Overview

Comprehensive Description

General Description

Colonies are often very dense and typically between 25-80 mm in length. They appear transparent, white, cream or yellowish in colour. In the creeping form, colonies closely adhere to the substrate, whereas erect colonies are raised off the substrate. The zooids form feathery or bushy clusters along a thick cylindrical stolon (up to 0.3 mm). The species is commonly found in the lower intertidal and shallow subtidal on algal or hard substrata throughout the NE Atlantic, Mediterranean and east coast USA. 

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Source: Bryozoa of the British Isles

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B. imbricata colonies have a creeping or somewhat upright and bushy growth pattern, with zooids forming clusters along a thick stolon which measures approximately 0.23 mm in diameter. Zooids are vase-shaped or subcylindrical. Individual functional zooids measure approximately 0.38 X 0.17 mm, while degenerated zooids measure 0.38 X 0.19 mm. Zooids and stolons of living colonies are studded with small, star-shaped black pigments. The polypide and lophophore are not pigmented. The lophophore measures approximately 0.246 in diameter, and bears 10 tentacles. Both the body wall and the lophophore are somewhat flexible to enhance scanning while feeding.
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Source: Indian River Lagoon Species Inventory

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Distribution

Loppens (1906) noemt deze soort tamelijk algemeen in zee en brak water, maar kon het onderscheid niet goed maken met Bowerbankia gracilis die hij toen B. imbricata var. caudata noemde, dit blijkt uit zijn opgave van het aantal tentakels. In het getijdengebied en in ondiepe kustwateren, op bruinwieren, op rotsen en houten constructies en op andere Bryozoa en Hydrozoa. Op beschutte plaatsen komen weelderige opgerichte bosjes voor. Vooral in troebel water van estuaria en op beschutte stranden. Komt voor in de Oosterschelde, in het kanaal van Goes en in het Kanaal door Zuid-Beveland (Faasse & De Blauwe, 2004). Kolonies van Bowerbankia gracilis (met 8 tentakels) en Bowerbankia imbricata (met 10 tentakels) groeien soms door elkaar heen.
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Virginian, south side of Cape Cod, and extending northward of the subprovince limit
  • North-West Atlantic Ocean species (NWARMS)
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Common throughout the NE Atlantic and Mediterranean. Range extends north to the Barents Sea and it has been reported from the Black Sea.

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In the western Atlantic, B. imbricata has been reported from cool water areas north of Florida; however, it is also known from warm water areas in the Mediterranean and the Red Sea. B. imbricata has been collected from the India River Lagoon at the Sebastian Inlet grass flats, and coastally at the Ft. Pierce breakwater. It is likely to have a wider distribution within the lagoon, but as yet, no documentation exists.
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Source: Indian River Lagoon Species Inventory

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Physical Description

Morphology

The colony can be creeping (densa) or erect and may vary between these two forms according to season; secondary erect zooids often develop in the late spring to summer. Zooids are arranged in dense, overlapping and irregular clusters on either one or all sides of the stolon to give the colony its feathery appearance. In the densa form, clusters are discrete and irregularly spaced with six to twenty zooids per cluster. In the erect form or on older parts of the colony there may be up to 50 zooids per cluster and often clusters merge to form a continuous series. The zooids are transparent with small star-shaped black pigment spots. The zooids are cylindrical and tend to be bulbous at the proximal end (closest to the stolon). They are unstalked and bud directly from the stolon, which is itself wider (up to 0.3 mm) than the width of a zooid. Zooid size ranges from 0.8-1.5 mm long and 0.25-0.27 mm wide. Zooids tend to have a square terminal office, but can be rounded when the polypide is regressing.

The stolon has regular septa and numerous secondary branches (dichotomous, cruciform or irregular) which may be raised from the substrate. On occasion the stolon develops basal rhizoids which serve as anchorage structures for the colony.

The lophophore has ten tentacles and an average diameter of 0.246 mm. This distinguishes B. imbricata from other British species within the genus which all have eight tentacles. The retracted lophophore and other muscular structure may be observed through the transparent wall of the zooids.

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Size

Functional zooids measure approximately 0.38 X 0.17 mm. Degenerated zooids measure 0.38 X 0.19 mm. Stolon diameter is approximately 0.23 mm in diameter. Lophophore diameter averages 0.246 mm.
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Source: Indian River Lagoon Species Inventory

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Diagnostic Description

description

Kolonie kruipend of opgericht, dichte vederige bosjes tot meer dan 5 cm lang. Uitloper cilindrisch en vaak breder dan de zoïden. In opgerichte kolonies vertakken de uitlopers dichotoom, in vastgehechte kolonies soms regelmatig kruisgewijs. Zoïden staan in groepjes op de uitlopers. Zoïden afgerond cilindrisch, proximaal wat gezwollen, distaal vierhoekig eindigend. Zoïden vrij groot: 0,8 tot 1,5 mm lang. Zoïden met een gedegenereerde polypide zijn korter en gezwollen met afgerond distaal einde. Polypide met 10 tentakels. Embryo’s diepgeel.
  • De Blauwe, H. (2009). Mosdiertjes van de Zuidelijke Bocht van de Noordzee. Determinatiewerk voor België en Nederland. Uitgave Vlaams Instituut voor de Zee, Oostende: 464pp.
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This species seems most nearly allied to the Setularia cedrina.Linn Syst Nat. Ed.13 p.1313.n.28 Pallaf. Zooph. p. 139, from which however it differs in the vesicles not surrounding the stem in any regular series and in their shape. Height, from one to three inches. Young shoots closely imbricated to their base, but older ones often naked: the smaller branches, which proceed from a main stem, have the vesicles placed bisariously, but their apex resume the imbricated form (Adams 1798)

