The present study aims to describe the ontogenetic changes in the skull of the loggerhead turtle,
Caretta caretta
by focusing on the stages of development in the western South Atlantic Ocean. Our ...hypothesis is based on the premise that changes in feeding habits will reflect changes in the shape and/or size of the skull. The existence of changes in skull of the loggerhead turtle were analyzed using traditional and geometric morphometrics on skulls collected from stranded individuals in the southern Brazilian coast. As a general result, a transformation pattern was observed: from younger specimens with smaller, elongated and flattened skulls towards a larger, rounded and more robust skull in older specimens. It is suggested that these skull changes are associated with the diet shift of the loggerhead turtle specimens, providing the skull with greater mechanical resistance and enabling a change in feeding strategy from soft organisms to hard-shelled preys. This result highlights the importance of southern Brazilian coast for the life cycle of the loggerhead turtle. In this region, the individuals undergo the process of ontogenetic diet shift, changing their skull shape to adapt to the newly occupied niche and ensuring the ecological success of the species.
In anuran amphibians, acoustic signals are fundamental mechanisms of mate recognition and mate choice, which makes frog calls a fundamental tool for anuran taxonomy. In this work, we describe the ...advertisement call of two species for the genus Melanophryniscus, M. cambaraensis and M. macrogranulosus and use the descriptions to try to solve a taxonomic problem between them. We collected data after heavy rains in three different sample sites in Rio Grande do Sul, Brazil, between 2012 and 2013. The advertisement call of both species is composed of two segments. It always begins with part A (about 0.44-6 seconds) composed of single modulated pulses separated by long time intervals. It is followed by part B, a long train of unmodulated pulses with short time intervals, lasting from 9 to 32.2 seconds. Principal Component Analysis (PCA) indicated some variation between temporal parameters of the two species, but Multivariate Analysis of Variance showed no significant differences. Within-individual Coefficient of Variation (CV) showed only two static parameters: pulse rate and peak frequency, both in the part B of the call. Despite intra-male variation in some acoustic parameters, it is not possible to differentiate between M. cambaraensis and M. macrogranulosus species only using bioacoustics.
Melanophryniscus admirabilis
is a frog endemic to the southern Atlantic Forest (Brazil), with restricted distribution and considered as critically endangered. The aim of this study was to evaluate ...possible alterations in biomarkers of metabolism (glycogen, proteins, and uric acid) and oxidative balance (superoxide dismutase, catalase, glutathione S-transferase, and lipoperoxidation) of tadpoles of
Melanophryniscus admirabilis
exposed to commercial herbicide formulations containing sulfentrazone (Boral® 500 SC: 130 and 980 μg a.i./L) and glyphosate (Roundup® Original: 234 and 2340 μg a.i./L). Mortality was not observed in any of the groups studied. Our results show that a 96-h exposure to the herbicides decreased glycogen levels, indicating increased energy demand for xenobiotic metabolism. Protein levels increased in the Boral group but decreased in the higher concentration of Roundup, and uric acid levels did not change significantly between the experimental groups. Lipoperoxidation decreased in the Boral group and in the higher concentration of Roundup. Decreased levels of superoxide dismutase in both treatments and of catalase in the lowest concentration of the herbicides were observed. Glutathione S-transferase activity increased in the Roundup group; this enzyme seems to be crucial in the metabolization of the herbicides and in the survival of the tadpoles. Our results suggest that
M. admirabilis
has a high antioxidant capacity, which guaranteed the survival of tadpoles. Nevertheless, exposure to pesticides could impose a serious risk to this species, especially considering its restricted distribution, habitat specificity, and high physiological demand to metabolize xenobiotics.
Anthropogenic noise is widespread in nature and has been shown to produce a plethora of impacts on wildlife. Sounds play a fundamental role in the lives of amphibians, with species relying on ...acoustic communication for social and reproductive behaviour, and thus noise can potentially interfere with these activities. Here, we provide a literature review on the effects of anthropogenic noise on anuran amphibians, based on 32 studies (63 species from 14 families) that document noise-driven changes in species behaviour, physiology and ecology caused by urbanisation, transportation and energy production. Experimental and observational studies found evidence that both airborne and seismic anthropogenic noise influence anuran calling activity, with consequences in mate selection, and induce physiological changes including increased stress, suppressed immune function and colouration changes. Negative noise effects in species abundance and attendance over the reproductive season were reported. Even though adaptations and behavioural adjustments enable species to respond to these noises, it is yet to be understood whether these changes alleviate the negative impacts. Furthermore, collaborative efforts between scientists, stakeholders and private/public institutions are imperative to create conservation guidelines and legal instruments to be implemented during urban expansion projects and mitigate the effects of noise pollution on amphibian anurans.
