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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03643

    Fusarium oxysporum causes black gill disease in narrow-clawed crayfish Pontastacus leptodactylus

    Yiğit Taştan, İfakat Tülay Çağatay*

    *Corresponding author:

    ABSTRACT: Morphological and molecular analyses were done to determine the causative agent of black gill disease in narrow-clawed crayfish Pontastacus leptodactylus specimens collected from 6 different lakes (Taşkısığı, Beyşehir, Karaidemir, Karataş, Manyas, and Gölhisar) in Turkey. Fungi were isolated from the tissues of crayfish displaying putative black gill disease symptoms. Morphological evaluation was conducted, and the isolates were determined to be similar to Fusarium oxysporum. Subsequent molecular cloning of the ITS region of nrDNA by PCR confirmed the species identification in that DNA sequences from all 6 isolates were found to be 99% similar to those of F. oxysporum. An experimental infection trial was conducted in triplicate using 1 of the 6 isolates to fulfill Koch’s postulates. Three different groups were created: (1) wounded and contaminated (WC), (2) wounded and not contaminated (WNC), and (3) non-wounded and contaminated (NWC). On Day 3, one individual died in the WC group. Throughout the total 74 d monitoring period, no other mortality was recorded. On Day 14, all crayfish in the WC group showed blackened gills, whereas all crayfish in the NWC displayed partial blackening. In the WNC group, all crayfish displayed normal gill coloration. F. oxysporum was re-isolated in pure culture from WC and NWC groups, and thus the disease was confirmed. Our results suggest that F. oxysporum causes black gill disease in P. leptodactylus crayfish. Moreover, we demonstrated that F. oxysporum can also infect non-wounded crayfish.