Starlet sea anemone (Nematostella vectensis)
Facts
| Kingdom | Animalia |
|---|---|
| Phylum | Cnidaria |
| Class | Anthozoa |
| Order | Actinaria |
| Family | Edwardsiidae |
| Genus | Nematostella (1) |
| Size |
Tentacle length: 15 mm (2) Tentacle diameter: 1 mm (2) |
Status
The starlet sea anemone is classified as Vulnerable (VU A1ce) on the IUCN Red List 2004 (1) and as Rare in the Red Data Book of Great Britain (3). It is also listed under Schedule 5 of the UK Wildlife and Countryside Act 1981 (3).
Description
This greyish-white anemone has a bulbous central section with a contracting column that enables it to burrow into soft mud. At the top of the column is an oral disk that contains the mouth and is surrounded by two rings of tentacles, totalling 16 to 20 (4).
Range
| You can view distribution information for this species at the National Biodiversity Network Gateway |  |
Biology
Sea anemones are largely sedentary, moving occasionally by creeping extremely slowly or by inflating slightly and allowing currents to move them. The starlet sea anemone pushes its lower half into the mud and contracts its column to burrow into the fine mud, securing itself against water currents. They feed by holding out their tentacles to catch passing food particles and transferring them to the mouth. The starlet sea anemone is not selective in its feeding habits, consuming mainly copepods and midge larvae (4).
It reproduces asexually year-round, dividing in half and re-growing each half. During summer and autumn, when resources are plentiful and the water quality is good, the starlet sea anemone will reproduce sexually, with simultaneous release of masses of gelatinous eggs by females and free-swimming sperm by males. There are several larval stages, ultimately metamorphosing into a tiny juvenile with just four tentacles after seven days. The juveniles become reproductively mature after 69 days (5).
Threats
Whilst populations are stable in the US and Canada, UK populations are small, patchy and at risk (4). British coastal habitats are being damaged by pollution, drainage and in-filling. Isolation of coastal pools can lead to isolation of populations and potential inbreeding depression. Coastal defence works are also responsible for the loss of some sea anemone habitat (3).
Conservation
Saline lagoons are a priority under the EC Habitats Directive, and the starlet sea anemone is protected under the Wildlife and Countryside Act. It has a Species Action Plan that proposes the maintenance of all viable populations at all known sites, as well as surveys to document the entire UK range of the species. It is also suggested that the starlet sea anemone be reintroduced to three sites during 2005 (3).
The UK Biodiversity Action Plan for this species is available at
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Further Information
For further information on this species see UK BAP website:
http://www.ukbap.org.uk/UKPlans.aspx?ID=471
Authentication
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Asexually: Of asexual reproduction: reproduction that does not involve the formation of sex cells (‘gametes'). In many species, asexual reproduction can occur by fission (or in plants ‘vegetative reproduction'); part of the organism breaks away and develops into a separate individual. Some animals, including vertebrates can develop from unfertilised eggs, this process - known as parthenogenesis - gives rise to offspring that are genetically identical to the parent.
Copepod: Large and diverse group of minute marine and freshwater crustaceans belonging to the subclass Copepoda. They usually have an elongated body and a forked tail.
Inbreeding depression: The reduction in viability, birth weight, and fertility that occurs in a population after one or more generations of inbreeding (interbreeding amongst close relatives).
Larvae: Stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
Larval: Of the stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
Metamorphosis: An abrupt physical change from the larval to the adult form.
References
- IUCN Red List (February, 2005)
http://www.redlist.org - Encyclopedia of Marine Life of Britain and Ireland (February, 2005)
http://www.habitas.org.uk/marinelife/index.html - UK BAP (February, 2005)
http://www.ukbap.org.uk/UKPlans.aspx?ID=471 - Animal Diversity Web (February, 2005)
http://animaldiversity.ummz.umich.edu/site/accounts/information/Nematostella_vectensis.html - Uhlinger, K.R. and Hand, C. (1992) The culture, sexual and asexual reproduction and growth of the sea anemone Nematostella vectensis. Biological Bulletin, 182 (2): 169 - 176.
