Prey Transport Research Articles

Characterizing the Variability of a Physical Driver of North Atlantic Right Whale Foraging Habitat Using Altimetric Indices

Physical ocean circulation features, especially the Gaspé Current (GC) intrusion, influence the transport and aggregation of whale prey, thereby influencing the whale foraging habitat in the Gulf of St. Lawrence (GSL), Canada. We employ satellite altimetry-derived sea level anomaly (SLA) indices to monitor interannual variations in the intensity of the GC in the North Atlantic Right Whale (Eubalaena glacialis; NARW) habitat in the GSL. Measurements of surface slope and volume transport are taken from the SLA profiles along a repeating ground track of the Jason-2/3 satellites. These are employed as complementary proxies in characterizations of physical processes in the GSL. The relationship between altimetric indices and indices of zooplankton abundance are explored in the southern GSL. Results demonstrate that an altimetric index estimated from surface slope (Indexslope−half) is correlated with river discharge of the St. Lawrence River and can be utilized to infer variations in GC intensities. Time series of the altimetric indices during 2009–2021 are found to exhibit interannual and seasonal environmental variability, which influence transport into the southern GSL. As captured by the altimetric indices, these features of the surface ocean circulation can be linked to zooplankton variations in the Shediac Valley, where NARWs are frequently observed. Therefore, in linking physical drivers of ocean dynamics to the NARW foraging habitat, variations in these indices can also potentially help describe some features of the distribution patterns of NARW sightings in this area.

XROMM Analysis of Feeding Mechanics in Toads: Interactions of the Tongue, Hyoid, and Pectoral Girdle

SynopsisDuring feeding in many terrestrial vertebrates, the tongue acts in concert with the hyoid and pectoral girdle. In frogs, these three elements are interconnected by musculature. While the feeding mechanics of the anuran tongue are well-studied, little is known of how the motions of the tongue relate to the movements of the skeleton or how buccal structures move following closure of the mouth. Although features such as the pectoral girdle and hyoid are not externally visible in frogs, their motions can be tracked in X-ray video. We used XROMM (X-ray Reconstruction of Moving Morphology) techniques to track the 3D movements of the tongue, hyoid apparatus, pectoral girdle, skull, and jaw during the feeding cycle of the cane toad, Rhinella marina. We show how the movements of these elements are integrated during tongue protrusion and prey capture, as well as during prey transport, swallowing, and recovery. Our findings suggest that the hyoid apparatus is important both for prey manipulation and swallowing. The tongue consistently stretches posterior to the skull during swallowing, often more than it stretches during protrusion to reach the prey. Feeding kinematics are similar between individuals, and the kinematics of unsuccessful strikes generally resemble those of successful strikes. Our data also provide a new perspective on the potential role of the pectoral girdle, an element with a predominant locomotor function, during feeding events. This work raises new questions about the evolution of feeding in frogs, as well as how the diversity of pectoral and buccal anatomy observed across anurans may influence feeding kinematics.

Dental structure and tooth attachment modes in the common fangtooth Anoplogaster cornuta (Valenciennes, 1833) (Actinopterygii; Trachichthyiformes; Anoplogastridae).

We studied the structure and attachment modes of the teeth of adult Anoplogaster cornuta using light- and scanning-electron microscopic techniques. All teeth were monocuspid, composed solely of orthodentin, and lacked a covering enameloid cap. Fourteen teeth were present in the oral jaws, with three teeth each on the left and right premaxilla and four teeth each on the left and right dentary. The anteriormost premaxillary and dentary teeth were considerably larger than the more posteriorly located ones. The oral jaw teeth were transparent, non-depressible and firmly ankylosed to their respective dentigerous bone by a largely anosteocytic bone of attachment. No evidence for replacement of the large oral jaw teeth was found in the analyzed adult specimens. The bone of attachment exhibited lower calcium and phosphorus concentrations and a higher Ca/P ratio than the orthodentin. The connection between dentinal tooth shaft and bone of attachment was stabilized by a collar of mineralized collagen fibers. In contrast to the oral jaw teeth, the pharyngeal teeth exhibited a ring-like fibrous attachment to their supporting bones. This mode of attachment provides the teeth with some lateral mobility and allows their depression relative to their supporting bones, which may facilitate intra-pharyngeal prey transport. In contrast, a firm ankylosis was observed in numerous small teeth located on the branchial arches. The function of these teeth is presumably to increase the tightness of the pharyngeal basket and thereby the retention of small prey items in a species living in a habitat with only sparse food supply. Our findings corroborate earlier statements on the tooth attachment modes of the oral jaw teeth of Anoplogaster cornuta, but provide new findings for the attachment modes of pharyngeal teeth in this species.

