Movements of fireflies visible on the surface of soil were measured under controlled laboratory conditions consisting of high and low ambient illumination. High illumination approximating the intensity of light prior to sunset constituted our light condition. Low illumination was consistent with ambient light levels after civil sunset, which we referred to as our dark condition. Surface movements were significantly more frequent during dark conditions compared to light conditions. Stemmata are the larval form of the insect eye and were the only identified visual organs present in Photuris larvae. We investigated whether stemmata provided larvae with the sensory information facilitating the light dependency of surface movements. We disrupted transmission of visual information from the larval eyes to the brain by severing the optic nerves. The amount of surface movement was compared between larvae with intact and severed optic nerves, under light and dark conditions. Light dependency of surface movements was preserved in larvae with cut optic nerves. The presence of the light dependency after cutting the optic nerves indicated that an alternative, extrastemmatal sensory pathway must be providing light intensity information to the animal. Light dependency was abolished upon removal of the head. Thus, these results suggested that the extraocular system providing light intensity information for regulating the frequency of surface movement was located in the head. The precise location of the suggested extraocular receptor and the nature of the associated sensory system remains unknown.

Fireflies use bioluminescent flashes to establish a dialogue between conspecific males and females. Through this dialogue, receptive females attract conspecific males for mating. In most firefly species, the males act as independent agents. That is, as they fly and flash in search of a responding female they do not appear to coordinate their activities with other males. In marked contrast, the males of some firefly species coordinate their flashes to coincide with those of other conspecific flashing males, resulting in synchronous flashing across local populations. We propose that the need for synchrony in these species may be driven by constraints imposed by the female visual system. Since males are flying while flashing and may appear to flash from different spatial locations, the female must attend to flashes over a wide visual field. But doing so has a drawback. She may see the flashes of multiple males within her wide visual field and their flashes could interfere with her ability to respond to any single male. We present evidence of a sensitive period during which extraneous flashes interfere with a female's response to a conspecific male and develop a model to predict how the number of independently flashing conspecific males affects the female's responsiveness. By coordinating their flashing, the males reduce the chance that any of them will flash during the female's sensitive period. This minimizes interference with establishing the male-female dialogue that would otherwise result by the presence of many patrolling males being in the female visual field. We conclude that the constraints imposed by the female visual system could be a factor driving the need for males to synchronize their flashing if they tend to fly and flash at high population density.

Fireflies (Coleoptera: Lampyridae) have distinct visual systems at different stages of development. Larvae have stemmata and adults have compound eyes. Adults use compound eyes to mediate photic communication during courtship. Larvae do not manifest this behavior, yet they are bioluminescent. We investigated the structure of stemmata in Photuris firefly larvae to identify anatomical substrates (i.e., rhabdomeres) conferring visual function. Stemmata were located bilaterally on the antero-lateral surfaces of the head. Beneath the ~ 130 µm diameter lens, we identified a pigmented eye-cup. At its widest point, the eye-cup was ~ 150 µm in diameter. The optic nerve exited the eye-cup opposite the lens. Two distinct regions, asymmetric in size and devoid of pigmentation, were characterized in stemmata cross-sections. We refer to these regions as lobes. Each lobe contained a rhabdom of a radial network of rhabdomeres. Pairs of rhabdomeres formed interdigitating microvilli contributed from neighboring photoreceptor cell bodies. The optic nerve contained 88 axons separable into two populations based on size. The number of axons in the optic nerve together with distinct rhabdoms suggests these structures were formed from ‘fusion stemmata.’ This structural specialization provides an anatomical substrate for future studies of visually mediated behaviors in Photuris larvae.

The barn ozol auditory system has been a productive model for the study of the neural mechanisms underlying sound localization. The two ears and their associated facial ruff, specialized feathers that form the ozol's external ear, are crucial for transforming the position of a sound into interaural time differences and interaural level differences. Once separated, these binaural cues are processed along two separate neural pathzoays. At the level of the ozol's inferior colliculus the neural information from the two pathzoays converge to form a neural map of auditory space. Experience plays a crucial role in allozoing the nervous system to calibrate itself so that the binaural cues can be effectively interpreted. This chapter summarizes aspects of sound localization by the barn ozol and presents results of a simple behavioral experiment that serves to illustrate the importance of sensory experience to produce meaningful sound localization behavior.

