Investigation into the fungal diversity within different regions of the gastrointestinal tract of <em>Panaque nigrolineatus</em>, a wood-eating fish

Abstract

The Amazonian catfish, Panaque nigrolineatus have several physiological adaptions enabling the scraping and consumption of wood (xylivory), facilitating a detritivorous dietary strategy. Composed of lignocellulose, wood is a difficult substrate to degrade and as yet, it is unclear whether the fish obtains any direct nutritional benefits from wood ingestion and degradation. However, there are numerous systems that rely on microbial symbioses to provide energy and other nutritional benefits for host organisms via lignocellulose decomposition. While previous studies on the microbial community of P. nigrolineatus have focused upon the bacterial population, the role of fungi in lignocellulose degradation in the fish has not yet been examined. This study describes the detection of fungi within the fish gastrointestinal tract. Using next generation sequencing, the effects of diet on enteric fungal populations were examined in each gastrointestinal tract region. Fungal species were found to vary in different regions of the gastrointestinal tract as a function of diet. This study is the first to examine the fungal community in a xylivorous fish and results support the hypothesis that diet influences fungal distribution and diversity within the gastrointestinal tract of P. nigrolineatus.

Effect of Diet on the Enteric Microbiome of the Wood-Eating Catfish Panaque nigrolineatus

“…Distinct communities have been identified in the fore, mid, and hindguts of the fish despite any well-defined anatomical features (e.g., sphincters or cecum) demarcating these regions. A diverse and distinct fungal community also resides and is associated with cellulose degradation in the GI tract (Marden et al, 2017). Culture-based analyses and biochemical tests confirmed the presence of a lignocellulolytic and diazotrophic community (Watts et al, 2013; McDonald et al, 2015).…”

The Intestinal Mycobiota in Wild Zebrafish Comprises Mainly Dothideomycetes While Saccharomycetes Predominate in Their Laboratory-Reared Counterparts

“…The current knowledge on fungal diversity in the gastrointestinal tract of fish is still limited to a small number species. It has recently been reported that the fungal communities in royal panaque vary across its intestinal tract ( Marden et al, 2017 ). In particular, the Saccharomycetes genus Metschnikowia was only detected in the foregut, while sequences similar to Tremellomycetes and the Agaricomycete genus Stereaceae were exclusively found in the hindgut.…”

“…Hence, it might influence the gut fungal composition ( Simonis et al, 2008 ; Shearer et al, 2009 ) in fish, as seen in the case of wild-caught zebrafish. Importantly, members of this class were only recently identified in the gastrointestinal tract of fish ( Marden et al, 2017 ). Members of this class have only been recently identified in the gastrointestinal tract of one other fish species ( Marden et al, 2017 ) and therefore the specific role of these fungi in fish physiology and metabolisms are poorly understood.…”

“…Importantly, members of this class were only recently identified in the gastrointestinal tract of fish ( Marden et al, 2017 ). Members of this class have only been recently identified in the gastrointestinal tract of one other fish species ( Marden et al, 2017 ) and therefore the specific role of these fungi in fish physiology and metabolisms are poorly understood. However, these saprotrophic fungi are important plant pathogens and cause disease in a broad range of species, such as wheat, maize, and barley ( Ohm et al, 2012 ).…”

“…For example, the fat contents and type of protein (animal versus plant) in the feed significantly altered the composition of gut microbiota in zebrafish ( Wong et al, 2015 ) and Atlantic salmon, Salmo salar ( Gajardo et al, 2017 ), respectively. A recent paper by Marden et al (2017) showed that the intestinal fungal community of the royal panaque ( Panaque nigrolineatus ) varied across its gastrointestinal tract and was affected by the wood content in their diet. Furthermore, the natural bacterial diversity of wild-caught woodrats ( Neotoma albigula and N. stephensi ) will be lost when they are reared in captivity ( Kohl et al, 2014 ).…”