02555nas a2200205 4500008004100000245012700041210006900168520186800237653002102105653002302126653001402149653002202163653000902185100002702194700002002221700002202241700002102263700001902284856004602303 2003 eng d00aSerial hearing organs in the atympanate grasshopper Bullacris membracioides (Orthoptera, Pneumoridae)0 aSerial hearing organs in the atympanate grasshopper iBullacris m3 a

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

10aacoustic insects10aauditory evolution10aCaelifera10achordotonal organ10aears1 avan Staaden, Moira, J.1 aRieser, Michael1 aOtt, Swidbert, R.1 aPabst, Maria, A.1 aRömer, Heiner uhttp://doi.wiley.com/10.1002/cne.v465%3A401855nas a2200157 4500008004100000022001300041245008300054210006900137260001600206300001400222490000800236520135700244100002701601700001901628856005001647 1998 eng d a0028083600aEvolutionary transition from stretch to hearing organs in ancient grasshoppers0 aEvolutionary transition from stretch to hearing organs in ancien cAug-08-1999 a773 - 7760 v3943 a

Ears of modern insects occur on a wide variety of body parts and are thought to have evolved from ubiquitous stretch or vibration receptors1,2,3,4. This relationship, based on comparative anatomy and similarities in the embryological development of ears in divergent taxa5,6,7, has led to the widespread assumption of homology of these structures in insects, although this has not been tested rigorously. Here we report on the hearing organs of a relatively ancient8, atympanate bladder grasshopper9,10,11 (Bullacris membracioides), which is capable of signalling acoustically over ∼2 km12. We show that, within single individuals of this species, serially repeated abdominal ears show functional continuity from simple to more complex forms. All 12 morphologically differentiated organs respond to sound frequencies and intensities that are biologically significant, and mediate adaptive behavioural responses. By linking observations at the anatomical, physiological and behavioural level, our experiments provide evidence for the transition in function and selective advantage during the evolutionary development of this complex structure13,14. It is possible that ancestral insects with only simple pleural receptors had auditory capability covering distances substantially greater than contemporary insects with tympanate ears.

1 avan Staaden, Moira, J.1 aRömer, Heiner uhttp://www.nature.com/doifinder/10.1038/2951702397nas a2200205 4500008004100000022001400041245010100055210006900156260001600225300001400241490000800255520172600263653002101989653002302010653001802033653001502051100002702066700002102093856007702114 2005 eng d a0005-795900aAlternate tactics in male bladder grasshoppers Bullacris membracioides (Orthoptera: Pneumoridae)0 aAlternate tactics in male bladder grasshoppers Bullacris membrac cJan-06-2005 a761 - 7780 v1423 a

Bladder grasshoppers (Orthoptera, Pneumoridae) are a unique group of nocturnal, specialized herbivores, endemic to coastal regions of Southern Africa. Adult males are characterized by an inflated abdomen, which develops at the final molt, and a signaling system capable of producing high intensity calls detectable by conspecifics at distances of up to 2 km. Female response to male calls leads to reciprocal duetting and pair formation. We have found an alternative form to the dominant inflated male tactic in three pneumorid species. These alternate males are incapable of flight and lack the air-filled abdominal bladder used in long-range acoustic communication; but may be found in copula with mature females in the field. Here we address the issue of neoteny/paedogenesis in the alternate male by comparing the morphology of inflated and uninflated adult male Bullacris membracioides with that of ultimate and penultimate nymphal instars, to determine whether these forms follow a common developmental trajectory. We then compare the behavioral responsiveness of inflated and noninflated morphs to conspecific advertisement calls, to ascertain whether alternate males have the potential to actively exploit the mate location system of duetting pairs. Morphometric analyses indicate that alternate males are a distinctly divergent form from the primary male developmental tactic. We conclude that males following the alternate tactic eavesdrop on the duets of inflated males and females to exploit the acoustic mate location system. This satellite tactic has potential impact on several aspects of pneumorid biology contributing to biasing sexual selection, sensory drive, and ultimately speciation events.

