''Membranipora membranacea'' is a very widely distributed species of marine

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a l ...

n known from the

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

and

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

Oceans, usually in

temperate In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout t ...

zone environments. This bryozoan is a

colonial organism In biology, a colony is composed of two or more conspecific individuals living in close association with, or connected to, one another. This association is usually for mutual benefit such as stronger defense or the ability to attack bigger prey. ...

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

kelp Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms. Kelp grows in "underwat ...

s.Barnes, R.D. (1982). Coasts and Estuaries pp 114-115. Hodder & Staughton, London.

Distribution

Northeast Atlantic including the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and from ...

English Channel The English Channel, "The Sleeve"; nrf, la Maunche, "The Sleeve" (Cotentinais) or ( Jèrriais), (Guernésiais), "The Channel"; br, Mor Breizh, "Sea of Brittany"; cy, Môr Udd, "Lord's Sea"; kw, Mor Bretannek, "British Sea"; nl, Het Kana ...

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 north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

and

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

. Also native to the North Pacific coastline of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

from

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

.De Haas, W. and F. Knorr (1966). Marine Life pp 212-213. Burke, London.North, W.J. (1976). Underwater California pp 161. University of California Press. The species was first recorded on the Atlantic coastline of the U.S. in 1987 in the

Gulf of Maine The Gulf of Maine is a large gulf of the Atlantic Ocean on the east coast of North America. It is bounded by Cape Cod at the eastern tip of Massachusetts in the southwest and by Cape Sable Island at the southern tip of Nova Scotia in the northeast ...

.Lambert, W.J., P.S. Levin and J. Berman (1992). Changes in the structure of a New England (USA) kelp bed: the effects of an introduced species? Marine Ecology Progress Series 88:303-307. In Canada's Atlantic coast, it was first observed in

Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native Eng ...

during the early 1990s, and had reached

Newfoundland and Labrador Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

by 2002. It now commonly occurs along the Northwest Atlantic from

Long Island Sound Long Island Sound is a marine sound and tidal estuary of the Atlantic Ocean. It lies predominantly between the U.S. state of Connecticut to the north and Long Island in New York to the south. From west to east, the sound stretches from the Eas ...

to northern

Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

, including coastal

Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...

New Brunswick New Brunswick (french: Nouveau-Brunswick, , locally ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. It is the only province with both English and ...

, and

Prince Edward Island Prince Edward Island (PEI; ) is one of the thirteen Provinces and territories of Canada, provinces and territories of Canada. It is the smallest province in terms of land area and population, but the most densely populated. The island has seve ...

Morphology and physiology

''Membranipora membranacea'' colonies consist of individual organisms called

zooid 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 zooi ...

s, each with a chitinous exoskeleton which is secreted by the

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...

.Barnes, R.D. (1974). Invertebrate Zoology, 3rd ed. Saunders, Philadelphia, PA:695-712. This exoskeleton, hardened with calcium carbonate, is known as the zooecium, which not only serves to protect the internal structures of the organism, but also keeps the individual permanently attached to the substrate and neighboring zooids.Wilmoth, J.H. (1967). Biology of invertebrata. Prentice-Hall, Englewood Cliffs, NJ:381-384. Zooids within a colony can communicate via pores in their interconnecting walls, through which coelomic fluid can be exchanged. The internal, living portion of the zooid is known as the

polypide The polypide in bryozoans encompasses most of the organs and tissues of each individual zooid 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. ...

, whose walls are formed by the outer epidermis and inner

peritoneum The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mesoth ...

. The

lophophore The lophophore () is a characteristic feeding organ possessed by four major groups of animals: the Brachiopoda, Bryozoa, Hyolitha, and Phoronida, which collectively constitute the protostome group Lophophorata.De Burgh, M.E. and P.V. Fankboner (1978). A nutritional association between the bull kelp Nereocystis luetkeana and its epizooic bryozoan ''Membranipora membranacea''. Oikos 31(1):69-72. When not feeding, the lophophore retracts into the polypide through the tentacular sheath. The lophophore is controlled by the zooid's nervous system, which consists of a

ganglion A ganglion is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system there are both sympatheti ...

at the lophophore base. This ganglion is responsible for motor and sensory impulses to and from the lophophore, as well as the epithelium and digestive tract. The lophophore retractor is the muscle which controls the movement of the lophophore. This species does not have the ovicells or

avicularia ''Avicularia'' is a genus of the family Theraphosidae containing various species of arboreal tarantulas. The genus is native to Panama, the Caribbean and tropical South America. Each species in the genus has very distinguishable pink foot pads. ...

seen in most other members of this phylum.

