Virgularia mirabilis

Researched By	Jacqueline Hill & Emily Wilson	Data Supplied By	MarLIN
Refereed by	This information is not refereed.
Taxonomy
Scientific name	Virgularia mirabilis	Common name	Slender sea pen
MCS Code	D618	Recent Synonyms	None
Phylum	Cnidaria	Subphylum
Superclass	Anthozoa	Class	Octocorallia
Subclass		Order	Pennatulacea
Suborder		Family	Virgulariidae
Genus	Virgularia	Species	mirabilis
Subspecies
Additional Information	As 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 form	Pinnate	Feeding method	Passive suspension feeder
Mobility/Movement	Temporary attachment	Environmental position	Epifaunal, Infaunal
Typical food types	Plankton and organic particles.	Habit	Attached
Bioturbator	Not relevant	Flexibility	Low (10-45 degrees)
Fragility	Fragile	Size	Large(>50cm)
Height	Up to 60 cm	Growth Rate	Insufficient information
Adult dispersal potential	Very limited (<1m)	Dependency	Independent
Sociability	Gregarious
Toxic/Poisonous?	No
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 & Ireland	Found of all British and Irish coasts but less frequent in the south.
Global distribution	Western Europe and Mediterranean, occurs throughout the North Atlantic possibly as far as North America.
Biogeographic range	Not researched	Depth range	10-400m
Migratory	Non-migratory / Resident
Distribution Additional Information	No text entered
Substratum preferences	Coarse clean sand, Fine clean sand, Mud, Muddy sand, Sandy mud	Physiographic preferences	Offshore seabed, Sealoch, Enclosed coast / Embayment
Biological zone	Lower Infralittoral, Upper Circalittoral, Lower Circalittoral, Circalittoral Offshore	Wave exposure	Sheltered, Very Sheltered, Extremely Sheltered, Ultra Sheltered
Tidal stream strength/Water flow	Weak (<1 kn), Very Weak (negligible)	Salinity	Full (30-40 psu)
Habitat Additional Information
AMBI Group (Borja et al., 2000)	I
Distribution References	Hayward & Ryland, 1995b, Hayward et al., 1996, Manuel, 1988
Reproduction/Life History
Reproductive type	Gonochoristic	Developmental mechanism	Lecithotrophic
Reproductive Season	June to October	Reproductive Location	Water column
Reproductive frequency	Annual episodic	Regeneration potential	No
Life span	See additional information	Age at reproductive maturity	Insufficient information
Generation time	Insufficient information	Fecundity	Insufficient information
Egg/propagule size	Insufficient information	Fertilization type	External
Larvae/Juveniles Larval/Juvenile dispersal potential >10km Larval settlement period Insufficinet information Duration of larval stage 2-10 days
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