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

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....
Sitvarin M, Gordon SD, Uetz GW, Rypstra A.  2016.  The wolf spider Pardosa milvina detects predator threat level using only vibratory cues.  Behaviour.  153:159-173

Sitvarin M, Gordon SD, Uetz GW, Rypstra A. 2016. The wolf spider Pardosa milvina detects predator threat level using only vibratory cues. Behaviour. 153:159-173

Predators may inadvertently signal their presence and threat level by way of signals in multiple modalities. We used a spider, Pardosa milvina, known to respond adaptively to chemotactile predator cues (i.e., silk, faeces and other excreta) to evaluate whether it could also discriminate predation risk from isolated vibratory cues. Vibrations from its prey, conspecifics, and predators (Tigrosa helluo and Scarites quadriceps) were recorded and played back to Pardosa. In addition, we recorded predator vibrations with and without access to chemotactile cues from Pardosa, indicating the presence of prey. Pardosa did not appear to discriminate between vibrations from prey or conspecifics, but the response to predators depended on the presence of cues from Pardosa. Vibrations from predators with access to chemotactile cues from prey induced reductions in Pardosa activity. Predator cues typically occur in multiple modalities, but prey are capable of imperfectly evaluating predation risk using a limited subset of information. Sitvarin M, Gordon SD, Uetz GW, Rypstra A.  2016.  The wolf spider Pardosa milvina detects predator threat level using only vibratory cues.  Behaviour. ...
Gordon SD, Windmill JFC.  2015.  Hearing ability decreases in ageing locusts.  J. of Experimental Biology.  218:1990-199

Gordon SD, Windmill JFC. 2015. Hearing ability decreases in ageing locusts. J. of Experimental Biology. 218:1990-199

Insects display signs of ageing, despite their short lifespan. However, the limited studies on senescence emphasize longevity or reproduction. We focused on the hearing ability of ageing adult locusts, Schistocerca gregaria. Our results indicate that the youngest adults (2 weeks post-maturity) have a greater overall neurophysiological response to sound, especially for low frequencies (<10 kHz), as well as a shorter latency to this neural response. Interestingly, when measuring displacement of the tympanal membrane that the receptor neurons directly attach to, we found movement is not directly correlated with neural response. Therefore, we suggest the enhanced response in younger animals is due to the condition of their tissues (e.g. elasticity). Secondly, we found the sexes do not have the same responses, particularly at 4 weeks post-adult moult. We propose female reproductive condition reduces their ability to receive sounds. Overall our results indicate older animals, especially females, are less sensitive to sounds. Gordon SD, Windmill JFC. 2015. Hearing ability decreases in ageing locusts. J. of Experimental Biology....
Gordon SD, Jackson JC, Rogers SM, Windmill JFC.  2014.  Listening to the Environment:  Hearing Differences from an Epigenetic Effect in Solitarious and Gregarious Locusts.  Proceedings of the Royal Society B. 281 no. 1795 20141693

Gordon SD, Jackson JC, Rogers SM, Windmill JFC. 2014. Listening to the Environment: Hearing Differences from an Epigenetic Effect in Solitarious and Gregarious Locusts. Proceedings of the Royal Society B. 281 no. 1795 20141693

Locusts display a striking form of phenotypic plasticity, developing into either a lone-living solitarious phase or a swarming gregarious phase depending on population density. The two phases differ extensively in appearance, behaviour, and physiology. We found that solitarious and gregarious locusts have clear differences in their hearing, both in their tympanal and neuronal responses. We identified significant differences in the shape of the tympana that may be responsible for the variations in hearing between locust phases. We measured the nanometre mechanical responses of the ear’s tympanal membrane to sound, finding that solitarious animals exhibit greater displacement. Finally, neural experiments signified that solitarious locusts have a relatively stronger response to high frequencies. The enhanced response to high frequency sounds in the nocturnally flying solitarious locusts suggests greater investment in detecting the ultrasonic echolocation calls of bats, to which they are more vulnerable than diurnally active gregarious locusts. This study highlights the importance of epigenetic effects set forth during development and begins to identify how animals are equipped to match their immediate environmental needs. Gordon SD, Jackson JC, Rogers SM, Windmill JFC.  2014.  Listening to the Environment:  Hearing Differences from an Epigenetic Effect in Solitarious and Gregarious Locusts.  Proceedings of the Royal Society B. 281 no. 1795...
Eberhard MJB*, Gordon SD*, Windmill JFC, Ronacher B.  2014. Temperature effects on the tympanal membrane and auditory receptor neurons in the locust. Journal of Comparative Physiology A.  200:837-847 * These authors contributed equally

Eberhard MJB*, Gordon SD*, Windmill JFC, Ronacher B. 2014. Temperature effects on the tympanal membrane and auditory receptor neurons in the locust. Journal of Comparative Physiology A. 200:837-847 * These authors contributed equally

