Placozoans: Placozoa

In aquariums and laboratories, placozoans have been observed to creep along by beating the hairlike structures on their When there is little food, placozoans move rapidly with frequent, random changes in shape. When there is much food, however, placozoans flatten themselves and move around less. (Illustration by Dan Erickson. Reproduced by permission.) bottom surface. They often lift themselves, forming a bag in which they digest their food. The feeding behavior of placozoans depends on the amount of available food. When there is little food, placozoans move rapidly with frequent, random changes in shape. When there is much food, however, placozoans flatten themselves and move around less.

Placozoans appear to use asexual (ay-SEK-shuh-wuhl) reproduction, or reproduction without the uniting of egg and sperm for the transfer of DNA from two parents, in three ways. In the first method, the body divides in half to make two new individuals. In the second method, small parts separate from the body and grow into new individuals. In the third method, buds develop on the parent, grow to full size, and then break off to live as new individuals. A few scientists have observed sexual reproduction in laboratory vessels containing two different clones of placozoans.