Prey Capture Mechanism Research Articles

An ultraconserved element probe set for velvet worms (Onychophora)

Onychophora are cryptic, soil-dwelling invertebrates known for their biogeographic affinities, diversity of reproductive modes, close phylogenetic relationship to arthropods, and peculiar prey capture mechanism. The 216 valid species of Onychophora are grouped into two families – Peripatopsidae and Peripatidae – and apart from a few relationships among major lineages within these two families, a stable phylogenetic backbone for the phylum has yet to be resolved. This has hindered our understanding of onychophoran biogeographic patterns, evolutionary history, and systematics. Neopatida, the Neotropical clade of peripatids, has proved particularly difficult, with recalcitrant nodes and low resolution, potentially due to rapid radiation of the group during the Cretaceous. Previous studies have had to compromise between number of loci and number of taxa due to limitations of Sanger sequencing and phylotranscriptomics, respectively. Additionally, aspects of their genome size and structure have made molecular phylogenetics difficult and data matrices have been affected by missing data. To address these issues, we leveraged recent, published transcriptomes and the first high quality genome for the phylum and designed a high affinity ultraconserved element (UCE) probe set for Onychophora. This new probe set, consisting of ∼ 20,000 probes that target 1,465 loci across both families, has high locus recovery and phylogenetic utility. Phylogenetic analyses recovered the monophyly of major clades of Onychophora and revealed a novel lineage from the Neotropics that challenges our current understanding of onychophoran biogeographic endemicity. This new resource could drastically increase the power of molecular datasets and potentially allow access to genomic scale data from archival museum specimens to further tackle the issues exasperating onychophoran systematics.

Mechanics reveals the role of peristome geometry in prey capture in carnivorous pitcher plants (Nepenthes)

Carnivorous pitcher plants (Nepenthes) are a striking example of a natural pitfall trap. The trap's slippery rim, or peristome, plays a critical role in insect capture via an aquaplaning mechanism that is well documented. While the peristome has received significant research attention, the conspicuous variation in peristome geometry across the genus remains unexplored. We examined the mechanics of prey capture using Nepenthes pitcher plants with divergent peristome geometries. Inspired by living material, we developed a mathematical model that links the peristomes' three-dimensional geometries to the physics of prey capture under the laws of Newtonian mechanics. Linking form and function enables us to test hypotheses related to the function of features such as shape and ornamentation, orientation in a gravitational field, and the presence of "teeth," while analysis of the energetic costs and gains of a given geometry provides a means of inferring potential evolutionary pathways. In a separate modeling approach, we show how prey size may correlate with peristome dimensions for optimal capture. Our modeling framework provides a physical platform to understand how divergence in peristome morphology may have evolved in the genus Nepenthes in response to shifts in prey diversity, availability, and size.

Quantifying the feeding behavior and trophic impact of a widespread oceanic ctenophore

Oceanic ctenophores are widespread predators on pelagic zooplankton. While data on coastal ctenophores often show strong top-down predatory impacts in their ecosystems, differing morphologies, prey capture mechanisms and behaviors of oceanic species preclude the use of coastal data to draw conclusion on oceanic species. We used high-resolution imaging methods both in situ and in the laboratory to quantify interactions of Ocyropsis spp. with natural copepod prey. We confirmed that Ocyropsis spp. uses muscular lobe contraction and a prehensile mouth to capture prey, which is unique amongst ctenophores. This feeding mechanism results in high overall capture success whether encountering single or multiple prey between the lobes (71 and 81% respectively). However, multiple prey require several attempts for successful capture whereas single prey are often captured on the first attempt. Digestion of adult copepods takes 44 min at 25 °C and does not vary with ctenophore size. At high natural densities, we estimate that Ocyropsis spp. consume up to 40% of the daily copepod standing stock. This suggests that, when numerous, Ocyropsis spp. can exert strong top-down control on oceanic copepod populations. At more common densities, these animals consume only a small proportion of the daily copepod standing stock. However, compared to data from pelagic fishes and oceanic medusae, Ocyropsis spp. appears to be the dominant copepod predator in this habitat.

