SALPS: Thaliacea

PHYSICAL CHARACTERISTICS

Salps are tiny, drifting sea animals that have a clear cylindrical body with openings at each end. Between the openings is a basketlike structure covered by a sheet of mucus. The jelly-like body wall contains bands of muscle. Most salps are 0.2 to 8 inches (5 millimeters to 20 centimeters) long. Some colonies are many feet (meters) long.

GEOGRAPHIC RANGE

Salps live in warm and cool seas.

HABITAT

Most salps live near the surface, but some live in deeper water.

DIET

Salps eat plant plankton, or microscopic plants drifting in water.

BEHAVIOR AND REPRODUCTION

Salps swim through the water by the movement of hairlike fibers on their bodies or by contracting muscles in the body wall to draw water into their intake opening and pump it out through their water-exit opening. Although they swim, salps are at the mercy of ocean currents for their entire lives.

When salps feed, water flows in through the mouth opening, through the mucus sheet covering the internal basket, and out the exit hole. Plankton and other small particles are caught on the mucus, which is moved to the mouth and eaten.

In some species of salps fertilized (FUR-teh-lyzed) eggs, or those that have been united with sperm, develop and hatch inside the animals. In other species the fertilized eggs hatch into larvae (LAR-vee), which are animals in an early stage that change form before becoming adults. Still other species alternate asexual and sexual stages of reproduction. Asexual (ay-SEK-shuh-wuhl) means without and sexual means with the uniting of egg and sperm for the transfer of DNA from two parents. An asexual generation buds into a sexual generation, which produces the eggs and sperm that fuse to produce the next asexual generation. This method of alternating asexual and sexual stages allows salps to reproduce extremely rapidly.

SALPS AND PEOPLE

There can be so many salps in an area that they use up all the food needed by animals that are eaten by fishes upon which humans rely. The fishes disappear from the area, and the humans lose their food and their work.

Did You Know?

Chains of salps can be as long as a blue whale.

UNDERSEA FERTILIZER

Vast swarms of salps eat huge amounts of plant plankton and produce massive amounts of feces (FEE-seez). The sinking feces supply carbon, an element essential to life, to the deep ocean.

CONSERVATION STATUS

Salps are not considered threatened or endangered.

PYROSOME (Pyrosoma atlanticum): SPECIES ACCOUNTS

Physical characteristics: Individual pyrosomes (PYE-ruh-sohms) are about 0.3 inches (8 millimeters) long and are embedded in a thick, clear tube that forms the base for a colony as long as 24 inches (60 centimeters). Colonies are pink or yellowish pink. The mouth openings of the pyrosomes face out from the tube, and the water-exit holes point toward the inside of the colony. Pyrosomes produce light, which appears in waves of a brilliant glow along the colony.

Geographic range: Pyrosomes live all over the world in warm to cool seas. Because they are found throughout the world, no distribution map is provided.

Habitat: Pyrosomes live in surface waters but each day travel down more than 2,500 feet (750 meters) and then return to the surface.

Diet: Pyrosomes eat plant plankton.

Behavior and reproduction: Water enters individual pyrosomes through the mouth holes and empties into the colony's common tube. The water exits the tube through an opening at one end of the colony, propelling the colony through the water. The water-pumping system also is used for feeding. Water entering each pyrosome passes through a mucus sheet that filters particles of plant plankton into the digestive system. Pyrosomes form swarms that produce huge amounts of feces.

Pyrosomes make both eggs and sperm. In each pyrosome of a colony a single egg is fertilized and then grows to a four-animal stage that leaves the parent to start a new colony by budding, which is a method of asexual reproduction by which a bump develops on an animal, grows to full size, and then breaks off to live as a new individual. This fast method of alternating asexual and sexual reproduction results in giant swarms of pyrosome colonies.

Pyrosomes and people: The brilliant light displays given off by colonies of pyrosomes have bewildered and fascinated sailors for generations.

Conservation status: Pyrosomes are not considered threatened or endangered. ∎

SALP (Thalia democratica): SPECIES ACCOUNTS

Physical characteristics: Salps in the asexual stage are about 0.5 inches (12 millimeters) long and have a pair of tentacles at their hind end. Salps in the sexual stage are about 0.2 inches (6 millimeters) long. The body covering is thick and has five muscle bands.

Geographic range: Salps live all over the world in warm to cool seas. Because they are found throughout the world, no distribution map is provided.

Habitat: Salps usually live in surface waters.

Diet: Salps eat plant plankton.

Behavior and reproduction: Salps swim actively through the water by contracting their muscles. Salps are one of the fastest growing many-celled animals. Their body length more than doubles within an hour. Salps in the asexual stage produce a tail on which bud rows of the sexual stage stay connected to one another, forming chains several feet (meters) long. Fertilized salp eggs develop directly into the asexual stage. New generations of salps are produced in as fast as a few days, resulting in huge swarms covering hundreds of square miles (kilometers) of open ocean.

Salps and people: Salps have no known importance to people.

Conservation status: Salps are not considered threatened or endangered. ∎

FOR MORE INFORMATION

Books:

Brusca, Richard C., Gary J. Brusca, and Nancy Haver. Invertebrates. 2nd ed. Sunderland, MA: Sinauer, 2002.

Byatt, Andrew, Alastair Fothergill, and Martha Holmes. The Blue Planet. New York: DK, 2001.

Periodicals:

Erickson, Paul. "Where Sea Jellies Hover." Sea Frontiers (fall 1995): 22–25.

Kunzig, Robert. "At Home with the Jellies." Discover (September 1997): 64–71.

Vogel, Steven. "Second-Rate Squirts." Discover (August 1994): 71–76.

Web sites:

"Hermaphroditic Salps." Monmouth County Department of Health. http://www.shore.co.monmouth.nj.us/health/environmental/coastal/salps.htm (accessed on March 3, 2005).

"Salps: Big Squirts That Swim the Sea." California Diving News.http://www.saintbrendan.com/cdnoct00/marine10.html (accessed on March 3, 2005).