Prey Detection Research Articles

Sensory-mediated feeding behaviour in the larvae of marble goby (Oxyeleotris marmorata)

This study was conducted to determine the senses that facilitate prey detection in the marble goby (Oxyeleotris marmorata) larvae. The ingestion ratios of live (generate chemical and mechanical stimuli) or frozen Artemia nauplii (generate chemical but no mechanical stimuli) by the intact or free neuromast (mechanoreceptor)-ablated O. marmorata larvae (11 mg/L streptomycin treatment before feeding) under the light or dark (fish vision was obstructed) condition were examined. Vision, mechano-, and chemoreceptions were all found to be essential in prey detection of the O. marmorata larvae. Prey movement has a significant influence as a visual stimuli on the O. marmorata larval feeding as the Artemia nauplii ingestion ratio was approximately 40% higher with significant (p = 0.001, d = 3.0), when the intact larvae were fed with the live (78.1 ± 1.5%), rather than the frozen (40.9 ± 2.8%) Artemia nauplii, under the light condition. This result was assured when no significant difference (p = 0.572, d = 0.2) was found between the ingestion ratios of frozen Artemia nauplii by the intact O. marmorata larvae under light and dark conditions. These findings demonstrate that prey detection in the O. marmorata larvae was facilitated by multi-modal senses, allowing O. marmorata larvae to survive in their natural habitats.

Large sensory volumes enable Southern elephant seals to exploit sparse deep-sea prey

The ability of echolocating toothed whales to detect and classify prey at long ranges enables efficient searching and stalking of sparse prey in these time-limited dives. However, nonecholocating deep-diving seals such as elephant seals appear to have much less sensory advantage over their prey. Both elephant seals and their prey rely on visual and hydrodynamic cues that may be detectable only at short ranges in the deep ocean, leading us to hypothesize that elephant seals must adopt a less efficient reactive mode of hunting that requires high prey densities. To test that hypothesis, we deployed high-resolution sonar and movement tags on 25 females to record simultaneous predator and prey behavior during foraging interactions. We demonstrate that elephant seals have a sensory advantage over their prey that allows them to potentially detect prey 5 to 10 s before striking. The corresponding prey detection ranges of 7 to 17 m enable stealthy approaches and prey-specific capture tactics. In comparison, prey react at a median range of 0.7 m, close to the neck extension range of striking elephant seals. Estimated search swathes of 150 to 900 m2 explain how elephant seals can locate up to 2,000 prey while swimming more than 100 km per day. This efficient search capability allows elephant seals to subsist on prey densities that are consonant with the deep scattering layer resources estimated by hydroacoustic surveys but which are two orders of magnitude lower than the prey densities needed by a reactive hunter.

Evolution of the highest sound pressure levels in mammalian echolocation calls

Recent work has shown that for some echolocating bat species there is a physical limit to the loudness of their echolocation signals, and this idea has been extended to suggest there is a physical limit to the loudness of echolocation signals of all species. This is at odds with the assumption that the loudness of a species call is driven by their body size, where louder species are larger species. This is also at odds with the prey detection hypothesis, where for echolocation calls the successful detection of prey at size extremes (both minima and maxima) drives the loudness of echolocation calls. A physical limit of loudness in echolocation calls may exist, but this has not been explored using comparative analysis. We compare the loudest echolocation calls across 63 echolocating mammals (including almost half of all aquatic echolocators) and show the assertion of a physical limit to loudness exists for bats in terrestrial habitats but breaks down for odontocetes in aquatic habitats. For aquatic echolocators, the loudness of their echolocation calls scales with body mass. We examine evolutionary and ecological pressures which may have led to these differences, and their influence on echolocation loudness.

