The presence, nature, and role of gut microflora in aquatic invertebrates: A synthesis

Abstract

This review of the literature concerns the gut microbiota of aquatic invertebrates and highlights the questions and processes that merit attention if an understanding of the role of gut microbes in the physiology of host invertebrates and nutrient dynamics of aquatic systems is to be gained. A substantial number of studies report the presence of gut microbes in aquatic invertebrates. Crustacea, Mollusca, and Echinodermata have received the most attention, with few studies involving other invertebrate groups. Different types of associations (e.g., ingestion, contribution of exoenzymes, incubation, parasitism) are reported to occur between gut microbes and aquatic invertebrates, and it is clear that gut bacterial communities cannot be treated as single functional entities, but that individual populations require examination. In addition, gut microbes may be either ingested transients or residents, the presence of which have different implications for the invertebrate. The most commonly reported genera of gut bacteria are Vibrio, Pseudomonas, Flavobacterium, Micrococcus, and Aeromonas. Quite a number of authors report the physiological properties of gut microbes (including enzyme activities and attributes such as nitrogen fixation), while less attention has been given to consideration of the colonization sites within the digestive tract, the density and turnover of gut bacteria, and the factors affecting the presence and nature of gut microflora. In addition, although a few studies have demonstrated a positive relationship between invertebrates and their gut microbiota, particularly with regard to nutrient gain by the invertebrate, very little conclusive evidence exists as to the role of bacteria in the physiology of host invertebrates. This has resulted from a lack of process-oriented studies. The findings for aquatic gut microbes are compared to those of gut bacteria associated with terrestrial invertebrates, where gut microbes contribute significantly to nutrient gain by the host in some environments.

Nitrous oxide emission by aquatic macrofauna

“…This overall pattern was also evident when the rate of nitrous oxide emission was expressed per milligram dry weight of the specimens (Table S1). Because FD-feeding species ingest greater numbers of microbes than predators do (10), this observation suggests microbial nitrogen conversions in the gut of the invertebrates as the source of nitrous oxide. Given anoxic conditions and the availability of easily degradable organic carbon in the gut of terrestrial and aquatic invertebrates (8,11), we hypothesized that nitrous oxide production was due to the activity of denitrifying bacteria in the animal gut.…”

Isolation of gut associated bacteria from mangrove crabs collected from different mangrove regions of Tamil Nadu, South east coast of India

“…The influence of the gut flora on the host is clearly of great interest in aquaculture, particularly where poor productivity and stock losses are widespread (Ravichandran and Kannupandi, 2005). Within aquatic and other marine animals, the colonization of the digestive system by microorganisms is influenced by a number of both host-related and non host-related factors (Harris, 1993). In the gut of another freshwater culture animal, the Chinese mitten crab, investigation illustrated that Proteobacteria and Bacteroidetes might be the dominant population .…”

Degradation of Plant-derived Carbohydrates in Wetlands

“…Differcording to the environmental condition. It was reported that intestinal flora of invertebrates was important to digest cellulose (Harris 1993). Acartia spinicauda could digest cellulose more efficiently with the flora suitable for the cellulose degradation in each habitat.…”