North American Photinus fireflies use bioluminescent flashes to communicate an individual’s species and sex, and to attract potential mates. A female firefly responds to a male firefly’s courtship flash with her own species-specific flash. We used a photic stimulator to produce male-like species-specific P. carolinus LED courtship flashes. These evoked species-specific response flashes from a female. The female’s flashes were preceded by a flash gesture comprising a sequence of abdominal postural adjustments (pitch, roll, and yaw). These gestures changed her lantern’s orientation which, at rest, was downward towards the substrate. Our results demonstrate that these gestures mediate a lateralization of the female’s response flashes towards the direction of the stimulating LED. That is, she directs her response to the left of midline when stimuli are presented from her left, and similarly, she directs her response to the right of midline when stimuli are presented from her right. The directional aspect of the flash gesture adds a new perspective to the complexity of the behaviors associated with flash communication in fireflies. Lateralization of the flash gesture suggests that the female’s visual system processes information about the location of male’s flashes as well as their temporal pattern.

Most firefly species (Coleoptera: Lampyridae) use bioluminescent flashes for signaling. In some species, the flashing between males occurs rhythmically and repeatedly (synchronically) with millisecond precision. We studied synchrony's behavioral role in the North American firefly, Photinus carolinus. We placed a female in a virtual environment containing artificial males that flashed at varying degrees of synchrony. Females responded to an average of 82% of synchronous flashes compared with as few as 3% of asynchronous flashes. We conclude that one function of flash synchrony is to facilitate a female's ability to recognize her conspecific male's flashing by eliminating potential visual clutter from other flashing males.

Neurons restore their function in response to external or internal perturbations and maintain neuronal or network stability through a homeostatic scaling mechanism. Homeostatic responses at synapses along the auditory system would be important for adaptation to normal and abnormal fluctuations in the sensory environment. We investigated at the electron microscopic level and after postembedding immunogold labeling whether projection neurons in the cochlear nucleus responded to modifications of auditory nerve activity. After unilaterally reducing the level of auditory inputs by ∼20 dB by monaural earplugging, auditory nerve synapses on bushy cells somata and basal dendrites of fusiform cells of the ventral and dorsal cochlear nucleus, respectively, upregulated GluR3 AMPA receptor subunit, while inhibitory synapses decreased the expression of GlyRα1 subunit. These changes in expression levels were fully reversible once the earplug was removed, indicating that activity affects the trafficking of receptors at synapses. Excitatory synapses on apical dendrites of fusiform cells (parallel fibers) with different synaptic AMPA receptor subunit composition, were not affected by sound attenuation, as the expression levels of AMPA receptor subunits were the same as in normal hearing littermates. GlyRα1 subunit expression at inhibitory synapses on apical dendrites of fusiform cells was also found unaffected. Furthermore, fusiform and bushy cells of the contralateral side to the earplugging upregulated the GluR3 subunit at auditory nerve synapses. These results show that cochlear nucleus neurons innervated by the auditory nerve, are able to respond to small changes in sound levels by redistributing specific AMPA and glycine receptor subunits.

Conclusions. We conclude that: (1) among several cues examined, the monaural cue of direct-to-reverberant (D/R) ratio in the ipsilateral ear provides the most information about sound-source distance; (2) interaural level difference (ILD) provides less information about sound-source distance; and (3) a comprehensive theory of three-dimensional auditory localization must incorporate the fact that all of the major acoustic cues change with distance. Objective. Neural mechanisms underlying auditory localization of distance are poorly understood. The present study was an initial step toward filling this gap in knowledge. Materials and methods. The binaural room impulse responses of adult barn owls were measured. The sound source was placed at various distances (up to 80 cm) and azimuths (0–90°) relative to the owl's head, with the elevation kept at 0°. Results. We determined the value of each cue for a 3–10 kHz band, and found that: (1) D/R ratio of signal amplitudes provided the most information about sound-source distance; (2) the ipsilateral D/R ratio represented distance more clearly than the contralateral or binaural-average D/R ratios; (3) ILD of direct signals increased with decreasing distance under certain conditions; (3) interaural time difference (ITD) of direct signals increased with decreasing distance at 90° azimuth; and (4) the spectral patterns of ILD and the monaural direct signals changed with distance in complex ways.

