We evaluated the use of oral deformities as reliable proxies for determining Batrachochytrium dendrobatidis (Bd) infection in tadpoles of six anuran species of the Atlantic Forest in southeastern Brazil. We examined oral discs of 2156 tadpoles of six species of anurans collected in 2016: Aplastodiscus albosignatus, Boana albopunctata, Boana faber, Scinax hayii, Crossodactylus caramaschii, and Physalaemus cuvieri. Three oral deformities were recognized: lack of keratinization only in upper and/or lower jaw sheaths, lack of keratinization only in upper or lower tooth rows, and both deformities together. A subsample composed of all the individuals possessing oral deformities (N = 195) plus randomly selected individuals without oral deformities (N = 184) were tested for Bd via qPCR. Oral deformities were observed in all six species, but only five were infected with Bd. Since we found that dekeratinization of tooth rows was not associated with the presence of Bd in any of the studied species we used a new proxy (jaw sheaths dekeratinization with or without dekeratinization in tooth rows: JSD-proxy) for Bd detection. Our results showed a nonrandom relationship between Bd infection and JSD-proxy in three species of the family Hylidae. However, the use of JSD-proxy for Bd detection in these species resulted in up to 30.8% false positives and up to 29.3% false negatives. The use of the JSD-proxy in species for which no relationship was found reached 100% of false positives. We conclude that the use of oral dekeratinization as a generalized proxy for Bd detection in tadpoles should not be used as a single diagnosis technique.

Events of mass malformations in amphibian populations that have exceeded historical records have been reported over the past thirty years. Many of these events have been linked to human activities that occurred near amphibian breeding habitats. The rise in biofuels has promoted, and continues to promote, the growth of sugarcane plantations in Brazil, with the northwest region of São Paulo State having experienced the largest sugarcane expansion over the past few decades. In this region, we sampled temporary ponds located in agroecosystems dominated to different degrees by sugarcane. We found several larvae of Scinax fuscovarius with eye malformations (anophthalmia, aphakia, microphthalmia and sub-development). In this study, we assessed whether the distance from the ponds to the nearest sugarcane crop, the proportion of sugarcane surrounding the ponds, the presence of pesticides in the ponds, or the proportion of land uses with potential teratogens that surround the ponds were related to the frequencies of amphibian eye malformations. We found pesticides present in 11 of the 18 ponds, but none of the predictor variables was associated with the frequencies of amphibian eye malformations. Thus, our results suggest that the observed frequencies of amphibian eye malformations could be a consequence of natural mutation rates, and these data could be used as a malformation baseline for the region. This malformation baseline is the first reported for amphibians in South America and may be useful in future surveys on amphibian populations in tropical agroecosystems.

Global demand for crops will continue increasing over the next few decades to cover both food and biofuel needs. This demand will put further pressure to expand arable land and replace natural habitats. However, we are only beginning to understand the combined effects of agrochemicals and land‐use change on tropical freshwater biodiversity. In this study, we analyzed how pond‐dwelling anuran larvae responded to pond characteristics, landscape composition, and agrochemical contamination in a sugarcane‐dominated agroecosystem in Brazil. Then we used an information theoretical approach with generalized linear models to relate species richness and abundance to predictor variables. The variation in tadpole abundance was associated with both agrochemical concentration (e.g., ametryn, diuron, and malathion) and landscape variables (e.g., percentage of forest, percentage of agriculture, and distance to closest forest). The relationship between species abundance and agrochemicals was species‐specific. For example, the abundances of Scinax fuscovarius and Physalaemus nattereri were negatively associated with ametryn, and Dendropsophus nanus was negatively associated with tebuthiuron, whereas that of Leptodactylus fuscus was positively associated with malathion. Conversely, species richness was associated with distance to forest fragments and aquatic vegetation heterogeneity, but not agrochemicals. Although we were unable to assign a specific mechanism to the variation in tadpole abundance based on field observations, the lower abundance of three species in ponds with high concentrations of agrochemicals suggest they negatively impact some frog species inhabiting agroecosystems. We recommend conserving ponds near forest fragments, with abundant stratified vegetation, and far from agrochemical runoffs to safeguard more sensitive pond‐breeding species.