Integrative and Comparative Biology

Laws of physics shape morphological and behavioral adaptations to locomotion at different body sizes. Water striders serve as a model taxon to study how simple physical constraints of water-surface habitats affect their behavior and morphology, and hydrodynamics of rowing by midlegs on the surface is well understood. However, the physics of the subsequent passive sliding has been less explored. We created a model of sliding on the water surface to simulate the effect of body mass, striding type, and wetted leg lengths on an insects ability to float on the surface and on the sliding resistance. The model predicts that to support their weight on the surface during sliding, the heavy species should either develop long forelegs that support the frontal part of its body during symmetrical striding (when two midlegs thrust) or use asymmetrical striding (when one forward-extended midleg supports the body while the other midleg and contra-lateral hindleg thrust). These predictions are confirmed by the behavior and morphology of various Gerridae species. Hence, the results illustrate how simple physical processes specific to a certain habitat type have far-reaching consequences for the evolution of morphological and behavioral diversification associated with body size among biological organisms in these habitats.

How animals jump and land on a variety of surfaces is an ecologically important problem relevant to bioinspired robotics. We investigated this topic in the context of the jumping biomechanics of the planthopper Lycorma delicatula (the spotted lanternfly, SLF), an invasive insect in the US that jumps frequently for dispersal, locomotion, and predator evasion. High-speed video was used to analyze jumping by SLF nymphs from take-off to impact on compliant surfaces. These insects used rapid hindleg extensions to achieve high take-off speeds (2.7-3.4 m/s) and accelerations (800-1000 ms-2), with midair trajectories consistent with zero-drag ballistic motion without steering. Despite rotating rapidly (5-45 Hz) in the air about time-varying axes of rotation, they landed successfully in 58.9% of trials; they also attained the most successful impact orientation significantly more often than predicted by chance, consistent with their using attitude control. Notably, these insects were able to land successfully when impacting surfaces at all angles, pointing to the emerging importance of collisional recovery behaviors. To further understand their rotational dynamics, we created realistic 3D rendered models of SLFs and used them to compute their mechanical properties during jumping. Computer simulations based on these models and drag torques estimated from fits to tracked data successfully predicted several features of their measured rotational kinematics. This analysis showed that SLF nymphs are able to use posture changes and drag torques to control their angular velocity, and hence their orientation, thereby facilitating predominately successful landings when jumping. SummaryHigh-speed video revealed that juvenile spotted lanternflies are adept at landing after tumbling rapidly midair during jumping. We present computer simulations and realistic 3D models to help explain these abilities.

Insects exhibit remarkable adaptability in their locomotive strategies across diverse environments, a crucial trait for foraging, survival, and predator avoidance. Microvelia, tiny 2-3 mm insects that adeptly walk on water surfaces, exemplify this adaptability by using the alternating tripod gait in both aquatic and terrestrial terrains. These insects commonly inhabit low-flow ponds and streams cluttered with natural debris like leaves, twigs, and duckweed. Using high-speed imaging and pose-estimation software, we analyze Microvelia spp.s movement across water, sandpaper (simulating land), and varying duckweed densities (10%, 25%, and 50% coverage). Our results reveal Microvelia maintain consistent joint angles and strides of their upper and hind legs across all duckweed coverages, mirroring those seen on sandpaper. Microvelia adjust the stride length of their middle legs based on the amount of duckweed present, decreasing with increased duckweed coverage and at 50% duckweed coverage, their middle legs strides closely mimic their strides on sandpaper. Notably, Microvelia achieve speeds up to 56 body lengths per second on water, nearly double those observed on sandpaper and duckweed (both rough, frictional surfaces), highlighting their higher speeds on low friction surfaces such as the waters surface. This study highlights Microvelias ecological adaptability, setting the stage for advancements in amphibious robotics that emulate their unique tripod gait for navigating complex terrains.

Dispersal over geographic barriers plays an essential role in colonization, gene flow, metapopulation dynamics, and invasion (Bowler and Benton 2005). Since dry lands strictly separate freshwater habitats, as expressed by the phrase "islands of water in a sea of dry land" (Faulks, Gilligan, and Beheregaray 2010), dispersal among freshwater waterbodies by themselves is challenging of aquatic organisms. Rumors have existed worldwide that freshwater fish eggs are dispersed by attaching to (ectozoochory) or excretion from (endzoochory) waterbirds (Hirsch et al. 2018). It is well documented that waterbirds disperse aquatic plants, zooplankton, and various aquatic invertebrates, which are co-distributed with fishes (Green et al. 2023). However, there is only two reported cases of empirical evidence of endzoochory in freshwater fishes and no scientific evidence of ectozoochory (Hirsch et al. 2018; Silva et al. 2019; Lovas-Kiss et al. 2020; Green et al. 2023). Here, we show that the southern medaka (Oryzias latipes, hereafter medaka) egg can travel passively by attaching to waterbirds.

