BIOTIC Species Information for Nematostella vectensis
Researched byCharlotte Marshall & Angus Jackson Data supplied byMarLIN
Refereed byDr Simon Davy & Dr Martin Sheader
Scientific nameNematostella vectensis Common nameStarlet sea anemone
MCS CodeD761 Recent SynonymsNone

PhylumCnidaria Subphylum
SuperclassAnthozoa ClassHexacorallia
Subclass OrderActiniaria
SuborderNynantheae FamilyEdwardsiidae
GenusNematostella Speciesvectensis

Additional InformationNo text entered
Taxonomy References Manuel, 1988, Howson & Picton, 1997, Stephenson, 1935, Carlgren, 1949, Sheader et al., 1997,
General Biology
Growth formCylindrical
Feeding methodPassive suspension feeder
Temporary attachment
Environmental positionEpifaunal
Typical food typesHydrobia, Chironomid and Littorina juveniles. HabitAttached
BioturbatorNot relevant FlexibilityHigh (>45 degrees)
FragilityFragile SizeSmall(1-2cm)
HeightUp to 15 mm Growth RateInsufficient information
Adult dispersal potentialNo information found DependencyIndependent
General Biology Additional InformationAlthough the column rarely exceeds 15 mm in length, exceptionally large individuals may reach 60 mm long when fully extended. Furthermore, food availability probably limits size in this species.
Only females are found in the south coast populations of England (Sheader et al., 1997) and there seems to be only asexual reproduction in the UK (M. Sheader, pers. comm), therefore male size at maturity is not relevant. See reproduction for further information.

Abundance generally varies with geographic area and time of year. In Pennington Lagoon, Hampshire, a peak in abundance of up to 2700 individuals / m² is seen from September to October whilst in the Fleet, Dorset, the population peaks at around 1500 individuals / m², in November and December (Sheader et al., 1997). In September 1974, more than 12500 / m² were found in a Norfolk pool and an estimate of over 5 million individuals in a single pool has even been made (William, unpubl., cited in Williams, R.B., 1983). On the south coast of England, individual population numbers tend to peak in late summer, the considerable increase probably being the result of asexual reproduction (Sheader et al., 1997).

Biology References Manuel, 1988, Stephenson, 1935, Sheader et al., 1997, Hand & Uhlinger, 1992, Hand & Uhlinger, 1994, Anonymous, 1999(k), Williams, 1991, Williams, R.B., 1983,
Distribution and Habitat
Distribution in Britain & IrelandFound on north coast of Norfolk, the east coast of Suffolk, the Blackwater Estuary and Hamford Water in Essex, the Hampshire coast and on the south coast of Dorset.
Global distributionIn North America from Nova Scotia to Georgia on the Atlantic coast, from Florida to Louisiana in the Gulf of Mexico and from California to Washington on the Pacific coast. Also found on the South and East coast of England.
Biogeographic rangeNot researched Depth range<1 m to 2 m max
MigratoryNon-migratory / Resident   
Distribution Additional InformationThe populations of this species in Britain may either be:
1) relicts from a larger earlier distribution,
2) have arrived in Britain from North America by natural mean or
3) have been introduced by human agency.
Dispersal between lagoons may be via floating mats of Chaetomorpha sp. thus extending their dispersal potential. Biological zone is not relevant because this species lives in lagoons, generally not exposed to tidal action.
Posey & Hines (1991) suggested that in the Rhode River, America, the distribution outside lagoons may be limited through predation by shrimps.

Nematostella vectensis is often found using Ruppia sp. or Chaetomorpha sp. as substrata (Williams, 1991).

Although the species is usually found in water less than 1 m deep, a few live down to 2 m water depth (M. Sheader, pers. comm.).

In English populations of Nematostella vectensis, the salinity in the vast majority of sites ranges between 2-42 ppt with the greatest abundance in ponds with seasonally varying salinity between 16-32 ppt. (Sheader et al., 1997).

