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Overview

Brief Summary

Hairy sea mat is a bryozoan which lives in a tiny box-shaped limy skeleton. As a colony, it forms a crust often broad or star-shaped, making it easy to identify. Every individual animal has 11 to 15 tentacles. They also have an average of 9 spines surrounding the soft front end. Unless it has broken off, there is always one larger spine, light brown in color, which is one of the characteristics of this bryozoan. It's this brownish spine that gives the colony a hairy appearance, and therefore its name. As a colony, hairy sea mat resembles a cluster of colorless seaweed. Colonies regularly wash ashore. Sometimes, the beaches are strewn with huge amounts of hairy sea mat. The entire coast of Holland was covered with hairy sea mat in November 1992.
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Comprehensive Description

General Description

Electra pilosa is an encrusting bryozoan species, common to the British intertidal zone and subtidal waters, down to approximately 50 m. The colonies form white circular, lobe- or star-shaped patches, several centimetres in diameter, often with a “hairy” appearance. E. pilosa is able to colonise shells, stones, the talli of red algae and the fronds of fucoid and kelp species. The shape and size of the colony is dependent on the substrata on which it is growing.

The species is widely distributed across the North Sea, the Wadden Sea, the north Atlantic and some Arctic and sub-Arctic regions (the White Sea and the Barents Sea). It is has been recorded from many British and European coasts, as well as from the Gulf on Maine. The species has also been recorded from New Zealand and Australia, where it is considered an introduced species.

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Description

 Electra pilosa may form star shaped or broad sheet colonies on the fronds of large algae (e.g. Laminaria and fucoids), small irregular patches on stones and shells, narrow tufts (independent of the substratum), or cylindrical incrustations around the fronds of small red algae (e.g. Mastocarpus stellatus). The zooids are ovate-oblong in shape, typically 0.5-0.6 by 0.25-0.35 mm. About half the front of the zooid is calcified but translucent, perforated by large pores, leaving an oval, membranous, frontal area distally, surrounded by 4-12 (often 9) spines. Spines vary in length but the median, proximal spine is always present and usually larger than the rest, although in some cases it may become well developed and longer than the zooid giving the colony a hairy appearance.Colonies of Electra pilosa growing on erect substrata (e.g. a hydroid) may continue to grow lengthways once they have used up the available substratum, forming narrow, bilaminar fronds of zooids side by side, once described as Electra verticillata. Colonies growing on small pieces of substratum (e.g. a shell) occasionally enclose the substratum forming an unattached spherical colony, 3-7cm in diameter (Hayward & Ryland, 1998).
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Distribution

Loppens (1906) en de collectie in het KBIN getuigen dat deze soort ook vroeger heel algemeen was. Groeit op zowat alles: stenen, schelpen, hydroïden, plastic, wieren, andere mosdiertjes. Beslist de algemeenste soort in de Zuidelijke bocht van de Noordzee (De Blauwe, 2009). Heel algemeen in België en Zeeland op strandhoofden en in jachthavens, ook uit de kust op stenen, schelpen en scheepswrakken (Zintzen, 2007), ook in binnenwater zoals de achterhaven van Zeebrugge en het Sas van Goes. Korstvormige kolonies zijn vaak aanwezig op aangespoeld materiaal zoals plastic en riemwiervoetjes. Het lijkt erop dat het aanspoelen van losse opgerichte koloniedelen steeds minder vaak optreedt.
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Arctic to Long Island Sound
  • North-West Atlantic Ocean species (NWARMS)
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Electra pilosa was first described by Linnaeus from the NE Atlantic, and it has subsequently been recorded from the NW Atlantic, the North Sea and the Wadden Sea. The species is known to occur in some Arctic and sub-Arctic regions (the White Sea and the Barents Sea) and extends south to the Mediterranean. The species has been recorded from New Zealand and Australia, where it is considered an introduced species.

