''Oscarella lobularis'' 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 order

Homosclerophorida Homosclerophorida is an order of marine sponges. It is the only order in the monotypic class Homoscleromorpha. The order is composed of two families: Plakinidae and Oscarellidae. Taxonomy Homoscleromorpha is phylogenetically well separated from ...

. It is native to the northeastern Atlantic Ocean and the Mediterranean Sea, where it forms encrusting colonies on rocks and other hard surfaces.

Description

''Oscarella lobularis'' is an encrusting sponge that forms a thick layer of soft, gelatinous consistency with a velvety surface, on rocks, stones and large seaweeds.

Colonies In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the '' metropolitan state'' ...

are up to wide and thick, with an irregularly lobed surface. The sides of the nodular lobes have a scattering of ostia through which water passes into the sponge, and at the top of each, a single round

osculum The osculum (plural "oscula") is an excretory structure in the living sponge, a large opening to the outside through which the current of water exits after passing through the spongocoel. Wastes diffuse into the water and the water is pumped thr ...

up to in diameter, through which water exits. This sponge has neither

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 ( ...

nor

spongin Spongin, a modified type of collagen protein, forms the fibrous skeleton of most organisms among the phylum Porifera, the sponges. It is secreted by sponge cells known as spongocytes. Spongin gives a sponge its flexibility. True spongin is found ...

fibres in its tissues. It is usually some shade of yellow or brown but can occasionally be red, violet, green or blue, often with a cream-coloured base layer.

Ecology

Like other sponges, ''Oscarella lobularis'' is a

filter feeder Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...

. Water is drawn into the interior of the sponge through the ostia, the

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

and organic particles on which the sponge feeds are filtered out, and the surplus water is expelling through the osculi. This sponge is a

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...

; ciliated larvae known as

parenchymella Parenchymella is a type of larva of a demosponge Demosponges (Demospongiae) are the most diverse class in the phylum Porifera. They include 76.2% of all species of sponges with nearly 8,800 species worldwide (World Porifera Database). T ...

larvae are liberated into the water and soon settle on the substrate 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 the adult form. This sponge can reproduce asexually. Colonies growing under overhangs can develop elongations that become shaped like tear-drops, dangle on threads of tissue and eventually detach, landing on the seabed below and growing into new colonies; the sponge has also been observed to develop bubble-like buds on its external surface which become detached and, being buoyant, are dispersed by currents in 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 ...

and rapidly grow into new colonies.

Research

''Oscarella lobularis'' has been used as a

model organism A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workin ...

for the study of

evolutionary biology Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life fo ...

and

developmental biology Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of Regeneration (biology), regeneration, asexual reproduction, metamorphosis, and the growth and di ...

, being particularly suitable because of its easy availability, its simple histology and cell composition, its robust epithelial structures and because it lacks a skeleton. Researchers have studied the different colour morphs of this sponge which sometimes grow alongside each other. There appears to be a cryptic complex and two species that had been synonymised in 1877 have been redescribed as ''O. lobularis'' (violet in colour) and '' O. tuberculata''; these species can be distinguished from each other

cytologically Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living and ...

, and by the former having a soft consistency and the latter a cartilaginous consistency. Several other new species have been described, mostly from caves.

References

External links

* {{Taxonbar, from=Q4116656 Homoscleromorpha Fauna of the Mediterranean Sea Taxa named by Eduard Oscar Schmidt Animals described in 1862