Social information use in herbivore prey can influence the success of biological control

Predation-risk effects (PEs), i.e. costly consequences of antipredator trait responses in prey, have been the focus of many theoretical and applied studies on predator–prey systems, but we still have limited knowledge on how prey functional traits – such as the ability to acquire and use inadvertent social information (ISI) – influence the susceptibility to strong PEs. In this study, I used an individual-based model to explore how ISI use alters the relative importance of consumptive and predation-risk effects on herbivore prey abundance and total consumption, a proxy for plant damage. I found that ISI use contributed to higher prey abundance by lowering predation-related mortality, but it also decreased prey total consumption through PE irrespective of the relation between prey and predator detection ranges and the type of prey social organisation. Moreover, due to its stronger effect on the non-consumptive component of the total predation effect, ISI use contributed to an overall reduction in prey feeding performance. The estimated strengths of different predator effect components were also comparable to previous experimental findings. These findings provide strong support for the idea that the access to and use of risk-related social information not only result in more prey individuals exhibiting the antipredator response but also leads to strong behavioural PEs with substantial consequences on prey consumption.

Cranial asymmetry in odontocetes: a facilitator of sonic exploration?

Directional cranial asymmetry is an intriguing condition that has evolved in all odontocetes which has mostly been associated with sound production for echolocation. In this study, we investigated how cranial asymmetry varies across odontocete species both in terms of quality (i.e., shape), and quantity (magnitude of deviation from symmetry). We investigated 72 species across all ten families of Odontoceti using two-dimensional geometric morphometrics. The average asymmetric shape was largely consistent across odontocetes – the rostral tip, maxillae, antorbital notches and braincase, as well as the suture crest between the frontal and interparietal bones were displaced to the right, whereas the nasal septum and premaxillae showed leftward shifts, in concert with an enlargement of the right premaxilla and maxilla. A clear phylogenetic signal related to asymmetric shape variation was identified across odontocetes using squared-change parsimony. The magnitude of asymmetry was widely variable across Odontoceti, with greatest asymmetry in Kogiidae, Monodontidae and Globicephalinae, followed by Physeteridae, Platanistidae and Lipotidae, while the asymmetry was lowest in Lissodelphininae, Phocoenidae, Iniidae and Pontoporiidae. Ziphiidae presented a wide spectrum of asymmetry. Generalized linear models explaining magnitude of asymmetry found associations with click source level while accounting for cranial size. Using phylogenetic generalized least squares, we reconfirm that source level and centroid size significantly predict the level of cranial asymmetry, with more asymmetric marine taxa generally consisting of bigger species emitting higher output sonar signal, i.e. louder sounds. Both characteristics theoretically support foraging at depth, the former by allowing extended diving and the latter being adaptive for prey detection at longer distances. Thus, cranial asymmetry seems to be an evolutionary pathway that allows odontocetes to devote more space for sound-generating structures associated with echolocation and thus increases biosonar search range and foraging efficiency beyond simple phylogenetic scaling predictions.

Mutational analysis of mechanosensitive ion channels in the carnivorous Venus flytrap plant

How the Venus flytrap (Dionaea muscipula) evolved the remarkable ability to sense, capture, and digest animal prey for nutrients has long puzzled the scientific community.1 Recent genome and transcriptome sequencing studies have provided clues to the genes thought to play a role in these tasks.2,3,4,5 However, proving a causal link between these and any aspect of the plant's hunting behavior has been challenging due to the genetic intractability of this non-model organism. Here, we use CRISPR-Cas9 methods to generate targeted modifications in the Venus flytrap genome. The plant detects prey using touch-sensitive trigger hairs located on its bilobed leaves.6 Upon bending, these hairs convert mechanical touch signals into changes in the membrane potential of sensory cells, leading to rapid closure of the leaf lobes to ensnare the animal.7 Here, we generate mutations in trigger-hair-expressed MscS-like (MSL)-family mechanosensitive ion channel genes FLYCATCHER1 (FLYC1) and FLYCATCHER2 (FLYC2)5 and find that double-mutant plants have a reduced leaf-closing response to mechanical ultrasound stimulation. While we cannot exclude off-target effects of the CRISPR-Cas9 system, our genetic analysis is consistent with these and other functionally redundant mechanosensitive ion channels acting together to generate the sensory system necessary for prey detection.

