Gordon SD. ter Hofstede HM. 2018. The influence of bat echolocation call duration and timing on auditory encoding of predator distance in noctuoid moths. The Journal of Experimental Biology

Gordon SD. ter Hofstede HM. 2018. The influence of bat echolocation call duration and timing on auditory encoding of predator distance in noctuoid moths. The Journal of Experimental Biology

by | Feb 2, 2018 |

Abstract: Animals co-occur with multiple predators, making sensory systems that can encode information about diverse predators advantageous. Moths in the families Noctuidae and Erebidae have ears with two auditory receptor cells (A1 and A2) used to detect the echolocation calls of predatory bats. Bat communities contain species that vary in echolocation call duration, and the dynamic range of A1 is limited by the duration of sound, suggesting that A1 provides less information about bats with shorter echolocation calls. To test this hypothesis, we obtained intensity-response functions for both receptor cells across many moth species for sound pulse durations representing the range of echolocation call durations produced by bat species in northeastern North America. We found that the threshold and dynamic range of both cells varied with sound pulse duration. The number of A1 action potentials per sound pulse increases linearly with increasing amplitude for long duration pulses, saturating near A2 threshold. For short sound pulses, however, A1 saturates with only a few action potentials per pulse at amplitudes far lower than the A2 threshold for both single sound pulses and pulse sequences typical of searching or approaching bats. Neural adaptation was only evident in response to approaching bat sequences at high amplitudes, not search phase sequences. These results show that, for short echolocation calls, a large range of sound levels cannot be coded by moth auditory receptor activity, resulting in no information about the distance of a bat, although differences in activity between ears might provide information about direction.   Gordon and ter Hofstede. 2018  The influence of bat echolocation call duration and timing on auditory encoding of predator...
Gordon SD, Klenschi E, Windmill JFC. 2017. Hearing on the fly: the effects of wing position on noctuid moth hearing. Journal of Experimental Biology. 220:1952-1955

Gordon SD, Klenschi E, Windmill JFC. 2017. Hearing on the fly: the effects of wing position on noctuid moth hearing. Journal of Experimental Biology. 220:1952-1955

by | Mar 21, 2017 |

The ear of the noctuid moth has only two auditory neurons, A1 and A2, which function in detecting predatory bats. However, the noctuid’s ears are located on the thorax behind the wings. Therefore, since these moths need to hear during flight, it was hypothesized that wing position may affect their hearing. The wing was fixed in three different positions: up, flat, and down. An additional subset of animals was measured with freely moving wings. In order to negate any possible acoustic shadowing or diffractive effects, all wings were snipped, leaving the proximal most portion and the wing hinge intact. Results revealed that wing position plays a factor in threshold sensitivity of the less sensitive auditory neuron A2, but not in the more sensitive neuron A1. Furthermore, when the wing was set in the down position, fewer A1 action potentials were generated prior to the initiation of A2 activity. Analyzing the motion of the tympanal membrane did not reveal differences in movement due to wing position. Therefore, these neural differences due to wing position are proposed to be due to other factors within the animal such as different muscle tensions.   Gordon SD, Klenschi E, Windmill JFC. 2017. Hearing on the fly: the effects of wing position on noctuid moth hearing. Journal of Experimental Biology....