Effects of acute temperature change on California moray prey manipulation and transport behavior

California moray eels, Gymnothorax mordax, are benthic predatory residents of southern California kelp forest ecosystems. California morays around Catalina Island move vertically through the water column to feed, exposing them to a wide range of temperatures. For a predatory fish, morays have a relatively large prey handling repertoire that enable them to manipulate their prey before swallowing. Prey manipulation behaviors include shaking, spinning, knotting, and ramming prey against other objects. Morays also have observable transport mechanics where they protract and retract their pharyngeal jaws to swallow prey. We examined prey manipulation and transport behaviors at four temperature treatments that simulated the range of environmental temperatures morays encounter in the wild. We hypothesized that higher temperatures will increase the prevalence, duration, and rate of whole body prey manipulation behaviors and decrease the duration of prey transport time. Previous temperature studies focused on fishes occupying intermediate trophic levels. Therefore, understanding how acute temperature affects feeding behavior of the California moray eel, an abundant predatory fish, is especially important, as changes in environmental temperature may have disproportionate effects in their marine community. Five morays were acutely exposed to 15, 18, 21, 24 °C temperatures and their subsequent feeding behaviors were filmed and quantified. Individuals were offered the same relative prey mass (15 %) in relation to their body mass throughout the study. We compared the number of times each prey manipulation behavior occurred, the mean time morays employed each behavior, and the rate (number of times per second) each behavior was performed across different temperatures. Our data demonstrates that absolute time spent knotting varies significantly across temperature. Knotting, often used to remove pieces from larger prey, was most frequent at 21 and 24 °C. The average duration of knotting also increased with temperature. The rates of prey manipulation behaviors did not vary significantly with temperature. Finally, transport behavior did not vary across treatments. Our study shows that knotting behavior in the California moray is responsive to environmental temperatures and that morays may be able to manipulate larger prey in warmer waters. These behavioral data may have important implications for predator-prey relationships under dynamic and future ocean conditions.

Notes on the feeding rhythm of a barn owls’ brood (<em>Tyto alba</em>) in an agricultural area of the province of Venice

The feeding rhythm of a brood of barn owls in an agricultural area of Venice (VE, NE Italy) was investigated. The results show that offspring are fed exclusively at nighttime, highlighting a peak of transport of prey to the nest in the first part of the night.

Nesting System and Foraging Behaviour of <i>Crematogaster (Nematocrema) stadelmanni </i>Mayr, 1895 (Hymenoptera: Formicidae: Myrmicinae) in Douala (Littoral-Cameroon)