Because Strepsiptera can fly vertically from a standing start, at least [1/4] of their body mass must be dedicated to flight muscle. Adult male Strepsiptera also do not feed and die within a few hours of eclosing, so much normal adult insect anatomy has been discarded, leading to a flight muscle to total mass ratio (FMR) of at least 30%--this is medial for Hymenoptera, but as the lower bound for Strepsiptera, it indicates substantial aerial ability. On account of their high FMR and low wing loading, Strepsiptera are capable of widely varied flight. Moreover, the often incongruous descriptions thereof (that they fly slowly, fly quickly, are clumsy, are graceful, etc.) are paralleled in well-established phases of sex pheromone tracking in moths. For nearly all of their brief eclosed adult lives, male Strepsiptera are airborne, for which they are well-adapted. Correspondingly, strepsipteran propagation is utterly dependent on flight. Thus, flight is the lens through which much strepsipteran ecology is clarified. Accordingly, I photographed free-flying Triozocera texana (nocturnal) in the field and analyzed the images. Strepsipteran wings are remarkably flaccid and potentially teneral, leading to certain flight advantages. At night, spatial acuity is especially poor in tiny insects, but halteres apparently compensate so well that even later derived diurnal Strepsiptera identify calling females chemotactilely--not visually--and shun resolution for high sensitivity. Future directions are discussed, as well as experimental techniques that are problematic when applied to Strepsiptera.

Male crickets engage in intense aggressive behavior, competing for resources. In this study, we focus on the quick movements during tactile combat in the cricket fight, to understand how they defeat the opponents. We performed kinematic analysis following high-speed cam recording of the fight. High-speed cam recordings showed that the attacker jumped to the head of the attacked cricket and thrusted it backwards. The attacked cricket was sometimes flipped over and tended to retreat. To understand how the attacker jumps effectively to flip over the opponent, we compared the attack-jump and escape-jump. The kinematics analysis demonstrated that the attack motion is different from the jump in the case of escaping from threats. The attacker cricket adjusted the direction of its body using its forelegs. The mandibles were used to hook onto the head of the attacked cricket. The attacked cricket moved its hindlegs with different kinematics to jump in the case of escape and exerted greater velocity. These findings advance our knowledge of how animals utilize their body depending on the situation.

Reliably capturing transient animal behavior in the field and laboratory remains a logistical and financial challenge, especially for small ectotherms. Here, we present home camera systems as affordable, accessible, and suitable alternatives for monitoring small, cold-blooded animals historically overlooked by commercial camera traps. Home security cameras are often weather-resistant, operate offline or online, and allow collection of time-sensitive behavioral data in laboratory and field conditions with continuous data storage for up to four weeks. These lightweight cameras can also utilize phone notifications over Wi-Fi, alerting users when animals enter a space of interest and enabling sample collection at proper time periods. We present our findings, both technological and scientific, in an effort to elevate tools that enable researchers to maximize use of their research budgets. We discuss the relative affordability of our system for researchers in South America, home to the largest ectotherm diversity.

Two Vorticella species undergo a synchronous transition from sessile zooids to motile telotrochs, which swarm enveloped in secreted mucus, subsequently forming dense aggregations on substrates and reverting to the zooid form. This cyclical process recurs on a daily basis. Each species exhibits a unique mode of swarming behavior. We hypothesize that these behaviors may serve to facilitate efficient feeding while concurrently acting as a mechanism for predator avoidance.

Centipedes coordinate body and limb flexion to generate propulsion. On flat solid surfaces, the limb-stepping patterns can be characterized according to the direction in which limbaggregates propagate, opposite to (retrograde) or with the direction of motion (direct). It is unknown how limb and body dynamics are modified in terrain with terradynamic complexity more representative of their natural heterogeneous environments. Here, we investigated how centipedes that use retrograde and direct limp-stepping patterns, S. polymorpha and S. sexspinosus, respectively, coordinate their body and limbs to navigate laboratory environments which present footstep challenges and terrain rugosity. We recorded the kinematics and measured the locomotive performance of these animals traversing two rough terrains with randomly distributed step heights and compared the kinematics to those on a flat frictional surface. S. polymorpha exhibited similar body and limb dynamics across all terrains and a decrease in speed with increased terrain roughness. Unexpectedly, when placed in a rough terrain, S. sexspinosus changed the limb-stepping pattern from direct to retrograde. Further, for both species, traversal of rough terrains was facilitated by hypothesized passive mechanics: upon horizontal collision of a limb with a block, the limb passively bent and later continued the stepping pattern. While centipedes have many degrees of freedom. our results suggest these animals negotiate limb-substrate interactions and navigate complex terrains, by offloading complex control and leveraging the innate flexibility of their limbs.