Alciporin, a pore-forming protein as complementary defense mechanism in Millepora alcicornis

Millepora alcicornis (Cnidaria: Hydrozoa), known as fire coral, is a tropical species settled in marine ecosystems of the Canary Islands in the last years. This hydrocoral biosynthesizes toxins involved in chemical defense and prey capture mechanisms. Toxicological studies have shown that the venom contained in the nematocysts of Millepora species is mainly composed of thermolabile proteins that display hemolytic activity, causing skin irritation and burn-like lesions upon contact. As a continuation of a previous study, the chromatographic fractionation of the aqueous extracts of M. alcicornis has confirmed the coexistence of proteins of different nature responsible for the hemolytic effects of red blood cells (RBCs) through two different mechanisms. Aside from the already described phospholipase A2 (PLA2) activity, in this work the presence of alciporin, a pore-forming protein (PFP), has been established for the first time for M. alcicornis. The sequence analysis revealed that alciporin fit an actinoporin with high homology to stichotoxins. The hemolytic effects of alciporin were analyzed and sphingomyelin was identified as its biological target. Also, the evolution of the hemolytic damage produced at the nanoscale has been studied using atomic force microscopy (AFM).

Mosquitoes Eating Mosquitoes: How Toxorhynchites amboinensis, Psorophora ciliata, and Sabethes cyaneus (Diptera: Culicidae) Capture Prey.

High-speed microcinematography was used to elucidate the details of prey capture by the larvae of three predatory mosquito species. The obligate predators Toxorhynchites amboinensis and Psorophora ciliata exhibited a high degree of convergence as both utilize three essential elements: 1) abdominally-generated hemostatic pressure to propel the head towards the prey; 2) lateral palatal brushes (LPB) opening and fanning into anterior-directed basket-like arrangements; 3) simultaneously with the LPB-basket formation, the wide opening of sharp-toothed mandibles. Thus, LPBs and mandibles are used for prey capture by both species. The facultative predator Sabethes cyaneus utilizes a vastly different prey-capture mechanism that involves ventro-lateral body arching and scooping of prey with axially pointed siphons into the grasp of open maxillae bearing elongate apical teeth. Prey consumption, which is typically incomplete in this species, then involves the action of teeth on the mandibles which cut into the held prey. Although prey consumption is incomplete, simple experiments show that Sa. cyaneus do gain nutritionally from consuming mosquito larvae and that they do discriminate heterospecific from conspecific larvae and actively approach heterospecific mosquito prey. These findings indicate that independent evolutionary pathways have produced diverse predatory behaviors and morphologies in aquatic environments where the immature stages of mosquitoes co-occur.

Paddling motion of a free-swimming jellyfish and Lagrangian coherent structure analysis

Swimming and prey capture by prolate and oblate jellyfishes are numerically examined in two-dimensions using multi-relaxation-time lattice Boltzmann (MRT-LB) and immersed boundary (IB) methods. The near-field fluid structure interaction (FSI) and predator-prey interaction mechanisms are revealed via the simulated Eulerian flow characteristics, finite-time Lyapunov exponent (FTLE) field, and Lagrangian coherent structures (LCS). We implement appropriate periodic body force (Fb) distribution at nodal points of the elastic bell in radial direction to model the paddled swimming as well as complex feeding behavior. For a paddling jellyfish the evolved starting and stopping vortices, as move close to each other in near-wake, create the necessary vortex induced thrust that facilitate the forward body motion. The forced bell contraction in power stroke assists quicker propulsive swimming, whereas passive bell expansion in resting phase facilitates the continued vortex induced forward movement for larger duration, via the refilled fluid momentum. For feeding the detailed prey interception and precise capture areas for various jellyfish models are identified hereby via the computed prey tracks, forward and backward time FTLE fields, and LCS. Swimming performances are analyzed based on interactive thrust and drag forces, input power (energy rate required for bell contraction), output power (thrust multiplied by centroid velocity), and cost of transport (COT). At low Reynolds number (Re) the COT becomes higher for an oblate jellyfish than that of a prolate one; while with increased Re the oblate species appears more economical. However, for enhanced paddling force (Fb) or reduced flapping frequency of bell, the COT for an oblate jellyfish steadily decreases. Hereby impacts of the varied force duration, flapping amplitude, flapping frequency, and bell-elasticity on the swimming are analyzed in greater detail. Notably, the propulsion efficiency increased for higher flapping frequency. The present numerical model efficiently unfolds prey capture mechanisms that are adopted by prolate and oblate medusae and quantifies their success rate (clearance rate, CR) in prey capture. Unlike in past studies, the FTLE fields and LCS that are computed here by tracking the transient motion of a large number of suspended Lagrangian prey particles exhibit the realistic predator-prey interaction and precise prey capture surface, which are difficult to measure or analyze empirically.

