The ander's organ: a mechanism for anti-predator ultrasound in a relict orthopteran

Abstract

The use of acoustics in predator evasion is a widely reported phenomenon amongst invertebrate taxa, but the study of ultrasonic anti-predator acoustics is often limited to the prey of bats. Here, we describe the acoustic function and morphology of a unique stridulatory structure – the Ander's organ – in the relict orthopteran Cyphoderris monstrosa (Ensifera, Hagloidea). This species is one of just eight remaining members of the family Prophalangopsidae, a group with a fossil record of over 90 extinct species widespread during the Jurassic period. We reveal that the sound produced by this organ has the characteristics of a broadband ultrasonic anti-predator defence, with a peak frequency of 58±15.5 kHz and a bandwidth of 50 kHz (at 10 dB below peak). Evidence from sexual dimorphism, knowledge on hearing capabilities and assessment of local predators, suggests that the signal likely targets ground-dwelling predators. Additionally, we reveal a previously undescribed series of cavities underneath the organ that probably function as a mechanism for ultrasound amplification. Morphological structures homologous in both appearance and anatomical location to the Ander's organ are observed to varying degrees in 4 of the 7 other extant members of this family, with the remaining 3 yet to be assessed. Therefore, we suggest that such structures may either be more widely present in this ancient family than previously assumed, or have evolved to serve a key function in the long-term survival of these few species, allowing them to outlive their extinct counterparts.

Acoustic and vibrational signaling in true katydid Nesoecia nigrispina: three means of sound production in one species

“…2G and 2H ). We carried out experiments in which these spinules were covered with a layer of wax to test whether these structures can be used in stridulation, like the Ander’s organs of Cyphoderris monstrosa (Prophalangopsidae) ( Woodrow et al, 2021 ) or abdominal fields with tubercules of representatives of Anostostomatidae ( Zhantiev, Kalinkina & Korsunovskaya, 1982 ) and Gryllacrididae ( Field & Bailey, 1997 ). They showed that the insects in this case were capable to emit wing protest signals.…”

“…Mechanisms for producing these sounds are different: males with a developed tegminal sound apparatus produce them in response to mechanical stimulation. Sounds of this kind, loud and prolonged, are, as in katydids of the tribe Zichyini ( Zhantiev, Korsunovskaya & Byzov, 1995 ; Elaeva & Korsunovskaya, 2012 ), apparently aimed at scaring away predators ( Masters, 1980 ; Low, Naranjo & Yack, 2021 ; Woodrow et al, 2021 ). Wing protest signals are emitted by both males, and females.…”

Auditory mechanics in the grig ( Cyphoderris monstrosa ): tympanal travelling waves and frequency discrimination as a precursor to inner ear tonotopy

“…The frequency response of the tympana was measured in seven female and 11 male specimens of C. monstrosa, totalling 36 individual ears of which 33 provided suitable data for analysis. Specimens were immobilized using a unique method under previous protocols [ 34 ]; by freezing at −2°C for 2 min. They were then mounted in a natural orientation to a copper platform with wax made of 50% beeswax (Fisher Scientific, Loughborough, UK) and 50% colophonium (Sigma-Aldrich Company Ltd, Dorset, UK).…”

Reviving the sound of a 150-year-old insect: The bioacoustics of Prophalangopsis obscura (Ensifera: Hagloidea)

“…Reduced flight is a well-established evolutionary mechanism to reduce or avoid predation by aerial predators, and in particular, bats [26]. The other extant species in this family, all of whom have lost the ability to fly, exhibit novel anti-predator defences, namely ultrasonic sound production organs [27], which likely evolved to act as a deterrent to a new host of predators they now face after switching to a terrestrial lifestyle. Such anti-predator adaptations are not present in P. obscura, nor are any other morphological adaptations associated with predation by bats such as enlarged cuticular spines [26].…”