacific region. Its range extends from the Red Sea, the Maldives and Sri Lanka to northern Australia, Indonesia, the Philippines and several Pacific island groups. It inhabits coastal waters and

reef A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock out ...

s, sand flats and

seagrass meadow A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and ...

s and occurs at depths down to about .

Ecology

''Synaptula recta'' is

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

and feeds on

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 ...

and

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic particles which it sweeps into its mouth with its feeding tentacles. It is often found moving over and feeding on debris on the surfaces of

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...

s. The sexes are separate and fertilisation is external. The larvae are planktonic, the first-stage auricularia larvae developing into barrel-shaped, doliolaria larvae which when sufficiently developed settle on the seabed and undergo

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

into juvenile sea cucumbers.

References

{{Taxonbar, from=Q2447989 Synaptidae Animals described in 1867