Cyclostomatida

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Cyclostomatida
Temporal range: Lower Ordovician–Recent
Tubulipora flabellaris (YPM IZ 088038).jpeg
Tubulipora flabellaris
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Bryozoa
Class: Stenolaemata
Order: Cyclostomatida
Subgroups

See List of Cyclostomatida families.

Cyclostomatida, or cyclostomata (also known as cyclostomes), are an ancient order of stenolaemate bryozoans which first appeared in the Lower Ordovician. [1] 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.

Contents

Taxonomy

Traditionally, cyclostomes have been divided into two groups according to the skeletal organization. In free-walled (or double-walled) cyclostomes, the exterior frontal walls of the zooids are uncalcified; autozooids have either a polygonal aperture bounded by vertical interior walls, or a subcircular aperture in species with kenozooids filling the spaces between the autozooids. By contrast, fixed-walled (or single-walled) cyclostomes have much of the exterior frontal wall calcified; autozooids normally have a subcircular aperture located at or close to the frontal wall.

Anatomy

Among cyclostome bryozoans, the calcitic skeleton is usually lamellar, consisting of tabular or lath-like crystallites stacked like tiles at a low angle to the wall surface. Cheilostome bryozoans may exhibit a similar ultrastructure but more commonly have fibrous skeletons consisting of needle-like or bladed crystallites oriented almost perpendicular to wall surfaces.

The skeletal parts of individual feeding zooids - autozooecia - are typically long, curved tubes with terminal apertures which are either circular or polygonal in shape. Colonies vary greatly in form according to species. Many cyclostomes have encrusting colonies, firmly cemented to hard substrates such as rocks and shells. These usually grow as subcircular sheets, spots or pimples, or systems of ramifying branches. Most erect cyclostomes develop bushy colonies with narrow, bifurcating branches. Feeding zooids are borne either evenly around the branch circumference or are absent from one face. New zooids are generally formed in distinct budding zones, for example, around the outer circumference of subcircular encrusting colonies, or at the tips of the branches in ramifying encrusting and bushy erect colonies.

All post-Palaeozoic cyclostomes have interzooidal connections via pores in the vertical walls separating adjacent zooids. In the fixed-walled forms, these narrow pores constitute the only coelomic connection, because the vertical walls contact and fuse with the calcified, exterior frontal walls. However, in free-walled forms, the frontal walls are uncalcified, and no contact is made with the vertical walls, creating a wider coelomic connection around the distal ends of the vertical walls.

Polymorphism of zooids is less conspicuous than in cheilostomes. However, almost all cyclostome species have enlarged zooids - gonozooids - for brooding larvae, and some species also possess non-feeding zooids - kenozooids - with space-filling and structural roles. Modern cyclostomes exhibit polyembryony: fertilized ova divide to produce multiple, genetically identical larvae which are housed in the spacious gonozooid before being released, swimming for a short period before settling and undergoing metamorphosis to establish new clonal colonies. Gonozooids are also very important in the taxonomy of cyclostomes, particularly in the largest suborder the Tubuliporina. Unfortunately, not all colonies develop gonozooids and infertile colonies may be difficult to identify even to family-level.

Differentiation

A colony is founded by a larva which settles and metamorphoses into a zooid, the ancestrula. In Cyclostomata it may be of two types: holoancestrula and artroancenstrula (in crisiids) The ancestrula gives rise to the second generation of zooids, which in turn gives rise to a third, and so on, in a process called astogeny. Generational variation among zooids is called astogenetic differentiation. In all species, there is a primary zone of differentiation, which is limited to the first few generations and followed by a much longer zone of repetition of nearly identical zooids. In some species, however, there is a secondary differentiated zone, which can take various forms. In species in which the colony branches, new branches normally arise by the division of a distal growing tip of an existing branch. An adventitious branch, in contrast, arises from the side of an existing branch, beginning with a short series of differentiated zooids, a secondary zone. Subsequent generations of zooids along the branch then typically return to the normal colony budding pattern.

Ecology

At the present day cyclostome bryozoans are exclusively marine and stenohaline, with most species living subtidally on the continental shelf. UK government-sponsored scientific reports in connection with renewable energy in 2014 uncovered the first recordings of Escharoides bishop and the non-native Fenestrulina delicia in British waters [2] Relative to cheilostomes, they appear to be less numerous and diverse in low latitudes - temperate and arctic environments host almost all of the large species. Although some cyclostomes encrust fleshy algae, the majority colonize hard substrates. Encrusting species can be especially numerous in cryptic habitats, for example, the concave interiors of bivalve shells. Cyclostomes are comparatively poor competitors for living space - they are routinely overgrown by larger animals such as sponges and ascidians, and also lose the majority of competitive encounters for space with cheilostome bryozoans. Tentacle size and number tend to be smaller in species of cyclostomes than cheilostomes. As a result, cyclostomes create less powerful feeding currents. Colony size is small in many encrusting species, suggesting a "weedy", opportunistic lifestyle. These small encrusting colonies probably live for less than a year, whereas some of the larger encrusting and erect colonies are undoubtedly perennials. However, scant data exists on growth rates in cyclostomes.

Little is known about predation specifically on cyclostomes although it is likely that they are preyed upon by the nudibranchs (sea-slugs), pycnogonids (sea-spiders), echinoids and fishes which consume other marine bryozoans. Little is known about the reproductive ecology of cyclostomes. Sperm are known to be released from the tips of the tentacles, as in other bryozoans, but fertilization of eggs has never been observed. It is unclear if each gonozooid broods single or multiple clutches of larvae, whether one or more clones of polyembryonous larvae are present per gonozooid, and what is the duration of the brooding period.

