The Microbiome of the Gastrointestinal Tract of a Range-Shifting Marine Herbivorous Fish

Abstract

Globally, marine species’ distributions are being modified due to rising ocean temperatures. Increasing evidence suggests a circum-global pattern of poleward extensions in the distributions of many tropical herbivorous species, including the ecologically important rabbitfish Siganus fuscescens. Adaptability of a species to such new environments may be heavily influenced by the composition of their gastrointestinal microbe fauna, which is fundamentally important to animal health. Siganus fuscescens thus provides an opportunity to assess the stability of gastrointestinal microbes under varying environmental conditions. The gastrointestinal microbial communities of S. fuscescens were characterized over 2,000 km of Australia’s western coast, from tropical to temperate waters, including near its current southern distributional limit. Sequencing of the 16S rRNA gene demonstrated that each population had a distinct hindgut microbial community, and yet, 20 OTUs occurred consistently in all samples. These OTUs were considered the ‘core microbiome’ and were highly abundant, composing between 31 and 54% of each population. Furthermore, levels of short chain fatty acids, an indicator of microbial fermentation activity, were similar among tropical and temperate locations. These data suggest that flexibility in the hindgut microbiome may play a role in enabling such herbivores to colonize new environments beyond their existing range.

Genetic selection for growth drives differences in intestinal microbiota composition and parasite disease resistance in gilthead sea bream

“…Differences in environment [46,52], season [48], age [36,50,51], sex [36], diet [18,42] or genetic background [53] can di cult comparisons among studies. In addition, technical differences, such as part of the intestine sampled [52,81], type of sample (adherent, transient or total microbiota) [82,83], DNA extraction techniques or analysis methodology [84,85], can also be a source of variation. However, even though we cannot make statistically sound comparisons among studies, it is safe to say that the typical microbial architecture of gilthead sea bream intestine was found in this study and the different genetic backgrounds of the families do not alter this core composition.…”

“…These studies were mainly focused on de ning baseline populations [35][36][37] or changes induced by diet [18,[38][39][40][41][42][43][44] or environmental conditions [45]. The microbiota is composed of very dynamic populations that are affected by different factors [18,36,[53][54][55]42,[46][47][48][49][50][51][52] such as diet, season, habitat, rearing density, age, sex and genetic background, the focus of the current study. There are not many studies de ning the effects of the host genome on intestinal microbiota composition in sh.…”

Core intestinal microbiomes of planktivorous and algae-farming coral reef damselfishes (Actinopterygii: Pomacentridae) reflects feeding behaviour

“…The facultative anaerobic bacterial classes Bacteroidia, Clostridia and Mollicutes were generally in higher abundance in the mid and posterior intestinal regions than the stomach. Differences in microbiomes along the intestinal tract have been recorded in the rabbit sh Siganus fuscescens [91], with midgut communities more representative of the environmental sources and hindguts hosting a microbiome more specialised to anaerobic conditions and fermentation [92]. The increase in Bacteroidia, Clostridia and Mollicutes along the intestines may be due some members of the class being mutualistic components of the sh gastrointestinal ora.…”

Influence of Seaweed Supplements on the Intestinal Bacteria in the Rabbitfish Siganus Fuscescens: Evidence for a Core Microbiome

“…In turn, many environmental and biological factors can affect the diversity and structure of microbiomes within the gastrointestinal (GI) tracts of sh [13]. Microbiomes in sh GI tracts are highly structured [14] with different parts housing very different microbial communities [15][16][17]. Fish ' rst feeding' is emerging as a critically important step in structuring their GI microbiomes throughout their lifespan [10].…”

“…We hypothesised that supplementation of diets with some of these seaweeds -particularly those with interesting bioactive compounds -at inclusion rates that are realistic in an industrial context, would lead to signi cant changes to the GI microbiomes in these sh. Recently, several other studies have characterised the GI microbiome of this species and revealed clear differences in microbial communities along the gut axis with more transient and food associated bacteria in the midgut compared to the hindgut, which harboured bacteria more likely to members of the host gut microbiome [15,17]. In addition to providing a useful baseline, these studies also provided us with an opportunity to compare hindgut microbiomes between distinct populations of the same sh species separated spatially (by thousands of kilometres) and temporally (11-20 months) and assess whether any particular experimental diets in uenced similarities between populations [15,17].…”