Distribution in Britain and Ireland
Nematostella vectensis is found on north coast of Norfolk, the east coast of Suffolk, the Blackwater Estuary and Hamford Water in Essex (Carol Reid, English Nature, pers. comm.), the Hampshire coast and on the south coast of Dorset. Nematostella vectensis was first described as a new species from brackish pools on the Isle of Wight.

Substratum preferencesMud
Physiographic preferencesIsolated saline water (Lagoon)
Biological zoneLagoonal
Wave exposureUltra Sheltered
Tidal stream strength/Water flowVery Weak (negligible)
SalinityVariable (18-40 psu)
Low (<18 psu)
Habitat Preferences Additional Information
Distribution References Manuel, 1988, Stephenson, 1935, Sheader et al., 1997, Hand & Uhlinger, 1992, Hand & Uhlinger, 1994, Posey & Hines, 1991,
Reproduction/Life History
Reproductive typeFission
Developmental mechanismSee additional information
Reproductive SeasonInsufficient information Reproductive LocationAs adult
Reproductive frequencyAnnual episodic Regeneration potential No
Life spanInsufficient information Age at reproductive maturity<1 year
Generation timeNot relevant FecundityUp to 2000 eggs
Egg/propagule size170-240 µm in diameter Fertilization typeInternal
Larval/Juvenile dispersal potentialInsufficient information Larval settlement periodInsufficient information
Duration of larval stage2-10 days   
Reproduction Preferences Additional InformationNematostella vectensis is known to reproduce both sexually and asexually. In the UK there seems to be only female asexual reproduction (M. Sheader, pers. comm.). males are absent from populations of Nematostella vectensis on the south coast of England suggesting that these populations produce all their offspring asexually (Sheader et al., 1997). Furthermore, it is likely that all the females are from one clone (M. Sheader, pers. comm.). Studies from American sexually reproducing populations have produced valuable information concerning gametes and larvae and some of this information is provided below. Unless otherwise stated, all the information in the asexual reproduction and sexual reproduction sections below are taken from Hand & Uhlinger (1995) and Hand & Uhlinger (1992) respectively.

Asexual reproduction

Transverse fission Asexual reproduction is achieved through transverse fission. Transverse fission is known in only four other sea anemones (Shick, 1991, cited in Hand & Uhlinger, 1994). In the laboratory, most fissions were found to take place at night and only in well expanded individuals. The fragment produced by fission is usually shorter than the oral piece and sometimes multiple fission occurs, producing two or three fragments. From the time of fission to the time of the first successful food capture, some fragments regenerated within three days. Although asexual division becomes common at about 10 weeks, it has been noted as early as seven weeks. Increased food intake leads to an increase in the frequency of fission and starvation can suppress the process (Hand & Uhlinger, 1995).
Budding Anemones with multiple oral-crowns are common in both natural and laboratory reared populations of Nematostella vectensis. Fission by such individuals produces normal single-crowned anemones. This is known as budding and is extremely rare in anemones.

Sexual reproduction

In the laboratory, Nematostella vectensis became sexually mature at 3-4 months old and at column lengths of between 1.5-3.5 cm. Gametes were found to be produced at all times of the year. Fritzenwanker & Technau (2002) found that, in the laboratory, a combination of feeding regime, dark-light cycle and temperature shift synergistically induced gametogenesis in adult polyps from the Rhode River in America. They summarized by saying that the combination of 4 days of feeding in the dark at 18 °C followed by illumination at 24 °C produced the highest number of eggs. The number of eggs is dependent on adult size. Large individuals reared in the laboratory can produce up to 2000 eggs. Eggs are 170-240 µm in diameter and are released embedded in a gelatinous mucoid mass. In the laboratory, spherical ciliated planula larvae emerge from the egg masses between 36-48 hours after fertilization. These larvae are active swimmers from the age of about 3 days old but spend periods of inactivity on the bottom. After a week they settle by which point they are between 250-500 µm long and have four tentacles. By the time they are two months old they are approaching sexual maturity, are 2-5 cm long and have up to 16 tentacles.
Reproduction References Stephenson, 1935, Sheader et al., 1997, Hand & Uhlinger, 1992, Fritzenwanker & Technau, 2002, Hand & Uhlinger, 1995,
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