BIOTIC Species Information for Virgularia mirabilis
Researched byJacqueline Hill & Emily Wilson Data supplied byMarLIN
Refereed byThis information is not refereed.
Taxonomy
Scientific nameVirgularia mirabilis Common nameSlender sea pen
MCS CodeD618 Recent SynonymsNone
PhylumCnidaria Subphylum
SuperclassAnthozoa ClassOctocorallia
Subclass OrderPennatulacea
Suborder FamilyVirgulariidae
GenusVirgularia Speciesmirabilis
Subspecies   
Additional InformationAs is the case for all octocorals, sea pens are actually colonies of polyps. What distinguishes sea pens is polyp dimorphism. One polyp grows very large and loses its tentacles, forming the central axis. The central axial polyp is divided into two regions: a lower peduncle or stalk, which never bears secondary polyps and functions as a burrowing organ, and an upper stem or rachis, from which numerous secondary polyps bud. Some of these secondary polyps, called autozooids, are typical feeding polyps. Others, the larger and fewer siphonozooids, serve as intakes for water, which circulates within the colony and helps keep it upright. The axial polyp contains a slender, unbranched, calcareous skeletal rod (axis). In this species the axis is round in section and often protrudes from the top of the colony.

Virgularia mirabilis live upright with their stalks thrust into a mucus-lined burrow into which the whole colony can withdraw when disturbed.
Taxonomy References Howson & Picton, 1997, Hayward & Ryland, 1995b, Hayward et al., 1996, Manuel, 1988,
General Biology
Growth formPinnate
 Feeding methodPassive suspension feeder
Mobility/MovementTemporary attachment
 Environmental positionEpifaunal
Infaunal
Typical food typesPlankton and organic particles. HabitAttached
BioturbatorNot relevant FlexibilityLow (10-45 degrees)
FragilityFragile SizeLarge(>50cm)
HeightUp to 60 cm Growth RateInsufficient information
Adult dispersal potentialVery limited (<1m) DependencyIndependent
SociabilityGregarious
Toxic/Poisonous?No
General Biology Additional Information
  • Typical abundance: usually found at densities of ca >5 individuals / m².
  • Flexibility: Eno et al., (1996) found that sea pens bent away from lobster pots dropping on top of them in a passive response to the pressure wave travelling ahead of the dropping pot.
  • Feeding: Virgularia mirabilis does possess nematocysts and so the species is probably capable of both passive predation on small zooplanktonic organisms and suspension feeding of suspended material (Hoare & Wilson, 1977). Laboratory experiments have shown that the polyps of Virgularia mirabilis are capable of capturing (by trapping with nematocysts) and ingesting small active organisms such as Artemia nauplii. However, Virgularia mirabilis is a passive carnivore, waiting for small animals that stumble, or are swept, into the tentacles of the sea pen. Suspension feeding occurs when very small particles become trapped in mucus on the tentacles and are then transported to the mouth by cilia. Suspension feeding is evidenced by the orientation of many colonies at right angles to the water current.
  • Evidence of predation on Virgularia mirabilis seems limited to a report by Marshall & Marshall (1882 in Hoare & Wilson, 1977) that the species was found in the stomach of haddock. Observations by Hoare & Wilson (1977) suggest however, that predation pressure on this species is low.
Biology References Hoare & Wilson, 1977,
Distribution and Habitat
Distribution in Britain & IrelandFound of all British and Irish coasts but less frequent in the south.
Global distributionWestern Europe and Mediterranean, occurs throughout the North Atlantic possibly as far as North America.
Biogeographic rangeNot researched Depth range10-400m
MigratoryNon-migratory / Resident   
Distribution Additional InformationNo text entered
Substratum preferencesCoarse clean sand
Fine clean sand
Mud
Muddy sand
Sandy mud
 Physiographic preferencesOffshore seabed
Sealoch
Enclosed coast / Embayment
Biological zoneLower Infralittoral
Upper Circalittoral
Lower Circalittoral
Circalittoral Offshore
 Wave exposureSheltered
Very Sheltered
Extremely Sheltered
Ultra Sheltered
Tidal stream strength/Water flowWeak (<1 kn)
Very Weak (negligible)
 SalinityFull (30-40 psu)
Habitat Preferences Additional Information
Distribution References Hayward & Ryland, 1995b, Hayward et al., 1996, Manuel, 1988,
Reproduction/Life History
Reproductive typeGonochoristic
 Developmental mechanismLecithotrophic
Reproductive SeasonJune to October Reproductive LocationWater column
Reproductive frequencyAnnual episodic Regeneration potential No
Life spanSee additional information Age at reproductive maturityInsufficient information
Generation timeInsufficient information FecundityInsufficient information
Egg/propagule sizeInsufficient information Fertilization typeExternal
Larvae/Juveniles
Larval/Juvenile dispersal potential>10km Larval settlement periodInsufficinet information
Duration of larval stage2-10 days   
Reproduction Preferences Additional Information
  • The sexes are separate in sea pens. Each colony of polyps is either male or female.
  • There is very little information on population structure or life cycles in any of the British sea pens, but the limited data available from other species would lead one to predict a similar pattern of patchy recruitment, slow growth and long life-span (Hughes, 1998(b)).
  • In other species of sea pen the eggs and sperm are released from the polyps and fertilization takes place externally. The sea pen Ptilosarcus guerneyi spawns in late March, with up to 200,000 eggs produced per female colony. Chia & Crawford, (1973) found free-swimming larvae of this species did not feed, suggesting a lecithotrophic larvae, and settled within seven days if a suitable substratum was encountered. Birkeland, (1974) found the life span of Ptilosarcus guerneyi to be up to 15 years, taking 5 or 6 years to reach sexual maturity.
Reproduction References Hughes, 1998(b), Birkeland, 1974, Chia & Crawford, 1973,
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