The Histopathological Effects of Ciguatera Toxins on Fish and Mammalian Tissues

This study was initiated to examine the effects of ciguatera toxins on fish tissues and to attempt to locate the binding site of ciguatera toxin in the mammalian brain. Previous studies indicated that ciguatera toxins produced histopathological effects in mice (Coombe et al., 1987; Hassan et al., 1991; Terao et al., 1988; Terao et al., 1989a). Capra et al. (1988) examined the effects of ciguatera toxin on fish tissues, intestine and gill. The tissues examined in this study were the liver, intestine and gill. The initial toxin, supplied by Flowers (1989) produced histopathological changes in the majority of tissues examined. Changes included disruption to the gill epithelium, disruption to the epithelial layer in the intestine and necrosis and glycogen loss in the liver. Later experiments utilised toxins extracted by the author and those supplied by the Professors Miller and Tindall from the Southern Illinois University. These toxins produced no changes in the gill and very few in the intestine. Changes in the liver included necrosis and complete loss of glycogen. Three species of fish used were, Pomacentrus wardi, Chromis nitida and Dascyllus aruanus. The latter two species are planktivores, and P. wardi is a browser. C. nitida was significantly more susceptible to the toxin then P. wardi, according to the recorded death times. The attempt to locate the binding site of ciguatera toxins in the mouse brain was unsuccessful. Ciguatera toxin has been shown to have a nonspecific affinity for IgG (Emerson et al., 1983). An immunocytochemical method was used to try and locate the ciguatera binding sites. A labelled avidin-biotin method was used (Guesdon et al., 1979). Two methods of preservation were attempted, formalin fixed and frozen sections. Methods of exposing the tissue to the toxin attempted were, pre- and post-preservation for frozen sections and prepreservation for the parafin sections