Temperature coupling in cricket acoustic communication

Summary Temperature effects on calling song production and recognition were investigated in the North American field cricket, Gryllus firmus. Temporal parameters of field-recorded G. firmus calling song are strongly affected by temperature. Chirp rate and syllable rate increase, by factors of 4 and 2, respectively, as linear functions of temperature over the range in which these animals sing in the field (12°–30 °C). Temperature affects syllable duration to a lesser extent, and does not influence calling song carrier frequency. Female phonotactic preference, measured on a spherical treadmill in the laboratory, also changes with temperature such that warmer females prefer songs with faster chirp and syllable rates. Best phonotaxis, measured as accuracy of orientation to the sound source, and highest walking velocity, occur in response to temperature-matched songs at 15°, 21°, and 30 °C. Experiments under semi-natural conditions in an outdoor arena revealed that females perform phonotaxis at temperatures as low as 13 °C. Taken together, the song and phonotaxis data demonstrate that this communication system is temperature coupled. A strategy is outlined by which temperature coupling may be exploited to test hypotheses about the organization of neural networks subserving song recognition.Abbreviations CP chirp period - SP syllable period - SD syllable duration     

Temperature coupling in cricket acoustic communication

Acoustic communication in Gryllus firmus is temperature-coupled: temperature induces parallel changes in male calling song temporal pattern, and in female preference for song. Temperature effects on song production and recognition networks were localized by selectively warming head or thorax or both head and thorax of intact crickets, then eliciting aggression song production (males) or phonotaxis to synthetic calling song (females). Because male song is produced by a thoracic central pattern generator (CPG), and because head ganglia are necessary for female song recognition, measurements of female phonotaxis under such conditions may be used to test the following competing hypotheses about organization of the song recognition network: 1. A set of neurons homologous to the male song CPG exist in the female, and are used as a template that determines preferred values of song temporal parameters for song pattern recognition (the common neural elements hypothesis), and 2. temporal pattern preference is determined entirely within the head ganglia. Neither selective warming of the head nor of the thorax was effective in changing female song preference, but simultaneous warming of head and thorax shifted preference toward a faster song in most preparations, as did warming the whole animal by raising ambient temperature. These results suggest that phonotactic preference for song temporal pattern is plurisegmentally determined in field crickets. Selective warming experiments during aggression song production in males revealed that syllable period is influenced but not completely determined by thoracic temperature; head temperature is irrelevant. The song CPG appears to receive some rate-setting information from outside the thoracic central nervous system.     

Stimulus-response properties of cricket cereal filiform receptors

The dynamic ranges and stimulus-response properties of a large sample of cereal filiform receptors in Acheta domesticus were investigated electrophysiologically. The relation between receptor response and stimulus velocity was a sigmoid function, the log-linear portion of which spanned 1–1.5 log units of peak air-current velocity. Different receptors responded over different but overlapping velocity ranges, such that the system velocity sensitivity range spanned at least 2.5 log units. Plots of receptor response amplitude vs. stimulus direction were sinusoidal, with a period of 360°. Long-hair receptors responded in phase with air-current velocity, and intermediate-hair receptors responded in phase with air-current acceleration. These results extend those of Shimozawa and Kanou (1984a) and Kämper and Kleindienst (1990), in which the dynamics of receptor responses were shown to depend on hair length. When individual hairs were directly mechanically deflected, their receptors responded in phase with the first derivative of hair deflection. The signal transform between the air-current stimulus and the receptor response is comprised of two processes, one biomechanical/aerodynamic and one membrane biophysical. The results of this study suggest that the parametric sensitivities of receptors are primarily determined by hair biomechanical/aerodynamic properties.Abbreviation IR infrared     

Mycoflora of cave cricket Troglophilus neglectus cadavers

By using different techniques and media, microfungi were isolated from cadavers of the cave cricket Troglophilus neglectus, collected on the walls of a Slovenian cave. The isolated mycobiota was consistently different for adult and larval stages of T. neglectus cadavers. Fungi isolated with the highest frequency from the larval stage were represented by five different species of the genus Mucor, the prevailing one being a newly described species, M. troglophilus. The dominating fungus isolated from the adult stage was the well-known fungal entomopathogen Beauveria bassiana. The other isolated fungi were mainly primary and secondary saprotrophic colonizers. This revised version was published online in June 2006 with corrections to the Cover Date.     

