It is a tiny roundworm used as the first food for larger kinds of newly-hatched fish, such as larval common carp.

[3] The microworm is widely used in aquaculture as food for a variety of fish and crustacean species.

One of thirteen currently recognized species of Panagrellus, P. redivivus is about 50 μm in diameter and just over 1 mm in length, barely visible to the naked eye.

[5] Females reach maturity in about three days and deliver live young rather than eggs, as most nematodes produce.

The microworm has been used in genetic analysis studies, but not nearly as universally as its relative, Caenorhabditis elegans.