Sinnesorgane im Bereich des Fl�gels der Feldgrille (Gryllus campestris L.) und ihre Bedeutung f�r die Kontrolle der Singbewegung und die Einstellung der Fl�gellage

Neuroethology of acoustic communication in field crickets - from signal generation to song recognition in an insect brain

Field crickets are best known for the loud calling songs produced by males to attract conspecific females. This review aims to summarize the current knowledge of the neurobiological basis underlying the acoustic communication for mate finding in field crickets with emphasis on the recent research progress to understand the neuronal networks for motor pattern generation and auditory pattern recognition of the calling song in Gryllus bimaculatus. Strong scientific interest into the neural mechanisms underlying intraspecific communication has driven persistently advancing research efforts to study the male singing behaviour and female phonotaxis for mate finding in these insects. The growing neurobiological understanding also inspired many studies testing verifiable hypotheses in sensory ecology, bioacoustics and on the genetics and evolution of behaviour. Over last decades, acoustic communication in field crickets served as a very successful neuroethological model system. It has contributed significantly to the scientific process of establishing, reconsidering and refining fundamental concepts in behavioural neurosciences such as command neurons, central motor pattern generation, corollary discharge processing and pattern recognition by sensory feature detection, which are basic building blocks of our modern understanding on how nervous systems control and generate behaviour in all animals.

Temperature coupling in cricket acoustic communication. II. Localization of temperature effects on song production and recognition networks in Gryllus firmus

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.

The locust wing hinge stretch receptors. I. Primary sensory neurones with enormous central arborizations

In locusts a single-celled stretch receptor (SR) neurone at the base of each wing monitors wing elevation and contributes to the control of the flight motor output. The central projections of these neurones are very complex but consistent in detail in the three species studied (Chortoicetes, Locusta and Schistocerca). The hindwing SR projects to the second and third thoracic ganglia, the forewing SR to the first, second and third thoracic ganglia. Both send fine axons into the abdominal connective. Within the ganglia each SR forms an extensive arborization, entirely ipsilateral and mainly in the dorsal neuropile, divided into medial, mediolateral, and lateral branches. The projections of the two ipsilateral SR neurones overlap almost completely in the second and third ganglia. There are recurrent loops between branches of a single neurone both within and between ganglia. Light microscope analysis shows apparent contacts between the SR aneurones and flight motor neurones and other wing sensory afferents, as well as long interneurones, other motor neurones and two types of multiaxonal neurones of unknown function. There are three groups of contacts between each SR and a flight motor neurone: laterally on the main branches, medially with the terminal twigs; and in the anterior dorso-medial glomerulus, where the inter ganglionic recurrent branch also terminates. All contacts are ipsilateral except for those with the contralateral branches of the dorsal longitudinal muscle motor neurones. We suggest that the SR neurones are multifunctional. Differential information transfer could result both from the spatial distribution of synaptic connections with the motor neurones and from filtering caused by low safety factors at branch junctions. Information in the lateral branching could be used for general excitation and control of firing frequency of the motor neurones; that in the medial branch for wing control and co-ordination.

Wing Movements of Calling Katydids: Fiddling Finesse

Stridulating Uhler's katydids produce the most complex song known for insects. Series of four types of sounds are made in stereotyped sequence. Sound-synchronized high-speed photography reveals that each type of sound is produced by a distinctively different wing-movement cycle. The most complex of these cycles includes a two-step closure and a nearly silent close-open movement.