Silver spotted anemone

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Onglets

Description

Distinguishing features

The silver spotted anemone is a squat organism, with a columnar body topped by tentacles. At the base of the column is an adhesive pedal disc, which it uses to attach itself to a substrate. The body varies from translucent to greyish-green and occasionally reddish in colour.

Silver spotted anemones have anywhere from 48 to 120 elongated tentacles arranged in four or five rows; each tentacle has a white ring around the middle and a white spot at its base. The oral disc has six fine, opaque white stripes extending from the mouth to the tentacles. Small adhesive bumps of a lighter colour can be seen on the body column.

Reproduction

Silver spotted anemones reproduce in two different ways.

In the case of asexual reproduction, they can divide through lateral fission, budding or fragmentation.

In the case of sexual reproduction, fertilization occurs externally when male and female anemones release their sperm and eggs into the water. The fertilized eggs develop into planula larvae, which swim for a while before attaching to a substrate, where they grow into polyps and eventually mature into adult silver spotted anemones.

Diet

Silver spotted anemones are carnivores that eat smaller animals such as fish, crustaceans and other small invertebrates. They capture prey using their tentacles, which are packed with tiny, poisonous stinging cells (a good reason to avoid touching anemones with your bare hands). On contact with prey, these stinging cells shoot out, releasing a paralyzing toxin into the prey’s body. The tentacles then carry the prey to the mouth where it is swallowed. Digestion takes place inside the body and waste is excreted through the same opening. Hence, the mouth and anus are one and the same.

Predators

Silver spotted anemones are preyed upon by nudibranchs, a type of mollusc also called a sea slug. When threatened, silver spotted anemones burrow into the ground and retract their tentacles.

Habitat

Silver spotted anemones live in the North Atlantic Ocean, from the Arctic to the Gulf of Maine. In Québec, they are found in the estuary and Gulf of St. Lawrence, and in the Saguenay Fjord. Their habitat is the littoral zone where sufficient light penetrates to support abundant algae growth; hence, they can be spotted at depths of up to 30 m. They also live in the intertidal zone and tidal pools.

Ecology, behaviour

Huge colonies of silver spotted anemones live concealed in rocky crevices teeming with algae. They sometimes burrow into the sand up to their tentacles, or hide under rocks.

Pebbles and shell fragments are often stuck to its body column. Perhaps this serves as camouflage to protect against nudibranchs!?

Their presence in tidal pools shows just how resistant they are to fluctuations in temperature and salinity. On hot summer days, the sun warms these tidal pools, surface evaporation occurs, which in turn causes salinity to increase. When it rains, the tidal pools fill up with fresh water and salinity decreases. And then there’s the issue of winter freezing to contend with.

French name

Anémone à points blancs

Scientific name

Aulactinia stella

Phylum

Cnidaria (coelenterata)

Class

Anthozoa

Order

Actiniaria

Family

Actiniidae

Size

Height: 4 cm Diameter: 5 cm

Weight

Between 70 and 90 g

Life span

Unknown, but some anemones can live to be 90 years old.

Status

Abundant in its habitat. The IUCN (2016) has not evaluated the status of this species.

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