The increase in intensity and frequency of surface air temperature extremes throughout the western South Atlantic coast.

The climate is changing. At this stage, it is important to specify an 'extreme' climate and identify patterns that indicate its potential harm worldwide, including the coastal zones. Herein, we considered extremes based on the "Peaks Over Threshold" method from the "Extreme Value Theory". We looked after geographical patterns of surface air temperature (SAT) extremes (e.g., Tmax, Tmin, daily temperature range (DTR), and inter-daily temperature range) over the last 40 years throughout the Brazilian coast. Overall, we found a trend increase in intensity and frequency, but the duration was barely affected. The latitudinal pattern of extremes and the temperatures considered extremes followed the settled perception that areas in higher latitudes will be more affected by the extent of warming. Additionally, the seasonal pattern of DTR demonstrated to be a good approach to make inferences about air mass changes, but joint analyses on extremes with other atmospheric variables are desirable. Given the potential effects of extreme climates on society and natural systems over the world, our study highlights the urge for action to mitigate the effects of the increase in SAT in coastal zones.

Sharing is living: The role of habitat heterogeneity in the coexistence of closely related species.

In biologically diverse ecosystems, an essential process to support competing species to coexist is ecological differentiation. Habitat heterogeneity is, hence, important in establishing species abundance and richness, favoring the coexistence of species due to habitat partition. In this context, shading and species thermal tolerance can be good factors to elucidate the role of habitat heterogeneity in the habitat partition among closely related species. Herein, we study shading effects in microhabitat selection, behavior, and physiological limitation on two species of fiddler crabs (Leptuca leptodactyla and Leptuca uruguayensis). Indeed, shading conditions influenced fiddler crabs species proportion over time, with L. leptodactyla more associated with nonshaded/warmer areas while the L. uruguayensis to shaded/cooler ones. They also adjusted their behavior differently from each other to deal with thermal stress. Finally, we have demonstrated that these effects are related to species' physiological limitations. We conclude that biologically diverse ecosystems, such as intertidal regions from estuaries (e.g., mudflats and mangroves), support the coexistence between closely related species by reducing competition due to habitat partition.

Combined effects of predator odor and alarm substance on behavioral and physiological responses of the pearl cichlid.

Several fish species trigger defensive behavioral responses when exposed to chemical cues that indicate predation risk. In these situations, physiological adjustments are also necessary to prepare the organism for a defensive response and increase survival odds. Chemical cues may be derived from predator odor or injured conspecifics. However, little is known about the effects of both cues combined. Therefore, our study evaluated the combined effects of predator odor (PO) and conspecific alarm substance (CAS) on the anti-predatory responses of the pearl cichlid (Geophagus brasiliensis). We set 4 experimental conditions 1) PO + CAS; 2) PO + Distilled Water (DW); 3) DW + CAS; and 4) DW + DW (negative control). Fish exposed to DW + CAS had values of ventilation rate and feeding latency significantly higher than when exposed to the other conditions, which yielded similar responses for both variables. Our data show that the combination of PO + CAS interfered with pearl cichlid behavior and physiology since it abolished CAS defensive responses. These results show that CAS plays an important role on the defensive responses of pearl cichlids, while PO does not, given that fish did not respond to PO by itself. Our findings point to different cue-specific strategies in pearl cichlids when dealing with different chemical cues that indicate predation risk.

Testing the dear enemy relationship in fiddler crabs: Is there a difference between fighting conspecific and heterospecific opponents?

Reduction of aggressiveness toward familiar neighbors, when compared to aggressiveness toward unfamiliar strangers, can decrease the costs of territory defense. This phenomenon is known as the "dear enemy effect". Individuals may shift their aggressiveness toward neighbors or strangers from the same or different species, depending on the relative threat associated with different opponents. Therefore, a reduced level of aggressiveness between heterospecific neighbors is expected in relation to conspecific intruders, since the latter compete not only for territory, but also for mates. Herein we investigated the occurrence of the dear enemy effect in territorial fights between conspecific pairs of Leptuca leptodactyla and heterospecific pairs of L. leptodactyla versus Leptuca uruguayensis. Across both conspecific and heterospecific fights, medium- and high-intensity fight components were more used in resident-stranger than in resident-neighbor fights. Thus, residents showed a dear enemy response, regardless of opponent species. Moreover, conspecific fights induced a greater number of low- and medium-intensity fight components than did fights between heterospecifics, both neighbors and strangers. Finally, conspecific resident-stranger fights took longer than heterospecific resident-stranger fights. Our results indicate that fiddler crabs adjust their territorial response according to the species and resident status of intruders, consistent with the risks posed by different intruder types.