''Myxilla incrustans'' 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), ...

demosponge Demosponges or common sponges are sponges of the class Demospongiae (from + ), the most diverse group in the phylum Porifera which include greater than 90% of all extant sponges with nearly 8,800 species A species () is often de ...

. It is an encrusting species and is usually yellow.

Description

''M. incrustans'' is an encrusting sponge occurring in patches up to across and high. It is usually some shade of yellow but can range through orange, pink and white. It has a bubbly-looking appearance with internal channels visible through the surface and large, raised oscules. The consistency is fairly soft and elastic but the surface feels crisp because of the vertical

spicule 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 ( ...

bundles supporting it. The skeleton is built out of tornotes, megascleres with spear-shaped ends with tiny spines on them. The microscleres are a mixture of curved, shovel-like chelae and C-shaped sigmas. Several other similar sponges grow in the same habitats and microscopic examination is necessary to identify the species.Marine Species Identification Portal
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Distribution

''M. incrustans'' was described from specimens collected in the Firth of Forth, Scotland, North Sea. It is reported from the

Arctic The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...

, round Bear Island and the

Faroe Islands The Faroe Islands ( ) (alt. the Faroes) are an archipelago in the North Atlantic Ocean and an autonomous territory of the Danish Realm, Kingdom of Denmark. Located between Iceland, Norway, and the United Kingdom, the islands have a populat ...

, on the coasts of

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...

and south along the Atlantic coast to the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

. In these areas, it is usually found between low-water mark and a depth of on vertical rocks and sites with clean water exposed to strong tidal flows. It also occurs in the north Pacific Ocean from Japan to California, where it is often found growing on the shells of scallops in the genus ''

Chlamys The chlamys (; genitive: ) was a type of ancient Greek cloak. It was worn by men for military and hunting purposes during the Classical, Hellenistic and later periods. By the time of the Byzantine Empire it was part of the state costume of the ...

''. It is unclear whether the free living Atlantic sponges and the Mutualistic pacific sponges are the same species.

Biology

''M. incrustans'' is

viviparous In animals, viviparity is development of the embryo inside the body of the mother, with the maternal circulation providing for the metabolic needs of the embryo's development, until the mother gives birth to a fully or partially developed juve ...

and in the months of August and September, developing

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

s are sometimes found inside the tissues. These are spherical and measure about across before becoming detached. Initiation of the sexual processes involved in reproduction depends on the water temperature. The male tissue releases sperm into the

water column The (oceanic) water column is a concept used in oceanography to describe the physical (temperature, salinity, light penetration) and chemical ( pH, dissolved oxygen, nutrient salts) characteristics of seawater at different depths for a defined ...

. These may get sucked into another sponge, and then fertilisation takes place. About 7% to 12% of the maternal tissue of the sponge is used up in the reproductive process, and there is some localized destruction of the tissue.

References

{{Taxonbar, from=Q2413584 Poecilosclerida Sponges described in 1842 Taxa named by George Johnston (naturalist)