Disentangling the role of surface topography and intrinsic wettability in the prey capture mechanism of Nepenthes pitcher plants

Nepenthes pitcher plants capture prey with leaves specialised as pitfall traps. Insects are trapped when they ‘aquaplane’ on the pitcher rim (peristome), a surface structured with macroscopic and microscopic radial ridges. What is the functional significance of this hierarchical surface topography? Here, we use insect pad friction measurements, photolithography, wetting experiments and physical modelling to demonstrate that the ridges enhance the trap's efficacy by satisfying two functional demands on prey capture: Macroscopic ridges restrict lateral but enhance radial spreading of water, thereby creating continuous slippery tracks which facilitate prey capture when little water is present. Microscopic ridges, in turn, ensure that the water film between insect pad and peristome remains stable, causing insects to aquaplane. In combination, the hierarchical ridge structure hence renders the peristome wettable, and water films continuous, so avoiding the need for a strongly hydrophilic surface chemistry, which would compromise resistance to desiccation and attract detrimental contamination.

Selective consumption of sacoglossan sea slugs (Mollusca: Gastropoda) by scleractinian corals (Cnidaria: Anthozoa).

Recent studies revealed that reef corals can eat large-sized pelagic and benthic animals in addition to small planktonic prey. As follow-up, we document natural ingestion of sea slugs by corals and investigate the role of sacoglossan sea slugs as possible prey items of scleractinian corals. Feeding trials were carried out using six sacoglossan species as prey, two each from the genera Costasiella, Elysia and Plakobranchus, and four free-living solitary corals (Danafungia scruposa, Fungia fungites, Pleuractis paumotensis and Heteropsammia cochlea) as predators. Trials were carried out under both in-situ and ex-situ conditions with the aim to observe ingestion and assess signs of prey consumption based on tissue loss of prey individuals over time. Significant differences were observed in both ingestion time and consumption state of prey between prey species, with three of them being ingested more rapidly and preferentially consumed over the others. Additionally, prey size was found to be a significant factor with larger prey (>12 mm) being ingested more slowly and rarely than smaller ones (<6 mm and 6–12 mm). Comparisons of consumption capability among predators showed no significant difference with all coral species showing similar preferences for prey species. While no specific mechanism of prey capture is proposed, we also document instances of kleptoparisitism and resuspension of prey items by wrasses. This study highlights the important distinction between opportunistic prey capture and true predation events.

The prey capture mechanism of micro structure on the Sarracenia Judith Hindle inner surface

Low friction surface has attracted considerable attention due to its potential application in various fields. As a typical carnivorous plant, Sarracenia Judith Hindle possesses unique slippery surface to capture prey especially in wet environment. In order to make clear the low friction mechanism, structural characterization was carried out and unique inclined micro-thorn structure was found on the inner wall surface. Micro-droplets harvest on the surface of the micro-thorn was discovered via the observation in wet environment. Friction force measurement was conducted by sliding the ants’ footpad on the inner surface and polymer replica surfaces, which demonstrated that the friction force decreases on those surfaces in wet environment or inward direction. Further analysis manifested that the slippery inner surface grown with hierarchical micro-thorn structure leads to the friction decrease, and that is the fundamental mechanism for prey capture and retention in the pitcher of carnivorous plant Sarracenia Judith Hindle.

