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As animals develop, demands on their physical form often change in response to ecological pressures. Structures associated with locomotion and habitat use can be particularly affected. Due to their smaller size, juvenile animals are often under selection to evade a larger and more diverse set of predators compared to adults of the same species. Adult Desert Horned Lizards, Phrynosoma platyrhinos, use a dorsoventral "shielding" as an anti-predator strategy to gape-limit potential predators. Because this strategy is likely size-dependent, we anticipated that juvenile lizards likely use different anti-predator strategies that would result in differences in habitat use, sprint performance, and morphology between age groups. We found differences in sprint speed and morphology, but not habitat use. Juvenile lizards had proportionally longer forelimbs and faster relative sprint speeds, potentially making juveniles more maneuverable than adults, though more work is needed to confirm this relationship. Our results suggest that selection for shielding behavior may constrain body shape throughout development, while shifts in limb lengths during development can enable juvenile lizards to evade their wider set of potential predators. [ABSTRACT FROM AUTHOR]

Many animals migrate across regions of their geographic range as part of extended events, with groups of individuals proceeding through areas of travel on several successive days. Early migrating individuals may have an advantage over late migrating individuals by gaining early access to the resources at the eventual destination. For situations where early access to resources would provide an advantage, specific sets of locomotor traits might be found among individuals that are earlier migrators. We tested for associations between migration timing and traits related to escape responses, climbing, and morphology in the amphidromous Hawaiian stream goby, 'o'opu nōpili (Sicyopterus stimpsoni). In this species, juvenile fish migrate in pulses over several days immediately following flash floods. We collected daily measurements of escape responses and waterfall climbing from juvenile fish arriving at streams from the ocean. We found that escape performance showed mainly stochastic variation across migrating individuals tested on successive days. In contrast, some metrics of climbing performance decrease over successive pulses during a migration event. We also found more variation in body shape among fish from early pulses during migration events compared to later in pulses. These results could have implications for guiding conservation efforts, identifying critical time windows for protection as periods with the greatest likelihood of successful migrants. [ABSTRACT FROM AUTHOR]

Species classification is an important task which is the foundation of industrial, commercial, ecological and scientific applications involving the study of species distributions, dynamics and evolution.While conventional approaches for this task use off‐the‐shelf machine learning (ML) methods such as existing Convolutional Neural Network (ConvNet) architectures, there is an opportunity to inform the ConvNet architecture using our knowledge of biological hierarchies among taxonomic classes.In this work, we propose a new approach for species classification termed hierarchy‐guided neural network (HGNN), which infuses hierarchical taxonomic information into the neural network's training to guide the structure and relationships among the extracted features. We perform extensive experiments on an illustrative use‐case of classifying fish species to demonstrate that HGNN outperforms conventional ConvNet models in terms of classification accuracy, especially under scarce training data conditions.We also observe that HGNN shows better resilience to adversarial occlusions, when some of the most informative patch regions of the image are intentionally blocked and their effect on classification accuracy is studied. [ABSTRACT FROM AUTHOR]

Populations exposed to sustained differences in predation pressure often diverge in morphological, behavioural or physiological features. However, predation pressures can also change throughout ontogeny, as individuals grow and/or migrate to new habitats. We examine how anti-predator traits differ in relation to predator regime through a comparative study of juvenile and adult waterfall-climbing goby fishes. On Hawai'i, gobies can migrate out of the range of aquatic predators, whereas on La Réunion aquatic predators and goby prey coincide. We predict that species and life stages that are freed from predation pressure would have reduced escape behaviour and performance. Because greater thrust production improves escape performance, we also predict that fishes coinciding with predators would have taller bodies than fish freed from predation. We simulated predator attacks and evaluated escape performance for juvenile and adult prey fishes from Hawai'i and La Réunion. Juvenile gobies of all species responded more frequently and had higher peak accelerations than adults. Additionally, fish released from predation pressures had the slowest peak accelerations and wider caudal peduncles than fish exposed to greater predation pressure. These results suggest that fishes released from predation pressure may have morphologies and performance that are more aligned with holding station than with the production of thrust to evade predators. [ABSTRACT FROM AUTHOR]

Teleost fishes have evolved a number of sound-producing mechanisms, including vibrations of the swim bladder. In addition to sound production, the swim bladder also aids in sound reception. While the production and reception of sound by the swim bladder has been described separately in fishes, the extent to which it operates for both in a single species is unknown. Here, using morphological, electrophysiological and modelling approaches, we show that the swim bladder of male plainfin midshipman fish ( Porichthys notatus ) exhibits reproductive state-dependent changes in morphology and function for sound production and reception. Non-reproductive males possess rostral 'horn-like' swim bladder extensions that enhance low-frequency (less than 800 Hz) sound pressure sensitivity by decreasing the distance between the swim bladder and inner ear, thus enabling pressure-induced swim bladder vibrations to be transduced to the inner ear. By contrast, reproductive males display enlarged swim bladder sonic muscles that enable the production of advertisement calls but also alter swim bladder morphology and increase the swim bladder to inner ear distance, effectively reducing sound pressure sensitivity. Taken together, we show that the swim bladder exhibits a seasonal functional plasticity that allows it to effectively mediate both the production and reception of sound in a vocal teleost fish.