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Behavioral changes constitute a common response of aquatic animals to predator chemical and/or visual cues. Tadpoles frequently use such signals to evaluate predator presence/activity and, consequently, alter their own behavior to reduce detectability and susceptibility to predation. The present study aimed to test how tadpoles of Bokermannohyla martinsi and Ololygon machadoi respond to the presence of a predator (Belostoma testaceopallidum), regarding background choice and activity levels. Results showed that O. machadoi tadpoles increased the use of yellow backgrounds in the presence of the predator perceived through either chemical or visual cues. Bokermannohyla martinsi, on the other hand, did not show preference for any specific background color or changed activity levels in the presence of any predator cue. Our results corroborate the hypothesis of disruptive coloration as a defense strategy in O. machadoi and indicate that the visible and active tadpoles of B. martinsi may employ a different defensive strategy, possibly relying on a more efficient post detection escape mechanism. This hypothesis is corroborated by the higher activity levels of B. martinsi and lack of response to predator presence regarding either modulation of activity levels or background choice. [ABSTRACT FROM AUTHOR]

A species diet offers information on its trophic level and its roles in the community. Tadpoles are known to be important components of aquatic food webs, however little is known about their feeding habits and food preferences. Tadpole ecomorphotypes have been shown to relate to their diet, but some consumed food resources are not available at preferred feeding microhabitats, such as pollen for benthic tadpoles. Pollen has high nutritive value, thus tadpoles may change their feeding behavior in order to explore it. We tested this hypothesis by offering fed or hungry tadpoles pollen on the water surface at three different depths, with or without an alternative food source. We noticed that pollen consumption decreased with increased depth, what is in accordance with optimal foraging theory, as the tadpoles have to make longer maneuvers to achieve the pollen from the bottom in deeper water. That is likely also the reason why tadpoles decreased pollen consumption when provided with alternative food on the bottom, where they usually forage. However, increased difficulty and alternative food sources did not prevent tadpoles to feed on pollen, showing that they can be flexible enough to change their feeding habits in order to opportunistically explore new nutritive food sources. [ABSTRACT FROM AUTHOR]

Roads have many detrimental effects on natural habitats and their fauna, ranging from altered microclimate to road kills. Animals which move slowly or are attracted to the road surface are particularly threatened. We studied herpetofauna road mortality in a Cerrado ecosystem in central Brazil. We sampled 51 km of state roads during 26 days distributed between dry and wet seasons in 2010 and recorded 109 dead individuals of 34 species of amphibians and reptiles. Including animals found alive on the road, we recorded 159 individuals across 39 species (estimated richness: 48). This number represents about 50% of the herpetofauna species richness expected to occur in a Cerrado site in central Brazil based on a concomitant species inventory. Our study indicates that roads can cause high mortality rates for the Cerrado herpetofauna. We consider that this problem requires urgent attention since economic growth is largely based on agriculture in the Cerrado and construction of more roads is planned to improve harvest transport. [ABSTRACT FROM AUTHOR]

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In amphibians solar basking far from water sources is relatively uncommon since the highly permeable amphibian skin does not represent a significant barrier to the accompanying risk of losing water by evaporation. A South American frog, Bokermannohyla alvarengai (Bokermann 1956), however, spends a significant amount of the day exposed to full sun and relatively high temperatures. The means by which this frog copes with potentially high rates of evaporative water loss and high body temperatures are unknown. Thus, in this study, skin colour changes, body surface temperature, and evaporative water loss rates were examined under a mixture of field and laboratory conditions to ascertain whether changes in skin reflectivity play an important role in this animal's thermal and hydric balance. Field data demonstrated a tight correlation between the lightness of skin colour and frog temperature, with lighter frogs being captured possessing higher body temperatures. Laboratory experiments supported this relationship, revealing that frogs kept in the dark or at lower temperatures (20°C) had darker skin colours, whereas frogs kept in the light or higher temperatures (30°C) had skin colours of a lighter hue. Light exhibited a stronger influence on skin colour than temperature alone, suggesting that colour change is triggered by the increase in incident solar energy and in anticipation of changes in body temperature. This conclusion is corroborated by the observation that cold, darkly coloured frogs placed in the sun rapidly became lighter in colour during the initial warming up period (over the first 5 min), after which they warmed up more slowly and underwent a further, albeit slower, lightening of skin colour. Surprisingly, despite its natural disposition to bask in the sun, this species does not possess a ‘waterproof’ skin, since its rates of evaporative water loss were not dissimilar from many hylid species that live in arboreal or semi-aquatic environments. The natural history of B. alvarengai is largely unknown and, therefore, it is likely that the herein reported colour change and basking behaviour represent a complex interaction between thermoregulation and water balance with other ecologically relevant functions, such as crypsis. [ABSTRACT FROM AUTHOR]

Leptodactylus syphax belongs to the L. pentadactylus group, one of five species groups defined for the genus. The tadpole of L. syphax develops in lotic habitats, as do the tadpoles of L. lithonaetes and L. rugosus. The tadpole of L. syphax is here described and differs from the tadpole of L. rugosus by having a less flattened and larger body, from the tadpole of L. lithonaetes by having a larger body in relation to total length and a larger oral disc in relation to body length. Further, it differs from the tadpole of L. rhodomystax by its color, body shape in dorsal profile and mouth shape, and from the tadpole of L. rhodonotus by its body shape in dorsal profile and spiracle position. A cluster analysis of several morphological and ecological features of adults and tadpoles from the species of the L. pentadactylus group grouped L. syphax with L. rhodomystax and L. rhodonotus, species with chest spines, moderate body size, relatively small head, unbarred lips, tadpoles with five tooth rows and aquatic development. The remaining species of the L. pentadactylus group were distributed among four additional clusters. [ABSTRACT FROM AUTHOR]

The interaction of widespread stressors such as nitrate pollution and increasing temperatures associated with climate change is likely to affect aquatic ectotherms such as amphibians. The metamorphic and physiological traits of amphibian larvae during the critical onset of metamorphosis are particularly susceptible to these stressors. We used a crossed experimental design subjecting Rana temporaria larvae to four constant rearing temperatures (18, 22, 26, 28°C) crossed with three environmentally relevant nitrate concentrations (0, 50, 100 mg l-1) to investigate the interactive and individual effects of these stressors on metamorphic (i.e. growth and development) and physiological traits (i.e. metabolism and heat tolerance) at the onset of metamorphosis. Larvae exposed to elevated nitrate concentrations and thermal stress displayed increased metabolic rates but decreased developmental rate, highlighting interactive effects of these stressors. However, nitrate pollution alone had no effect on either metamorphic or physiological traits, suggesting that detoxification processes were sufficient to maintain homeostasis but not in combination with increased rearing temperatures. Furthermore, larvae exposed to nitrate displayed diminished abilities to exhibit temperature-induced plasticity in metamorphosis timing and heat tolerance, as well as reduced acclimation capacity in heat tolerance and an increased thermal sensitivity of metabolic rate to higher temperatures. These results highlight the importance of considering the exposure to multiple stressors when investigating how natural populations respond to global change., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)