@article {57950, title = {Listening when there is no sexual signalling? Maintenance of hearing in the asexual bushcricket Poecilimon intermedius}, year = {2007}, abstract = {

Unisexual reproduction is a widespread phenomenon in invertebrates and lower vertebrates. If a former sexual reproducing species becomes parthe- nogenetic, we expect traits that were subject to sexual selection to diminish. The bushcricket Poecilimon intermedius is one of the few insect species with obli- gate but diploid parthenogenetic reproduction. We contrasted characters that are involved in mating in a sexually sibling species with the identical structures in the parthenogenetic P. intermedius. Central for sexual communication are male songs, while receptive females approach the males phonotactically. Com- pared to its sister-species P. ampliatus, the morphology of the hearing organs (acoustic spiracle, crista acustica) and the function of hearing (acoustic threshold) are reduced in P. intermedius. Nonetheless, hearing is clearly maintained in the parthenogenetic females. Natural selection by acoustic hunting bats, pleiotropy or a developmental trap may explain the well main- tained hearing function.

}, keywords = {Auditory ecology, bioacoustics, neuroanatomy, Regression, Vestigialization}, doi = {10.1007/s00359-007-0209-y}, url = {http://link.springer.com/10.1007/s00359-007-0209-y}, author = {Gerlind U.C. Lehmann and Strau{\ss}, Johannes and Lakes-Harlan, Reinhard} } @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} } @article {40437, title = {The evolutionary origin of auditory receptors in Tettigonioidea: the complex tibial organ of Schizodactylidae}, journal = {Naturwissenschaften}, volume = {96}, year = {2009}, month = {Jan-01-2009}, pages = {143 - 146}, abstract = {

Audition in insects is of polyphyletic origin. Tympanal ears derived from proprioceptive or vibratory receptor organs, but many questions of the evolution of insect auditory systems are still open. Despite the rather typical bauplan of the insect body, e.g., with a fixed number of segments, tympanal ears evolved at very different places, but only ensiferans have ears at the foreleg tibia, located in the tibial organ. The homology and monophyly of ensiferan ears is controversial, and no precursor organ was unambig- uously identified for auditory receptors. The latter can only be identified by comparative study of recent atympanate taxa. These atympanate taxa are poorly investigated. In this paper, we report the neuroanatomy of the tibial organ of Comicus calcaris (Irish 1986 ), an atympanate Schizodactylid (splay-footed cricket). This representative of a Gondwana relict group has a tripartite sensory organ, homologous to tettigoniid ears. A comparison with morphology-based cladistic phylogeny indicates that the tripartite neuronal organization present in the m ajority of Tettigonioidea presumably preceded evolution of a hearing sense in the Tettigonioidea. Furthermore, the absence of a tripartite organ in Grylloidea argues against a monophyletic origin and homology of the cricket and katydid ears. The tracheal attachment of sensory neurons typical for ears of Tettigo- nioidea is present in C. calcaris and may have facilitated cooption for auditory function. The functional auditory organ was presumably formed in evolution by successive non-neural modifications of trachea and tympana. This first investigation of the neuroanatomy of Schizodactylidae suggests a non-auditory chordotonal organ as the precursor for auditory receptors of related tympanate taxa and adds evidence for the phylogenetic position of the group.

}, keywords = {hearing, neuroanatomy, Schizodactylidae, sensory evolution}, issn = {0028-1042}, doi = {10.1007/s00114-008-0450-4}, url = {http://link.springer.com/10.1007/s00114-008-0450-4}, author = {Strau{\ss}, Johannes and Lakes-Harlan, Reinhard} } @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} }