ISOLATION OF ACHOLEPLASMA-LAIDLAWII FROM CENTRARCHIDS IN A CENTRAL FLORIDA LAKE

In 1991, the poor physical condition of largemouth bass Micropterus sa lmoides from Lake Harris, Florida. was associated with the decline of the lake's fishery. The swim bladders of emaciated bass had mild infla mmation and ecchymotic hemorrhages. A mycoplasma-like organism isolate d from swim bladders was initially believed to be the causative agent. The organism was later identified as Acholeplasma laidlawii by using a fluorescent antibody procedure and was demonstrated to be nonpathoge nic. Parenteral injection of the organism into healthy largemouth bass fingerlings produced no signs of disease or difference in growth rate compared with control fish during a 16-month period. Field studies re sulted in isolation of A. laidlawii from black crappies Pomoxis nigrom aculatus, bluegills Lepomis macrochirus, and redear sunfish L. microlo phus, but not from noncentrarchids in Lake Harris or from any fish spe cies in a control fishery (Lake Holly, Florida). The absence of organi sms in all emaciated bass, our inability to reproduce the disease, and isolation of the organism from seemingly healthy fish suggest this or ganism was not pathogenic.