Nesting system, diet behaviour, activity rhythm and predatory behaviour of <i>Crematogaster (Nematocrema) stadelmanni</i> Mayr, 1895 were studied in the field situation in suburbs of Douala (Littoral-Cameroon). Polycalic and polydomous nesting system were recorded. Large independent nests were positioned on the bark surface of trunks (50.8%) or the underside bark of the fork of large branches (49.2%) of cultivated or wild trees (45.8% and 54.2% respectively). Workers collected nectar from 18 plants from eight families: Asteraceae, Costaceae, Ehretiaceae, Euphorbiaceae, Mimosaceae Phyllantaceae, Poaceae and Rutaceae. They collected honeydew from Aleyrodidae and four Hemipteran families from Sternorrhyncha suborder: Aphididae, Coccidae Pseudococcidae and Stictococcidae. These Hemipterans proliferated on 11 plant families: Anacardiaceae, Annonaceae, Apocynaceae, Asteraceae, Costaceae, Euphorbiaceae, Myrtaceae, Poaceae, Rutaceae, Solanaceae and Urticaceae. Solid particles brought back to the nest were mostly from plants (72.5%) and weakly preys (27.5%). Sugary liquids were preferred over fats, carbohydrate sources, and even preys. Products were collected continuously (day and night) in the foliage of the host plant and neighbouring plants, shrubs and grasses. Workers occasionally brought back to the nest dead or dying larvae of grasshoppers and small particles of other arthropods (ants, flies, caterpillars). The sequence of behavioural acts recorded during the capture of larvae of <i>Ruspolia differens</i> (Orthoptera: Tettigoniidae) and adults of <i>Zonocerus variegatus</i> (Orthoptera: Pyrgomorphidae) (3 to 5 mm and 15 to 20 mm long respectively) were compared. The main sequence presented succession of seven acts: (1) detection by contact; (2) antennation; (3) attack-seizure; (4) short-range recruitment of nestmates in the vicinity; (5) spread-eagling of preys; (6) cutting up the prey on the spot; and (7) transport of pieces or whole prey to the nest. The stinging phase was not recorded. The duration of the capture of small prey (66 min. to 1 hr. 25 sec.; mean ± se: 1 hr. 57 min. 25 sec. ± 12 min. 2 sec.; 10 essays) was lower than that of large preys (2 hrs. 33 sec. to 4 hrs. 16 sec.; 2 hrs. 58 min. 32 sec. ± 17 min. 15 sec.; 10 essays; Mann-Withney test: T = 72.00; p = 0.014). The long duration of captures suggested that spread-eagling and cutting up preys on the spot lasted a long time. <i>Cr. stadelmanni</i> is a poor predator indirectly harmful for wild or cultivated trees since their predatory aptitude is low compared to aggressive dominant arboreal-nesting ants and is counterbalanced by the propensity to honeydew.

Sundering of earthworms by the Fairy Pitta (Pitta nympha): an unexplored strategy of prey preparation for brood provisioning by avian vermivores

Ecological specialists utilize a restricted range of resources and have evolved adaptations to exploit their specialized resources. For example, avian insectivores that feed nestlings with grasshoppers, beetles, or moths perform insect prey preparation before feeding nestlings so that the nestlings are able to swallow the prey. This behavior is generally not expected for soft prey such as earthworms. However, an overview of photographic evidence available online suggested that earthworms are sundered by parents before bringing the prey to the nestlings in a range of species from several families of vermivores worldwide. Reports on the provisioning of nestlings by the vermivores are relatively scant and no report on earthworm sundering has been published. We studied earthworm sundering performed by parents provisioning their broods at four nests of the Fairy Pitta in Korea. The birds sundered earthworms more often when nestlings were smaller and when the earthworm was longer. This is the first quantitative description of earthworm sundering in avian vermivores. We present and evaluate four hypotheses for the function of sundering: provisioning of small nestlings, decreased detectability, hunting multiple prey, and transport of prey. Among these, provisioning of small nestlings seems the most feasible explanation of sundering by the Fairy Pitta as sundering the earthworm allows parents to efficiently provision the younger/smaller nestlings who would have difficulties swallowing unsundered earthworms. This specialized prey preparation technique of vermivores suggests a tight adaptive match between their parental behaviors and their diet (vermivory).

Feeding behaviour and functional morphology of the neck in the long-snouted aquatic fossil reptile Champsosaurus (Reptilia: Diapsida) in comparison with the modern crocodilian Gavialis gangeticus.

