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Dynamic visual cues induce jaw opening and closing by tiger beetles during pursuit of prey.

ABSTRACT: In dynamic locomotory contexts, visual cues often trigger adaptive behaviour by the viewer, yet studies investigating how animals determine impending collisions typically employ either stationary viewers or objects. Here, we describe a dynamic situation of visually guided prey pursuit in which both impending prey contact and escape elicit observable adaptive behaviours in the pursuer, a predatory beetle. We investigated which visual cues may independently control opening and closing of the beetle's jaws during chases of prey dummies. Jaw opening and closing typically occur when prey is within the 60° binocular field, but not at specific distances, angular sizes or time-to-collision. We show that a sign change in the expansion rate of the target image precedes jaw opening (16 ms) and closing (35 ms), signalling to the beetle that it is gaining on the target or that the target is getting away. We discuss the 'sloppiness' of such variation in the lag of the behavioural response, especially jaw closing, as an adaptation to uncertainty about target position due to degradation of the target image by motion blur from the fast-running beetle.

SUBMITTER: Zurek DB

PROVIDER: S-EPMC4261868 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature

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Dynamic visual cues induce jaw opening and closing by tiger beetles during pursuit of prey.

Zurek Daniel B DB Perkins Madeleine Q MQ Gilbert Cole C

Biology letters 20141101 11

In dynamic locomotory contexts, visual cues often trigger adaptive behaviour by the viewer, yet studies investigating how animals determine impending collisions typically employ either stationary viewers or objects. Here, we describe a dynamic situation of visually guided prey pursuit in which both impending prey contact and escape elicit observable adaptive behaviours in the pursuer, a predatory beetle. We investigated which visual cues may independently control opening and closing of the beetl ...[more]

PMID: 25376803

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Project description:BackgroundTiger beetles (Coleoptera: Cicindelidae) are fast running predatory insects preying on different small insects and other terrestrial arthropods. Prey is located by sight and captured after short and fast pursuit interspersed with pause-and-look behaviour. At least some tiger beetle species can recognise the size and location of prey using memory, which probably allows them to achieve greater hunting success.Material and methodsTwo eurytopic tiger beetle species known to occur in different types of habitat were used in the study: Cicindela hybrida hybrida, a very common central European beetle found even in artificial habitats such as sandy roads or gravel pits, and Calomera littoralis nemoralis, a species widely distributed in southern European countries and occurring on sandy sea beaches, in salt marshes, as well as on sandy banks of rivers and lakes. Both species are very similar in body size. Specimens used in the study were collected in the field and later tested in the laboratory. We checked whether tiger beetles use different hunting strategies when attacking prey of different sizes and abilities to escape as well as whether the sex of the studied species makes a difference in its hunting behaviour.ResultsThe hunting strategies of both tiger beetle species consist of the following main phases: identification, pursuit (often with stops), attack, and optional release of the prey, and then the secondary attack, abandonment of the prey, or consumption of the prey. Considerable differences were noticed in hunting behaviour depending on the type of prey, its movement ability and escape potential. Caterpillars were attacked without pursuit, in the head or directly behind the head where a concentration of nerves and main muscles responsible for walking are located. Effective attacks on beetles were executed at the connection between the thorax and the abdomen. Calomera littoralis strongly preferred slow moving prey, while Cicindela hybrida preferred in equal measure slow moving prey and medium-sized fast moving prey. The experiment on the preferred size of prey indicated small beetles and small caterpillars as favoured by Calomera littoralis, while Cicindela hybrida preferred medium-sized fast moving prey and large caterpillars.DiscussionThe hunting behaviour of Calomera littoralis and Cicindela hybrida is complicated and includes a number of phases allowing to locate, capture and kill the prey. Beetles are able to discriminate between different types of prey and apply different behavioural tactics to hunt it. As the particular strategies are used to increase hunting success, and as a result allow to accumulate energy for future activity of the predator, it can be expected that such a type of hunting behaviour is characteristic also of other tiger beetle species.

Project description:Caecilians (Lissamphibia: Gymnophiona) are unique among vertebrates in having two sets of jaw-closing muscles, one on either side of the jaw joint. Using data from high-resolution X-ray radiation computed tomography scans, we modelled the effect of these two muscle groups (mm. levatores mandibulae and m. interhyoideus posterior) on bite force over a range of gape angles, employing a simplified lever arm mechanism that takes into account muscle cross-sectional area and fibre angle. Measurements of lever arm lengths, muscle fibre orientations and physiological cross-sectional area of cranial muscles were available from three caecilian species: Ichthyophis cf. kohtaoensis; Siphonops annulatus; and Typhlonectes natans. The maximal gape of caecilians is restricted by a critical gape angle above which the mm. levatores mandibulae will open the jaw and destabilize the mandibular joint. The presence of destabilizing forces in the caecilian jaw mechanism may be compensated for by a mandibular joint in that the fossa is wrapped around the condyle to resist dislocation. The caecilian skull is streptostylic; the quadrate-squamosal complex moves with respect to the rest of the skull. This increases the leverage of the jaw-closing muscles. We also demonstrate that the unusual jaw joint requires streptostyly because there is a dorsolateral movement of the quadrate-squamosal complex when the jaw closes. The combination of the two jaw-closing systems results in high bite forces over a wide range of gape angles, an important advantage for generalist feeders such as caecilians. The relative sizes and leverage mechanics of the two closing systems allow one to exert more force when the other has a poor mechanical advantage. This effect is seen in all three species we examined. In the aquatic T. natans, with its less well-roofed skull, there is a larger contribution of the mm. levatores mandibulae to total bite force than in the terrestrial I. cf. kohtaoensis and S. annulatus.

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Dynamic visual cues induce jaw opening and closing by tiger beetles during pursuit of prey.

Publications

Dynamic visual cues induce jaw opening and closing by tiger beetles during pursuit of prey.

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