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Look Alikes

B. imbricata in the Indian River Lagoon could be confused with B. pustulosa, a related bryozoan. In overall morphology, zooid clusters of B. imbricata have largely been described as non-helical; however, in IRL specimens, zooids of this species did form a partial helix around the stolon (Winston 1982). They thus resemble the overall morphology of B. pustulosa. These species can be differentiated base on the number of tentacles present: B. imbricata has 10 tentacles, while B. pustulosa has 8 tentacles.
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Source: Indian River Lagoon Species Inventory

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Ecology

Habitat

Commonly grows on algal substrata, but is also frequently found on the underside of boulders or rocks, or on concrete constructions. B. imbricata is known to range from the intertidal zone down to depth of ~ 55 m. In sheltered areas, large erect colonies may develop. This species is tolerant of fluctuations in salinity and is known to occur, often in abundance, in brackish water.

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Depth range based on 8 specimens in 1 taxon.
Water temperature and chemistry ranges based on 5 samples.

Environmental ranges
  Depth range (m): 0 - 150
  Temperature range (°C): 15.041 - 15.511
  Nitrate (umol/L): 0.267 - 0.943
  Salinity (PPS): 38.605 - 38.926
  Oxygen (ml/l): 5.228 - 5.576
  Phosphate (umol/l): 0.088 - 0.123
  Silicate (umol/l): 1.395 - 1.583

Graphical representation

Depth range (m): 0 - 150

Temperature range (°C): 15.041 - 15.511

Nitrate (umol/L): 0.267 - 0.943

Salinity (PPS): 38.605 - 38.926

Oxygen (ml/l): 5.228 - 5.576

Phosphate (umol/l): 0.088 - 0.123

Silicate (umol/l): 1.395 - 1.583
 
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Trophic Strategy

B. imbricata, like all bryozoans, is a suspension feeder. Each individual zooid in a colony has 10 ciliated tentacles that are extended to filter phytoplankton less than 0.045 mm in size (about 1/1800 of an inch) from the water column. Bullivant (1967; 1968) showed that the average individual zooid in a colony can clear 8.8 ml of water per day.Both the polypide and the body wall of B. imbricata are highly flexible. With the polypide retracted, the zooid is compressed against the substratum; with the polypide expanded, the zooid elongates and rises to a vertical or diagonal position with respect to the substratum. B. imbricata holds its tentacles straight while feeding. The polypides slowly scan the water column in a circular motion in search of appropriately sized particulates. Adjacent lophophores in this species are well separated. Polypides of neighboring zooids may occasionally touch each other while scanning, but they will quickly withdraw.Habitats: Typical habitat for ectoprocts in the Indian River Lagoon include seagrasses, drift algae, oyster reef, dock, pilings, breakwaters, and man-made debris (Winston 1995).
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Source: Indian River Lagoon Species Inventory

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Associations

Plant / epiphyte
Bowerbankia imbricata grows on Fucus serratus

Plant / epiphyte
Bowerbankia imbricata grows on Ascophyllum nodosum
Other: major host/prey

Plant / epiphyte
Bowerbankia imbricata grows on Seaweeds

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Frequently grows attached to intertidal and shallow subtidal seaweeds of the species Fucus vesiculosus, Fucus serratus and Ascophyllum nodosum. Common on Corralina officinalis. B imbricata may also grow epizooically on other Bryozoa such as Flustra, Vesicularia and Alcyonidium

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Seagrasses as well as floating macroalgae, provide support for bryozoan colonies. In turn, bryozoans provide habitat for many species of juvenile fishes and their invertebrate prey such as polychaete worms, amphipods and copepods (Winston 1995).Bryozoans are also found in association with other species that act as support structures: mangrove roots, oyster beds, mussels, etc. At Sebastian Inlet, B. imbricata is commonly found in association with algae, especially Solieria tenera, a common Rhodophyte. However, at other IRL and coastal locations, B. imbricata is found attached to the undersides of rocks and ledges, and in holes in worm-reef (Phragmatopoma spp.) mounds (Winston 1982).
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Source: Indian River Lagoon Species Inventory

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Population Biology

B. imbricata was collected from March to September in the IRL. Little information on its abundance exists.Locomotion: Sessile
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Source: Indian River Lagoon Species Inventory

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Life History and Behavior

Reproduction

Embryos are deep yellow in colour and are brooded within the tentacle sheath. Embryos have been observed from May to October in the British Isles, Iceland and the USA. Larvae are coronate.

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Growth

Colonies grow through asexual budding

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The embryology of B. imbricata is unknown.
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Source: Indian River Lagoon Species Inventory

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Relevance to Humans and Ecosystems

Benefits

Benefit in IRL: Bryozoans are ecologically important in the Indian River Lagoon due to their feeding method. As suspension feeders, they act as living filters in the marine environment. For example, Winston (1995) reported that bryozoan colonies located in 1 square meter of seagrass bed could potentially filter and recirculate an average of 48,000 gallons of seawater per day.
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