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Physical Description

Morphology

Electra pilosa forms white encrusting colonies, which often have a hairy appearance. The colony form varies according to substrate: small, irregular patches are typical on stones and shells, while cylindrical encrustations form around the branching fronds of small red algae (e.g. Gigartina and Mastocarpus stellatus).  Broad or star-shaped sheets, where several series of zooids grow rapidly in opposing directions, may form on the smooth, homogenous fronds of the kelp, Laminaria, and the red algae, Rhodymenia. Narrow tufts, independent of the substrate, may form when colonies encrusting branched or cylindrical substrata grow rapidly away from the substrate. This growth form was previously referred to as a separate species (Electra verticillata) and is thought to arise when a colony encrusting a substratum of limited extend e.g. an erect hydroid, rapidly utilizes the entire available surface.

Zooids are oval or rounded-rectangles which narrow towards the proximal end (closest to the colony origin). In the encrusting forms, zooids are arranged in a parallel rows, with adjacent zooids slight offset from each other such that a regular series of quincunxes (five zooids in a square, with one zooid at each corner and one in the middle) are apparent. In the extended linear growth form (previously Electra verticillata), the zooids comprising adjacent rows lie side by side without alternation.

The size of zooids varies greatly, but is frequently between 0.5-0.6 by 0.25-0.35 mm. The calcified section of the frontal surface (the gymnocyst) occupies one half to one third of the total frontal surface. The calcification is light and the polypide (which has 11-15 tentacles) is typically visible through the frontal surface.  The non-calcified section of the frontal surface (the frontal membrane) and the underlying space (opesia) are oval in shape with a distinct rim. Between 4 and 12 (often 9) spines surround the frontal membrane and opesia. A large spine, light brown in colour, is located in the middle of the zooid, towards the proximal end and is always present. This spine is characteristic of the species, but it is frequently broken off and therefore not visible. This spine can become enlarged, reaching 2-3 times the length of the zooid, and is responsible for the “hairy” appearance of E. pilosa colonies.

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Size

The size of zooids varies greatly, but is frequently between 0.5-0.6 by 0.25-0.35 mm

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Diagnostic Description

Description

De kolonie vormt een korst. Bij gebrek aan substraat vormt de kolonie opgerichte bladen van rug-aan-rug groeiende zoïden. De dunne doorschijnende frontale verkalking neemt tot de helft van het frontale oppervlak in. Opvallend en kenmerkend zijn de grote ronde poriën. 4 tot 12 (vaak 9) stekels rond de ovale opesia. De proximale stekel is altijd aanwezig, doorgaans langer dan andere stekels en soms 2 tot 3 x zo lang als de zoïde. In dit geval ziet de kolonie er harig uit. Operculum transparant, met een dunne chitineuze verharding.
  • 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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Look Alikes

Several bryozoan form similar encrusting white colonies. In particular M.membranacea bears a superficial resemblance to Electra pilosa, having a similar colony form and colour and occupying similar habitats. M. membranacea can be distinguished by its rectangular zooids, compared to the rounded zooids of E.pilosa. Zooids of E.pilosa also have a characteristic large central spine.

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Ecology

Habitat

infralittoral and circalittoral of the Gulf and estuary
  • North-West Atlantic Ocean species (NWARMS)
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Depth range based on 633 specimens in 1 taxon.
Water temperature and chemistry ranges based on 185 samples.

Environmental ranges
  Depth range (m): -1.55 - 260
  Temperature range (°C): 3.446 - 17.140
  Nitrate (umol/L): 0.211 - 17.262
  Salinity (PPS): 6.180 - 38.444
  Oxygen (ml/l): 4.910 - 8.164
  Phosphate (umol/l): 0.051 - 1.316
  Silicate (umol/l): 1.247 - 17.288

Graphical representation

Depth range (m): -1.55 - 260

Temperature range (°C): 3.446 - 17.140

Nitrate (umol/L): 0.211 - 17.262

Salinity (PPS): 6.180 - 38.444

Oxygen (ml/l): 4.910 - 8.164

Phosphate (umol/l): 0.051 - 1.316

Silicate (umol/l): 1.247 - 17.288
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Electra pilosa is common on sheltered rocky shores down to depths of around 50 m. E. pilosa colonises almost any substratum including shells, the talli of red algae, various hydroid species, the fronds of fucoid species (Fucus serratus) and kelp species (Laminaria). Of the three British species of Electra, E.pilosa is the only species which doesn’t appear to prefer estuarine conditions, but nonetheless has been recorded from brackish environments e.g. the Tamar Estuary and the Baltic Sea.