Temperate bats may alter calls to partially compensate for weather-induced changes in detection distance.

Echolocation is the use of self-emitted calls to probe the surrounding environment. The atmosphere strongly absorbs sound energy, particularly high frequencies, thereby limiting the sensory range of echolocating animals. Atmospheric attenuation varies with temperature and humidity, which both vary widely in the temperate zone. Since echolocating insectivorous bats rely on ultrasound to capture insects, their foraging success might decrease with seasonal and daily variations in weather. To counteract weather-induced variations in prey detection, we hypothesised that European bats decrease call frequency and increase call energy when atmospheric attenuation increases, thereby maintaining their prey detection distance. Using acoustic localisation and automated call analysis, we measured call frequency and energy in free-flying bats of three common European insectivorous species. One species, Pipistrellus nathusii/kuhlii, increased call frequency, but simultaneously decreased call energy, while the two other species (P. pipistrellus and Myotis daubentonii) did not alter call parameters. We estimated the detection distance for prey based on the recorded call parameters and prey characteristics, using a custom-developed theoretical model. None of the three species maintained prey detection distance (it decreased by 1.7 to 3.4 m) when atmospheric attenuation increased. This study contributes to a better understanding of the sensory challenges faced by animals in fluctuating environments.

Estimating predation rates from molecular gut content analysis.

Several methods have been published to estimate per capita predation rates from molecular gut content analysis relying on intuitive understanding of predation, but none have been formally derived. We provide a theoretical framework for estimating predation rates to identify an accurate method and lay bare its assumptions. Per capita predation can be estimated by multiplying the prey decay rate and the prey quantity in the predators. This assumes that variation in per capita predation rate is approximately normally distributed, prey decay occurs exponentially, and predation is in steady state. We described several ways to estimate steady state predation, including using only qualitative presence-absence data to estimate the decay rate and in addition, we provided a method for estimating per capita predation rate when predation is not in steady state. We used previously published data on aphid consumption by a ladybird beetle in a feeding trial to calculate the predation rate and compare published methods with this theoretically derived method. The estimated predation rate (3.29 ± 0.27 aphids/h) using our derived method was not significantly different from the actual predation rate, 3.11 aphids/h. In contrast, previously published methods were less accurate, underestimating the predation rate (0.33 ± 0.02 to 1.66 ± 0.8 aphids/h) or overestimating it (3.64 ± 0.30 aphids/h). In summary, we provide methods to estimate predation rates even when variation in predation rates is not exactly normally distributed and not in steady state and demonstrate that the prey decay rate, and not the prey detection period, is required.

Blown away? Wind speed and foraging success in an acoustic predator

Foraging animals must contend with fluctuating environmental variables that affect foraging success, including conditions like wind noise, which could diminish the usefulness of particular sensory modes. Although the documented impact of anthropogenic noise on animal behavior has become clear, there is limited research on natural noise and its potential influence on mammalian behavior. We investigated foraging behavior in the myrmecophagous bat-eared fox (Otocyon megalotis), a species known to rely predominantly on hearing for prey detection. For a year, we monitored the foraging behavior of 18 bat-eared foxes from a habituated population in South Africa, amidst varying wind speeds (0–15.5 km/h). In contrast to expectations, foraging rates did not generally decline with increasing wind speed, except for foraging rate outside termite patches in fall. Furthermore, wind speed had little correlation with time spent in patches. In winter, however, we observed an increase in foraging rate with increasing wind speed both within and outside patches. At the observed wind speeds, these acoustically driven insectivores continue to forage effectively despite potentially distracting or masking noises. With anthropogenic noise producing sound across a broader frequency range, it is important to examine the responses of these canids to artificial sources of acoustic disturbance as well.

