Different fungal communities were detected across tissue regions and dietary regimens, indicating diet and tissue type affects fungal diversity in fish. Since P. nigrolineatus does not appear to gain energy directly from the digestion of wood , it is possible that enteric fungal communities are important for wood-only diets that lacks readily available carbon and nitrogen by supplying a digestible source of carbon or other micronutrients. This study is the first to examine the fungal community in a xylivorous fish and our results indicate the presence of a diverse fungal population that may play critical roles in cellulose degradation with potential nutritional benefits for the fish. Furthermore, these previously under-studied fungal species may have novel cellulolytic and lignin degrading capabilities that could have implications for biofuel generation. Understanding the role of the fungal communities in lignocellulose degradation and their interaction with GI tract bacteria in this process is the focus of future studies.