Predator Evasion Research Articles

The development of compensatory ability for a sexually-selected ornament in stalk-eyed flies

Female preference for longer eyespan has driven exaggerated sexual dimorphism in several species of stalk-eyed flies. Longer eyespan increases a fly’s moment of inertia, and flies experience significant increase in body mass across age as they mature sexually. These costs may impact flight behavior and fitness through maneuverability and predator evasion, and appear ameliorated by co-selection for compensatory traits, as flies with longer eyespans tend to have larger thoraces and wings, allowing them to perform turns similar to flies with shorter eyespans. However, the capacity to compensate for a potentially costly ornament may not be limited to morphological traits which are fixed at the time of eclosion: as flies age, they also accumulate thorax mass and improve their flight performance. The purpose of this study was to investigate the compensatory ability of two populations of stalk-eyed flies (Teleopsis dalmanni and Diasemopsis meigenii) through comparing morphology and flight performance relative to eyespan. ‘Over-compensators’ should exhibit greater morphological and/or performance traits relative to eyespan, whereas ‘under-compensators’ should exhibit relatively less across these metrics. Flight performance was assessed using high-speed videography and variable-density gas-mixtures to determine maximal flight capacity. Young adult flies eclosed as ‘under-compensators’, with less thorax mass, wing velocity and flight capacity relative to their eyespan as compared to older flies. As flies aged and accumulated thorax mass, they became ‘over-compensators’. Thus, compensation for long eye-stalks is not a fixed trait; instead, variation in compensatory ability appears to be associated with the development of thorax muscle and flight performance across age.

Do interspecific differences in morphology influence foraging efficiency of juvenile crappie?

Sympatric black crappie ( Pomoxis nigromaculatus Lesueur in Cuvier and Valenciennes, 1829) and white crappie ( Pomoxis annularis Rafinesque, 1818) often differ in ecological performance, such that white crappie outnumber black crappie in turbid waterbodies and black crappie predominate in clear waters with abundant cover. Recent work suggests that this performance difference is driven by juvenile white crappie having a limnetic body form and juvenile black crappie having a littoral body form, resulting in differential predation mortality between the species within open-water and vegetated environments. We tested whether these morphologies also lead to interspecific differences in foraging efficiency between the congeners in structure and open water. Juvenile black crappie spent more time pursuing fish prey than white crappie across all trials, suggesting that energetic gains of piscivory may differ between species. However, both species had similar capture efficiencies when attacking fathead minnows ( Pimephales promelas Rafinesque, 1820) within vegetated and open-water habitats. We conclude that variation in morphology between juvenile black crappie and white crappie does not have a large influence on foraging efficiency, at least on fish prey, in dense cover or open water, and suggest their performance in sympatry is likely not driven by predatory capabilities at the onset of piscivory within these different environmental contexts. Instead, the relationship between morphology and predator evasion may drive the distribution and relative abundance of crappie species within sympatric populations.

Developmental Social Experience Changes Behavior in a Threatening Environment in Corydoras Catfish

ABSTRACTCoordinated responses to threats are important for predator evasion in many species. This study examines the effect of developmental social experience on antipredator behavior and group cohesion in a highly gregarious catfish that communicates via tactile interaction, Corydoras aeneus. We reared fish either in a mixed‐age group of age‐matched peers and adult C. aeneus (mixed‐age condition, or MAC), or with age‐matched peers only (same‐age condition, or SAC). A startle test was conducted with small groups of subadults from either social rearing condition. Prior to any startle events, SAC subadults had increased tactile communication compared to MAC subadults, but SAC individuals were overall less active. SAC fish exhibited a stronger antipredator response to startles, and were more likely to freeze or take refuge in cover in response to a startle than MAC fish. MAC fish tended to respond to startle events by maintaining or decreasing their cohesion, whereas SAC fish tended to maintain or increase their cohesion. These behavioral differences are attributed to MAC fish developing with group protection as a result of shoaling with adults, resulting in reduced antipredator responses when reared with adults. This study underscores how social context during development can be critical in shaping how individuals perceive and respond to potential threats in their environment.