Marine mammals and humans are apex predators and both may compete for fish in ecosystems under continuous fishing pressure. We assessed the degree of trophic overlap between prey species found in the ...diet of 5 marine mammals (39 specimens of sea lion Otaria flavescens, 61 fur seals Arctocephalus australis, 76 franciscana dolphins Pontoporia blainvillei, 25 bottlenose dolphins Tursiops truncatus and 28 Lahille’s bottlenose dolphins T. gephyreus) and the catches of the 6 main commercial fishing gears used in southern Brazil (coastal gillnets, oceanic gillnets, purse seine, demersal pair trawling, bottom single trawl and double-rig trawling) between 1993 and 2016. An adjusted general overlap index indicated an overall moderate to high overlap. Specific overlap analysis showed that O. flavescens and T. truncatus presented high trophic relationships with fisheries, followed by T. gephyreus. Smaller interactions were observed for A. australis and P. blainvillei, even though they also exploit commercial fishing resources. Coastal gillnet and pair bottom trawling are the fisheries that most target the fish species favoured by O. flavescens, T. gephyreus and T. truncatus. The information presented in this study on trophic interactions may assist decision making for both fishery management and conservation measures for these apex predators. Commercial fishing activities are a major threat to marine mammals both regionally and globally. Current levels of fishing or its intensification may lead to dramatic changes in the coastal marine food web, including additional threats to coastal marine mammal populations in southern Brazil.
The green turtle Chelonia mydas has a circumtropical distribution and is globally endangered. This long-lived, migratory turtle has a spatially complex life cycle that encompasses initial development ...in oceanic habitat, with subsequent recruitment to neritic habitat. In the coastal waters of the western South Atlantic Ocean, juvenile green turtles are a notable component of the marine megafauna. As a result of incidental capture and other anthropogenic causes, dead specimens are commonly found stranded on beaches. Knowledge of age and growth is critical to understanding population life history and dynamics, as well as for conservation planning. We applied skeletochronology to estimate age and growth rates for green turtles stranded throughout 16 yr (1994 to 2010) in southern Brazil. Curved carapace length (CCL) ranged from 31 to 61 cm (mean = 41 cm) and estimated ages from 2 to 13 yr (mean = 5 yr, mode = 3 yr). Green turtles recruit to the neritic environment in this area around 30 cm CCL and aged 2 to 3 yr, remaining in this region until reaching about 50 cm and 7 yr. The mean growth rate of the whole sample was 3.7 cm CCL yr−1, and both age and size had a significant influence on growth.
Although non-front fanged snakes account for almost two-thirds of snake diversity, most studies on venom composition and evolution focus exclusively on front-fanged species, which comprise most of ...the clinically relevant accidents. Comprehensive reports on venom composition of non-front fanged snakes are still scarce for several groups. In this study, we address such shortage of knowledge by providing new insights about the venom composition among species of Phalotris, a poorly studied Neotropical dipsadid genus. Phalotris are known for their specialized venom delivery system and toxic venoms, which can cause life-threatening accidents in humans. We evaluate the venom-gland transcriptome of Phalotris, comparing the following three South American species: P. reticulatus for the Araucaria Pine forests, P. lemniscatus for the Pampa grasslands, and P. mertensi for the Brazilian Cerrado. Our results indicate similar venom profiles, in which they share a high expression level of Kunitz-type inhibitors (KUNZ). On the other hand, comparative analyses revealed substantial differences in the expression levels of C-type lectins (CTL) and snake venom metalloproteinases (SVMP). The diverse set of SVMP and CTL isoforms shows signals of positive selection, and we also identified truncated forms of type III SVMPs, which resemble type II and type I SVMPs of viperids. Additionally, we identified a CNP precursor hosting a proline-rich region containing a BPP motif resembling those commonly detected in viperid venoms with hypotensive activity. Altogether, our results suggest an evolutionary history favoring high expression levels of few KUNZ isoforms in Phalotris venoms, contrasting with a highly diverse set of SVMP and CTL isoforms. Such diversity can be comparable with the venom variability observed in some viperids. Our findings highlight the extreme phenotypic diversity of non-front fanged snakes and the importance to allocate greater effort to study neglected groups of Colubroidea.
