Phylum: Rotifera

Description: Rotifers have a variety of body forms, and the body is usually divided into three parts: head, trunk and foot. Few rotifers reach 2-3mm but most less than 1mm.

Distribution: Mostly freshwater, but marine forms are known.

Locomotion: Most are motile and quite active swimmers or crawlers. Swimming is accomplished by beating the coronal cilia, forcing water along the body in a posterior direction, driving the animal forward.

Food gathering: Rotifers are ciliary suspension feeders, with developed coronal cilia and grinding mastax. They mainly feed on organic detritus or small organisms. The feeding current is produced by action of cilia and rotifers already have complete gut.

Gas exchange: There are no special organs for internal transport or exchange of gases. The small body size is an adaptation to facilitate transport and exchange of gases.

Reproduction: Sexual copulation occurs either by insertion of male copulatory organ into the cloacal area of the female or by hypodermic impregnation (inject sperm directly into pseudocoelom), where they somehow find their way to the female reproductive tract, where fertilization takes place. Asexually, females produce other females by parthenogenesis.

Interesting facts: Males are reduced in abundance, size and complexity, so if you find a rotifer, chances are it will be female! Rotifers are used as live feed for larval and juvenile fish in aquaculture.