Comparison Study of Hydrodynamic Characteristics in Different Swimming Modes of Carassius auratus

This study utilized particle image velocimetry (PIV) to analyze the kinematic and hydrodynamic characteristics of juvenile goldfish across three swimming modes: forward swimming, burst and coast, and turning. The results demonstrated that C-shaped turning exhibited the highest speed, enabling rapid and agile maneuvers for predator evasion. Meanwhile, forward swimming was optimal for sustained locomotion, and burst-and-coast swimming was suited for predatory behaviors. A vorticity analysis revealed that vorticity around the tail fin was the primary source of propulsive force, corroborating the correlation between vorticity magnitude and propulsion found in previous research. The findings emphasize the crucial role of the tail fin in swimming efficiency and performance. Future research should integrate ethology, biomechanics, and physiology to deepen the understanding of fish locomotion, potentially informing the design of efficient biomimetic underwater robots and contributing to fish conservation efforts.

The complex effects of modern oncogenic environments on the fitness, evolution and conservation of wildlife species.

Growing evidence indicates that human activities are causing cancer rates to rise in both human and wildlife populations. This is due to the inability of ancestral anti-cancer defences to cope with modern environmental risks. The evolutionary mismatch between modern oncogenic risks and evolved cancer defences has far-reaching effects on various biological aspects at different timeframes, demanding a comprehensive study of the biology and evolutionary ecology of the affected species. Firstly, the increased activation of anti-cancer defences leads to excessive energy expenditure, affecting other biological functions and potentially causing health issues like autoimmune diseases. Secondly, tumorigenesis itself can impact important fitness-related parameters such as competitiveness, predator evasion, resistance to parasites, and dispersal capacity. Thirdly, rising cancer risks can influence the species' life-history traits, often favoring early reproduction to offset fitness costs associated with cancer. However, this strategy has its limits, and it may not ensure the sustainability of the species if cancer risks continue to rise. Lastly, some species may evolve additional anti-cancer defences, with uncertain consequences for their biology and future evolutionary path. In summary, we argue that the effects of increased exposure to cancer-causing substances on wildlife are complex, ranging from immediate responses to long-term evolutionary changes. Understanding these processes, especially in the context of conservation biology, is urgently needed.

ROS-Induced Autophagy of Skeletal Muscle Confers Resistance of Rice Flower Carp (Cyprinus carpio) to Short-Term Fasting.

Starvation is one of the main stresses for fish due to food shortage, the evasion of predators, and intraspecific competition. This research evaluated the impact of brief fasting periods on reactive oxygen species (ROS) levels, antioxidant response, mRNA expression of antioxidants, autophagy-related signaling genes, and autophagosome development in the muscle tissue of rice flower carp. Following a three-day fasting period, the levels of ROS and MDA rose. Additionally, after 3 d of fasting, there was a notable upregulation of NRF2 and significant increases in the levels of GSH and the activities of enzymes such as SOD, CAT, GST, GR, and GPX, while the expression of the autophagy marker gene LC3B did not change (p < 0.05). After 7 d of fasting, the content of the ROS, the activity of SOD and GR, and the GSH content reached the maximum (p < 0.05). Concurrently, there was a significant rise in the quantity of autophagosomes. An RT-qPCR analysis revealed that seven d of starvation significantly elevated the mRNA expression of genes associated with the initiation and expansion of autophagosome membranes, vesicle recycling, and cargo recruitment, including ULK1, BECLIN1, LC3B, ATG3, ATG4B, ATG4C, ATG5, ATG9, and P62. After feeding resumed for 3 d, the mRNA level of BECLIN1, ATG3, ATG4B, ATG4C, ATG5, LC3B, and P62 still remained at a high level. The LC3II protein reached its highest level. All autophagy-related gene expression decreased in the 7-day resumed feeding group. Our data implied that short-term fasting can cause oxidative stress and disrupt the antioxidant system first and then induce autophagy in the muscles of rice flower carp. These findings shed light on how fasting affects muscle homeostasis in fish. ROS-induced autophagy of the skeletal muscle may confer the resistance of rice flower carp to short-term fasting.

Behavioral transcriptomic effects of triploidy and probiotic therapy (Bifidobacterium, Lactobacillus, and Lactococcus mixture) on juvenile Chinook salmon (Oncorhynchus tshawytscha).