During their period of summer dormancy, Australian Bogong moths Agrotis infusa undertake seemingly random evening flights, filling the air with densities in the dozens per cubic metre. The purpose of these flights is unknown, but they may serve an important role in Bogong moth navigation, which remarkably enables them to return to the same exact summer sites-- generation after generation--after migrating around 1000 km, and with no opportunity to learn their route or destination from prior generations. The recent development of the camera-based insect monitoring method, Camfi, enables quantitative observations of Bogong moth behaviour at an unprecedented scale. To gain a better understanding of the summer evening flights of Bogong moths, we have extended Camfi to facilitate automated video tracking of flying insects, taking the already-high throughput of the method to a new level. We used this new method to record the evening flight behaviour of Bogong moths in two elevational transects below the summit of Mt. Kosciuszko, NSW, on a single night in February 2021, and found that these flights were not random, but were systematically oriented in directions relative to the azimuth of the summit of the mountain. These results stimulate interesting and plausible hypotheses relating to previously unexplained summer evening flight behaviour of Bogong moths, and the mechanisms of their long-distance navigation.

Odor-plume-guided navigation, tracking an odor plume to its source, is a primordial behavior used by most animals to search beyond the visual range. Here we report the first laboratory observations of octopuses performing this behavior, demonstrating that they can use odor plumes to find food. In a three-station discrimination task carried out in the dark, octopus showed a strong preference to move upstream towards the food-baited target, supporting the hypothesis that they are performing odor-guided search. When seeking a single baited target, also in the dark, octopuses not only preferred to move upstream towards the food source, but they also displayed characteristic motions associated with odor-gated rheotaxis, a commonly used odor tracking strategy used by many animals, which includes pausing, switchbacks, and across-stream redirections to the bait. Additionally, when approaching single baited stations the octopus often made reactive fast lunging motions. The observation of these fast arm-aligned motions (FAAM), taken together with the observation that the octopus did not have a characteristic body axis orientation to the bait, as would be expected if bilaterally symmetric organs such as the olfactory pits guided this behavior, supports the hypothesis that the suckers are the primary chemosensory organs driving octopus odor-guided behaviors.

The control and stability of flying and swimming animals is typically determined by measuring their responses to discrete gust perturbations. For the rigorous measurement and analysis of such responses, it is necessary to generate gusts that are precise, controllable and repeatable. Here, we present a method to generate discrete gusts under laboratory conditions using a vortex ring. Unlike other methods of gust generation, the vortex ring can be well characterized and is highly controllable. We first outline the theoretical basis for the design of a gust generator, and then describe an apparatus that we developed to generate discrete gusts. As a case study, we tested the efficacy of this method on freely-flying soldier flies Hermetia illucens. The method described here can be used to study diverse phenomena ranging from natural flight and swimming in insects, birds, bats and fishes, to the artificial flight of drones and micro-aerial vehicles.

Systematic descriptions of the underlying interaction rules that insects use to support group and swarm flight has the potential to contribute to mathematics, biology, and robotics, including aerial swarming under sensory and computational limitations. This study analyzes 1,000 trajectories of flying honeybees in crowded conditions approaching a moving stimulus and finds how during this stimulus, honeybees coordinate flight through pairwise interactions involving a novel three-zone decision-making process. The experimental setup consists of 3-D position reconstructions via a high speed camera system recording honeybee foragers returning to a hive entrance actuated to move robotically. The analysis consists of neighborhood identification through three methods (cross-correlation, distance threshold, and average distance threshold), which reveals the dominant interaction is pairwise. The individual leader-follower pair interactions are then tested against three regulation candidates: optic flow, relative velocity, and optical expansion rate, based on minimizing root mean square error. The results show that each follower demonstrates a three stage process involving a feedback rule change, linked by an intermediate observation/decision phase. During the initial "lock" phase, an insect maintains a consistent optical expansion rate until inter-agent distance closes to 10 cm. The regulation candidates then undergo large variations during a relatively long observation/decision zone, with 1.04 seconds being the average time in the decision zone. 79% of the paired insect entries into the decision zone result in subsequent re-engagement to track the same initial leader, while 21% result in disengagement from the group behavior. Visual regulation candidate comparison in the third stage indicates that upon re-engagement, the follower relative velocity is regulated to provide consistent velocity matching between agents. The third stages velocity tracking is consistent with a closed-loop feedback proportional-integral (PI) controller regulating velocity tracking error. Across the insect population studied, the proportional gain remained showed minimal variability over individuals, a derivative gain was considered and found negligible, and the integral gain varied by individual. Collectively, these findings underscore the existence of an alternative swarm architecture, highlighting individual decision-making capabilities, feedback regulation target changes, and the presence of reactive, deliberative, and moderate (PI control) timescale interaction rules contained within aerial groups.

