@article {58027, title = {Diversity of acoustic tracheal system and its role for directional hearing in crickets}, year = {2013}, abstract = {

Background: Sound localization in small insects can be a challenging task due to physical constraints in deriving sufficiently large interaural intensity differences (IIDs) between both ears. In crickets, sound source localization is achieved by a complex type of pressure difference receiver consisting of four potential sound inputs. Sound acts on the external side of two tympana but additionally reaches the internal tympanal surface via two external sound entrances. Conduction of internal sound is realized by the anatomical arrangement of connecting trachea. A key structure is a trachea coupling both ears which is characterized by an enlarged part in its midline (i.e., the acoustic vesicle) accompanied with a thin membrane (septum). This facilitates directional sensitivity despite an unfavorable relationship between wavelength of sound and body size. Here we studied the morphological differences of the acoustic tracheal system in 40 cricket species (Gryllidae, Mogoplistidae) and species of outgroup taxa (Gryllotalpidae, Rhaphidophoridae, Gryllacrididae) of the suborder Ensifera comprising hearing and non hearing species.

Results: We found a surprisingly high variation of acoustic tracheal systems and almost all investigated species using intraspecific acoustic communication were characterized by an acoustic vesicle associated with a medial septum. The relative size of the acoustic vesicle - a structure most crucial for deriving high IIDs - implies an important role for sound localization. Most remarkable in this respect was the size difference of the acoustic vesicle between species; those with a more unfavorable ratio of body size to sound wavelength tend to exhibit a larger acoustic vesicle. On the other hand, secondary loss of acoustic signaling was nearly exclusively associated with the absence of both acoustic vesicle and septum.

Conclusion: The high diversity of acoustic tracheal morphology observed between species might reflect different steps in the evolution of the pressure difference receiver; with a precursor structure already present in ancestral non-hearing species. In addition, morphological transitions of the acoustic vesicle suggest a possible adaptive role for the generation of binaural directional cues.

}, keywords = {Acoustic tracheal system, cricket, directional hearing, Interaural intensity difference (IID), Pressure difference receiver, Sound localization}, doi = {10.1186/1742-9994-10-61}, url = {http://frontiersinzoology.biomedcentral.com/articles/10.1186/1742-9994-10-61}, author = {Schmidt, Arne KD and R{\"o}mer, Heiner} } @article {40443, title = {The World{\textquoteright}s Most Unusual Gryllacridid (Orthoptera: Gryllacrididae)}, journal = {Journal of Orthoptera Research}, volume = {6}, year = {1997}, pages = {57-68}, chapter = {57}, abstract = {

Gryllacridid behavior and morphology is referred to an unusual Raspy Cricket from south-east Queensland is described in a new genus and species, Urogryllacris gwinganna gen. \& sp. nov. The species is unique in the Gryllacrididae in having an extraordinarily developed male subgenital plate which terminates in an elongate whip-like structure. The new genus and species are described with emphasis given to the proventriculus, the male subgenital plate and the egg. A mating sequence is described with a discussion concerning the possible function of the peculiar subgenital plate.

}, url = { http://www.jstor.org/stable/3503536}, author = {D. C. F. Rentz} } @article {40435, title = {Neuroanatomy and Physiology of the Complex Tibial Organ of an Atympanate Ensiferan, Ametrus tibialis (Brunner von Wattenwyl, 1888) (Gryllacrididae, Orthoptera) and Evolutionary Implications}, journal = {Brain, Behavior and Evolution}, volume = {71}, year = {2008}, month = {Jan-01-2008}, pages = {167 - 180}, abstract = {

We investigated the neuroanatomy and physiology of the complex tibial organ of an atympanate ensiferan, the Gryllacridid Ametrus tibialis. This represents the first analysis of internal mechanoceptors in Gryllacridids. The complex tibial organ is tripartite consisting of a subgenual organ, intermediate organ and a homologue organ to the crista acustica of tympanate ensiferan taxa of Tettigoniidae, Haglidae, and Anostostomatidae. The crista homologue contains 23 \± 2 receptor neurons in the foreleg. It is associated with the leg trachea and found serially in all three thoracic leg pairs. Central projections of the sensory nerve of the complex tibial organ bifurcate in two lobes in the prothoracic ganglion, which do not reach the midline. The axonal endings project into the mVAC, the main vibratory-auditory neuropile of Ensifera. Recordings of the tibial nerve show that the tibial organ is sensitive to vibrational stimuli with a minimum threshold of 0.02 to 0.05 ms\–2 at 200\–500 Hz, but rather insensitive to airborne sound. The main function of the tibial organ is therefore vibration sensing, although the specific function of the crista homologue remains unclear. The presence of the crista acustica homologue is interpreted in phylogenetic context. Because ensiferan phylogeny is unresolved, two alternative scenarios can be deduced: (a) the crista homologue is a precursor structure which was co-opted as an auditory system and represent a morphologically highly specialized structure before acquisition of its new function; (b) a previously functional tibial ear is evolutionary reduced but the neuronal structures are maintained. Based on comparison of neuroanatomical details, the crista acustica homologue of A. tibialis could present the neuronal complement of an ear evolutionary precursor structure, which was successively made sensitive to airborne sound by elaboration of cuticular tympana, auditory spiracle and trachea for sound propagation.

}, keywords = {Ametrus tibialis, auditory system, Ensifera, Gryllacrididae, hearing organ, neuroanatomy, vibrational communication}, issn = {0006-8977}, doi = {10.1159/000114405}, url = {http://www.karger.com/doi/10.1159/000114405}, author = {Strau{\ss}, Johannes and Lakes-Harlan, Reinhard} } @article {40433, title = {Sound production in primitive Orthoptera from Western Australia: sounds used in defence and social communication in Ametrus sp. and Hadrogryllacris sp. (Gryllacrididae: Orthoptera)}, journal = {Journal of Natural History}, volume = {31}, year = {1997}, month = {Jan-07-1997}, pages = {1127 - 1141}, abstract = {

Sound production in two undescribed species of Gryllacrididae belonging to the genus Ametrus sp. and Hadrogryllacris sp. takes the form of defensive stridulation and intra-specific signalling by drumming on the substrate. Defensive stridulation is produced as part of an elaborate visual display, by femoro-tergal stridulation. Two rows of spines on abdominal tergites II and III of both species are rubbed by an elongate area of tubercules on the inner femoral surface of the hind legs. Analysis showed that the motion of the leg relative to the abdomen involves a complex counter-rotation of the leg between leg and abdomen. The defensive display may be performed in day light. Social signalling in both species occurs after dark, and involves drumming on the substrate by both hind legs in loose synchrony. Drumming is rhythmic and species\&$\#$39; specific. Males respond to playback calls and females duet with males. The evolution of this calling behaviour is discussed and comparisons are made with the other primitive ensiferan family known to produce both tergo-abdominal defensive stridulation and femoral drumming behaviour, the Stenopelmatidae.

}, keywords = {defence, duetting, social communication, sound production, substrate vibration}, issn = {0022-2933}, doi = {10.1080/00222939700770591}, url = {http://www.tandfonline.com/doi/abs/10.1080/00222939700770591}, author = {Field, L.H. and Winston J. Bailey} }