Aquaculturists use polyploid fish to maximize production albeit with some unintended consequences including compromised behaviors and physiological function. Given benefits of probiotic therapies (e.g., improved immune response, growth, and metabolism), we explored probiotic supplementation (mixture of Bifidobacterium, Lactobacillus, and Lactococcus), to overcome drawbacks. We first examined fish gut bacterial community composition using 16S metabarcoding (via principal coordinate analyses and PERMANOVA) and determined probiotics significantly impacted gut bacteria composition (p = 0.001). Secondly, we examined how a genomic disruptor (triploidy) and diet supplements (probiotics) impact gene transcription and behavioral profiles of hatchery-reared Chinook salmon (Oncorhynchus tshawytscha). Juveniles from four treatment groups (diploid-regular feed, diploid-probiotic feed, triploid-regular feed, and triploid-probiotic feed; n = 360) underwent behavioral assays to test activity, exploration, neophobia, predator evasion, aggression/sociality, behavioral sensitivity, and flexibility. In these fish, transcriptional profiles for genes associated with neural functions (neurogenesis/synaptic plasticity) and biomarkers for stress response and development (growth/appetite) were (i) examined across treatments and (ii) used to describe behavioral phenotypes via principal component analyses and general linear mixed models. Triploids exhibited a more active behavioral profile (p = 0.002), and those on a regular diet had greater Neuropeptide Y transcription (p = 0.02). A growth gene (early growth response protein 1, p = 0.02) and long-term neural development genes (neurogenic differentiation factor, p = 0.003 and synaptysomal-associated protein 25-a, p = 0.005) impacted activity and reactionary profiles, respectively. Overall, our probiotic treatment did not compensate for triploidy. Our research highlights novel applications of behavioral transcriptomics for identifying candidate genes and dynamic, mechanistic associations with complex behavioral repertoires.

Automated escape system: identifying prey's kinematic and behavioral features critical for predator evasion.

Identifying the kinematic and behavioral variables of prey that influence the evasion from predator attacks remains challenging. To address this challenge, we have developed an automated escape system that responds quickly to an approaching predator and pulls the prey away from the predator rapidly, as real prey. Reaction distance, response latency, escape speed, and other variables can be adjusted in the system. By repeatedly measuring the response latency and escape speed of the system, we demonstrated the system's ability to exhibit fast and rapid responses while maintaining consistency across successive trials. Using the live predatory fish species, Coreoperca kawamebari, we show that escape speed and reaction distance significantly affect the outcome of predator-prey interactions. These findings indicate that the developed escape system is useful for identifying kinematic and behavioral features of prey that are critical for predator evasion, as well as for measuring the performance of predators.

Escape behavior lateralization of pointed‐belly frog (Leptodactylus podicipinus) (Anura, Leptodactylidae) in the southern Pantanal

AbstractFunctional lateralization in directional preference for predator evasion was examined in 45 Pointed‐belly frogs (Leptodactylus podicipinus). T‐maze trials revealed a preference for rightward escape, though individual bias was minimal, at only 33%, to evade predictability. Sex and size didn't influence escape decisions, aligning with predator avoidance strategies.Abstract in Portuguese is available with online material.

Odorant Receptors Expressing and Antennal Lobes Architecture Are Linked to Caste Dimorphism in Asian Honeybee, Apis cerana (Hymenoptera: Apidae).

Insects heavily rely on the olfactory system for food, mating, and predator evasion. However, the caste-related olfactory differences in Apis cerana, a eusocial insect, remain unclear. To explore the peripheral and primary center of the olfactory system link to the caste dimorphism in A. cerana, transcriptome and immunohistochemistry studies on the odorant receptors (ORs) and architecture of antennal lobes (ALs) were performed on different castes. Through transcriptomesis, we found more olfactory receptor genes in queens and workers than in drones, which were further validated by RT-qPCR, indicating caste dimorphism. Meanwhile, ALs structure, including volume, surface area, and the number of glomeruli, demonstrated a close association with caste dimorphism. Particularly, drones had more macroglomeruli possibly for pheromone recognition. Interestingly, we found that the number of ORs and glomeruli ratio was nearly 1:1. Also, the ORs expression distribution pattern was very similar to the distribution of glomeruli volume. Our results suggest the existence of concurrent plasticity in both the peripheral olfactory system and ALs among different castes of A. cerana, highlighting the role of the olfactory system in labor division in insects.