The extinct freshwater choristoderan reptiles Champsosaurus and Simoedosaurus are characterised by large body size and an elongated snout. They have often been considered as eco-analogues of crocodilians based on superficial similarities. The slender-snouted Champsosaurus has been described as a 'gavial-like reptile', which implies it feeds underwater with a lateral swipe of the head and neck, as in the living slender-snouted crocodilians such as Gavialis gangeticus. In contrast, the short-snouted Simoedosaurus is often compared with short-snouted living crocodilians and is considered to take single prey items. However, the neck mobility and flexibility needed for feeding movements are poorly understood even in extant crocodilians. This study explores the relationship between cervical morphology and neck flexion, focusing particularly on lateral and dorsal movements in G. gangeticus by comparison with shorter-snouted crocodilians. The paper also describes a method to estimate the maximum angle of neck dorsiflexion in choristoderes based on the cervical morphology of extant crocodilian species. Three indices were used in this study, of which Index 3 is newly proposed, to compare cervical morphology and intervertebral joint flexibility: (1) Enclosed zygapophyseal angles (EZA) as an index of dorsoventral/ bilateral flexibility, (2) moment arm (M) of dorsiflexor muscles as an Index of resistance against ventroflexion and (3) the orientations of zygapophysial facets for a maximum angle of dorsiflexion. These Indices were validated using µCT scanning of fresh specimens of G. gangeticus and Caiman latirostris in lateral and dorsal flexion. A unique mechanism of lateral flexion was identified in G. gangeticus that uses a combination of the following features: (1) lateral flexion mainly restricted to the anterior cervical vertebrae (v2/v3: high EZA, with more horizontal zygapophyses) and (2) high degree of dorsiflexion at the v3/v4 and v4/v5 joints with potential for dorsal flexibility through the middle-posterior neck, which is used in inertial feeding. In contrast, Champsosaurus and Simoedosaurus possess relatively short cervical vertebrae, as in short-snouted crocodilians. The middle-posterior cervical vertebrae of Champsosaurus are specialised for lateral flexion (high EZA), and there is only limited capacity for dorsiflexion throughout the neck. Like G. gangeticus, therefore, Champsosaurus may have used its slender snout to grab fish from shoals using lateral sweeping motions of the head and neck, but the movement is through the neck, not the craniocervical joint. However, inertial feeding is less likely to have occurred in this genus, and the aligned palatal dentition may have aided the lingual transport of prey into the mouth. Simoedosaurus, on the other hand, appears to have been less specialised, with a neck that combined lateral and dorsolateral flexion, a move that could have been effective in catching both terrestrial and aquatic prey. Where these two choristoderan genera occurred in the same place, they may have divided their niche by prey types.

How much to carry? Implications of maximum load carrying capacity for prey use of urban and rural Northern Goshawks Accipiter gentilis

ABSTRACT Capsule: Compared to their rural counterparts, urban Northern Goshawks Accipiter gentilis potentially maximize their energy delivery to the nest by exploiting heavier prey species close to their maximum carrying capacity. Aims: We aimed to assess prey use of a raptor species with distinct reversed sexual size dimorphism from a perspective of physical limitations during foraging and the transportation of prey. Methods: We estimated the theoretical maximum load carrying capacity (MLCC) of fully developed Northern Goshawks based on their flight muscle mass. Additionally, we collected data on the breeding season diet of Northern Goshawks in urban and rural habitats in Germany. By linking MLCC estimates to the diet we explained the relevance of prey size from a viewpoint of load carrying capacity. Results: Estimates for the mean (± sd) additional portable loads were 684 g (± 237) for males and 971 g (± 235) for females, accounting for 96% and 84% of their body mass, respectively. Overall prey weight averaged higher for urban areas compared to rural ones, while the majority of prey items were between 200 and 500 g and below the estimated MLCC of both sexes, with the exception of single heavy species. Results suggest that prey use of Northern Goshawks during the breeding season is barely limited by prey transportability, since both sexes are physically capable of carrying the majority of prey species to their nest. Conclusions: Urban Northern Goshawks can exploit heavier, available prey species compared to their rural counterparts, allowing them to hunt larger prey closer to their MLCC. Ultimately, by maximizing their energy delivery to the nest, this presumably constitutes one key factor why Goshawks successfully colonized European cities. This study is the first to link estimates of physical limitations in prey transportation for a free-living raptor species to its prey composition in the light of colonizing urban environments.

Shoreward intrusion of oceanic surface waters alters physical and biological ocean structures on the Antarctic continental shelf during winter: Observations from instrumented seals

