The biology and ecology of lotic rotifers and gastrotrichs

1. The occurrence of Rotifera and Gastrotricha in the meiobenthos of lotic habitats is reviewed. About 150 rotifer and 30 gastrotrich species are repo rted in such habitats worldwide. 2. The two phyla share some morphological and biological features that migh t account for their presence In the meiofauna. Small-size, a soft and elong ate body, adhesive glands on the posterior body end, movement through cilia , relatively short life cycles, parthenogenesis and dormant stages are comm on characteristics. 3. Most species of both taxa inhabiting the superficial sediments in stream s and rivers may move downward into the hyporheos in response to both bioti c (predation) and abiotic (spates, erosion, desiccation) disturbances.