Impact of exploration behavior, aptitude for pellet consumption, and the predation practice on the performance in consecutive live prey foraging tests in a piscivorous species

Within the predator–prey relationship, predator behavior is less studied. Even in natural populations, it shows great diversity, and the factors influencing this are even less known. Among these factors, the personality type of the individual, (including exploration, and neophilia) and the practice significantly influence the success of adapting to a changing environment and switching to new prey types. In the present study, we investigated the first five consecutive foraging trials on live fish prey in naïve pikeperch individuals, which previously consumed or refused pelleted food. We hypothesized that individuals which were willing to consume alternative (pelleted) food would also show higher foraging success on living prey and that the practice would influence the learning process. Our results show that the timing of prey detection is influenced by exploratory behavior, the latency of the first attack by the aptitude for consuming pellets, and both traits by the individual's practice. However, neither of the factor affects the latency and success rate of capturing the prey, suggesting that predation is an independent behavioral trait.

The structure and diversity of retinal ganglion cells in the masked greenling Hexagrammos octogrammus Pallas, 1814 (Pisces: Scorpaeniformes: Hexagrammidae).

The authors studied the structure and diversity of retinal ganglion cells (GC) in the masked greenling Hexagrammos octogrammus. In vivo labelling with horseradish peroxidase revealed GCs of various structures in retinal wholemounts. A total of 154 cells were camera lucida drawn, and their digital models were generated. Each cell was characterized by 17 structural and topological parameters. Using nine clustering algorithms, a variety of clusterings were obtained. The optimum clustering was found using silhouette analysis. It was based on a set of three variables associated with dendritic field size and dendrite stratification depth in the retina. A total of nine cell types were discovered. A number of non-parametric tests showed significant pair-wise between-cluster differences in at least four parameters with medium and large effect sizes. Three large-field types differed mainly in dendritic field size, total dendrite length, level of dendrite stratification in the retina and position of somata. Six medium- to small-field types differed mainly in the structural complexity of dendritic arbors and level of dendrite arborization. Cells similar and obviously homologous to types 1-4 were identified in many fish species, including teleosts. Potential homologues of type 5 cells were identified in fewer teleost species. Cells similar to types 6-9 in relative dendritic field size and dendrite arborization pattern were also described in several teleostean species. Nonetheless, their homology is more questionable as their stratification patterns do not match so well as they do in large types. Potential functional matches of the GC types were identified in a number of teleostean species. Type 1 and 2 cells probably match spontaneously active units with the large receptive field centre, so-called dimming and lightening detectors; type 4 may be a counterpart of changing contrast detectors with medium receptive field centre size preferring fast-moving stimuli. Type 3 (biplexiform) cells have no obvious functional matches. Probable functional matches of types 6, 8 and 9 belong to ON-centre elements with small receptive fields such as ON-type direction-selective cells, ON-type spot detectors or ON-type spontaneously active units. Type 5 and 7 cells may match ON-OFF type units, in particular, changing contrast detectors or orientation-selective units. Potential functional matches of GC types presently described are involved in a wide spectrum of visual reactions related to adaptation to gradual change in illumination, predator escape, prey detection and capture, habitat selection and social behaviour.

DNA High-Throughput Sequencing for Arthropod Gut Content Analysis to Evaluate Effectiveness and Safety of Biological Control Agents.

The search for effective biological control agents without harmful non-target effects has been constrained by the use of impractical (field direct observation) or imprecise (cage experiments) methods. While advances in the DNA sequencing methods, more specifically the development of high-throughput sequencing (HTS), have been quickly incorporated in biodiversity surveys, they have been slow to be adopted to determine arthropod prey range, predation rate and food web structure, and critical information to evaluate the effectiveness and safety of a biological control agent candidate. The lack of knowledge on how HTS methods could be applied by ecological entomologists constitutes part of the problem, although the lack of expertise and the high cost of the analysis also are important limiting factors. In this review, we describe how the latest HTS methods of metabarcoding and Lazaro, a method to identify prey by mapping unassembled shotgun reads, can serve biological control research, showing both their power and limitations. We explain how they work to determine prey range and also how their data can be used to estimate predation rates and subsequently be translated into food webs of natural enemy and prey populations helping to elucidate their role in the community. We present a brief history of prey detection through molecular gut content analysis and also the attempts to develop a more precise formula to estimate predation rates, a problem that still remains. We focused on arthropods in agricultural ecosystems, but most of what is covered here can be applied to natural systems and non-arthropod biological control candidates as well.