AbstractOcean circulation plays a key role in structuring marine ecosystems in the Southern Ocean. However, the seasonal dynamics of ocean circulation are poorly understood in the ice‐covered continental shelves due to difficulties in conducting observations. We, therefore, investigated spatial and temporal variations in oceanographic conditions and their biological effects on the continental shelf off East Antarctica (35°E–50°E) by deploying conductivity–temperature–depth (CTD) tags on Weddell seals. The seals moved up to 633 km east from the tagging location. We successfully obtained 1254 CTD casts from seven seals. Winter Water (WW) was most prevalent (77.4% of the total data), followed by Supercooled Water (14.2%), Antarctic Surface Water (AASW: 7.4%), Modified Circumpolar Deep Water (mCDW; 0.9%), and Modified Shelf Water (0.1%). During our study period, landfast ice broke up extensively, and the easterly wind was most prevalent during autumn. AASW was observed in the subsurface layer over the shelf in autumn, suggesting that AASW intruded from the surface of off‐shelf areas through Ekman transport. Particular water masses (mCDW, AASW, and WW below the AASW) had positive effects on the seals' foraging behavior. These results highlight the importance of easterly wind‐driven shoreward intrusion of oceanic surface waters onto the shelf in autumn. This physical process may enhance transport and accumulation of additional prey and increase local prey availability during winter. Such a process may play important roles in the Antarctic coastal marine ecosystems that are influenced by landfast ice.

Hydrodynamics of Prey Capture and Transportation in Choanoflagellates

Choanoflagellates are unicellular microscopic organisms that are believed to be the closest living relatives of animals. They prey on bacteria through the act of the continuous beating of their flagellum, which generates a current through a crown-like filter. Subsequently, the filter retains bacterial particles from the suspension. The mechanism by which the prey is retained and transported along the filter remains unknown. We report here on the hydrodynamic effects on the transportability of bacterial prey of finite size using computational fluid dynamics. Here, the loricate choanoflagellate Diaphaoneca grandis serves as the model organism. The lorica is a basket-like structure found in only some of the species of choanoflagellates. We find that although transportation does not entirely rely on hydrodynamic forces, such forces positively contribute to the transportation of prey along the collar filter. The aiding effects are most possible in non-loricate choanoflagellate species, as compared to loricate species. As hydrodynamic effects are strongly linked to the beat and shape of the flagellum, our results indicate an alternative mechanism for prey transportation, especially in biological systems where having an active transport mechanism is costly or not feasible. This suggests an additional potential role for flagella in addition to providing propulsion and generating feeding currents.

Prey Fragmentation and Transport in Six Tropical Arboreal Ant Species

Prey fragmentation and transport modalities were studied in Myrmicaria opaciventris, Platythyrea conradti, Cremtogaster sp., Crematogaster clariventris, Tetramorium aculeatum and Oecophylla longinoda, six tropical ant species with varying levels of adaptation to foraging in the tree canopy. Termites and grasshoppers of different sizes were used as prey and deposited on a hunting arena. After prey capture, we investigated the strategy adopted by each ant species to fragment and transport their prey. The data were analyzed with classification tree, using Chi-squared Automatic Interaction Detection method to find the variation in prey fragmentation strategies and transportation modalities between arboreal ant species in relation with prey type and prey size. The results showed that prey fragmentation did not occur systematically after capture and varied between ant species with prey type and prey size. Studied ant species cut their prey either completely into tiny pieces or partially into two or three large pieces before cutting them totally into tiny pieces or not at all. Fragmentation strategy, induced variation in transport modalities including (a) transport of large pieces, each by a single worker; (b) transport of large pieces, each, by a group of workers; (c) transport of tiny pieces after total cutting, and (c) transport of entire prey in the nest without fragmentation. Prey fragmentation and transport modalities varied between ant species in relation with their level of adaptation to arboreal area.

Behavioral Records on Neotropical Species of Anoplius Dufour (Hymenoptera: Pompilidae)

Nesting, prey transportation mechanisms, and host preference are described for two Neotropical pompilid wasp species: Anoplius sp. and Anoplius triquetrus (Fox). Observations were made in a restinga area, in Regencia district, Espirito Santo state, Brazil. Several Anoplius sp. individuals were observed foraging in small patches of vegetation along a beach, whereas A. triquetrus was observed and subsequently caught carrying a Psauridae spider into a nest on a sandy trail in a restinga forest. This is the first behavioral record for the genus Anoplius in South America. Finally, we formally move Psammochares triquetra (Fox) to the Anoplius subgenus Notiochares Banks.

An XROMM Study of Food Transport and Swallowing in Channel Catfish.