Proportional variation and scaling in the hindlimbs of hopping mammals, including convergent evolution in argyrolagids and jerboas

Bipedal hopping is a mode of locomotion seen today in four rodent lineages and one clade of marsupials. The Argyrolagidae, marsupials from the Oligocene to Pliocene of South America, have also been considered to be hoppers. These lineages all convergently evolved similar general morphologies, with elongated hindlimbs, reduced forelimbs, and elongated tails, and their similarities and variations may be informative in understanding the evolution of hopping in mammals. This study uses principal components analysis and log-log regressions to investigate variation in the hindlimb proportions of these hopping mammals and how this relates to body mass. We find that the distribution of hopping mammal masses is bimodal, divided at roughly 500 g. These two domains among hopping mammals may reflect optimisation for different forms of hopping locomotion; species under 500 g tend to have more elongated metatarsals relative to the rest of their hindlimbs, perhaps to facilitate rapid vertical jumps for predator evasion, a behaviour not seen in larger hoppers. Despite this bimodal distribution in body mass, hindlimb proportions cluster more by clade than mass, with some similarities among clades being especially noteworthy. The jerboas (Dipodidae, Rodentia) and Argyrolagidae share a particularly extreme degree of metatarsal elongation. The drivers of this convergence are unclear, but we hypothesise that the elongation may be related to the reduction/fusion of metatarsals in these groups, or a greater reliance on bipedality at slow speeds, as jerboas are known to utilise multiple bipedal gaits in addition to hopping.

Ancestral photoreceptor diversity as the basis of visual behaviour.

Animal colour vision is based on comparing signals from different photoreceptors. It is generally assumed that processing different spectral types of photoreceptor mainly serves colour vision. Here I propose instead that photoreceptors are parallel feature channels that differentially support visual-motor programmes like motion vision behaviours, prey capture and predator evasion. Colour vision may have emerged as a secondary benefit of these circuits, which originally helped aquatic vertebrates to visually navigate and segment their underwater world. Specifically, I suggest that ancestral vertebrate vision was built around three main systems, including a high-resolution general purpose greyscale system based on ancestral red cones and rods to mediate visual body stabilization and navigation, a high-sensitivity specialized foreground system based on ancestral ultraviolet cones to mediate threat detection and prey capture, and a net-suppressive system based on ancestral green and blue cones for regulating red/rod and ultraviolet circuits. This ancestral strategy probably still underpins vision today, and different vertebrate lineages have since adapted their original photoreceptor circuits to suit their diverse visual ecologies.

Personality affects female mate choice: frogs displaying more consistent bold behaviors are choosier

Abstract Mate choice is an important cause of natural and sexual selection and drives the evolution and elaboration of male ornaments. Yet mate choice decisions are often neither consistent nor uniform, and a range of factors have been identified to influence variation between and within individuals. A potential source of variation influencing preferences and/or choosiness is animal personality, that is, repeatable among-individual differences in behaviors. Not only may individuals differ in average personality phenotype but also vary in how consistently they display said personality. Distinguishing between personality and consistency is important because both aspects are potentially naturally selected traits that may yet influence how sexually selected ornaments are evaluated. Here, we use a predator evasion assay to test whether there is variation in boldness among female gray treefrogs (Hyla versicolor), and then examine whether personality traits (spectrum of shy to bold) are correlated with choosiness for longer duration calls. We document substantial and repeatable between-individual variation in boldness, suggesting the presence of animal personality. Results also reveal that the consistency with which females expressed boldness is independent from average personality phenotype and that it is correlated with choosiness: more consistently bold females were choosier.

An Alignment-Free Explanation for Collective Predator Evasion in Moving Animal Groups

Moving animal groups consist of many distinct individuals but can operate and function as one unit when performing different tasks. Effectively evading unexpected predator attacks is one primary task for many moving groups. The current explanation for predator evasion responses in moving animal groups require the individuals in the groups to interact via (velocity) alignment. However, experiments have shown that some animals do not use alignment. This suggests that another explanation for the predator evasion capacity in at least these species is needed. Here we establish that effective collective predator evasion does not require alignment, it can be induced via attraction and repulsion alone. We also show that speed differences between individuals that have directly observed the predator and those that have not influence evasion success and the speed of the collective evasion process, but are not required to induce the phenomenon. Our work here adds collective predator evasion to a number of phenomena previously thought to require alignment interactions that have recently been shown to emerge from attraction and repulsion alone. Based on our findings we suggest experiments and make predictions that may lead to a deeper understanding of not only collective predator evasion but also collective motion in general.