Dietary Variation Is Driven by Landscape Heterogeneity in an Insular Omnivorous Endemic Lizard, Revealed by DNA Metabarcoding

Living on islands entails numerous challenges for animals, among which population density approaching the carrying capacity of trophic resources stands out. To overcome this limitation, many insular lizards can supplement their insectivorous diet with increasing portions of plant material. The Madeira wall lizard, Teira dugesii, is a medium-sized lacertid, endemic to the Madeira and Selvagens archipelagos. As common in this family, adults are sexually dimorphic with males being bigger than females. Previous dietary studies on morphological scatology identified a higher proportion of plant over animal prey items, changing according to the location and sex. Here, we used DNA metabarcoding to examine the diet of this lizard species quantifying it at a higher taxonomical resolution and enhancing the detection of soft-body prey that often go undetected in morphology-based studies. In a sample of 151 faecal samples from eight populations including different habitats and altitudes in Madeira, we identified 289 prey items belonging to eight animal and three plant Classes, encompassing 58 distinct orders and 140 families. Of these, 63 were identified up to the species level. The results support a strong trend towards herbivory in this species with plants representing almost 74% of the diet occurrences in contrast to the 26% of animal prey. Remarkably, the plant fraction of the diet remained stable across localities but varied with size and mass in males. As males grew bigger and heavier, they significantly increased their plant matter intake. Likely, larger bodies and abdomens allowed allocating longer and more complex digestive tracts harbouring intestinal flora to better decompose plant organic compounds. This allowed heavier animals to have a richer diet regime. However, diet richness and composition were not affected by either sex or size, while the locality had a significant effect on both diet components likely in response to local variation in prey availability. By including an increasing plant fraction into a primarily insectivorous diet, this insular lizard has not only enlarged its trophic niche but is also able to exploit more efficiently the highly variable resources provided by insular environments.

Nanopore short‐read sequencing: A quick, cost‐effective and accurate method for DNA metabarcoding

AbstractDietary and predator–prey studies are more frequently relying on DNA metabarcoding methods, typically achieving results that have a better taxonomic resolution (e.g., species‐level) than previous methods. With the continuous advancement in sequencing technology, what was previously accessible only as a large, fixed structure in a laboratory, which had a limited number of users, has now advanced to a small and readily usable device. In this study, we used the gut (content and lining) from juvenile lanternfish (Hygophum) specimens to compare the short‐read sequencing capability of the portable Nanopore MinION with the Illumina MiSeq. Primers common in dietary DNA metabarcoding work (COI “Leray primers” and 18S rRNA V4 “Zhan primers”) were used, with an additional comparison of cost‐effective COI “Lobo primers” (targeting the same COI fragment) for the proficiency in species detection of a broad range of taxa. Our results indicate high congruency between sequencing machines for, not only taxonomic assignments, but also relative read abundance of the main dietary items. We also identified that Nanopore sequencing is more cost‐effective. The Lobo primers are comparable to that of Leray, but substantially reduce the primer set price without compromising detection of taxa. Using both COI and 18S broadened the taxonomic scope, providing greater prey detection. Overall, this preliminary study was successful in creating a foundation for future dietary work involving larvae and transformation stage fishes whereby the content of the gut need not be separated from the gut lining to detect prey. The Hygophum diet detected here aligns with previous research that suggests the main dietary items to be calanoid copepods, but using molecular methods, soft prey was more readily identified compared to studies using visual methods of identification of dietary items. Overall, this study found that Nanopore sequencing is suitable for short‐read DNA metabarcoding and can provide rapid access to sequencing results.

