No common name

Saccoglossus kowalevskii

ORDER

No order designation

FAMILY Harrimaniidae

TAXONOMY

Saccoglossus kowalevskii Agassiz 1873.

Saccoglossus KowalevskiiSaccoglossus

H Rabdopleura normani H Saccoglossus kowalevskii H Saxipendium coronatum

OTHER COMMON NAMES None known.

PHYSICAL CHARACTERISTICS

Adults are wormlike animals with a pointed proboscis, followed by a short collar and a long trunk. They range 4.0-5.9 in (10-15 cm) long. The proboscis is generally whitish yellow or light pink, the collar is orange, and the trunk can be pink to orange-brown.

DISTRIBUTION

North Atlantic, off the coast of Europe and the United States from Massachusetts to South Carolina.

HABITAT

Intertidal zones, typically sandy or silty areas. BEHAVIOR

When threatened, an individual of this and other species of the genus Saccoglossus will swell its proboscis to serve as a holdfast in its burrow while drawing in the rest of its body. A mostly subterranean animal, Saccoglossus is most often seen with its proboscis poking out from its sea-bottom burrow. Its reproductive activity appears to be affected by seawater temperature, with spawning stimulated when temperatures shift from 80.6 to 71.6°F (27 to 22°C).

FEEDING ECOLOGY AND DIET

Saccoglossus kowalevskii gathers food from the uppermost layer of sediment in its immediate surroundings. Food items may include bacteria, microalgae and diatoms that live in the sediment, and dissolved or particulate organic material in the water. Each day, individuals of this species may take in as much as 300 times their body weight in sediment. Research in dicates that this acorn worm is induced to feed by the presence of microalgae and diatom populations as well as other food sources that are high in chlorophyll.

REPRODUCTIVE BIOLOGY

Fertilization is external. Females release mucus-bound eggs into the water, males respond by releasing sperm, and fertilization occurs in the sea water. The eggs, which average about 0.02 in (0.4 mm) in diameter, hatch in seven days into wormlike young that begin a sessile lifestyle immediately. Saccoglossus kowalevskii is a direct-developing species that hatches from eggs into the adult form without the planktonic larval stage common to many other hemichordates.

CONSERVATION STATUS

Not listed by IUCN.

SIGNIFICANCE TO HUMANS None known. ♦

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