Tree cricket baffles are manufactured tools

Tree crickets use sound to attract mates and make acoustic baffles to increase their sound production efficiency. It has been recently discovered that these insects use a flexible yet inherited behavioural programme to make acoustically optimal baffles. Whether these baffles qualify as tools, however, remains controversial. Here, baffle‐using and baffle‐making behaviours are analysed using the most current and authoritative definition of tool use. The current definition of tool use does not require the tool to be detached from the substrate and includes attached but manipulable external objects. Given this schema, tree cricket baffles, which are attached but manipulated prior to use, must be considered tools. The mode of manufacture for a baffle is “Subtract,” and the mode of use is “Drape”.     

Information transfer during cricket frog contests

We investigated information transfer during vocal interactions between cricket frogs, Acris crepitans, with a specific focus on information about size and intention. In response to opponents, cricket frogs alter both temporal and spectral (frequency) aspects of their calls. Previous work suggests that males use dominant frequency, which is correlated with size, to provide information about fighting ability, and use temporal call characters, which are independent of size, to provide information about aggressive intent. We tested this hypothesis by investigating the relationship between call characters and contest behaviour. We presented a focal male with a simulated opponent, and categorized his behavioural response as attack, abandon or tolerate. We found that information about opponent size does not appear to influence a male's decision to fight, flee or tolerate an intruder. Whether or not males use the size information that is encoded in call frequency remains unclear. In contrast, changes in call frequency, which are not correlated with size, predicted the outcome of simulated contests, suggesting that male cricket frogs signal information about agonistic intent. Temporal call characters indicated whether or not a resident tolerated an opponent, but they did not predict contest outcome (attack versus abandon). Furthermore, the difference between the temporal call characters of a focal male and the simulated opponent predicted whether the resident tolerated the opponent. We suggest, therefore, that temporal call changes may be a cooperative signal designed to facilitate assessment of size through physical contact in wrestling bouts. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Directional hearing in a silicon cricket

Phonotaxis is the ability to orient towards or away from sound sources. Crickets can locate conspecifics by phonotaxis to the calling (mating) song they produce, and can evade bats by negative phonotaxis from echolocation calls. The behaviour and underlying physiology have been studied in some depth, and the auditory system solves this complex problem in a unique manner. Experiments conducted on a simulation model of the system indicated that the mechanism output a directional signal to sounds ahead at calling song frequency and to sounds behind at echolocation frequencies. We suggest that this combination of responses helps simplify later processing in the cricket. To further explore this result, an analogue, very large scale integrated (aVLSI) circuit model of the mechanism was designed and built; results from testing this agreed with the simulation. The aVLSI circuit was used to test a further hypothesis about the potential advantages of the positioning of the acoustic inputs for sound localisation during walking. There was no clear advantage to the directionality of the system in their location. The aVLSI circuitry is now being extended to use on a robot along with previously modelled neural circuitry to better understand the complete sensorimotor pathway.     

Rapid postembryonic development of a cricket flight muscle

The metathoracic dorsal longitudinal muscle (DLM) of the cricket Teleogryllus oceanicus differentiated and developed rapidly over the last nymphal instar. Within eight days, the muscle mass increased by a factor of 15 and the relative volume of mitochondria quadrupled, while the relative amounts of myofibril and sarcoplasmic reticulum decreased. Tracheoblasts began to invade the muscle fibers immediately before the adult molt. Muscle mass continued to increase until four days after the adult molt, but the relative volumes of the ultrastructural components did not change. Within two weeks following the adult molt, the muscles in some of the animals began to degenerate.     

Olfactory memory capacity of the cricket Gryllus bimaculatus

Olfactory learning in insects is a useful model for studying neural mechanisms underlying learning and memory, but memory storage capacity for olfactory learning in insects has not been studied. We investigate whether crickets are capable of simultaneously memorizing seven odour pairs. Fourteen odours were grouped into seven A/B pairs, and crickets in one group were trained to associate A odours with water reward and B odours with saline punishment for all the seven pairs. Crickets in another group were trained with the opposite stimulus arrangement. Crickets in all the groups exhibited significantly greater preference for the odours associated with water reward for all the seven odour pairs. We conclude that crickets are capable of memorizing seven odour pairs at the same time.     

Conservation and the cricket culture in China

Several species of Tettigoniidae and Grylloidea are collected and traded as singing or fighting insects in China. There is anecdotal evidence that this trade is causing a reduction in the ranges and populations of some species. However, before any conservation status can be assigned to any species reliably, it will be necessary to reconcile the long-established traditional classification system of singing and fighting insects with scientific classification, determine the ranges and monitor the populations of selected species of commonly traded species, and initiate an educational programme for invertebrate conservation using these crickets as flagship taxa.