Nematostella vectensis
ORDER
Actiniaria
FAMILY
Edwardsiidae
TAXONOMY
Nematostella vectensis Stephenson, 1935, Isle of Wight, England.
OTHER COMMON NAMES
English: Athenarian burrowing anemone; dwarf mud anemone.
PHYSICAL CHARACTERISTICS
Tiny worm-like anemone, rarely more than 0.6 in (15 mm) in length, with 9–18 relatively long (up to 0.4 in [10 mm]) tentacles arranged in two rings; column is smooth with a rounded base called a physa; largely translucent with white bands on the tentacles.
DISTRIBUTION
Atlantic and Pacific coasts of North America; southern and eastern coasts of England. It is thought to have been introduced to England from North America.
HABITAT
Intertidal to shallow subtidal zones; burrows in mud of estuaries and salt marshes. Tolerates a broad range of salinities (8.96–51.54 ppt) and temperatures (30 to 82°F [-1 to 28°C]).
BEHAVIOR
When disturbed, the anemone can completely withdraw into its burrow. It may also move completely out of the burrow and climb onto algae and aquatic vegetation.
FEEDING ECOLOGY AND DIET
Feeds mainly on snails; however, copepods, ostracods, insects, and nematodes also have been found in the coelenteron.
REPRODUCTIVE BIOLOGY
Gonochoristic, broadcast spawner; females release gelatinous egg masses that contain as few as five or as many as 2000 ova and hundreds to thousands of nematosomes, which are spherical, flagellated bodies containing nematocysts and are unique to this species. Planktotrophic larvae may settle in 7 days. Asexual reproduction may be more common than sexual reproduction. Several unisex populations have been discovered in North America, while no males have been observed in England. The starlet sea anemone is one of only five anemone species known to reproduce asexually by transverse fission and is the only anemone known to release gelatinous masses of eggs.
CONSERVATION STATUS
Although as many as five million individuals have been found in a single pond, this species is listed as vulnerable on the IUCN Red List. It is considered rare and endangered in the United Kingdom, largely because of its restricted habitat.
SIGNIFICANCE TO HUMANS
Used in laboratory studies of developmental genetics.