Natural history

Life cycle

''Membranipora membranacea'' begins its life cycle as a plankton-feeding larva, triangular in shape. After several weeks, the larva attach to a substrate and undergo

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

.Harvell, C.D., H. Caswell and P. Simpson (1990). Density effects in a colonial monoculture: experimental studies with a marine bryozoan (''Membranipora membranacea'' L.). Oecologia 82(2):227-237. The larvae typically settle on their preferred substrates in May, and then the colony undergoes growth, stasis and

reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual or ...

, shrinkage, and

senescence Senescence () or biological aging is the gradual deterioration of functional characteristics in living organisms. The word ''senescence'' can refer to either cellular senescence or to senescence of the whole organism. Organismal senescence inv ...

around September, except in regions where temperature allows them to persist further into the winter. The presence of

conspecifics Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organis ...

may cause a colony to stop growing and begin stasis and reproduction early. The presence of predators also reduces growth of a colony.

Reproduction

Colonies of ''M. membranacea'' are protandrous

sequential hermaphrodites Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes its sex at some point in its life. In particular, ...

, where colonies transition from male to female reproductive stages, allowing fertilization to occur between colonies or within colonies. Fertilization takes places in the coelomic fluid of female colonies, and the eggs are released through an opening in the lophophore known as the coelomophore. Reproduction or growth of the colony can also take place by

budding Budding or blastogenesis is a type of asexual reproduction in which a new organism develops from an outgrowth or bud due to cell division at one particular site. For example, the small bulb-like projection coming out from the yeast cell is know ...

in a radial pattern from the first established zooid, the ancestrula.

Ecology

Habitat

''M. membranacea'' prefers shallow marine habitats between the mid

intertidal The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of Marine habitat, habitats with var ...

to the shallow

sublittoral The littoral zone or nearshore is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely inundated), to coastal area ...

. It may also be found in brackish water. It is typically found attached in colonies to seaweed, shells, or artificial substrates.

Feeding

''M. membranacea'' can eat food particles such as

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

flagellates A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and their ...

diatoms A diatom (New Latin, Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group com ...

, and other small, planktonic organisms by extracting them from the water with their lophophore. They can also supplement their diet with dissolved organic nutrients through the absorptive epidermis.

Predation

Nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to matc ...

s or sea slugs are the primary predators of ''M. membranacea''. To defend themselves against these predators, the ''M. membranacea'' produce chitinous spines which protrude from the corners of the zooid. These spines make it difficult for the nudibranchs to access the polypide of the zooid. However, the energy and resources needed to produce the spines may result in decreased growth and reproduction of the colony.Yoshioka, P.M. (1982). Predator induced polymorphism in the bryozoan ''Membranipora membranacea'' (L.). Journal of Experimental Marine Biology and Ecology 61(3):233-242.

Ecological significance

''M. membranacea'' has become an

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

in many places, and is believed to have a potentially negative impact on marine ecosystems by limiting the ability of seaweeds to reproduce, specifically by interfering with spore release from the kelp blade. The colonies of this bryozoan are also known to interrupt nutrient uptake by seaweed.Saier, B. and A. S. Chapman (2004). Crusts of the alien bryozoan ''Membranipora membranacea'' can negatively impact spore output from native kelps (''Laminaria longicruris''). Botanica Marina 47(4): 265-271. ''M. membranacea'' also decreases density and size of kelp plants within kelp beds by increasing tissue loss and blade breakage.Hepburn, C.D., C.L. Hurd and R.D. Frew (2006). Colony structure and seasonal differences in light and nitrogen modify the impact of sessile epifauna on the giant kelp ''Macrocystis pyrifera'' (L.) C Agardh. Hydrobiologia 560:373-384. Additionally, ''M. membranacea'' also affects photosynthetic processes in kelp, since their encrustations may result in reduced concentrations of the primary and accessory pigments in the kelp blade tissue.

References

{{Taxonbar, from=Q2906141 Cheilostomatida Fauna of the Atlantic Ocean Fauna of the Pacific Ocean Taxa named by Carl Linnaeus Animals described in 1767