10aalternative male10abehavioral tactics10acommunication10amorphology1 avan Staaden, Moira, J.1 aDonelson, Nathan uhttp://booksandjournals.brillonline.com/content/10.1163/156853905472908802236nas a2200193 4500008004100000022001400041245009700055210006900152260001600221300001600237490000800253520158600261653002701847653002201874653001601896100002701912700002401939856007901963 2006 eng d a0005-795900aFemale preferences for male calling songs in the bladder grasshopper Bullacris membracioides0 aFemale preferences for male calling songs in the bladder grassho cJan-12-2006 a1439 - 14560 v1433 a

Male acoustic signals and the information they convey are often critical determinants of female mate choice. Bladder grasshoppers are one of numerous orthopteran taxa utilizing sound as the basis of courtship and ultimately mating. However, despite the extreme specializations for long-distance acoustic communication in this family, female mating preferences for male calls have not been previously investigated. Here we examine female acoustic responses to playbacks of male calls in Bullacris membracioides. Females were tested in three separate contexts, viz. response to conspecific calls of different individuals, response to degraded conspecific calls, and response to the calls of two heterospecifics. Female response was significantly correlated with seven of eight measured call features within B. membracioides, indicating sexual selection to be operating in this species. Females also responded to conspecific calls with degradation levels equivalent to a male calling 150 m away, but intensity equivalent to one at 25 m, identifying call amplitude rather than degradation as the factor limiting female response. However, as response decreased with increasing call degradation, signal quality remains a factor in female preference. Calls of the sister taxon B. intermedia were equally attractive to B. membracioides females as were conspecific calls, while the more distinct calls of B. serrata were less preferred than those of both B. membracioides and B. intermedia. This indicates a lack of discriminatory ability against a similar sounding heterospecific.

10aacoustic communication10afemale preference10aPneumoridae1 avan Staaden, Moira, J.1 aCouldridge, Vanessa uhttp://booksandjournals.brillonline.com/content/10.1163/15685390677936703502264nas a2200217 4500008004100000022001400041245009300055210006900148260001300217300001300230490000800243520163100251653002801882653001201910653001101922653001701933653000901950100002701959700001901986856004102005 1997 eng d a0022-094900aSexual signalling in bladder grasshoppers: tactical design for maximizing calling range.0 aSexual signalling in bladder grasshoppers tactical design for ma c1997 Oct a2597-6080 v2003 a

Pair formation in the bladder grasshopper (Bullacris membracioides) is by duetting and male phonotaxis. Low-frequency stridulatory signals are emitted by an abdominal resonator in the male and are answered by females using a species-specific time delay. Acoustic transmission in the natural environment was studied using playback of sexual signals over distances of 450m under two atmospheric conditions (day and night). Upward-refracting sound conditions and a sound shadow zone beyond approximately 50m prevailed during the day. Acoustic enhancement was demonstrated at night when downward-refracting temperature inversions created a tunnel effect with sound caught between the ground and zones of different temperatures. Transmission conditions are almost ideal at night when the species actually calls; calling distances of 150m for the male signal in the afternoon increased to 1.5-1.9km at night, arguably the largest calling distance yet reported for insects. In contrast, female calls transmit over a maximum of 50m, signifying a marked discrepancy in the active space of sex-specific signals. Transmission distance may, however, be profoundly affected by levels of masking noise. Adaptations to increase the signal range may variously be found in the signal itself, in behaviour patterns or in the sensory system. Here we demonstrate aspects of the first two types of adaptation in the sexual signalling system of a grasshopper in which maximizing the calling range appears to be the major selection pressure, with lesser effects imposed by inter- and intraspecific pressures and by the transmission channel.

10aanimal sexual behaviour10aAnimals10afemale10agrasshoppers10amale1 avan Staaden, Moira, J.1 aRömer, Heiner uhttps://bio.acousti.ca/es/node/20902