Global pollinator decline urgently requires effective methods to assess their trends, distribution and behaviour. Passive acoustics is a non-invasive and cost-efficient monitoring tool increasingly ...employed for monitoring animal communities. However, insect sounds remain highly unexplored, hindering the application of this technique for pollinators. To overcome this shortfall and support future developments, we recorded and characterized wingbeat sounds of a variety of Iberian domestic and wild bees and tested their relationship with taxonomic, morphological, behavioural and environmental traits at inter- and intra-specific levels. Using directional microphones and machine learning, we shed light on the acoustic signature of bee wingbeat sounds and their potential to be used for species identification and monitoring. Our results revealed that frequency of wingbeat sounds is negatively related with body size and environmental temperature (between-species analysis), while it is positively related with experimentally induced stress conditions (within-individual analysis). We also found a characteristic acoustic signature in the European honeybee that supported automated classification of this bee from a pool of wild bees, paving the way for passive acoustic monitoring of pollinators. Overall, these findings confirm that insect sounds during flight activity can provide insights on individual and species traits, and hence suggest novel and promising applications for this endangered animal group. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.
In many primates, including humans, the vocalizations of males and females differ dramatically, with male vocalizations and vocal anatomy often seeming to exaggerate apparent body size. These traits ...may be favoured by sexual selection because low-frequency male vocalizations intimidate rivals and/or attract females, but this hypothesis has not been systematically tested across primates, nor is it clear why competitors and potential mates should attend to vocalization frequencies. Here we show across anthropoids that sexual dimorphism in fundamental frequency (F0) increased during evolutionary transitions towards polygyny, and decreased during transitions towards monogamy. Surprisingly, humans exhibit greater F0 sexual dimorphism than any other ape. We also show that low-F0 vocalizations predict perceptions of men's dominance and attractiveness, and predict hormone profiles (low cortisol and high testosterone) related to immune function. These results suggest that low male F0 signals condition to competitors and mates, and evolved in male anthropoids in response to the intensity of mating competition.
More than a million insects and approximately 11,000 vertebrates utilize flapping wings to fly. However, flapping flight has only been studied in a few of these species, so many challenges remain in ...understanding this form of locomotion. Five key aerodynamic mechanisms have been identified for insect flight. Among these is the leading edge vortex, which is a convergent solution to avoid stall for insects, bats and birds. The roles of the other mechanisms - added mass, clap and fling, rotational circulation and wing-wake interactions - have not yet been thoroughly studied in the context of vertebrate flight. Further challenges to understanding bat and bird flight are posed by the complex, dynamic wing morphologies of these species and the more turbulent airflow generated by their wings compared with that observed during insect flight. Nevertheless, three dimensionless numbers that combine key flow, morphological and kinematic parameters - the Reynolds number, Rossby number and advance ratio - govern flapping wing aerodynamics for both insects and vertebrates. These numbers can thus be used to organize an integrative framework for studying and comparing animal flapping flight. Here, we provide a roadmap for developing such a framework, highlighting the aerodynamic mechanisms that remain to be quantified and compared across species. Ultimately, incorporating complex flight maneuvers, environmental effects and developmental stages into this framework will also be essential to advancing our understanding of the biomechanics, movement ecology and evolution of animal flight.
Aromatase-expressing neuroendocrine neurons in the vertebrate male brain synthesize estradiol from circulating testosterone. This locally produced estradiol controls neural circuits underlying ...courtship vocalization, mating, aggression, and territory marking in male mice. How aromatase-expressing neuronal populations control these diverse estrogen-dependent male behaviors is poorly understood, and the function, if any, of aromatase-expressing neurons in females is unclear. Using targeted genetic approaches, we show that aromatase-expressing neurons within the male posterodorsal medial amygdala (MeApd) regulate components of aggression, but not other estrogen-dependent male-typical behaviors. Remarkably, aromatase-expressing MeApd neurons in females are specifically required for components of maternal aggression, which we show is distinct from intermale aggression in pattern and execution. Thus, aromatase-expressing MeApd neurons control distinct forms of aggression in the two sexes. Moreover, our findings indicate that complex social behaviors are separable in a modular manner at the level of genetically identified neuronal populations.
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•MeApd aromatase neurons regulate male aggression, but not marking, singing, or mating•MeApd aromatase neurons regulate maternal aggression, but not female sexual behavior•MeApd aromatase neurons regulate specific components of aggression in both sexes•MeApd aromatase neurons control aggression in a modular manner
Aromatase controls sexually dimorphic social behaviors in both sexes. Unger et al. show that the small population of aromatase-expressing neurons in the medial amygdala is required for intermale and maternal aggression, but not other sexually dimorphic behaviors. Thus, aromatase-expressing medial amygdalar neurons control complex social behaviors in a modular manner.
