Gill histopathology of two species of buffalo fish from a contaminated Swamp

Two species of buffalo fish, smallmouth buffalo (Ictiobus bubalus) and bigmouth buffalo (Ictiobus cyprinellus), were collected from a contaminated (multiple metals and organic chemicals) Mississippi River Basin ecosystem, Devilʹs Swamp and a control site, Tunica Swamp, both near Baton Rouge, Louisiana, USA. The buffalo fish were examined for general health and histopathological effects. This research consists of an analysis of the prevalence of infectious and non-infectious disease from the contaminated vs the relatively uncontaminated control site. Tissue burdens were also determined by chemical analysis of buffalo fish muscle (fillets) samples. Both bigmouth buffalo (BMB) and smallmouth buffalo (SMB) from Devilʹs Swamp accumulated metals in muscle tissue and generally had a higher prevalence of gill lesions than fish collected from the control site, Tunica Swamp. SMB from Devilʹs Swamp had higher prevalences of lesions than BMB from Devilʹs Swamp. The primary types of infectious gill lesions observed in the buffalo fish were protozoan infections in the gill filament cartilage and gill lamellae. Chondrolysis, chondritis and bronchitis were associated with parasitic infection. Eosinophils were the predominant cell type involved with bronchitis and chondritis. The proliferative lesions observed were chondroplasia, chloride cell hyperplasia, mucus cell hyperplasia, and epithelial cell hyperplasia and fusion. Based on these preliminary findings, SMB appeared to be a potentially sensitive biomarker of exposure.