Nepenthes pitchers are CO2-enriched cavities, emit CO2 to attract preys

Carnivorous plants of the genus Nepenthes supplement their nutrient deficiency by capturing arthropods or by mutualistic interactions, through their leaf-evolved biological traps (pitchers). Though there are numerous studies on these traps, mostly on their prey capture mechanisms, the gas composition inside them remains unknown. Here we show that, Nepenthes unopened pitchers are CO2-enriched ‘cavities’, when open they emit CO2, and the CO2 gradient around open pitchers acts as a cue attracting preys towards them. CO2 contents in near mature, unopened Nepenthes pitchers were in the range 2500–5000 ppm. Gas collected from inside open N. khasiana pitchers showed CO2 at 476.75 ± 59.83 ppm. CO2-enriched air-streaming through N. khasiana pitchers (at 619.83 ± 4.53 ppm) attracted (captured) substantially higher number of aerial preys compared to air-streamed pitchers (CO2 at 412.76 ± 4.51 ppm). High levels of CO2 dissolved in acidic Nepenthes pitcher fluids were also detected. We demonstrate respiration as the source of elevated CO2 within Nepenthes pitchers. Most unique features of Nepenthes pitchers, viz., high growth rate, enhanced carbohydrate levels, declined protein levels, low photosynthetic capacity, high respiration rate and evolved stomata, are influenced by the CO2-enriched environment within them.

Prey capture by Dionaea muscipula A review of scientific literature with supplementary original research

Many descriptions of prey capture by Dionaea muscipula (Venus flytrap) in popular publications and educational literature are inaccurate. Here we review well documented literature on prey capture in this plant’s natural habitat and add observations on prey capture and attraction mechanisms we have observed in plants cultivated in a greenhouse and garden.

Labrid cleaner fishes show kinematic convergence as juveniles despite variation in morphology.

Cleaning, a dietary strategy in which mucus or ectoparasites are removed and consumed off other taxa, is performed facultatively or obligately in a variety of species. We explored whether species in the Labridae (wrasses, parrotfishes) of varying ecological specialization employ similar mechanisms of prey capture. In investigating feeding on attached prey among juveniles of 19 species of wrasses, we found that patterns of biting in wrasses are influenced by the interaction between the maxilla and a feature of the premaxilla which we term the maxillary crest. Premaxillary motion during biting appears to be guided by the relative size of the crest. In many cases, this results in a 'premaxillary bite' wherein the premaxillae rapidly move anteroventrally to meet the lower jaws and deliver a protruded bite. Cleaners in the Labrichthyini tribe, however, exhibited reduced or absent maxillary crests. This coincided with a distinct kinematic pattern of prey capture in these labrichthyine cleaners, coupled with some of the fastest and lowest-excursion jaw movements. Although evidence of kinematic specialization can be found in these labrichthyines (most notably in the obligate cleaners in Labroides), we found that facultative cleaners from other lineages similarly evolved reductions in excursions and timing. Convergence in feeding kinematics is thus apparent despite varying degrees of cleaning specialization and underlying morphological features.

Functional relationships in the jaw apparatus of the chameleons and the evolution of adaptive complexes

The distinctive features of the jaw apparatus in chameleons (hyperstreptostyly, amphikinetism reduction, transformation of the cranial roof into a “casque,” the jugo-mandibular ligament, the shape and position of quadrate bones, and the structure of jaw adductors) emerged as adaptations for the refinement of the mechanism of prey capture by the tongue. The development of another group of features (loss of the epipterygoid, m. levator pterygoidei, and structures associated with the middle ear) was an indirect consequence of the adaptations listed above. The formation of a specialized mechanism for prey capture by the tongue played a role of a key innovation (macromorphosis) in the phylogeny of chameleons. The ontogenetic relationships between the aforementioned features of the jaw apparatus of the chameleons are adaptive correlations, and the evolutionary transformations of these correlations correspond to biological coordinations. The evolutionary mechanisms underlying the formation of correlation and coordination interrelations in the organism are considered.

Dining dichotomy: aquatic and terrestrial prey capture behavior in the Himalayan newt Tylototriton verrucosus.