Poikilothermic animals are affected by variations in environmental temperature, as the basic properties of nerve cells and muscles are altered. Nevertheless, insect sensory systems, such as the auditory system, need to function effectively over a wide range of temperatures, as sudden changes of up to 10 °C or more are common. We investigated the performance of auditory receptor neurons and properties of the tympanal membrane of Locusta migratoria in response to temperature changes. Intracellular recordings of receptors at two temperatures (21 and 28 °C) revealed a moderate increase in spike rate with a mean Q10 of 1.4. With rising temperature, the spike rate–intensity–functions exhibited small decreases in thresholds and expansions of the dynamic range, while spike durations decreased. Tympanal membrane displacement, investigated using microscanning laser vibrometry, exhibited a small temperature effect, with a Q10 of 1.2. These findings suggest that locusts are affected by shifts in temperature at the periphery of the auditory pathway, but the effects on spike rate, sensitivity, and tympanal membrane displacement are small. Robust encoding of acoustic signals by only slightly temperature-dependent receptor neurons and almost temperature-independent tympanal membrane properties might enable locusts and grasshoppers to reliably identify sounds in spite of changes of their body temperature. Eberhard MJB*, Gordon SD*, Windmill JFC, Ronacher B.  2014. Temperature effects on the tympanal membrane and auditory receptor neurons in the locust. Journal of Comparative Physiology A.  200:837-847 * These authors contributed...
Mortimer B, Gordon SD, Holland C, Siviour CR, Vollrath F, Windmill JFC. 2014. The Speed of Sound in Silk: Linking Material Performance to Biological Function. Adv. Mater. 26:5179-5183.

Mortimer B, Gordon SD, Holland C, Siviour CR, Vollrath F, Windmill JFC. 2014. The Speed of Sound in Silk: Linking Material Performance to Biological Function. Adv. Mater. 26:5179-5183.

Whilst renowned for exceptional mechanical properties, [ 1 ] little is known about the sonic properties of silk. This is surprising given its widespread use by the spider for remote sensing and communication, as well as current industrial research efforts in the production of multifunctional materials. [ 2,3 ] To address this gap in our knowledge and provide further bioinspiration, this paper presents a systematic study confirming the physical basis of spider silk’s sonic properties through a unique combination of laser vibrometry and high-rate ballistic impact. We report that modification of silk’s modulus allows the spider to finely control the sonic properties: achieved either actively by spider spinning behavior or passively in response to the environment. Interpreting our results in the context of whole webs, we propose silk fi bers are “tuned” to a resonant frequency that can be accessed through spider “plucking” behavior, which enables them to locate both prey and structural damage. Through comparison to cocoon silk and other industrial fibers, we find that spider dragline silk has the largest wavespeed range of any known material, making it an ideal model for fabrication of adjustable, green multifunctional materials.   Mortimer B, Gordon SD, Holland C, Siviour CR, Vollrath F, Windmill JFC. 2014. The Speed of Sound in Silk: Linking Material Performance to Biological Function. Adv. Mater....
Uetz GW, Roberts JA, Clark DL, Gibson JS, Gordon SD.  2013.  Active space of multimodal signals of wolf spiders in a complex litter environment.  Behavioral Ecology & Sociobiology. 67:1471-1482

Uetz GW, Roberts JA, Clark DL, Gibson JS, Gordon SD. 2013. Active space of multimodal signals of wolf spiders in a complex litter environment. Behavioral Ecology & Sociobiology. 67:1471-1482

Abstract Multimodal signals may compensate for environmental constraints on communication, as signals in different modalities vary in efficacy. We examined the influence of complex microhabitats on transmission of vibratory and visual signals of courting male Schizocosa ocreata wolf spiders (Araneae: Lycosidae) with laser Doppler vibrometry (LDV) and behavioral observations in lab and field. We measured maximum potential detection distance of visual and vibratory signals by females in laboratory mesocosms, recorded vibration signal attenuation on different substrates, and estimated transmission distances for male vibration signals in the field. We also determined effective line-of sight visual detection distances in the field with laser distance measures. Together, these data were used to estimate the potential and effective active space of multimodal signals. LDV measures show leaves are highly conductive substrates for wolf spider vibratory signals compared to others (soil, wood, rock). For both visual and vibratory modes, lab estimates of maximum potential distance for signal transmission and detection (behavior studies) exceeded estimates of effective active space (signal attenuation, “vanishing point,” and “line-of-sight” measures). Field estimates of transmission distance for signal modes overlap, such that in close range (<20 cm), vibratory signals are more likely to be detected, while farther away, visual signals are more likely to be seen. These findings thus support current  hypotheses regarding how multimodal communication might extend the range of overall signal active space or compensate for environmental constraints. Uetz GW, Roberts JA, Clark DL, Gibson JS, Gordon SD.  2013.  Active space of multimodal signals of wolf spiders in a complex litter environment.  Behavioral Ecology & Sociobiology. 67:1471-1482...
Gordon SD, Uetz GW.  2011.  Multimodal communication of wolf spiders on different substrates:  evidence for behavioral flexibility.  Animal Behaviour.  81:367-375.

Gordon SD, Uetz GW. 2011. Multimodal communication of wolf spiders on different substrates: evidence for behavioral flexibility. Animal Behaviour. 81:367-375.