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 Colonizes a variety of substrata in marine habitats from low water into the shallow sublittoral, particularly macroalgae such as Fucus serratus and laminarians.
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Trophic Strategy

Like all bryozoans, Electra pilosa is a suspension feeder. It feeds on small phytoplankton using ciliated tentacles of the lophophore.

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Associations

Plant / epiphyte
Electra pilosa grows on frond of Laminaria
Other: major host/prey

Plant / epiphyte
Electra pilosa grows on Seaweeds
Other: major host/prey

Plant / epiphyte
Electra pilosa grows on Fucus serratus
Other: major host/prey

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Electra pilosa is able colonise hydroids, the fronds of fucoid species (Fucus serratus), kelp species (Laminaria), red algae species (e.g. Gigartina, Mastocarpus stellatus and Rhodymenia) and other bryozoan species such as Flustra foliacea.  In Britain, except in the south west, E. pilosa is the main food source of the dorid nudibranch Adalaria prxima. The nudibranch larvae settle in early summer and only metamorphose when they are in contact with E. pilosa. Small pycnogonids such as Achelia longipes may also be found associated with E. pilosa colonies.

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Life History and Behavior

Behavior

Diet

small microorganisms, including diatoms and other unicellar algae
  • North-West Atlantic Ocean species (NWARMS)
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Life Cycle

The founding zooid (ancestrula) develops into a young colony, and later into an adult colony through asexual budding. Sexually produced embryos develop into larvae which are released into the plankton. Larvae settle after liberation and metamorphose into an ancestrula.

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Reproduction

The founding zooid (ancestrula) develops into a young colony, and later into an adult colony through asexual budding. Sexually produced embryos develop into larvae which are released into the plankton. Larvae settle after liberation and metamorphose into an ancestrula.

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Growth

Colonies grow through asexual budding of new zooids at the periphery.

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Molecular Biology and Genetics

Molecular Biology

Barcode data: Electra pilosa

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There is 1 barcode sequence available from BOLD and GenBank.

Below is the sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.

See the BOLD taxonomy browser for more complete information about this specimen.

Other sequences that do not yet meet barcode criteria may also be available.

ACTCTTTATTTTATGTTTGGCTTATGAGCCGGAATGGTGGGGAGAGGGCTT---AGTTTCTTAATTCGTGTGGAACTATCACAGCCAGGAAGGTTGTTAGGCAAT---GATCAACTTTATAATGTAATTGTCACTGCCCATGCTTTTGTAATAATTTTCTTTATAGTAATACCTGTAATAATTGGAGGCTTCGGAAATTGATTAATTCCCCTAATA---TTAGGGGTTCCGGATATAGGTTTTCCTCGGTTAAATAATATAAGGTTTTGGCTACTTCCTCCAGCTTTATTCCTATTACTACTAAGATCTATAGTAGAATCCGGAGCTGGTACAGGTTGAACTGTTTACCCCCCTCTGAGCCATTCTATTGCTCACAGGGGATCCTCAGTGGACTTG---GCCATTTTTAGACTTCATTTGGCTGGAGTTTCTTCTATTTTAGGAGCTATCAACTTTATGACTACTATTATTAATATGCGAAGTAACCTAATGACTTTAAGTCGAATTACTTTATTTGCATGATCTGTTTTTATTACAGCATTACTACTTCTTTTAAGTTTACCCGTGTTAGCAGGA---GCTATTACTATACTTTTAACAGATCGTAATTTAAATACTTCTTTTTTTGACCCGGCTGGAGGGGGTGATCCTATTCTTTACCAGCATTTA
-- end --

Download FASTA File

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Statistics of barcoding coverage: Electra pilosa

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 1
Specimens with Barcodes: 1
Species With Barcodes: 1
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