(02/27/1998) --- Bill Kroeger, an aquatic technician for the Bionetics Corporation, examines an oyster toadfish (Opsanus tau), like those that are part of the Neurolab payload on Space Shuttle Mission STS-90, in its holding tank in the Space Station Processing Facility. Each fish is between eight and 14 inches long. Toadfish live in an estuarine environment and are native to areas along the Northeast coast of the United States. Investigations during the Neurolab mission will focus on the effects of microgravity on the nervous system. This fish is an excellent model for looking at vestibular function because the architecture of its inner and middle ear are similar to those of mammals with respect to the vestibular apparatus. The crew of STS-90, slated for launch April 16 at 2:19 p.m. EDT, includes Commander Richard Searfoss, Pilot Scott Altman, Mission Specialists Richard Linnehan, Dafydd (Dave) Williams, M.D., and Kathryn (Kay) Hire, and Payload Specialists Jay Buckey, M.D., and James Pawelczyk, Ph.D