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•We generate annotated transcriptomes for three Phalotris species.•We uncover unexpectedly similar profiles for major expressed toxin transcripts families.•We report independent evolutionary history of Kunitz-type inhibitor toxins.•We provide a new classification for SVMP P-III toxins for Phalotris.•We describe a highly different composition of SVMP toxins isoforms.
Since the Moreno's et al. (2005) work, no study was done to update the distribution patterns of Stenella dolphins in the southwestern Atlantic Ocean. Ecological niche modeling was used to redefine ...the distribution patterns of Stenella dolphins in this area of Atlantic Ocean. Maximum entropy method (Maxent) was employed to generate models using a set of environmental variables as explanatory variables of the location records obtained by sighting and accidental captures. All ecological niche models performed returned AUC values >0.9. Areas with high environmental suitability for pantropical spotted dolphin (Stenella attenuata), Clymene dolphin (Stenella clymene) and spinner dolphins (Stenella longirostris) are found in warm (>25°C) and deep waters (≥1000m). High environmental suitability for Atlantic spotted dolphin (Stenella frontalis) seems to occur between 20.5°S and 30°S in the southeastern Brazilian coastal waters. The projected maps of species distributions showed patterns closely related to environmental changes at a fine spatial scale and added valuable information about the offshore limits of those oceanic species. The results suggest that the different species of Stenella have distinct environmental requirements in the southwestern Atlantic Ocean.
•We used ecological niche modeling to estimate the potential distribution of Stenella dolphins in the southwestern Atlantic Ocean.•Our results suggest that the different species of Stenella have distinct environmental requirements in the southwestern Atlantic Ocean.•We propose that the Stenella species exhibit habitat partitioning with some degree of spatial separation.•This manuscript also adds significant insights about the offshore limit of Stenella dolphins in the southwestern Atlantic Ocean.
The franciscana (Pontoporia blainvillei) is the most threatened small cetacean of South America. The species is endemic to coastal waters of the western South Atlantic Ocean, where it is distributed ...from Itaúnas (Brazil) to Golfo San Matias (Argentina). Its range was divided in four Franciscana Management Areas (FMAs) for conservation purposes. However, the distribution of the franciscana is not continuous along its range, with two hiatuses proposed in southeastern Brazilian coast. The absence of franciscana records in these regions has been confirmed by multiple years of research, however the reasons for this discontinuous distribution is not well understood. In this study, information on the distribution of the franciscana in south and southeastern Brazil is updated and new limits for FMAs are proposed. NicheA 3.0 software was used to investigate the environmental suitability of distributional gaps in relation to four weakly correlated, allegedly relevant descriptors of franciscana's distribution. In total, 788 records from dedicated aerial and boat surveys and bycatch were used to verify and to confirm the new FMAs limits proposed by franciscana's experts previously. The distributional gaps were reshaped and defined as following: Gap I from Piraquê-Açu River Mouth, Santa Cruz (19°57′S) in the state of Espírito Santo to Barra de Itabapoana (21°18′S) in the state of Rio de Janeiro; and Gap II from Armação dos Búzios (22°44′S) to Piraquara de Dentro (22°59′S) in Rio de Janeiro. The ecological niche model indicated that distributional gaps are inside franciscana's fundamental niche, and are relatively suitable in terms of salinity, temperature, diffuse attenuation and bathymetry. However, the narrow of continental shelf seems to be the main factor explaining the absence of franciscanas in the distributional gaps as well as for the differentiation of some of the FMAs proposed. Narrowness of continental shelf seems to be intensifying the dynamics of biotic interactions promoting food competition for example, and/or causing geographic limitation to maintain minimal viable population size in present or past times periods.
•The franciscana dolphin is endemic and the most threatened small cetacean of South America.•We analyzed its distribution in Brazil, mainly in relation to its distributional gaps.•Narrowness of the continental shelf seems to explain the absence of franciscana within the gaps.•Loss of shelf habitat could intensify biotic interactions (predation/competition).•Historical factors could also play a role to explain this biogeographical pattern.
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