Environmental and anthropogenic features mediate risk from human hunters and wolves for moose

AbstractLandscape characteristics, seasonal changes in the environment, and daylight conditions influence space use and detection of prey and predators, resulting in spatiotemporal patterns of predation risk for the prey. When predators have different hunting modes, the combined effects of multiple predators are mediated by the physical landscape and can result in overlapping or contrasting patterns of predation risk. Humans have become super‐predators in many anthropogenic landscapes by harvesting game species and competing with large carnivores for prey. Here, we used the locations of wolf (Canis lupus)‐killed and hunter‐killed moose (Alces alces) in south‐central Scandinavia to investigate whether environmental and anthropogenic features influenced where wolves and hunters killed moose. We predicted that the combined effects of wolves and hunters would result in contrasting spatial risk patterns due to differences in hunting modes. We expected these contrasting spatial risk patterns also to differ temporally. During the hunting season, the probability of a wolf kill increased with distance to bogs, whereas it decreased with increasing building density and distance to clearcuts and young forests. After the hunting season, the probability of a wolf kill increased with increasing terrain ruggedness and decreased with increasing building density, distance to main roads, and distance to clearcuts and young forests. The probability of a hunter kill was highest closer to bogs, main and secondary roads, in less rugged terrain and in areas with lower building density. Hunters killed all moose during the day, whereas wolves killed most moose at night during and after the hunting season. Our findings suggest that environmental and anthropogenic features mediate hunting and wolf predation risk. Additionally, we found that hunter‐ and wolf‐killed moose exhibited contrasting spatial associations to landscape features, most likely due to the different hunting modes displayed by hunters and wolves. However, wolf predation and hunting risks also contrasted over time since wolves killed mostly at night and hunters were restricted to hunting during daytime and during the hunting season. This temporal segregation in risk might therefore suggest that moose could minimize risk exposure by taking advantage of spatiotemporally vacant hunting domains.

Using colour pattern edge contrast statistics to predict detection speed and success in triggerfish (Rhinecanthus aculeatus).

Edge detection is important for object detection and recognition. However, we do not know whether edge statistics accurately predict the detection of prey by potential predators. This is crucial given the growing availability of image analyses and their application across non-human visual systems. Here, we investigated whether Boundary Strength Analysis (BSA), Local Edge Intensity Analysis (LEIA) and the Gabor Ratio (GabRat) could predict the speed and success with which triggerfish (Rhinecanthus aculeatus) detected patterned circular stimuli against a noisy visual background, in both chromatic and achromatic presentations. We found various statistically significant correlations between edge statistics and detection speed depending on treatment and viewing distance; however, individual pattern statistics only explained up to 2% of the variation in detection time, and up to 6% when considering edge statistics simultaneously. We also found changes in fish response over time. While highlighting the importance of spatial acuity and relevant viewing distances in the study of visual signals, our results demonstrate the importance of considering explained variation when interpreting colour pattern statistics in behavioural experiments. We emphasize the need for statistical approaches suitable for investigating task-specific predictive relationships and ecological effects when considering animal behaviour. This is particularly important given the ever-increasing dimensionality and size of datasets in the field of visual ecology.