ABSTRACTTransitions between aquatic and terrestrial prey capture are challenging. Trophic shifts demand a high degree of behavioral flexibility to account for different physical circumstances between water and air to keep performance in both environments. The Himalayan newt, Tylototriton verrucosus, is mostly terrestrial but becomes aquatic during its short breeding period. Nonetheless, it was assumed that it lacks the capability of trophic behavioral flexibility, only captures prey on land by its tongue (lingual prehension) and does not feed in water. This theory was challenged from stomach content analyses in wild populations that found a variety of aquatic invertebrates in the newts' stomachs during their breeding season. Accordingly, we hypothesized that T. verrucosus actively changes its terrestrial prey capture mechanism to hunt for aquatic prey at least during its aquatic stage. In fact, the kinematic analyses showed that T. verrucosus uses lingual prehension to capture prey on land but changes to suction feeding for aquatic strikes. The statistical analyses revealed that terrestrial and aquatic strikes differ significantly in most kinematic parameters while behavioral variability does not differ between both behaviors. In turn, the movement patterns in suction feeding showed a higher degree of coordination between jaw and hyoid movements compared to the putative primary feeding mode, namely lingual prehension. We conclude that T. verrucosus, though relatively slow compared to trophic specialists, benefits from a high degree of behavioral flexibility that allows exploiting food sources efficiently from two very different habitats.

Fragilicetus velponi: a new mysticete genus and species and its implications for the origin of Balaenopteridae (Mammalia, Cetacea, Mysticeti)

A new extinct genus, Fragilicetus gen. nov., is described here based on a partial skull of a baleen-bearing whale from the Early Pliocene of the North Sea. Its type species is Fragilicetus velponi sp. nov. This new whale shows a mix of morphological characters that is intermediate between those of Eschrichtiidae and those of Balaenopteridae. A phylogenetic analysis supported this view and provided insights into some of the morphological transformations that occurred in the process leading to the origin of Balaenopteridae. Balaenopterid whales show specialized feeding behaviour that allows them to catch enormous amounts of prey. This behaviour is possible because of the presence of specialized anatomical features in the supraorbital process of the frontal, temporal fossa, glenoid fossa of the squamosal, and dentary. Fragilicetus velponi gen. et sp. nov. shares the shape of the supraorbital process of the frontal and significant details of the temporal fossa with Balaenopteridae but maintains an eschrichtiid- and cetotheriid-like squamosal bulge and posteriorly protruded exoccipital. The character combination exhibited by this cetacean provides important information about the assembly of the specialized morphological features responsible for the highly efficient prey capture mechanics of Balaenopteridae. © 2015 The Linnean Society of London

Independent Evolution of Suction Feeding in Neobatrachia: Feeding Mechanisms in Two Species of Telmatobius (Anura:Telmatobiidae).

The most common feeding mechanism among aquatic vertebrates as fishes, turtles, and salamanders is inertial suction. However, among the more than 6,400 species of anurans, suction feeding occurs only in pipids. Pipidae is a small basal lineage relative to Neobatrachia, an enormous clade that contains about 96% of extant anurans. The Andean neobatrachian frogs of the genus Telmatobius include strictly aquatic and semiaquatic species. Diet analyses indicate that some species of Telmatobius feed on strictly aquatic prey, but until now their feeding mechanisms have been unknown. Herein, the feeding mechanisms in two species of Telmatobius, that represent the two predominant modes of life in the genus, are explored. The semiaquatic T. oxycephalus and the fully aquatic T. rubigo are studied using high-speed cinematography and standard anatomical techniques to provide a qualitative approach to feeding behavior and a detailed morphological description of the mouth, tongue, hyoid and related muscles. T. oxycephalus uses similar mechanisms of aquatic prey capture as do the vast majority of anurans that are capable of forage in water, whereas the fully aquatic T. rubigo is an inertial suction feeder. This is the first report of an objective record of this unique feeding behavior in a Neobatrachian. Several morphological characters seem to be related with this function and are convergent with those of pipids.

Functional morphology and kinematics of terrestrial feeding in the largescale foureyes (Anableps anableps).