SynopsisMost predatory ray-finned fishes swallow their food whole, which can pose a significant challenge, given that prey items can be half as large as the predators themselves. How do fish transport captured food from the mouth to the stomach? Prior work indicates that, in general, fish use the pharyngeal jaws to manipulate food into the esophagus, where peristalsis is thought to take over. We used X-Ray Reconstruction of Moving Morphology to track prey transport in channel catfish (Ictalurus punctatus). By reconstructing the 3D motions of both the food and the catfish, we were able to track how the catfish move food through the head and into the stomach. Food enters the oral cavity at high velocities as a continuation of suction and stops in the approximate location of the branchial basket before moving in a much slower, more complex path toward the esophagus. This slow phase coincides with little motion in the head and no substantial mouth opening or hyoid depression. Once the prey is in the esophagus, however, its transport is surprisingly tightly correlated with gulping motions (hyoid depression, girdle retraction, hypaxial shortening, and mouth opening) of the head. Although the transport mechanism itself remains unknown, to our knowledge, this is the first description of synchrony between cranial expansion and esophageal transport in a fish. Our results provide direct evidence of prey transport within the esophagus and suggest that peristalsis may not be the sole mechanism of esophageal transport in catfish.

Multiple Degrees of Freedom in the Fish Skull and Their Relation to Hydraulic Transport of Prey in Channel Catfish.

SynopsisFish perform many complex manipulation behaviors without hands or flexible muscular tongues, instead relying on more than 20 movable skeletal elements in their highly kinetic skulls. How fish use their skulls to accomplish these behaviors, however, remains unclear. Most previous mechanical models have represented the fish skull using one or more planar four-bar linkages, which have just a single degree of freedom (DoF). In contrast, truncated-cone hydrodynamic models have assumed up to five DoFs. In this study, we introduce and validate a 3D mechanical linkage model of a fish skull that incorporates the pectoral girdle and mandibular and hyoid arches. We validate this model using an in vivo motion dataset of suction feeding in channel catfish and then use this model to quantify the DoFs in the fish skull, to categorize the motion patterns of the cranial linkage during feeding, and to evaluate the association between these patterns and food motion. We find that the channel catfish skull functions as a 17-link, five-loop parallel mechanism. Despite having 19 potential DoFs, we find that seven DoFs are sufficient to describe most of the motion of the cranial linkage, consistent with the fish skull functioning as a multi-DoF, manipulation system. Channel catfish use this linkage to generate three different motion patterns (rostrocaudal wave, caudorostral wave, and compressive wave), each with its own associated food velocity profile. These results suggest that biomechanical manipulation systems must have a minimum number of DoFs to effectively control objects, whether in water or air.

Functional morphology of the sting in two digger wasps (Hymenoptera: Crabronidae) with different types of prey transport

Digger wasps of the family Crabronidae (Insecta: Hymenoptera) are generally known to use their sting to paralyze or kill a prey. However, only a few species of digger wasps transport their prey to the nest impaled on the sting. How sting morphology correlates with this peculiar type of prey carriage is still unclear. We examined the sting morphology of two phylogenetically closely-related species of digger wasps of similar size, which hunt for similar preys but use different types of prey transportation. Data from light microscopy (LM), scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were analyzed to find possible correlations between shape, material composition, and function of the stings. The similarity of the material composition in the stings of the two species suggests that the material of stings does not play a dominant role in their functional differences. On the contrary, differences in the curvature and surface sculpture of sting elements likely result in different stress distributions under mechanical loading.

From apparent competition to facilitation: Impacts of consumer niche construction on the coexistence and stability of consumer‐resource communities

Abstract In addition to their direct trophic effects, some consumers have a positive indirect effect on their resource, due to niche construction. A predator can facilitate its prey resource acquisition, through prey transport, or through modifications of nutrient cycling. Alternatively, a predator may defend its prey against other predators, or actively manage it, as in agriculture, which is found in numerous taxa such as humans, ants, beetles, fishes and microbes. Here, we investigate the ecological consequences of considering such positive effects in a simple two‐resource–one‐consumer module, in which the consumer has a positive effect on one of the resources. We consider several scenarios, in which the positive effect on the resource is either not costly, that is resulting from a by‐product of the consumer phenotype such as nutrient cycling, or costly. The cost either decreases the exploitation of the cultivated resource or the opportunity to forage the alternative resource. We investigate how the intensity of niche construction impacts species coexistence, the distribution of biomass among the three species and the stability of the community. We show that by modifying the trophic interactions in the module, niche construction alters the apparent competition between the resources, thereby impacting their coexistence. When niche construction has little or no cost to the consumer, it leads to higher consumer and cultivated resource densities, while decreasing the alternative resource density. Alternatively, when niche construction has higher costs, the alternative resource can increase in density, niche construction thereby leading to the emergence of facilitative interactions among resource species. A free Plain Language Summary can be found within the Supporting Information of this article.

