Changes in the gut microbial community of the eastern newt (Notophthalmus viridescens) across its three distinct life stages

ABSTRACT Understanding the forces that shape vertebrate gut microbial community assembly and composition throughout development is a major focus of the microbiome field. Here, we utilize the complex life cycle of the eastern newt (Notophthalmus viridescens) as a natural wild model to compare the effects of host and environmental factors on gut microbiome development. We compared bacterial inventories of each of the newt's three physiologically distinct developmental stages to determine if each hosted a unique community, or if the two stages which share an aquatic habitat (larvae and adults) harbored more similar communities than those of the third stage, the terrestrial juvenile eft. Additionally, we assessed how the contribution of selective processes to gut microbial assembly changed through development. We found that structurally, each life stage harbored a distinct community, which may be attributable to host factors. Further, across development, we found that community assembly processes shifted from a predominance of neutral to selective forces. However, habitat may also be important in determining community membership and diversity due the uniqueness of eft communities based on these metrics. Our results are similar to those in other vertebrate taxa, suggesting that gut microbiota assembly processes may be conserved across diverse lineages.

Roadkill of Eastern Newts (Notophthalmus viridescens) in a protected area in Quebec

Roadkill is a threat to populations of many amphibian species, including Eastern Newt (Notophthalmus viridescens), which is widespread in eastern Canada and the northeastern United States. Little is known about the level of road mortality experienced by dispersing Eastern Newts in Canada. During extensive road surveys from May to October 2016 and 2017, 279 dead Eastern Newt efts were found on roads in Gatineau Park, Quebec. We found 107 dead Eastern Newts along a 425 m section of road in 2016, but only 30 dead individuals at the same location in 2017. Thus, although the amount of roadkill can vary annually, it may pose a significant threat to the species in some areas.

An Investigation into Tetrodotoxin (TTX) Levels Associated with the Red Dorsal Spots in Eastern Newt (Notophthalmus viridescens) Efts and Adults

We investigated the concentration of tetrodotoxin (TTX) in sections of skin containing and lacking red dorsal spots in both Eastern newt (Notophthalmus viridescens) efts and adults. Several other species, such as Pleurodeles waltl and Echinotriton andersoni, have granular glands concentrated in brightly pigmented regions on the dorsum, and thus we hypothesized that the red dorsal spots of Eastern newts may also possess higher levels of TTX than the surrounding skin. We found no difference between the concentrations of TTX in the red spots as compared to neighboring skin lacking these spots in either efts or adults. However, efts with more red dorsal spots had elevated TTX levels relative to efts with fewer spots.