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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. [1]

Collagen is the main structural protein in the extracellular space in the various connective tissues in the body. As the main component of connective tissue, it is the most abundant protein in mammals, making 25% to 35% of the whole-body protein content. Collagen consists of amino acids wound together to form triple-helices l of elongated fibrils. It is mostly found in fibrous tissues such as tendons, ligaments, and skin.

Protein biological molecule consisting of chains of amino acid residues

Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific three-dimensional structure that determines its activity.

Skeleton body part that forms the supporting structure of an organism

The skeleton is the body part that forms the supporting structure of an organism. It can also be seen as the bony frame work of the body which provides support, shape and protection to the soft tissues and delicate organs in animals. There are several different skeletal types: the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside the body, the hydroskeleton, and the cytoskeleton. The term comes from Greek σκελετός (skeletós), meaning 'dried up'.

Spongin gives a sponge its flexibility. True spongin is found only in members of the class Demospongiae. [2]

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Invertebrate Animals without a vertebrate column

Invertebrates are animals that neither possess nor develop a vertebral column, derived from the notochord. This includes all animals apart from the subphylum Vertebrata. Familiar examples of invertebrates include arthropods, mollusks, annelids, and cnidarians.

Sponge Animals of the phylum Porifera

Sponges, the members of the phylum Porifera, are a basal Metazoa (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 them, consisting of jelly-like mesohyl sandwiched between two thin layers of cells. The branch of zoology that studies sponges is known as spongiology.

Hexactinellid class of sponges

Hexactinellid sponges are sponges with a skeleton made of four- and/or six-pointed siliceous spicules, often referred to as glass sponges. They are usually classified along with other sponges in the phylum Porifera, but some researchers consider them sufficiently distinct to deserve their own phylum, Symplasma.


Choanocytes are cells that line the interior of asconoid, syconoid and leuconoid body type sponges that contain a central flagellum, or undulipodia, surrounded by a collar of microvilli which are connected by a thin membrane. They make up Choanoderm, a type of cell layer found in sponges. The cell has the closest resemblance to the choanoflagellates which are the closest related single celled protists to the animal kingdom (metazoans). The flagellae beat regularly, creating a water flow across the microvilli which can then filter nutrients from the water taken from the collar of the sponge. Food particles are then phagocytosed by the cell.


The telson is the posterior-most division of the body of an arthropod. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca may be present. The shape and composition of the telson differs between arthropod groups.

Demosponge A class of sponges in the phylum Porifera with spongin or silica spicules

Demospongiae is the most diverse class in the phylum Porifera. They include 76.2% of all species of sponges with nearly 8,800 species worldwide. They are predominantly leuconoid in structure. Their "skeletons" are made of spicules consisting of fibers of the protein spongin, the mineral silica, or both. Where spicules of silica are present, they have a different shape from those in the otherwise similar glass sponges.

Tube-dwelling anemone order of cnidarians

Tube-dwelling anemones or ceriantharians look very similar to sea anemones but belong to an entirely different subclass of anthozoans. They are solitary, living buried in soft sediments. Tube anemones live inside and can withdraw into tubes, which are composed of a fibrous material made from secreted mucus and threads of nematocyst-like organelles known as ptychocysts. Ceriantharians were formerly classified in the taxon Ceriantipatharia along with the black corals but have since been moved to their own subclass, Ceriantharia.

Mesoglea refers to the tissue found in jellyfish that functions as a hydro-static skeleton. Mesohyl generally refers to tissue found in sponges.


Mesenchyme, in vertebrate embryology, is a type of connective tissue found mostly during the development of the embryo. It is composed mainly of ground substance with few cells or fibers. It can also refer to a group of mucoproteins found in certain types of cysts (etc.), resembling mucus. It is most easily found as a component of Wharton's jelly.

The mesohyl, formerly known as mesenchyme or as mesoglea, is the gelatinous matrix within a sponge. It fills the space between the external pinacoderm and the internal choanoderm. The mesohyl resembles a type of connective tissue and contains several amoeboid cells such as amebocytes, as well as fibrils and skeletal elements. For a long time, it has been largely accepted that sponges lack true tissue, but it is currently debated as to whether mesohyl and pinacoderm layers are tissues.

In taxonomy, the Dendroceratida are an order of sponges of the class Demospongiae. They are typically found in shallow coastal and tidal areas of most coasts around the world. They are generally characterized by concentric layers of fibers containing spongin, and by large flagellated chambers that open directly into the exhalant canals. Along with the Dictyoceratida, it is one of the two orders of demosponges that make up the keratose or "horny" sponges, in which a mineral skeleton is minimal or absent and a skeleton of organic spongin-containing fibers is present instead.

Taxonomy of commonly fossilised invertebrates

Although the phylogenetic classification of non-vertebrate animals remains a work-in-progress, the following taxonomy attempts to be useful by combining both traditional (old) and new (21st-century) paleozoological terminology.

<i>Anheteromeyenia argyrosperma</i> species of sponge

Anheteromeyenia argyrosperma is a freshwater sponge found across North America.

Manoalide chemical compound

Manoalide is a calcium channel blocker. It has antibiotic, analgesic and anti-inflammatory effects and is found in some sponges, including the West Pacific species Luffariella variabilis.

In zoology, the epidermis is an epithelium that covers the body of a eumetazoan. Eumetazoa have a cavity lined with a similar epithelium, the gastrodermis, which forms a boundary with the epidermis at the mouth.

Clionaidae family of sponges

Clionaidae is a family of demosponges which are found worldwide. This family is known for parasitically boring holes in calcareous material such as mollusc shells and corals, using both chemical and mechanical processes.

<i>Agelas</i> genus of sponges

Agelas is a genus of demosponge. It is the only member of the family Agelasidae.

Agelas schmidti, the brown tubular sponge, is a species of demosponge. It occurs at moderate depths in the Gulf of Mexico and the Caribbean Sea and often has a colonial coral growing over the surface. The type locality is Puerto Rico.

Oscarella carmela, commonly known as the slime sponge, is a species of sponge in the order Homosclerophorida that was first described in 2004 by G. Muricy and J.S. Pearse. It is believed to be native to intertidal waters in the north east temperate Pacific Ocean and was first found in seawater aquaria in that region. It is used as a model organism in evolutionary biology.

<i>Oscarella lobularis</i> species of sponge

Oscarella lobularis is a species of sponge in the order Homosclerophorida. It is native to the northeastern Atlantic Ocean and the Mediterranean Sea, where it forms encrusting colonies on rocks and other hard surfaces.


  1. Anderson, D. (2001). Invertebrate Zoology. Oxford University Press.
  2. Brusca, R.; Brusca, G. (2003). Invertebrate Zoology. Sinauer Associates. p. 191.