A major challenge for aquatic vertebrates that invade land is feeding in the terrestrial realm. The capacity of the gape to become parallel with the ground has been shown to be a key factor to allow fishes to feed on prey lying on a terrestrial surface. To do so, two strategies have been identified that involve a nose-down tilting of the head: (1) by pivoting on the pectoral fins as observed in mudskippers, and (2) curling of the anterior part of the body supported by a long and flexible eel-like body as shown in eel-catfish. Although Anableps anableps successfully feeds on land, it does not possess an eel-like body or pectoral fins to support or lift the anterior part of the body. We identified the mechanism of terrestrial prey capture in A. anableps by studying kinematics and functional morphology of the cranial structures, using high-speed video and graphical 3D reconstructions from computed tomography scans. In contrast to the previously described mechanisms, A. anableps relies solely on upper and lower jaw movement for re-orientation of the gape towards the ground. The premaxilla is protruded anteroventrally, and the lower jaw is depressed to a right angle with the substrate. Both the lower and upper jaws are selectively positioned onto the prey. Anableps anableps thereby uses the jaw protrusion mechanism previously described for other cyprinodontiforms to allow a continued protrusion of the premaxilla even while closing the jaws. Several structural adaptations appear to allow more controlled movements and increased amplitude of anterior and ventral protrusion of the upper jaw compared with other cyprinodontiforms.

Hit or miss: Functional mechanisms underlying prey capture efficiency in three cordylid lizards

Prey capture is one of the most important behaviours in organisms as it directly determines energy acquisition, which in turn is vital for fitness and survival. The contribution of specific prey capture mechanisms to prey capture efficiency, however, remains largely unresolved, especially in groups where a variety of mechanisms is present, such as lizards. Using three sympatric cordylid lizards as model organisms, we investigated (1) the effect of lingual prehension on prey capture efficiency when feeding on small prey (i.e. termites) and (2) whether in species that use jaw prehension to capture prey, prey capture efficiency decreases with increasing predator-prey size ratio. Prey capture efficiency, defined as the proportion of termites that was captured at first attempt, was higher in the species using lingual prehension than in the similarly-sized species using jaw prehension. In contrast, the two species using jaw prehension had a similar prey capture efficiency, despite differences in body size. The observed variation in prey capture efficiency between lingual and jaw prehension is discussed in the light of foraging mode in lizards.

The Effect of Food Type on Prey Capture Kinematics in the Mudminnow,Umbra limi

Abstract Energy acquisition is of fundamental importance to the survival of any organism. Thus, the morphology, or tools, that an organism uses to capture food can be under intense selective pressure. We studied the prey capture mechanics of the central mudminnow (Umbra limi), a benthic-dwelling fish species with a varied diet. A morphology suited for one specific prey type may not be as well suited for another prey type. Thus, we might expect that mudminnow are more successful at capturing one sort of prey over another. Specifically, we sought to determine if there were any changes in prey capture success and underlying prey capture mechanics when faced with highly elusive prey, live feeder fish (guppies), versus a non-elusive invertebrate larvae (midges of the family Chironomidae), commercially known as “blood worms.” Our results indicated that the more elusive prey caused mudminnow to have a slightly slower but a slightly more extreme premaxillary protrusion and expansion events. However, these differe...

Velvet Worms (Onychophora) in Folklore and Art: Geographic Pattern, Types of Cultural Reference and Public Perception

Aims: To document and preserve folkloric beliefs and art inspired by velvet worms (Onychophora), rare invertebrates that are considered living fossils, have full placental organs and capture prey with a rough net built in a fraction of a second. Study Design: This study is a combination of field interviews, online surveys and automatic database search. Methods: We asked open-ended questions to farmers who know the worms, consulted experts and searched the Internet to document folkloric and artistic instances using all the names that these animals receive in English, Spanish and Portuguese (languages of the countries where they occur) as well as other languages, and automatic image search, in Web of Science, CrossRef, Google Scholar and Google. Results: We found more than 80 cases of direct references to velvet worms in folklore and art, Short Research Article Monge-Najera and Morera-Brenes; BJESBS, 10(3): 1-9, 2015; Article no.BJESBS.18945 2 mostly from the USA, Australia, Brazil, Costa Rica and New Zealand. Per capita the countries with more cases are New Zealand (24 cases per million inhabitants), Costa Rica (16 cases per million inhabitants) and Australia (3 cases per million inhabitants). The most frequent expressions are cartoons, followed by tourism agencies using velvet worms in their ads, products with velvet worm representations, folkloric beliefs, and music bands or songs named after them. In almost all cases the animals are seen in a favorable light, inspiring folklore and art that highlight their extraordinary nature. Conclusion: The unique prey capture mechanism of velvet worms seems to have inspired an unexpected number of artistic and folkloric expressions, preserved for the future in the present article, which starts a totally new line of research: the effect of living fossils on human culture.