Related Research Articles

Bryozoa Phylum of colonial aquatic invertebrates called moss animals

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. One genus is solitary; all the rest are colonial.

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.

Cheilostomatida Order of moss animals

Cheilostomatida, also called Cheilostomata, is an order of Bryozoa in the class Gymnolaemata.

Membraniporidae Family of moss animals

Membraniporidae is a bryozoan family in the order Cheilostomatida. Membranipora form encrusting or erect colonies; they are unilaminar or bilaminar and weakly to well-calcified. Zooids have vertical and basal calcified walls, but virtually no frontal calcified wall: most of the frontal surface is occupied by frontal membrane. An intertentacular organ is also present. The larvae are not brooded. The ancestrula is generally twinned. Kenozooids may be present in a few species; modified zooids analogous to avicularia are rare.

<i>Membranipora membranacea</i> Species of moss animal

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 sea-mat or lacy crust bryozoan and is often abundantly found encrusting seaweeds, particularly kelps.

Malacostegina Order of moss animals

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).

Smittinidae Family of moss animals

The Smittinidae is a family within the bryozoan order Cheilostomatida. Colonies are encrusting on shells and rocks or upright bilaminar branches or sheets. The zooids generally have at least one adventitious avicularia on their frontal wall near the orifice. The frontal wall is usually covered with small pores and numerous larger pores along the margin. The ovicell, which broods the larvae internally, is double-layered with numerous pores in the outer layer, and sits quite prominently on the frontal wall of the next zooid.

Stomachetosellidae Family of moss animals

The Stomachetosellidae is a family within the bryozoan order Cheilostomatida. Colonies are encrusting on shells and rocks or upright bilaminar branches or sheets. The zooids generally have at least one adventitious avicularia on their frontal wall near the orifice. The frontal wall is usually covered with small pores and numerous larger pores along the margin. The ovicell, which broods the larvae internally, is double-layered with numerous pores in the outer layer, and sits quite prominently on the frontal wall of the next zooid.

Bitectiporidae Family of moss animals

The Bitectiporidae is a family within the bryozoan order Cheilostomatida. Colonies are encrusting on shells and rocks or upright bilaminar branches or sheets. The zooids generally have at least one adventitious avicularia on their frontal wall near the orifice. The frontal wall is usually covered with small pores and numerous larger pores along the margin. The ovicell, which broods the larvae internally, is double-layered with numerous pores in the outer layer, and sits quite prominently on the frontal wall of the next zooid.

Amathia vidovici is a species of colonial bryozoans with a tree-like structure. It is found in shallow waters over a wide geographical range, being found in both the Atlantic and Pacific Oceans and adjoining seas.

Amathia verticillata, commonly known as the spaghetti bryozoan, is a species of colonial bryozoans with a bush-like structure. It is found in shallow temperate and warm waters in the western Atlantic Ocean and the Caribbean Sea and has spread worldwide as a fouling organism. It is regarded as an invasive species in some countries.

<i>Conopeum seurati</i> Species of moss animal

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.

<i>Cryptosula pallasiana</i> Species of moss animal

Cryptosula pallasiana is a species of colonial bryozoan in the order Cheilostomatida. It is native to the Atlantic Ocean where it occurs in northwestern Europe and northern Africa, and the eastern seaboard of North America. It has been accidentally introduced to the western coast of North America and to other parts of the world.

<i>Watersipora subtorquata</i> Species of moss animal

Watersipora subtorquata, commonly known as the red-rust bryozoan, is a species of colonial bryozoan in the family Watersiporidae. It is unclear from where it originated but it is now present in many warm-water coastal regions throughout the world, and has become invasive on the west coast of North America and in Australia and New Zealand.

<i>Electra posidoniae</i> Species of bryozoan (marine moss animal)

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.

<i>Chorizopora brongniartii</i> Species of bryozoan (marine moss animal)

Chorizopora brongniartii is a species of bryozoan in the family Chorizoporidae. It is an encrusting bryozoan, the colonies forming spreading patches. It has a widespread distribution in tropical and temperate seas.

Bicellariella ciliata is a species of bryozoan belonging to the family Bugulidae. It is found in shallow water on both sides of the Atlantic Ocean, the Mediterranean Sea and the Indo-Pacific region.

Crisularia plumosa is a species of bryozoan belonging to the family Bugulidae, commonly known as the feather bryozoan. It is native to the Atlantic Ocean.

<i>Bugulina flabellata</i> Marine invertebrate

Bugulina flabellata is a species of bryozoan belonging to the family Bugulidae. It is found in shallow water in the northeastern Atlantic Ocean and the Mediterranean Sea.

Walkeria uva is a species of colonial bryozoan in the order Ctenostomatida. It occurs on either side of the Atlantic Ocean, in the Baltic Sea, in the Mediterranean Sea and in the Indo-Pacific region.

References

  1. ↑ "World Register of Marine Species". Archived from the original on 2011-08-26. Retrieved 10 October 2021.
  2. ↑ Wasson B & de Blauwe H (2014). Two new records of cheilostome Bryozoa from British waters. Marine Biodiversity Records 7: e123 DOI: https://doi.org/10.1017/S1755267214001213
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