Inadvertent cues can be refined into signals through coevolution between signalers and receivers, yet the earliest steps in this process remain elusive. In Hawaiian populations of the Pacific field ...cricket, a new morph producing a novel and incredibly variable song (purring) has spread across islands. Here we characterize the current sexual and natural selection landscape acting on the novel signal by (1) determining fitness advantages of purring through attraction to mates and protection from a prominent deadly natural enemy, and (2) testing alternative hypotheses about the strength and form of selection acting on the novel signal. In field studies, female crickets respond positively to purrs, but eavesdropping parasitoid flies do not, suggesting purring may allow private communication among crickets. Contrary to the sensory bias and preference for novelty hypotheses, preference functions (selective pressure) are nearly flat, driven by extreme inter-individual variation in function shape. Our study offers a rare empirical test of the roles of natural and sexual selection in the earliest stages of signal evolution.
Highlights ► The ascending mesolimbic cholinergic system initiates negative emotional state. ► The ascending mesolimbic dopaminergic system initiates positive emotional state. ► The negative and ...positive states are signaled by 22 kHz and 50 kHz vocalizations. ► State-specific vocalizations can change emotional state of the recipients. ► Species-specific signals changing state of recipients are ethotransmitters.
Animals of all sizes form groups, as acting together can convey advantages over acting alone; thus, collective animal behavior has been identified as a promising template for designing engineered ...systems. However, models and observations have focused predominantly on characterizing the overall group morphology, and often focus on highly ordered groups such as bird flocks. We instead study a disorganized aggregation (an insect mating swarm), and compare its natural fluctuations with the group-level response to an external stimulus. We quantify the swarm's frequency-dependent linear response and its spectrum of intrinsic fluctuations, and show that the ratio of these two quantities has a simple scaling with frequency. Our results provide a new way of comparing models of collective behavior with experimental data.
Mosquitoes exhibit unusual wing kinematics; their long, slender wings flap at remarkably high frequencies for their size (>800 Hz)and with lower stroke amplitudes than any other insect group. This ...shifts weight support away from the translation-dominated, aerodynamic mechanisms used by most insects, as well as by helicopters and aeroplanes, towards poorly understood rotational mechanisms that occur when pitching at the end of each half-stroke. Here we report free-flight mosquito wing kinematics, solve the full Navier-Stokes equations using computational fluid dynamics with overset grids, and validate our results with in vivo flow measurements. We show that, although mosquitoes use familiar separated flow patterns, much of the aerodynamic force that supports their weight is generated in a manner unlike any previously described for a flying animal. There are three key features: leading-edge vortices (a well-known mechanism that appears to be almost ubiquitous in insect flight), trailing-edge vortices caused by a form of wake capture at stroke reversal, and rotational drag. The two new elements are largely independent of the wing velocity, instead relying on rapid changes in the pitch angle (wing rotation) at the end of each half-stroke, and they are therefore relatively immune to the shallow flapping amplitude. Moreover, these mechanisms are particularly well suited to high aspect ratio mosquito wings.
Social behaviors, including behaviors directed toward young offspring, exhibit striking sex differences. Understanding how these sexually dimorphic behaviors are regulated at the level of circuits ...and transcriptomes will provide insights into neural mechanisms of sex-specific behaviors. Here, we uncover a sexually dimorphic role of the medial amygdala (MeA) in governing parental and infanticidal behaviors. Contrary to traditional views, activation of GABAergic neurons in the MeA promotes parental behavior in females, while activation of this population in males differentially promotes parental versus infanticidal behavior in an activity-level-dependent manner. Through single-cell transcriptomic analysis, we found that molecular sex differences in the MeA are specifically represented in GABAergic neurons. Collectively, these results establish crucial roles for the MeA as a key node in the neural circuitry underlying pup-directed behaviors and provide important insight into the connection between sex differences across transcriptomes, cells, and circuits in regulating sexually dimorphic behavior.
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•Medial amygdala controls parenting and infanticide in a sexually dimorphic manner•GABAergic, but not glutamatergic, neurons promote parenting behavior in females•Scalable activation of GABAergic neurons in males controls parenting versus infanticide•scRNA-seq reveals molecular sex differences specifically within GABAergic neurons
Sexually dimorphic displays of parenting and infanticide are differentially controlled by GABAergic neurons in the medial amygdala in an activity level-dependent manner. Single-cell transcriptomic analysis reveals cell type-specific molecular sex differences in GABAergic neurons, highlighting a connection between sexual dimorphism at levels of molecules, cells, circuits, and behavior.
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