Biology subjects

Palaoro, A. V.

Publications and source records attributed to Palaoro, A. V..

4 recordsLinked to original sources

bioRxiv2025

Regional heterothermy in Megasoma gyas is not related to active heat dissipation by the horns

Animals rely on physiological and behavioral processes to maintain thermal balance. Some animals, however, bear structures that help dissipate excess heat when body temperatures rise. Although widespread in animals, animal weapons--exaggerated morphological structures with multiple characteristics that can make them good at dissipating heat--have rarely been studied in the context of thermoregulation. Here, we investigated whether the horns of the Rhinoceros Beetle (Megasoma gyas) acted as a thermal window. We heated live and dead beetles to 30{o}C and allowed them to cool to 20{o}C while measuring surface temperature changes in four body regions: the cephalic and thoracic horns, the scutellum, and the abdomen. If horns actively dissipated heat, they would show the lowest cooling rate among body regions. Contrary to this expectation, we found that the cephalic horn had the highest cooling rate, followed by the abdomen, thoracic horn, and scutellum, respectively. This suggests that the horns are not used for active heat dissipation in M. gyas. The low cooling rate of the scutellum can be explained by the presence of large flight muscles in the thorax, which play a role in heat generation, but could also aid in heat dissipation by pumping hemolymph across tagmata or through the low-insulated cuticle to prevent thoracic overheating. We also demonstrate that beetles show regional heterothermy even in the absence of exercise or stress. As such, we propose that regional heterothermy may result from both active (control of hemolymph flow) and passive (heat dissipation through poorly insulated structures) processes within individuals.

animal behavior and cognition↗

bioRxiv2024

The evolution of male weapons is associated with the type of breeding site in a clade of Neotropical frogs

Male weaponry evolution is often linked to resource or female defense polygyny. This pattern emerges from highly studied taxa, such as arthropods and mammals. However, whether factors such as breeding site type influence weaponry evolution remains an open question. We explore this question using frogs of the subfamily Leptodactylinae, where males of species spawning in exposed sites (water bodies) fight to hold oviposition sites or dislodge rivals during amplexus. Conversely, males of species spawning in concealed sites (ground nests and crevices) rarely engage in intense physical contests. We hypothesize that male weaponry evolution would be associated with reproduction in exposed sites. Using two complementary phylogenetic comparative methods, we first found a macroevolutionary correlation between male weapons and breeding site type. The presence of weapons is consistently associated with exposed sites, while their absence is linked to concealed sites. We explore how this macroevolutionary pattern can also be influenced by female mate choice. Second, we found that both gains and losses of weapons occurred more frequently in species spawning in exposed sites. This unexpected finding suggests that the dynamics of weapon evolution are more intricate than anticipated. We propose some explanations aspiring to stimulate further investigations with other external fertilizer species.

evolutionary biology↗

bioRxiv2020

The hidden links between animal weapons, fighting style and their expression on contest resolution

In many species that fight over resources, individuals use specialized structures to gain mechanical advantage over their rivals during contests (i.e., weapons). Although weapons are widespread across animals, how they affect the probability of winning contests is still debated. According to theory, understanding the weapons function in contests depends on identifying differences in how weapons are measured (e.g., weapon length versus shape), and in how weapons are used during fights. Here, we developed a meta-analysis spanning 1,138 studies, from which were drawn 52 species and 107 effect sizes to identify: (1) what aspects of animal weapons are measured in the literature, and how these measures bias our knowledge; (2) how animals use their weapons during fights - i.e., weapon function; and (3) if weapon function correlates to the magnitude of how weapons influence contest resolution. First, we found that most of the literature focuses on linear measures of weapons, such as length. The few reports on weapon performance (e.g., biting force) were found only for Crustacea and Squamata. This bias highlights that measuring performance of weapons such as horns and spines might increase the breadth of our knowledge on weapons. Furthermore, we also found that linear measures showed stronger effects on contest success than performance measures. Second, we divided weapon function into displays and fighting style (i.e., how the weapon is used during fights). Regarding displays, most species displayed their weapons before contests (59.61%), rather than the body (34.61%). A minority (three species, 5.76%) engaged in fights without any type of display. Thus, species that bear weapons almost always perform displays before engaging in physical contact, a common hypothesis in contest theory that was never tested across taxa until now. Regarding fighting style, we found that most weapons were used for more than one behaviour during fights (e.g., squeezing and pushing). Further, pushing seems to be the most common behaviour among species, but it is usually accompanied by another behaviour, such as lifting or squeezing. Thus, oversimplifying fighting style can bias results because some styles might impose contrasting biomechanical pressures (e.g., pushing vs squeezing). Third, we found that display type did not influence the importance of weapon size on contests. Fighting style, on the other hand, influenced the effect of weapon size on contest outcome significantly. Species that used their weapons to impact, pierce or squeeze showed smaller differences between winners and losers when compared to pushing or lifting (and multifunctional weapons). Thus, pushing and lifting seem important for selecting larger weapons - even though some of them might also be used for squeezing, piercing or impacting. Overall, our results show that we have a biased understanding of animal weapons, built mostly on weapon size alone. Further, our analyses show that the importance of weapon size differs depending on the fighting style. If we lessen those biases, we will have a better and broader understanding of how weapons evolve and diversify.

evolutionary biology↗

bioRxiv2020

Performance, but not size, of hindleg weaponry is sexually dimorphic in the giant mesquite bug (Thasus neocalifornicus)

In many species, males possess specialized weaponry that have evolved to confer a benefit during aggressive interactions. Because male weaponry is typically an exaggerated or extreme version of pre-existing body parts, females often possess reduced or weaponry. Although much research has investigated sexual dimorphism in the sizes of such weapons, other weapon components, such as weapon performance or alternative weapon forms can also explain the evolution of weapon sexual dimorphisms. Here, we investigated the allometry and variation of multiple weapon components of hindleg weaponry in the male and female giant mesquite bugs, Thasus necalifornicus. Despite theory predicating greater allocation in male weaponry, we found that females allocated more into the lengths of their hindlegs compared to males. Despite this allocation, males possess relatively wider hindlegs, which likely increase area of muscle mass. Indeed, the squeezing performance of male hindlegs was much greater than that of female hindlegs. Lastly, we also described the allometry and variation in a male weapon component, prominent tibial spines, which likely are used to damage competitors during aggressive interaction. Overall, our findings highlight the intricacies of weapon sexual dimorphism and demonstrate the importance of measuring multiple weapon components and not a single measure.

zoology↗