@article {57944, title = {Sensory evolution of hearing in tettigoniids with differing communication systems}, journal = {Journal of Evolutionary Biology}, volume = {27}, year = {2014}, month = {Jan-01-2014}, pages = {200 - 213}, abstract = {

In Tettigoniidae (Orthoptera: Ensifera), hearing organs are essential in mate detection. Male tettigoniids usually produce calling songs by tegminal stridu- lation, whereas females approach the males phonotactically. This unidirec- tional communication system is the most common one among tettigoniids. In several tettigoniid lineages, females have evolved acoustic replies to the male calling song which constitutes a bidirectional communication system. The genus Poecilimon (Tettigoniidae: Phaneropterinae) is of special interest because the ancestral state of bidirectional communication, with calling males and responding females, has been reversed repeatedly to unidirec- tional communication. Acoustic communication is mediated by hearing organs that are adapted to the conspecific signals. Therefore, we analyse the auditory system in the Tettigoniidae genus Poecilimon for functional adapta- tions in three characteristics: (i) dimension of sound-receiving structures (tympanum and acoustic spiracle), (ii) number of auditory sensilla and (iii) hearing sensitivity. Profound differences in the auditory system correlate with uni- or bidirectional communication. Among the sound-receiving structures, the tympana scale with body size, whereas the acoustic spiracle, the major sound input structure, was drastically reduced in unidirectional communicating species. In the unidirectional P. ampliatus group, auditory sensilla are severely reduced in numbers, but not in the unidirectional P. propinquus group. Within the P. ampliatus group, the number of auditory sensilla is further reduced in P. intermedius which lost acoustic signalling due to parthenogenesis. The auditory sensitivity correlated with the size of the acoustic spiracle, as hearing sensitivity was better with larger spiracles, espe- cially in the ultrasonic range. Our results show a significant reduction in auditory structures, shaped by the differing sex roles during mate detection.

}, keywords = {animal communication, insect hearing, regressive evolution, sensory ecology, sensory evolution, tympanal organ}, doi = {10.1111/jeb.2014.27.issue-110.1111/jeb.12294}, url = {http://doi.wiley.com/10.1111/jeb.2014.27.issue-1}, author = {Strau{\ss}, J. and Lehmann, A. W. and Gerlind U.C. Lehmann} } @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 {20904, title = {Evolutionary diversification of the auditory organ sensilla in Neoconocephalus katydids (Orthoptera: Tettigoniidae) correlates with acoustic signal diversification over phylogenetic relatedness and life history}, journal = {Journal of Evolutionary Biology}, year = {2017}, month = {Jan-03-2017}, abstract = {

Neoconocephalus tettigoniids are a model for the evolution of acoustic signals as male calls have diversified in temporal structure during the radiation of the genus. Tettigoniidae have hearing organs in the forelegs with species-specific numbers of auditory sensilla in a linear crista acustica. We investigated changes of the hearing organs during an evolutionary radiation with divergence of intraspecific acoustic signals. We compared the neuroanatomy of the crista acustica from 9 Neoconocephalus species with different temporal call features, life histories, and from different phylogenetic positions. Average numbers of auditory sensilla were species-specific, ranging between 32\–35 sensilla. It is likely under sexual selection for detection of male calls and natural selection for detection of bat calls. We found statistically significant differences in sensillum numbers among species, but no relationship of crista acustica length or sensillum number with phylogenetic position or life history. Statistically significant correlations existed with call patterns: species with slow pulse rates had significantly higher numbers of auditory sensilla and a longer crista acustica. Further, species with a derived double-pulsed calls had longer cristae, and continuous callers had a higher number of auditory sensilla. Correlations with crista length were stronger than with the number of auditory sensilla. The hearing organs show considerable diversity between species despite their recent divergence and morphological and ecological similarities. Thus, they have the potential to respond to various selective pressures, including divergence of temporal and spectral signal properties. Phylogenetic constraints are unlikely to limit the evolutionary change of the auditory systems.

}, keywords = {hearing organ, insects, radiation, sensory evolution, sexual selection, signal evolution, tympanal organ}, doi = {10.1111/jeb.13066}, url = {http://doi.wiley.com/10.1111/jeb.13066}, author = {Strau{\ss}, Johannes and Alt, Joscha A. and Ekschmitt, Klemens and Schul, Johannes and Lakes-Harlan, Reinhard} }