The evolution of early land vertebrates from aquatic forms of life was a biological milestone. The transition to land was accompanied with expectedly challenging physiological and morphological evolutionary hurdles. So far, fossil records have provided substantial information on the origin of quadrupedal locomotion. However, fossil evidence alone is insufficient to understand how the soft-tissue-dependent motor functions and locomotion were acquired and developed. In the present study, we focus on locomotion of the sturgeon, an extant primitive fish, as a new experimental model, to investigate behavioural plasticity. Their locomotion in low-water-level conditions was similar to an escape response in water, the C-start escape response, which is used by most fish and amphibian juveniles to avoid predation. Sturgeons were also found to have mastered rolling-over in response to low water levels, resulting in the improvement of their trunk-twisting action. Sturgeons acquired an efficient shift in their centroid, thereby improving their mobility. We hypothesise that the escape response triggered by environmental hazards drove the development of locomotion, which was accompanied by a variety of behaviours.

Arboreal insects have developed various strategies to navigate their discontinuous habitats. Many insects, including leafhoppers, katydids, and praying mantises, exhibit the ability to actively leap across their leafy platforms and land on a distant substrate. This behavior is especially important for non-winged insects, including nymphal forms of winged insects, which cannot fly between these substrates. To make a targeted jump, an animal must first orient towards the target, estimate the target distance and angular location, and jump with the appropriate take-off speeds and angles to land on their intended substrate. In three-dimensional space, jumping from one point to another requires estimating distance, as well as azimuthal and elevational angles. Jumping insects such as mantises typically reorient their bodies on the substrate to align with the azimuthal direction of the target. This behavior effectively reduces the task to a two-dimensional problem, in which they must estimate only the distance to the target and its elevational angle. Many insects, including praying mantises, perform rhythmic lateral head movements called peering before performing a targeted jump. Although previous studies suggest that mechanisms such as motion parallax while peering are used for distance estimation, the full repertoire of behaviors that enable mantises to jump to arbitrarily located substrates remains unclear. We hypothesized that mantises have distinct behaviors for distance and elevation angle estimation, which enable them to independently modulate their take-off speeds and angles before jumping. To test this hypothesis, we developed behavioral assays in which mantises were placed on a launch platform and jumped to a target platform positioned at variable distances and angles. Using this apparatus, we filmed the jumps of Giant Asian mantis nymphs (Hierodula spp.) with high-speed videography and tracked body parts to quantify take-off speed and angle. Because mantis jumps are ballistic, their trajectories can be modeled as projectile motion. Our results indicate that mantises estimate target distance and elevation angle using two separate behavioral strategies: distance is assessed through peering maneuvers that generate motion parallax, whereas elevation angle is determined through visual fixation of the target accompanied by specific postural adjustments. By combining these behaviors, mantises modulate the magnitude and direction of propulsive force to achieve successful jumps.

Bats are fast fliers with great maneuverability. Many species sense and communicate through echolocation, relying on acoustic signals in the environment. Bats also form large colonies, which necessitates that they fly in groups. When the group size increases or obstacles are in their flight paths, the acoustic space can become cluttered, posing a non-trivial challenge for navigation. How do they interact with their environment and conspecifics, and how do they balance social and environmental cues? Recent research has uncovered individual adaptations to calling and flight patterns when flying in the groups or avoiding obstacles. Studies also suggest coordination when foraging, as well as strategies used by the group to mitigate acoustic clutter. However, there has yet to be a study on how bats weigh different navigational tasks when flying in spatially complex environments. Here, we collected stereoscopic video data on a wild colony of gray bats, Mytotis grisescens, navigating their usual foraging flight paths in the presence of novel obstacles. We find that bats tend to stay close to a wall, but space out when flying in groups. We developed a data-informed agent-based model which revealed that their social repulsive behavior is strengthened when challenged to navigate novel obstacles.