Communication in complex environments poses challenges of potential loss of intended messages, but some animals may compensate by using multimodal signalling. Courtship displays of male Schizocosa ocreata (Hentz) wolf spiders are multimodal, consisting of visual and seismic signals. The microhabitat of S. ocreata is complex, including leaf litter, wood/bark, soil and rocks. Results from laser vibrometer measurements in the present study indicated that leaf litter transmitted male courtship signals with greater efficacy. Mating success was significantly greater on leaf litter (∼85%) compared to other substrates (∼30%), even though latency to male courtship did not vary among substrates. Given these results, selection should favour spiders that increase their mating potential on nonconducting substrates. We tested whether spiders detect substrate differences in a choice test, and found that when males and females visited all substrates, they spent significantly more time on leaf litter. We isolated courting male spiders on each substrate and scored courtship behaviours to see whether signals varied with substrate. Males used significantly more visual signals (waves and arches) on substrates that attenuated seismic signals (soil and rocks), but other behaviours showed no differences. Taken together, these results suggest that combined visual/seismic components of multimodal displays may serve as ‘backup signals’, ensuring reception under different environmental conditions. Results also suggest that male S. ocreata have the flexibility to compensate for environmental constraints by seeking microhabitats with more effective vibration conduction properties, and/or by increasing visual signals on substrates where seismic communication is less effective. Gordon SD, Uetz GW.  2011.  Multimodal communication of wolf spiders on different substrates:  evidence for behavioral flexibility.  Animal Behaviour. ...
Gordon SD, Strand MR.  2009.  The polyembryonic wasp Copidosoma floridanum produces two castes by differentially parceling the germ line to daughter embryos during embryo proliferation.  Development, Genes, Evolution.  219:445-454.

Gordon SD, Strand MR. 2009. The polyembryonic wasp Copidosoma floridanum produces two castes by differentially parceling the germ line to daughter embryos during embryo proliferation. Development, Genes, Evolution. 219:445-454.

Abstract Eggs of the polyembryonic wasp Copidosoma floridanum undergo a clonal phase of proliferation, which results in the formation of thousands of embryos called secondary morulae and two castes called reproductive and soldier larvae. C. floridanum establishes the germ line early in development, and prior studies indicate that embryos with primordial germ cells (PGCs) develop into reproductive larvae while embryos without PGCs develop into soldiers. However, it is unclear how embryos lacking PGCs form and whether all or only some morulae contribute to the proliferation process. Here, we report that most embryos lacking PGCs form by division of a secondary morula into one daughter embryo that inherits the germ line and another that does not. C. floridanum embryos also incorporate 5-bromo-2′-deoxyuridine (BrdU), which allows PGCs and other cell types to be labeled during the S phase of the cell cycle. Continuous BrdU labeling indicated that all secondary morulae cycle during the proliferation phase of embryogenesis. Double labeling with BrdU and the mitosis marker anti-phospho-histone H3 indicated that the median length of the G2 phase of the cell cycle was 18 h with a minimum duration of 4 h. Mitosis of PGCs and presumptive somatic stem cells in secondary morulae was asynchronous, but cells of the inner membrane exhibited synchronous mitosis. Overall, our results suggest that all secondary morulae contribute to the formation of new embryos during the proliferation phase of embryogenesis and that PGCs are involved in regulating both proliferation and caste formation. Gordon SD, Strand MR.  2009.  The polyembryonic wasp Copidosoma floridanum produces two castes by differentially parceling the germ line to daughter embryos during embryo proliferation.  Development,...
Lohrey AK, Clark DL, Gordon SD, Uetz GW.  2009.  Anti-predator responses of wolf spiders (Araneae:  Lycosidae) to sensory cues representing an avian predator.  Animal Behaviour.  77:813-821.

Lohrey AK, Clark DL, Gordon SD, Uetz GW. 2009. Anti-predator responses of wolf spiders (Araneae: Lycosidae) to sensory cues representing an avian predator. Animal Behaviour. 77:813-821.

Predator detection and subsequent antipredator response behaviours have been documented in many vertebrate and invertebrate animals, although the degree of specificity in predator recognition and response varies. We examined responses of actively courting adult male Schizocosa ocreata (Hentz) wolf spiders to cues indicating the presence of an avian predator, including visual, seismic (substrate vibration) and acoustic (airborne) stimuli. Spiders responded to acoustic (bird call) and seismic (simulated beak tap) stimuli with cessation of courtship and movement, but increased locomotion when presented with a visual stimulus (bird shadow). Spiders responded to experimental playback of avian acoustic stimuli with antipredator behaviour significantly more often and took longer to return to courtship than when exposed to nonthreatening stimuli. Tests of responses on different substrata to isolate sensory modes revealed that spiders perceive airborne sound from bird calls as substratum-conducted vibration. Results indicate that S. ocreata are capable of recognizing sensory cues associated with avian predators and distinguishing them from nonthreatening stimuli, suggesting that bird predation has been a selection factor in shaping behaviour of this wolf spider species. Lohrey AK, Clark DL, Gordon SD, Uetz GW.  2009.  Anti-predator responses of wolf spiders (Araneae:  Lycosidae) to sensory cues representing an avian predator.  Animal Behaviour. ...