''Halisarca caerulea'' 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 ...

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 ...

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 ...

Halisarcidae Halisarcidae is a family of sea sponges within the order Chondrillida. Members of the family are characterised by having long tubular, branched choanocyte chambers; they have no spicules Spicules are any of various small needle-like anatomical ...

. It is native to the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

and was first described in 1987 by the French marine biologists

Jean Vacelet Jean Vacelet is a French marine biologist who specialises in the underwater fauna of the Mediterranean. After earning his licence at the Faculté des Sciences de Marseille and learning to dive in 1954, he specialised in the study of sponges at th ...

and Claude Donadey.

Description

''Halisarca caerulea'' is a thinly encrusting species forming patches about thick. The texture is fleshy, and the skin is strengthened by the presence of bundles of

collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whole ...

fibres which give a reticulated pattern to the smooth, slightly slimy surface. This sponge has long tubular,

choanocyte Choanocytes (also known as "collar cells") are cells that line the interior of asconoid, syconoid and leuconoid body types of sponges that contain a central flagellum, or ''cilium,'' surrounded by a collar of microvilli which are connected by a th ...

chambers, which are sometimes branched, and no

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 ( ...

. The oscula are about in diameter, each being at the centre of a conspicuous star-shaped group of superficial canals. These star-shaped systems are separated by smooth areas and are regularly arranged over the surface of the sponge, which is a bright blue colour in living specimens.

Ecology

Sponges feed by drawing water in through small pores, filtering out the bacteria and organic particles and pumping the water out through the oscula. The waters of the Caribbean are very poor in nutrients, and researchers found that this sponge had to pump large quantities of water in order to extract sufficient essential nutrients for its requirements. From the amount of carbon filtered out of the water, theoretically the sponges should have grown rapidly, but in fact they hardly grew at all. The researchers found that the

cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

were dividing every five or six hours. Although they were proliferating so rapidly, growth was minimal; there was no evidence of

cell death Cell death is the event of a biological cell ceasing to carry out its functions. This may be the result of the natural process of old cells dying and being replaced by new ones, as in programmed cell death, or may result from factors such as dis ...

, but instead, the sponge was sloughing off choanocyte cells almost as fast as they were formed. The researchers hypothesized that the fast turnover in cells might be useful in coping with the pollutants and

toxin A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849– ...

s contained in the water that the sponge inevitably encountered while filter feeding. It has since been realised that in casting off this cell debris, the sponges are part of a sponge loop, absorbing large quantities of

dissolved organic carbon Dissolved organic carbon (DOC) is the fraction of organic carbon operationally defined as that which can pass through a filter with a pore size typically between 0.22 and 0.7 micrometers. The fraction remaining on the filter is called particu ...

, and returning the carbon to the

water column A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...

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 ...

, which is available for consumption by other animals.

References

{{Taxonbar, from=Q2324682 Verongimorpha Fauna of the Caribbean Animals described in 1987 Taxa named by Jean Vacelet