David L. Hu

An ant atop a layer of human earwax. Ancalle et al. show that earwax acts as a natural defense against insect intruders: earwax is both slick and sticky to ants, reducing their chance of entering the ear.

Bloodworms, Glycera dibranchiata , possess an eversible proboscis that normally remains concealed within their bodies but explosively everts if the worm attacks or burrows. How does the bloodworm evert quickly and reliably? In this experimental study, we characterized bloodworm kinematics, pressure, and material properties to estimate the criteria for safe eversion without rupture of the proboscis. We predicted the proboscis can withstand pressures 50 times higher and bending strains up to three times higher than the respective values observed in the live worm. We presented a dimensional analysis of eversion, finding that everting animals, from frogs to snails to sharks, do not satisfy Froude’s law for equivalence of velocities. Our findings may help inspire the development of pressure-driven soft robots with efficient retraction capabilities.

Mosquito-borne diseases cause several hundred thousand deaths worldwide every year. Deciphering mosquito host-seeking behavior is essential to prevent disease transmission through mosquito capture and surveillance. Despite recent substantial progress, we still lack a comprehensive quantitative understanding of how visual and other sensory cues guide mosquitoes to their targets. Here, we combined three-dimensional infrared tracking of Aedes aegypti mosquitoes with Bayesian dynamical systems inference to learn a quantitative biophysical model of mosquito host-seeking behavior. Trained on more than 20 million data points, each corresponding to an instantaneous position and velocity in mosquito free-flight trajectories recorded in the presence of visual and carbon dioxide cues, the model accurately predicts how mosquitoes respond to human targets. Our results provide a quantitative foundation for optimizing mosquito capture and control strategies, a key step toward mitigating the impact of mosquito-borne diseases.

Synopsis: Outreach events are an excellent way to expose science disciplines to the public beyond the ivory tower of academics. In this paper, we describe how a zoo-academia collaborative team designed and hosted an interdisciplinary outreach event exposing thousands to the wonders of bio-inspired design and biomechanics. Over the past 4 years, we have run such a collaborative outreach event which has attracted 26,750 people, allowing children and adults to be exposed to diverse research fields through our annual Zoo Biomechanics Day. In partnering with labs, companies, and student organizations, we have hosted 17 unique booths highlighting human, plant, and animal biomechanics and bio-inspiration to showcase engaging demonstrations of science, technology, engineering, arts, and medicine principles. This event is low-cost ($\\lt \$300$ annually) while increasing attendance at the zoo by over 65% compared to similar non-event days. Furthermore, participating researchers get connected to the zoo, allowing discussions of new collaborative research between the zoo and universities. This paper will serve as a framework for others to host events which highlight the zoo-university collaborations that enhance the dual objectives of outreach and research at modern zoos.

Bloodworms, Glycera dibranchiata , possess an eversible proboscis that normally remains concealed within their bodies but explosively everts if the worm attacks or burrows. How does the bloodworm evert quickly and reliably? In a series of experiments, we characterize bloodworm kinematics, pressure, and material properties to estimate the criteria for eversion safely without rupture of the proboscis. We predict the proboscis can withstand pressures 50 times higher and bending strains up to three times higher than the respective values observed. We also present a dimensional analysis of eversion, finding that everting animals, from frogs to snails to sharks, do not satisfy Froude’s law for equivalence of velocities. Our findings may help inspire the development of pressure-driven soft robots with efficient retraction capabilities.

Synopsis: Seventy percent of mammals copulate using repeated pelvic thrusting, while the transfer of sperm requires just a single intromission. Why did thrusting evolve to be the dominant form of sexual intercourse? In this study, we investigate how the rate of sexual pelvic thrusting changes with body size. By analyzing films of copulating mammals, from mice Mus musculus to elephants Elephantidae, we find that bigger animals thrust slower. The rate of pelvic thrusting decreases from 6 Hz for the pocket mouse Pergonathus to 1.3–1.8 Hz for humans to an absence of thrusting for the rhino Rhinocerotidae and elephant Elephantidae families. To understand this dependence on body size, we consider the spring-like behavior of the legs, which is associated with the elasticity of the body's muscles, tendons, and ligaments. For both running and thrusting, greater displacment and energy savings can be achieved if the system is oscillated at its resonant or natural frequency. Resonant frequencies, as measured through previous studies of running in dogs Canis familiaris and horses Equus ferus caballus, show good agreement with sexual thrusting frequencies. Running and sexual thrusting have nothing in common from a behavioral perspective, but from a physical perspective, they are both constrained by the same musculoskeletal systems, and both take advantage of resonance. Our findings may provide improved treatments for human sexual dysfunction as well as improving breeding strategies for domestic mammals.