Larvaceans: Appendicularia

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LARVACEANS: Appendicularia

NO COMMON NAME (Oikopleura labradoriensis): SPECIES ACCOUNT

PHYSICAL CHARACTERISTICS

Larvaceans (lar-VAY-shuns) are small, clear sea animals that make a complex net, or house, of mucus. They live their entire lives as tadpoles, or larvae, even when they are adults and ready to reproduce. Larvae (LAR-vee) are animals in an early stage that change form before becoming adults. The body of larvaceans is made up of a trunk containing most of the internal organs and of a tail with a notochord running down the middle. A notochord (NOH-tuh-koord) is a flexible rod of cells that supports the body of some simple animals. The trunk secretes the mucus house, which encloses the entire animal or only the tail, depending on the species. The body and house are jellylike. The body of larvaceans is 0.04 to 1 inches (1 to 25 millimeters) long. The house is 0.2 inches to 7 feet (4 millimeters to 2 meters) across.

Larvaceans have an amazing filtering mechanism. The wall of the house contains two filters, and a filter in the trunk is connected to the animal's mouth. The filters are made of strands of mucus that allow only the smallest food particles, those less than 0.0004 inches (1 micrometer) in diameter, into the tube leading to the mouth.

GEOGRAPHIC RANGE

Larvaceans live in ocean currents all over the world.

HABITAT

Larvaceans live in open ocean and near the shore in surface waters and in middle depths.

DIET

Larvaceans eat plant plankton that they filter from the water that passes through them. Plankton is microscopic plants and animals drifting in water.

BEHAVIOR AND REPRODUCTION

Larvaceans move their tail inside their house to make a current that filters food particles and moves the house through the water. If the filters become clogged or something bumps the house, the larvacean leaves the house through a trap door. The beginnings of a new house lie on the trunk of the animal's body, and the larvacean inflates the new house and flips inside.

Some larvaceans have glowing grains in their house wall. Some scientists believe that predators eat an empty house that is flashing light while the larvacean swims away to make another house. Surface waters of some bays and harbors sometimes glow brilliantly because of the presence of large groups of larvaceans.

Larvaceans make both eggs and sperm, which are released directly into the water. The sperm are released first, and then the eggs burst out of the body wall, a process that results in the death of the animal. Fertilization (FUR-teh-lih-ZAY-shun), or the joining of egg and sperm to start development, and development take place in the open water. These animals reproduce rapidly. If there is a great deal of plant plankton in an area, huge swarms of larvaceans can form, sometimes in a matter of a few days.

LARVACEANS AND PEOPLE

Larvaceans can clear an area of plant plankton, eating the food needed by sea animals that fishes eat. The fishes leave the area, and people lose their food and their jobs.

CONSERVATION STATUS

Larvaceans are not considered threatened or endangered.

NO COMMON NAME (Oikopleura labradoriensis): SPECIES ACCOUNT

Physical characteristics: Oikopleura labradoriensis larvaceans are about 0.2 inches (6 millimeters) long. The trunk makes up about one-third of the animal's length and the tail about two-thirds of the length. The house is approximately 0.4 inch (9 millimeters) across.

Geographic range: Oikopleura labradoriensis (abbreviated to O. labradoriensis) larvaceans live all over the world. Because they are found throughout the world, no distribution map is provided.

Habitat: O. labradoriensis larvaceans live in cool to cold waters near the surface. They live in the open sea as well as closer to shore.

Diet: O. labradoriensis larvaceans eat only the smallest of plant particles, those less than 0.0004 inches (1 micrometer) in diameter.

Behavior and reproduction: O. labradoriensis larvaceans have glowing grains in the walls of their houses that may help confuse predators, which eat empty houses rather than animals that have abandoned the houses. O. labradoriensis larvaceans make both eggs and sperm. They release sperm first then release eggs by rupturing their body wall, a process that results in the death of the animal. Fertilization and development take place in the open water.

Oikopleura labradoriensis and people: O. labradoriensis larvaceans have no known importance to people.

Conservation status: O. labradoriensis larvaceans are not considered threatened or endangered. ∎