@article {57943, title = {Serial hearing organs in the atympanate grasshopper Bullacris membracioides (Orthoptera, Pneumoridae)}, year = {2003}, abstract = {

In different insect taxa, ears can be found on virtually any part of the body. Comparative anatomy and similarities in the embryological development of ears in divergent taxa suggest that they have evolved multiple times from ubiquitous stretch or vibration receptors, but the homology of these structures has not yet been rigorously tested. Here we provide detailed analysis of a novel set of hearing organs in a relatively \“primitive\” atympanate bladder grasshopper (Bullacris membracioides) that is capable of signaling acoustically over 2 km. We use morphological, physiological, and behavioral experiments to demonstrate that this species has six pairs of serially repeated abdominal ears derived from proprioceptive pleural chordotonal organs (plCOs). We demonstrate continuity in auditory function from the five posterior pairs, which are simple forms comprising 11 sensilla and resembling plCOs in other grasshoppers, to the more complex anterior pair, which contains 2000 sensilla and is homologous to the single pair of tympanate ears found in \“modern\” grasshoppers. All 12 ears are morphologically differentiated, responsive to airborne sound at frequencies and intensities that are biologically significant (tuned to 1.5 and 4 kHz; 60\–98 dB SPL), and capable of mediating behavioral responses of prospective mates. These data provide evidence for the transition in function and selective advantage that must occur during evolutionary development of relatively complex organs from simpler precursors. Our results suggest that ancestral insects with simple atympanate pleural receptors may have had hearing ranges that equal or exceed those of contemporary insects with complex tympanal ears. Moreover, auditory capability may be more prevalent among modern insect taxa than the presence of overt tympana indicates

}, keywords = {acoustic insects, auditory evolution, Caelifera, chordotonal organ, ears}, doi = {10.1002/cne.v465:410.1002/cne.10871}, url = {http://doi.wiley.com/10.1002/cne.v465\%3A4}, author = {Moira J. van Staaden and Rieser, Michael and Ott, Swidbert R. and Pabst, Maria A. and Heiner R{\"o}mer} } @article {40441, title = {Neuroanatomy of the complex tibial organ of Stenopelmatus (Orthoptera: Ensifera: Stenopelmatidae)}, journal = {The Journal of Comparative Neurology}, volume = {511}, year = {2008}, month = {Jan-11-2008}, pages = {81 - 91}, abstract = {

Stenopelmatidae (or \“Jerusalem crickets\”) belong to the atympanate Ensifera, lacking hearing organs in the foreleg tibiae. Their phylogenetic position is controversial, either as a taxon in Tettigonioidea or within the clade of Gryllacridoidea. Similarly, the origin of tibial auditory systems in Ensifera is controversial. Therefore, we investigated the neuronal structures of the proximal tibiae of Stenopelmatus spec. with the hypothesis that internal sensory structures are similar to those in tympanate Ensifera. In Stenopelmatus the complex tibial organ consists of three neuronal parts: the subgenual organ, the intermediate organ, and a third part with linearly arranged neurons. This tripartite organization is also found in tympanate Ensifera, verifying our hypothesis. The third part of the sense organ found in Stenopelmatus can be regarded by the criterion of position as homologous to auditory receptors of hearing Tettigonioidea. This crista acustica homolog is found serially in all thoracic leg pairs and contains 20 \± 2 chordotonal neurons in the foreleg. The tibial organ was shown to be responsive to vibration, with a broad threshold of about 0.06 ms\−2 in a frequency range from 100\–600 Hz. The central projection of tibial sensory neurons terminates into two equally sized lobes in the primary sensory neuropil, the medial ventral association center. The data are discussed comparatively to those of other Ensifera and mapped phylogenetically onto recently proposed phylogenies for Ensifera. The crista acustica homolog could represent a neuronal rudiment of a secondarily reduced ear, but neuronal features are also consistent with an evolutionary preadaptation.

}, keywords = {chordotonal organ, Ensifera, neuroanatomy, sensory evolution, Stenopelmatidae, vibrational communication}, issn = {00219967}, doi = {10.1002/cne.v511:110.1002/cne.21836}, url = {http://doi.wiley.com/10.1002/cne.v511\%3A1}, author = {Strau{\ss}, Johannes and Lakes-Harlan, Reinhard} }