Compensation for a costly ornament depends on the development of flight performance in stalk-eyed flies

Several species of stalk-eyed flies exhibit exaggerated sexual dimorphism where females favor males with longer eyespans. Longer eyespan increases a fly’s moment of inertia, and may, therefore, impact flight behavior and fitness, specifically maneuverability and predator evasion. However, these putative costs may be ameliorated by co-selection for compensatory traits, as flies with longer eyespans tend to have larger thoraces and wings, which allows them to perform turns similar to flies with shorter eyespans. Furthermore, the capacity to compensate for a potentially costly ornament may not be fixed across the life-history of the adult stage, as stalk-eyed flies achieve sexual maturity at 3-4 weeks of age, accompanied by significant growth of reproductive tissues and organs. Thus, growth of the abdomen and body mass over time may impose constraints on flight performance that may affect whether an adult reaches the age of reproductive viability. The purpose of this study was to investigate the flight performance of stalk-eyed flies and its relationship to body morphology and development. The flight performance of 1-to-30 day oldTeleopsis dalmanni(n=124) andDiasemopsis meigenii(n=83) were assessed by presenting normoxic, variable-density mixtures of heliox (O2, N2and He) in 10% increments ranging from air to pure heliox; the least-dense gas allowing flight represented maximal performance. Flight kinematics were analyzed using high-speed (5930fps) videography. Immediately following flight assessment, flies were euthanized, photographed, dissected and weighed. In both species, total body mass, thorax and abdominal mass increased across age. Wing kinematics and maximal flight capacity were associated with thorax mass, and increased with age as flies became heavier. Although flies with longer eyespans were indeed heavier, they had larger wings and thoraces; however, maximal flight capacity and kinematics were generally independent of eyespan. Thus, bearing long eye-stalks did not impair flight performance, nor did the increase in mass attributable to reproductive maturation. Instead, variation in flight performance appears associated with the development of the flight motor, and improved ratio of thorax-to-total mass, across age.

Floods drive functional zooplankton diversity in a core area of the Brazilian Pantanal Biosphere Reserve

ABSTRACT Water dynamics in floodplains are fundamental in structuring aquatic communities. Our research investigated zooplankton communities in the Pantanal ecosystem. Different hydroperiod phases can influence the functioning of aquatic ecosystems, but an understanding of the taxonomic and functional diversity of zooplankton in these areas is lacking. Over 3 years (2018–2020), we assessed the zooplankton community in habitats along the Paraguay River at the Taiamã Ecological Station, considering the flood, ebb, drought, and inundation phases. We used indices such as Rao’s quadratic entropy (RaoQ), functional evenness (FEve), functional divergence (FDiv), community weighted means (CWM), and fourth-corner RLQ to investigate the potential relationships between the taxonomic and functional diversity of zooplankton and the hydroperiod phases and limnological variables. We identified 153 species of zooplankton, with greater richness in the families Lecanidae and Brachionidae (rotifers) and Chydoridae and Daphnidae (cladocerans). Species composition varied significantly between flood and drought phases. We observed positive relationships between chlorophyll a, total nitrogen/phosphorus, and species with larger body size, pelagic habitat, filter-feeding mode, and medium predator evasion capacity, whereas littoral species and those with low predator evasion capacity showed negative relationships. CWM exhibited differences in functional traits between hydroperiod phases. FDiv analysis indicated well-defined ecological functions among the community species, and the low FEve value during the flood phase indicated the dominance of certain functional attributes. These results emphasize the relationship between hydrological processes and the distribution of zooplankton communities, highlighting the importance of functional diversity in understanding ecological interactions.

Putting a new spin on insect jumping performance using 3D modeling and computer simulations of spotted lanternfly nymphs.

How animals jump and land on diverse surfaces is ecologically important and relevant to bioinspired robotics. Here, we describe the jumping biomechanics of the planthopper Lycorma delicatula (spotted lanternfly), an invasive insect in the USA that jumps frequently for dispersal, locomotion and predator evasion. High-speed video was used to analyze jumping by spotted lanternfly 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-1) and accelerations (800-1000 m s-2), with mid-air trajectories consistent with ballistic motion without drag forces or steering. Despite rotating rapidly (5-45 Hz) 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 importance of collisional recovery behaviors. To further understand their rotational dynamics, we created realistic 3D rendered models of spotted lanternflies 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 the measured rotational kinematics. This analysis showed that the rotational inertia of spotted lanternfly nymphs is predominantly due to their legs, enabling them to use posture changes as well as drag torque to control their angular velocity, and hence their orientation, thereby facilitating predominately successful landings when jumping.

