Sponges, the members of the phylum Porifera, 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 them, consisting of jelly-like mesohyl sandwiched between two thin layers of cells.
The choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals. Choanoflagellates are collared flagellates, having a funnel shaped collar of interconnected microvilli at the base of a flagellum. Choanoflagellates are capable of both asexual and sexual reproduction. They have a distinctive cell morphology characterized by an ovoid or spherical cell body 3–10 µm in diameter with a single apical flagellum surrounded by a collar of 30–40 microvilli. Movement of the flagellum creates water currents that can propel free-swimming choanoflagellates through the water column and trap bacteria and detritus against the collar of microvilli, where these foodstuffs are engulfed. This feeding provides a critical link within the global carbon cycle, linking trophic levels. In addition to their critical ecological roles, choanoflagellates are of particular interest to evolutionary biologists studying the origins of multicellularity in animals. As the closest living relatives of animals, choanoflagellates serve as a useful model for reconstructions of the last unicellular ancestor of animals.
The calcareoussponges are members of the animal phylum Porifera, the cellular sponges. They are characterized by spicules made of calcium carbonate, in the form of high-magnesium calcite or aragonite. While the spicules in most species are triradiate, some species may possess two- or four-pointed spicules. Unlike other sponges, calcareans lack microscleres, tiny spicules which reinforce the flesh. In addition, their spicules develop from the outside-in, mineralizing within a hollow organic sheath.
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 feeding are clams, krill, sponges, baleen whales, and many fish. Some birds, such as flamingos and certain species of duck, are also filter feeders. Filter feeders can play an important role in clarifying water, and are therefore considered ecosystem engineers. They are also important in bioaccumulation and, as a result, as indicator organisms.
A spongocoel, also called paragaster, is the large, central cavity of sponges. Water enters the spongocoel through hundreds of tiny pores (ostia) and exits through the larger opening (osculum). Depending on the body plan of the sponge, the spongocoel could be a simple interior space of the sponge or a complexly branched inner structure. Regardless of body plan or class, the spongocoel is lined with choanocytes, which have flagella that push water through the spongocoel, creating a current.
Porocytes are tubular cells which make up the pores of a sponge known as ostia.
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. They are sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or calcite. 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. Some species, in particular from the Antarctic, obtain the silica for spicule building from the ingestion of siliceous diatoms.
Anheteromeyenia argyrosperma is a freshwater sponge found across North America.
The Urmetazoan is the hypothetical last common ancestor of all animals, or metazoans. It is universally accepted to be a multicellular heterotroph — with the novelties of a germline and oogamy, an extracellular matrix (ECM) and basement membrane, cell-cell and cell-ECM adhesions and signaling pathways, collagen IV and fibrillar collagen, different cell types, spatial regulation and a complex developmental plan, and relegated unicellular stages.
Xestospongia testudinaria is a species of barrel sponge in the family Petrosiidae. More commonly known as Giant Barrel Sponges, they have the basic structure of a typical sponge. Their body is made of a reticulation of cells aggregate on a siliceous scaffold composed of small spikes called spicules. Water is taken into the inner chamber of the sponge through ostia. Flagellated choanocytes line the inner chamber and help generate water currents through the sponge.
Amphimedon compressa, the erect rope sponge, red tree sponge, red tubular sponge, or red sponge is a demosponge found in southern Florida, the Caribbean Sea, and the Bahamas. It can be deep red, orange, brown, or black.
Callyspongia (Cladochalina) aculeata, commonly known as the branching vase sponge is a species of Porifora, meaning sea sponge, in the family Callyspongiidae. Poriferans are typically characterized by ostia, pores that filter out plankton, with an osculum as the opening which water leaves through, and choanocytes trap food particles.
Agelas schmidti, commonly known as 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.
Neofibularia nolitangere, commonly known as the touch-me-not sponge, is a species of sea sponge in the family Biemnidae. It is found in shallow waters in the Western Atlantic Ocean and the Caribbean Sea.
Callyspongia truncata is a species of marine sea sponge. Like all marine sponges, C. truncata is a member of phylum Porifera and is defined by its filter-feeding lifestyle and flagellated choanocytes, or collar cells, that allow for water movement and feeding. It is a species of demosponge and a member of Demospongiae, the largest class of sponges as well as the family Callyspongiidae. C. truncata is most well known for being the organism from which the polyketide Callystatin A was identified. Callystatin A is a polyketide natural product from the leptomycin family of antibiotics. It was first isolated in 1997 from this organism, which was collected from the Goto Islands in the Nagasaki Prefecture of Japan by the Kobayashi group. Recent studies have revealed numerous other bioactive compounds that have been found in this species.
Until the late 1950s, the Precambrian was not believed to have hosted multicellular organisms. However, with radiometric dating techniques, it has been found that fossils initially found in the Ediacara Hills in Southern Australia date back to the late Precambrian. These fossils are body impressions of organisms shaped like disks, fronds and some with ribbon patterns that were most likely tentacles.
Salpingoeca rosetta is a species of Choanoflagellates in the family Salpingoecidae. It is a rare marine eukaryote consisting of a number of cells embedded in a jelly-like matrix. This organism demonstrates a very primitive level of cell differentiation and specialization. This is seen with flagellated cells and their collar structures that move the cell colony through the water.
Similar low level cellular differentiation and specification can also be seen in sponges. They also have collar cells and amoeboid cells arranged in a gelatinous matrix.
Unlike S. rosetta, sponges also have other cell-types that can perform different functions. Also, the collar cells of sponges beat within canals in the sponge body, whereas Salpingoeca rosetta’s collar cells reside on the inside and it lacks internal canals. Despite these minor differences, there is strong evidence that Proterospongia and Metazoa are highly related.
Eocyathispongia is a genus of sponge-like organisms which lived in the Ediacaran period about 60 million years before the Cambrian. The current fossil record has found this genus in only one location, the Doushantuo Formation in Guizhou, China. It lived in the shallow parts of seas, filter feeding.
Halisarca caerulea is a species of sponge in the family Halisarcidae. It is native to the Caribbean Sea and was first described in 1987 by the French marine biologists Jean Vacelet and Claude Donadey.
Diaphanoeca grandis is a species of choanoflagellate in the family Acanthoecidae which is the type species of the genus Diaphanoeca. It is a unicellular micro-heterotroph with a large protective lorica that is found beneath sea ice in a wide distribution.