In the presence of wind or background image motion, flies are able to maintain a constant retinal-image velocity via regulating flight speed to the extent permitted by their locomotor capacity. Here we investigated the speed regulation of semi-tethered blue-bottle flies (Calliphora vomitoria) flying along an annular corridor in a magnetically levitated flight mill enclosed by two motorized cylindrical walls. We perturbed the flies retinal-image motion via spinning the cylindrical walls, generating bilaterally-averaged velocity perturbations from -0.3 to 0.3 m{middle dot}s-1. Flies compensated retinal-image velocity perturbations by adjusting airspeed up to 20%, thereby maintaining a relatively constant retinal-image velocity. When the retinal-image velocity perturbation became greater than [~]0.1 m{middle dot}s-1, the compensation weakened as airspeed plateaued, suggesting that flies were unable to further change airspeed. The compensation gain, i.e., the ratio of airspeed compensation and retinal-image velocity perturbation, depended on the spatial frequency of the grating patterns, being the largest at 12 m-1.

Despite its ubiquity in natural flows, the effects of turbulence on fish locomotion and behavior remain poorly understood. The prevailing hypothesis is that these effects depend on the spatial and temporal scales of the turbulence relative to the fishs size and swimming speed. But in conventional facilities, turbulence usually increases with mean flow, which forces higher swimming speeds and can leave these relative scales unchanged. We therefore present a novel experimental facility that leverages a jet array to decouple the turbulence from the mean flow and systematically control its scales. This approach allows the ratio of turbulent to fish inertial scales to be varied over an order of magnitude, providing a controlled framework for quantifying fish-turbulence interactions. The facility also supports experiments probing strategies fish may use to cope with turbulence, including collective behaviors. Insights from this work have broader implications for ecological studies and engineering applications, including the design of effective fishways and bio-inspired underwater vehicles.

We explored the nonlinear movement patterns of Anacridium aegyptium during terrestrial locomotion, providing insights into the walking dynamics of this large grasshopper species. Using video recordings, we analysed the trajectory of an insect and quantified key metrics, including curvature, tortuosity and fractal dimension. Curvature analysis revealed irregular turning behaviors with sharp directional changes, suggesting that locomotion was not random but deliberate. Compared with simulated linear trajectories, the curvature exhibited distinct peaks, highlighting the presence of statistically significant nonlinear features in the movement patterns. Phase space reconstruction revealed repetitive patterns indicating the potential presence of a limit cycle attractor. The trajectory remained confined within a specific region of the phase space, highlighting structured dynamics rather than unbounded behaviour. Fractal dimension analysis and Lyapunov exponent were consistent with a stable and predictable system over time, rather than one governed by chaos. These findings align with the behavioral ecology of A. aegyptium, suggesting that its walking dynamics are governed by efficient spatial exploration and obstacle negotiation rather than erratic or chaotic motion. Our study underscores the value of advanced mathematical and computational methods in boosting behavioural studies of locomotion. The insights derived from our analysis enhance our understanding of insect locomotion strategies and hold potential applications in the field of biomimetic robotics, where adaptive and efficient movement is mandatory. Future research could explore the impact of environmental factors, such as substrate type and food availability, on the observed nonlinear patterns, providing deeper context to the intricate locomotion behaviour of Anacridium aegyptium.

Behavioral studies have predominantly focused on organisms within the phyla Craniata and Arthropoda. Yet, there has been a growing interest in studying the behavior of organisms from alternative phyla, such as mollusks, owing to the research opportunities they offer. Among mollusks, cephalopods have emerged as a prominent subject of inquiry. However, behavioral research on Mexicos endemic species, Octopus maya (Om), remains conspicuously scarce. Om exhibits favorable attributes for utilization as a standardized animal model in neuroscience research, primarily due to its adaptability to laboratory settings and the successful raising of multiple generations. A comprehensive understanding of Oms behavior within laboratory environments is essential to harness its potential as a research model. Thus, the main goal of this study was to establish a comprehensive behavioral catalog for Om under laboratory conditions. Thirteen Om subjects (6 to 20 grams) were housed in controlled tank environments. Our findings reveal that Om exhibits a diverse behavioral repertoire, comprising a minimum of twenty-one distinct behaviors categorized into six behavioral classes. Additionally, Om displays discernable diurnal and nocturnal activity patterns, with increased activity levels, altered behavior distributions, and varying activity frequencies predominantly during daylight hours. This expanded knowledge of Oms behavior enhances its suitability as a research model organism.