Early life skin microbial trajectory as a function of vertical and environmental transmission in Bornean foam-nesting frogs

Background The amphibian skin microbiome is an important mediator of host health and serves as a potential source of undiscovered scientifically significant compounds. However, the underlying modalities of how amphibian hosts obtain their initial skin-associated microbiome remains unclear. Here, we explore microbial transmission patterns in foam-nest breeding tree frogs from Southeast Asia (Genus: Polypedates) whose specialized breeding strategy allows for better delineation between vertically and environmentally derived microbes. To facilitate this, we analyzed samples associated with adult frog pairs taken after mating—including adults of each sex, their foam nests, environments, and tadpoles before and after environmental interaction—for the bacterial communities using DNA metabarcoding data (16S rRNA). Samples were collected from frogs in-situ in Brunei, Borneo, a previously unsampled region for amphibian-related microbial diversity. Results Adult frogs differed in skin bacterial communities among species, but tadpoles did not differ among species. Foam nests had varying bacterial community composition, most notably in the nests’ moist interior. Nest interior bacterial communities were discrete for each nest and overall displayed a narrower diversity compared to the nest exteriors. Tadpoles sampled directly from the foam nest displayed a bacterial composition less like the nest interior and more similar to that of the adults and nest exterior. After one week of pond water interaction the tadpole skin microbiome shifted towards the tadpole skin and pond water microbial communities being more tightly coupled than between tadpoles and the internal nest environment, but not to the extent that the skin microbiome mirrored the pond bacterial community. Conclusions Both vertical influence and environmental interaction play a role in shaping the tadpole cutaneous microbiome. Interestingly, the interior of the foam nest had a distinct bacterial community from the tadpoles suggesting a limited environmental effect on tadpole cutaneous bacterial selection at initial stages of life. The shift in the tadpole microbiome after environmental interaction indicates an interplay between underlying host and ecological mechanisms that drive community formation. This survey serves as a baseline for further research into the ecology of microbial transmission in aquatic animals.

First description of immature stages of Gastropini, Gastrops willistoni Cresson (Diptera: Ephydridae) preying on eggs in a foam nest of Leptodactylus knudseni Heyer (Anura: Leptodactylidae) in Central Amazon

The third instar larva and puparium of Gastrops willistoni Cresson (Diptera: Ephydridae), preying on eggs in a foam nest of Leptodactylus knudseni Heyer (Anura: Leptodactylidae), in a central Amazonian dryland forest (Brazil) are described for the first time. The fusiform larva has a short breathing tube, its anterior spiracles are fan-shaped and posterior spiracles with three spircular openings. Pupa is ovoid with a broad anterior margin and bifurcate posterior tip. The taxonomic relationship of the frog egg predators, Gastrops Williston and Typopsilopa Cresson, are discussed.

A frog that eats foam: predation on the nest of Polypedates sp. (Rhacophoridae) by Euphlyctis sp. (Dicroglossidae)

Amphibians in terms of their predatory behaviour depend mainly upon the ambush technique. Other than predation, amphibians have also been recorded to scavenge to acquire food resources. This is an opportunistic observation of predatory behaviour of an amphibian species (Euphlyctis sp.) on the foam nest of another species (Polypedates sp.). The behaviour was recorded during a routine field sampling, which is broadly written in the body of this write up. Such an observation to our knowledge has not been reported earlier. This observation will have implications in terms of amphibian ecology, behavioural studies, and also diversity studies in the range of foraging behaviour.

Foam nest construction and first report of agonistic behaviour in Pleurodema tucumanum (Anura: Leptodactylidae)

Reproductive strategies are the combination of physiological, morphological, and behavioural traits interacting to increase species reproductive success within a set of environmental conditions. While the reproductive strategies of Leiuperinae are known, few studies have been conducted regarding the reproductive behaviour that underlies them. The aim of this study was to document the structural characteristics of nesting microsites, to describe the process of foam nest construction, and to explore the presence of male agonistic and chorus behaviour in Pleurodema tucumanum. Nests were found close to the edge of a temporary pond and the mean temperature of the foam nests was always close to the mean temperature of the pond water. Our observations corroborate that the foam nest construction phases for P. tucumanum are similar to those described for other Leiuperinae, including dispersion and the beating of the foam, realized by male hind limbs. We also recorded the first scientific observations of male agonistic encounter in Pleurodema tucumanum.