Comparative anatomical study of the hyoid apparatus of Bosk\u2019s fringe-toed lizard and spotted fan-toed gecko (Squamata: Lacertidae and Phyllodactylidae)

BackgroundThe present study aimed to illustrate comparative morphological, histological, and functional variations of the hyoid apparatus of Acanthodactylus boskianus and Ptyodactylus guttatus.ResultThe hyoid apparatuses and musculature of the two investigated species are well-developed. The hyoid apparatuses exhibit high mobility with different articulation sites between their skeletal elements. The degree of ossification of the hyoid apparatus of gecko is more developed than that of the lacertid lizard. In P. guttatus, a well-developed synchondrosis articulation appears between the basihyoid and ceratobranchialis of the hyoid apparatus. Meanwhile, in A. boskianus, the articular ligament which appears between basihyoid and ceratobranchialis is less developed and also appears as a ligament connection between the two parts of hyoid cornua in which ligaments provide more mobility to the hyoid of lacertid lizard.ConclusionThe results reflect a phylogenetically informative character about these clad and explain the different functional demands imposed on the hyoid apparatus as well as confirm the important role of hyoid apparatus in the movement of the tongue during the prey transport.

Channel catfish use higher coordination to capture prey than to swallow.

When animals move they must coordinate motion among multiple parts of the musculoskeletal system. Different behaviours exhibit different patterns of coordination, however, it remains unclear what general principles determine the coordination pattern for a particular behaviour. One hypothesis is that speed determines coordination patterns as a result of differences in voluntary versus involuntary control. An alternative hypothesis is that the nature of the behavioural task determines patterns of coordination. Suction-feeding fishes have highly kinetic skulls and must coordinate the motions of over a dozen skeletal elements to draw fluid and prey into the mouth. We used a dataset of intracranial motions at five cranial joints in channel catfish ( Ictalurus punctatus), collected using X-ray reconstruction of moving morphology, to test whether speed or task best explained patterns of coordination. We found that motions were significantly more coordinated (by 20-29%) during prey capture than during prey transport, supporting the hypothesis that the nature of the task determines coordination patterns. We found no significant difference in coordination between low- and high-speed motions. We speculate that capture is more coordinated to create a single fluid flow into the mouth while transport is less coordinated so that the cranial elements can independently generate multiple flows to reposition prey. Our results demonstrate the benefits of both higher and lower coordination in animal behaviours and the potential of motion analysis to elucidate motor tasks.

Eye Movements in Frogs and Salamanders-Testing the Palatal Buccal Pump Hypothesis.

SynopsisIn frogs and salamanders, movements of the eyeballs in association with an open palate have often been proposed to play a functional role in lung breathing. In this “palatal buccal pump,” the eyeballs are elevated during the lowering of the buccal floor to suck air in through the nares, and the eyeballs are lowered during elevation of the buccal floor to help press air into the lungs. Here, we used X-Ray Reconstruction of Moving Morphology to investigate eye movements during lung breathing and feeding in bullfrogs and axolotls. Our data do not show eye movements that would be in accordance with the palatal buccal pump. On the contrary, there is a small passive elevation of the eyeballs when the buccal floor is raised. Inward drawing of the eyeballs occurs only during body motion and for prey transport in bullfrogs, but this was not observed in axolotls. Each eye movement in bullfrogs has a vertical, a mediolateral, and an anteroposterior component. Considering the surprisingly weak posterior motion component of the eyeballs, their main role in prey transport might be fixing the prey by pressing it against the buccal floor. The retraction of the buccal floor would then contribute to the posterior push of the prey. Because our study provides no evidence for a palatal buccal pump in frogs and salamanders, there is also no experimental support for the idea of a palatal buccal pump in extinct temnospondyl amphibians, in contrast to earlier suggestions.