Comparative proteomic analysis of tail regeneration in the green anole lizard, Anolis carolinensis.

As amniote vertebrates, lizards are the most closely related organisms to humans capable of appendage regeneration. Lizards can autotomize, or release their tails as a means of predator evasion, and subsequently regenerate a functional replacement. Green anoles (Anolis carolinensis) can regenerate their tails through a process that involves differential expression of hundreds of genes, which has previously been analyzed by transcriptomic and microRNA analysis. To investigate protein expression in regenerating tissue, we performed whole proteomic analysis of regenerating tail tip and base. This is the first proteomic data set available for any anole lizard. We identified a total of 2,646 proteins - 976 proteins only in the regenerating tail base, 796 only in the tail tip, and 874 in both tip and base. For over 90% of these proteins in these tissues, we were able to assign a clear orthology to gene models in either the Ensembl or NCBI databases. For 13 proteins in the tail base, 9 proteins in the tail tip, and 10 proteins in both regions, the gene model in Ensembl and NCBI matched an uncharacterized protein, confirming that these predictions are present in the proteome. Ontology and pathways analysis of proteins expressed in the regenerating tail base identified categories including actin filament-based process, ncRNA metabolism, regulation of phosphatase activity, small GTPase mediated signal transduction, and cellular component organization or biogenesis. Analysis of proteins expressed in the tail tip identified categories including regulation of organelle organization, regulation of protein localization, ubiquitin-dependent protein catabolism, small GTPase mediated signal transduction, morphogenesis of epithelium, and regulation of biological quality. These proteomic findings confirm pathways and gene families activated in tail regeneration in the green anole as well as identify uncharacterized proteins whose role in regrowth remains to be revealed. This study demonstrates the insights that are possible from the integration of proteomic and transcriptomic data in tail regrowth in the green anole, with potentially broader application to studies in other regenerative models.

Settleable atmospheric particulate matter affects the swimming performance and aerobic metabolic rate of Nile tilapia (Oreochromis niloticus)

Atmospheric particulate matter (APM) produced by the steel industry comprises a complex mixture of particles that includes a wide variety of metals and metallic nanoparticles. These particles settle out onto areas surrounding the industries. There is evidence that this ‘settleable’ APM (SePM) may cause air-to-water cross-contamination with significant effects on aquatic biota. Recent investigations have reported sublethal impacts on the gill structure and blood oxygen-carrying capacity of fishes, which raises the hypothesis that there will be consequences for gas exchange capacity and ability to support aerobic activities. Therefore, we investigated the effects of an environmentally relevant level of SePM contamination on swimming performance and associated aerobic metabolic rates in Nile tilapia, Oreochromis niloticus. Short-term exposure (96 h) to SePM reduced critical swimming speed, energetic efficiency of aerobic swimming, standard metabolic rate, maximum metabolic rate, and aerobic scope. The compromised swimming performance could have adverse ecological effects by limiting foraging ability, predator evasion, territorial protection, and migration. The impairments to aerobic capacity could also affect overall fish performance by influencing long-term energy balance and allocation to growth and reproduction. Thus, despite being sublethal, SePM contamination is considerably debilitating, and if its limiting effects are not compensated for in the longer term, this may reduce the survival and fitness of fish populations.

Gene expression underlying variation in the survival skills of red drum larvae (Sciaenops ocellatus).

Mortality rates of marine fish larvae are incredibly high and can determine year-class strength. The major causes of larval mortality are predation and starvation, and the performance of larvae in survival skills that can mitigate this mortality (predator evasion, foraging) varies among individuals and cohorts, but the causes of the variation are not known. Transcriptomics can link gene expression variation to phenotypic variation at the whole-system level to investigate the molecular basis of behavioural variation. We used tag-based RNA-sequencing to examine the molecular basis of variation in predator evasion and routine swimming (trait related to foraging efficiency) in the larval red drum, Sciaenops ocellatus. We looked for functional gene networks in which interindividual variation would explain variation in larval behavioural performance. We identified co-expressed gene groups ("modules") associated with predator evasion traits and found enrichment of motor, neural and energy metabolism pathways. These functional associations and pattern of correlations between modules and traits suggest that energy availability and allocation were responsible for the magnitude of startle responses, while differential neural and motor activation were associated with differences in response latency.