Surface newt Calotriton asper acclimation to cave conditions improved their foraging ability in darkness

Caves in temperate regions are characterized by food scarcity compared to surface habitats. Therefore, hypotheses on adaptation to cave life suggest that many characteristics, such as resistance to starvation, reduced energy demand, and increased food-finding ability, have evolved among cave dwellers to cope with food frugality. To test the hypothesis involving increased food-finding ability, the prey detection performances of three surface and three subterranean populations of the Pyrenean newt, Calotriton asper, were compared. First, the rapidity of surface individuals in capturing prey at short distances inside a restricted aquarium under dark and light conditions and their score for capturing prey in a larger aquarium under similar conditions were measured. Simultaneously the scores obtained from individuals in cave populations in darkness were compared. Individuals from one of the surface population were maintained in darkness for approximately five years and retested. The surface C. asper individuals captured prey faster at short distances under light conditions than in total darkness; however, the differences were not significant. The scores of the surface C. asper individuals in the large aquarium were significantly better in darkness than in light conditions. In addition, the scores of cave populations at short distances in darkness were better than those of epigean populations in light conditions; however, the differences were not significant. Finally, the scores of surface individuals maintained in darkness for five years improved. To explain these results, it should be noted that surface C. asper populations forage at night using non-visual cues (e.g., chemical and mechanical cues), further suggesting that vision may somewhat inhibit other senses. This ability to forage at night may be favorable for cave colonization. Moreover, some hypogean populations, when the use of prey-detecting non-visual senses has developed, may start to exhibit adaptivity.

Prey localization in spider orb webs using modal vibration analysis

Spider webs are finely tuned multifunctional structures, widely studied for their prey capture functionalities such as impact strength and stickiness. However, they are also sophisticated sensing tools that enable the spider to precisely determine the location of impact and capture the prey before it escapes. In this paper, we suggest a new mechanism for this detection process, based on potential modal analysis capabilities of the spider, using its legs as distinct distributed point sensors. To do this, we consider a numerical model of the web structure, including asymmetry in the design, prestress, and geometrical nonlinearity effects. We show how vibration signals deriving from impacts can be decomposed into web eigenmode components, through which the spider can efficiently trace the source location. Based on this numerical analysis, we discuss the role of the web structure, asymmetry, and prestress in the imaging mechanism, confirming the role of the latter in tuning the web response to achieve an efficient prey detection instrument. The results can be relevant for efficient distributed impact sensing applications.

Predator responses to prey camouflage strategies: a meta-analysis.

Although numerous studies about camouflage have been conducted in the last few decades, there is still a significant gap in our knowledge about the magnitude of protective value of different camouflage strategies in prey detection and survival. Furthermore, the functional significance of several camouflage strategies remains controversial. Here we carried out a comprehensive meta-analysis including comparisons of different camouflage strategies as well as predator and prey types, considering two response variables: mean predator search time (ST) (63 studies) and predator attack rate (AR) of camouflaged prey (28 studies). Overall, camouflage increased the predator ST by 62.56% and decreased the AR of prey by 27.34%. Masquerade was the camouflage strategy that most increased predator ST (295.43%). Background matching and disruptive coloration did not differ from each other. Motion camouflage did not increase ST but decreases AR on prey. We found no evidence that eyespot increases ST and decreases AR by predators. The different types of predators did not differ from each other, but caterpillars were the type of prey that most influenced the magnitude of camouflage's effect. We highlight the potential evolutionary mechanisms that led camouflage to be a highly effective anti-predatory adaptation, as well as potential discrepancies or redundancies among strategies, predator and prey types.

A novel antennal form in trilobites

AbstractKnown antennae of trilobites are all flagelliform, in marked contrast to the varied first antennae of marine pancrustaceans. An exceptionally preserved specimen of the Early Ordovician (late Tremadocian) asaphidAsaphellus tataensisVidal, 1998, from the Fezouata Shale in Morocco, exhibits both antennae in situ; they are relatively short, widen distally, and bear a series of round, dome-shaped organs along both their dorsal and ventral surfaces. These organs are vastly larger than chemo- or mechanosensory sensilla on the antennae of other arthropods, rendering their homology and function uncertain. The clavate antennae ofAsaphellusreveal the furthest deviation from the inferred ancestral state of the trilobite antenna known to date. This could be an adaptation for detection of prey, because most Asaphidae have been claimed as predators and scavengers on the basis of specialized features of the calcified exoskeleton.