Salinella: Monoblastozoa

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SALINELLA: Monoblastozoa

PHYSICAL CHARACTERISTICS

Monoblastozoa (MAHN-uh-blast-uh-zoh-uh) has only one species, Salinella salve. This animal was found in 1892 in a culture of material from salt beds in Argentina. Because Salinella has not been observed since its discovery, some scientists doubt that it exists. According to the scientist who wrote the only published record of Salinella, the body consists of a single cell layer and lacks tissues and organs.

Salinella differs from other simple animals because it lacks internal cells. In this regard, Salinella appears to be more closely related to one-celled living things than to animals. If researchers are able to find new specimens of Salinella and study them in detail, they may find that this species represents an intermediate stage between one-celled living things and animals.

The body of Salinella consists of about one hundred cells in a single cell layer enclosing a digestive cavity. The digestive cavity is open at both ends. The opening at one end functions as a mouth and that at the other end as an anus (AY-nuhs). There are bristles around the mouth and anus. The top surface of the animal is covered with a sparse collection of bristles. The bottom surface is somewhat flattened but is covered with tiny hairlike fibers. The cell walls facing the inner cavity also are heavily covered with these hairlike fibers.

GEOGRAPHIC RANGE

Salinella has been found only in Argentina.

HABITAT

Scientists do not know where Salinella lives under natural conditions.

DIET

Salinella eats by ingesting small particles into its internal cavity. Undigested particles are carried to the anus by the movement of hairlike fibers.

BEHAVIOR AND REPRODUCTION

Salinella moves by gliding on its hairlike fibers. It uses asexual (ay-SEK-shuh-wuhl) reproduction, or reproduction without the uniting of egg and sperm for the transfer of DNA from two parents, by splitting in half and growing into two full-sized individuals. However, another mode of reproduction was seen in culture. Salinella appeared to form a cyst by the coupling of two individuals. Although the details of the process are unknown, a one-celled individual that possibly came from the cyst was found in the culture. It is not known whether sexual (SEK-shuh-wuhl) reproduction, or reproduction by the uniting of egg and sperm and the transfer of DNA from two parents, takes place within the cyst.