Species accounts

Giant green anemone

Anthopleura xanthogrammica

ORDER Actiniaria

FAMILY Actiniidae

TAXONOMY

Actinia xanthogrammica Brandt, 1835, Sitka, Alaska, United States.

OTHER COMMON NAMES Portuguese: Anémona-verde-gigante.

PHYSICAL CHARACTERISTICS

Large, flat oral disk up to 9.8 in (25 cm) diameter; column densely covered with hollow adhesive wartlike protuberances known as verrucae; tentacles and disk are emerald green, column is olive or brownish.

DISTRIBUTION

Western coast of North America from Alaska south to Baja California.

HABITAT

Low intertidal to shallow subtidal zones on exposed coastlines where it is subject to strong wave action; it often forms carpets of individuals in surge channels.

BEHAVIOR Nothing is known.

Reproduction Biology

FEEDING ECOLOGY AND DIET

Feeds on sea urchins, crabs, and mussels dislodged by floating debris. One study found that A. xanthogrammica benefits when urchins fleeing from predatory seastars fall into the anemone's tentacles. Mussels that are detached by wave action also are eaten. Also derives nutrition from symbiotic association with zooxanthellae and zoochlorellae.

REPRODUCTIVE BIOLOGY

Gonochoristic; reaches sexual maturity in 5-10 years; plank-totrophic larvae feed on algae. No asexual reproduction known.

CONSERVATION STATUS Not listed by IUCN.

SIGNIFICANCE TO HUMANS

Produces toxins known as anthopleurins that stimulate heart muscle and that were considered for medical use. ♦

Starlet sea anemone

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.

Dendronephthya Hemprichi

I Corallium rubrum I Dendronephthya hemprichi I Nematostella vectensis

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. ♦

Frilled anemone

Metridium senile

ORDER

Actiniaria

FAMILY Metridiidae

TAXONOMY

Priapus senilis Linnaeus, 1761, Baltic Sea.

OTHER COMMON NAMES

English: Plumose anemone (Britain); French: Anémone plumeuse; German: Seenelke; Norwegian: Sjonellik.

PHYSICAL CHARACTERISTICS

Tall, to 11.8 in (30 cm), with hundreds to thousands of small, slender tentacles on a lobed crown giving a feathery or plumelike appearance; column smooth with a distinct collar below tentacles; with numerous threadlike acontia arising from bases of septa that can be discharged through column pores known as cinclides; color varies from white to brownish-orange.

DISTRIBUTION

Circumpolar, boreo-Arctic; found as far south as New Jersey, United States, in the western Atlantic; Bay of Biscay in the eastern Atlantic; southern California, United States, in the eastern Pacific; and South Korea in the western Pacific. Introduced populations have been found in South Africa and the Adriatic Sea.

HABITAT

Attached to rock, shell, wood, and other hard substrates from the intertidal zone to 540 ft (166 m) deep; tolerates temperatures between 32-80°F (0-27°C).

BEHAVIOR

Adjusts the length of the body column according to current flow. Uses catch tentacles equipped with specialized nemato-cysts to attack other species in competition for space; tips of the catch tentacles remain attached to the victim.

FEEDING ECOLOGY AND DIET

Passive suspension feeder that traps prey in mucus-coated tentacles; these particles are carried to the mouth by ciliary action.

Human Body Cysts The Mouth

I Metridium senile I Heteractis magnifica

Prey items include copepods and polychaetes; and decapod, bivalve, and gastropod larvae.

REPRODUCTIVE BIOLOGY

Gonochoristic, broadcast spawner; planktotrophic larvae feed primarily on dinoflagellates, but also on copepods, chaetog-naths and other cnidarian larvae. Asexual reproduction by pedal laceration and fission.

CONSERVATION STATUS

Not listed by the IUCN or CITES.

SIGNIFICANCE TO HUMANS None known. ♦

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