Bryozoa are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about 0.5 millimetres long, they have a special feeding structure called a lophophore, a "crown" of tentacles used for filter feeding. Most marine bryozoans live in tropical waters, but a few are found in oceanic trenches and polar waters. The bryozoans are classified as the marine bryozoans (Stenolaemata), freshwater bryozoans (Phylactolaemata), and mostly-marine bryozoans (Gymnolaemata), a few members of which prefer brackish water. 5,869 living species are known. Originally all of the crown group Bryozoa were colonial, but as an adaptation to a mesopsammal life or to deep-sea habitats, secondarily solitary forms have since evolved. Solitary species has been described in four genera; Aethozooides, Aethozoon, Franzenella and Monobryozoon). The latter having a statocyst-like organ with a supposed excretory function.
Entoprocta, or Kamptozoa, is a phylum of mostly sessile aquatic animals, ranging from 0.1 to 7 millimetres long. Mature individuals are goblet-shaped, on relatively long stalks. They have a "crown" of solid tentacles whose cilia generate water currents that draw food particles towards the mouth, and both the mouth and anus lie inside the "crown". The superficially similar Bryozoa (Ectoprocta) have the anus outside a "crown" of hollow tentacles. Most families of entoprocts are colonial, and all but 2 of the 150 species are marine. A few solitary species can move slowly.
Stenolaemata are a class of exclusively marine bryozoans. Stenolaemates originated and diversified in the Ordovician, and more than 600 species are still alive today. All extant (living) species are in the order Cyclostomatida, the third-largest order of living bryozoans.
Membranipora membranacea is a very widely distributed species of marine bryozoan known from the Atlantic and Pacific Oceans, usually in temperate zone environments. This bryozoan is a colonial organism characterized by a thin, mat-like encrustation, white to gray in color. It may be known colloquially as the coffin box, sea-mat or lacy crust bryozoan and is often abundantly found encrusting seaweeds, particularly kelps.
Cyclostomatida, or cyclostomata, are an ancient order of stenolaemate bryozoans which first appeared in the Lower Ordovician. It consists of 7+ suborders, 59+ families, 373+ genera, and 666+ species. The cyclostome bryozoans were dominant in the Mesozoic; since that era, they have decreased. Currently, cyclostomes seldom constitute more than 20% of the species recorded in regional bryozoan faunas.
A zooid or zoöid is a single animal that is part of a colonial animal. This lifestyle has been adopted by animals from separate unrelated taxa. Zooids are multicellular; their structure is similar to that of other solitary animals. The zooids can either be directly connected by tissue or share a common exoskeleton. The colonial organism as a whole is called a zoon, plural zoa.
In the bryozoan order Cheilostomatida, the operculum is a calcareous or chitinous lid-like structure that protects the opening through which the polypide protrudes.
The polypide in bryozoans encompasses most of the organs and tissues of each individual zooid. This includes the tentacles, tentacle sheath, U-shaped digestive tract, musculature and nerve cells. It is housed in the zooidal exoskeleton, which in cyclostomes is tubular and in cheilostomes is box-shaped. Polypides can undergo cycles of regression and regeneration, in which the zooid forms a new polypide as the old one accumulates waste and dies.
Malacostegina is a sub-order of marine, colonial bryozoans in the order Cheilostomatida. The structure of the individual zooids is generally simple, with an uncalcified, flexible frontal wall. This sub-order includes the earliest known cheilostome, in the genus Pyriporopsis (Electridae).
The avicularium in cheilostome bryozoans is a modified, non-feeding zooid. The operculum, which normally closes the orifice when the zooids tentacles are retracted, has been modified to become a mandible. Strong muscles operate it. The polypide is greatly reduced, and the individual receives nourishment from neighboring zooids. The shape of the avicularian zooid can be identical to the feeding autozooid, but is usually elongated in the direction of the mandible.
The Adeonellidae is a family within the bryozoan order Cheilostomatida. Colonies are often upright bilaminar branches or sheets. The zooids generally have one or more adventitious avicularia on their frontal wall. Instead of ovicells the adeonids often possess enlarged polymorphs which brood the larvae internally.
Celleporidae is a family of bryozoans – colonial, aquatic, invertebrates – in the order Cheilostomatida. Structurally, they are defined by densely packed zooids. The zooids usually have irregular direction, and are defined by morphological characteristics. Masses of the dead animals can form shallow sediments. Members of the family are recorded from every ocean, even around Antarctica, where they are represented primarily by the genus Osthimosia. Fossils of the family exist as old as from 235 million years ago, during the Triassic period.
Phylactolaemata is a class of the phylum Bryozoa whose members live only in freshwater environments. Like all bryozoans, they filter feed by means of an extensible "crown" of ciliated tentacles called a lophophore, and like nearly all bryozoans, they live in colonies, each of which consists of clones of the founding member. Unlike those of some marine bryozoans, phylactolaemate colonies consist of only one type of zooid, the feeding forms known as autozooids. These are supported by an unmineralized "exoskeleton" made of gelatinous material or protein, secreted by the zooids. The class contains only one extant order, Plumatellida.
Fenestrata is an extinct order of bryozoan, dating from the Upper Arenig. Most fenestrate bryozoans formed net-like colonies, often in funnel- or fan-shaped forms, with a single layer of zooids facing one direction. The colony shape served as a filter-feeding apparatus that water currents flowed through, with autozooecial apertures only on the side of the colony facing into the current. This colony structure was vulnerable to predators, so some fenestrate bryozoans produced skeletal superstructures, likely to strengthen or protect the colony, and others had protective spines surrounding their autozooecial apertures.
Conopeum seurati is a species of colonial bryozoan in the order Cheilostomatida. It is native to the northeastern Atlantic Ocean, the North Sea and the Mediterranean Sea. This species has been introduced to New Zealand and Florida.
Electra pilosa is a species of colonial bryozoan in the order Cheilostomatida. It is native to the northeastern and northwestern Atlantic Ocean and is also present in Australia and New Zealand.
Bugula neritina is a cryptic species complex of sessile marine animal in the genus Bugula. It has a practically cosmopolitan distribution, being found in temperate and tropical waters around the world, and it has become an invasive species in numerous locations. It is often found in hard substrates, such as rocks, shells, pillars and ship hulls, where it can form dense mats, contributing to biofouling. B. neritina is of biomedical interest because it harbors a bacterial symbiont that produces a group of bioactive compounds with potential applications in the treatment of numerous diseases.
Beania magellanica is a species of colonial bryozoan in the family Beaniidae. It has a cosmopolitan distribution, occurring in shallow waters in the Atlantic and Pacific Oceans and in Antarctica.
Electra posidoniae is a species of bryozoan in the family Electridae. It is endemic to the Mediterranean Sea, and is commonly known as the Neptune-grass bryozoan because it is exclusively found growing on seagrasses, usually on Neptune grass, but occasionally on eelgrass.
Callopora lineata is a species of colonial bryozoan in the family Calloporidae. It is found on rocky shores in the Atlantic Ocean and the Mediterranean Sea.