An inexpensive miniature stage goniometer compatible with a conventional optical microscope was developed to study the size and distribution of ommatidia facets across the compound eye of fireflies (Coleoptera: Lampyridae). The goniometer device was used to take sequential overlapping images of the hemispherical surface along longitudinal great-circle arcs of each eye of Photinus carolinus firefly and Photuris sp. males and females. Images covering the entire eye required 7 great circle scans at increments of 26° rotation. Using the multiple images, we minimized distortions associated with imaging a spherical surface in 2 dimensions and measured surface features with an error of <1.5%. A polar plot provided a consistent display format to relate facet area with location on the surface of the eye. We tested the functionality of the goniometer on a small number of male and female fireflies. It enabled us to make accurate measurements of surface features and address whether there is sexual dimorphism in firefly eyes. Within our limited sample, our results indicated that male eyes were larger than female eyes. In both firefly species the difference between the two sexes in the eye surface area was found statistically significant (P< 0.0001, unpaired t-tests). Male and female eyes also exhibited regional variation in facet area. We hypothesize that the sexual dimorphism and regional variation of firefly eye reflect functional and behavioral capabilities.

The flash communication system of Photinus carolinus in Great Smoky Mountain National Park (Tennessee) is characterized by male firefly synchrony. Photinus carolinus males signal a conspecific female with synchronic trains of flashes. A solitary responding female attracts several males, which is not common in North American rover fireflies. The female and the group of males that she attracts are called a cluster. It is hypothesized that the first male attracted to the female would land closer to the female than would additional males because there would be less tendency for visual confusion. This hypothesis is explored under controlled conditions by replacing the responsive female with an appropriately flashing light-emitting diode (LED) located in the center of a flat target area. When infra-red videography is used to measure the first male and the additional males' landing distances from the counterfeit female (LED), most fireflies land within 15 cm of the target LED, and the first male does not land closer than the additional males. It is suggested that cluster formation is a by-product of male synchrony and is facilitated by the tendency of males to land near, but not on, females.

The principles of neurophysiology continue to be challenging topics to teach in the context of undergraduate neuroscience education. Laboratory classes containing neurophysiological demonstrations and exercises are, therefore, an important and necessary complement for covering those subjects taught in lecture-based courses. We developed a number of simple yet very instructive exercises, described below, which make use of extracellular recordings from different sensory systems of the cockroach (Periplanta americana). The compendium we developed provides students with hands-on demonstrations of several commonly taught topics of neurophysiology including sensory coding by neural activity.

Studies of the neural system mediating auditory localization in the barn owl provide insight as to how sensory information is processed across and within multiple brain structures. The current study investigates the ability of the adult barn owl to adapt its auditory orienting behavior in reaction to imposed displacement of its vision. The specific aim is to test the hypothesis that adulthood plasticity that compensates for the discordance between vision and audition is enhanced when the owl engages in active prey capture - a behavior that makes use of combined auditory and visual information. Our observation supports the hypothesis. Behavioral evidence of plasticity is interpreted using a computational model of the neural mechanisms associated with the adaptive response

Blue-throated hummingbirds produce elaborate songs extending into the ultrasonic frequency range, up to 30 kHz. Ultrasonic song elements include harmonics and extensions of audible notes, non-harmonic components of audible syllables, and sounds produced at frequencies above 20 kHz without corresponding hearing range sound. To determine whether ultrasonic song elements function in intraspecific communication, we tested the hearing range of male and female blue-throated hummingbirds. We measured auditory thresholds for tone pips ranging from 1 kHz to 50 kHz using auditory brainstem responses. Neither male nor female blue-throated hummingbirds appear to be able to hear above 7 kHz. No auditory brainstem responses could be detected between 8 and 50 kHz at 90 dB. This high-frequency cutoff is well within the range reported for other species of birds. These results suggest that high-frequency song elements are not used in intraspecific communication. We propose that the restricted hummingbird hearing range may exemplify a phylogenetic constraint.

Synchronic flashing in fireflies is a precisely timed behavior. This is a potentially useful tool to study sensory processing, the location and circuitry of the flash oscillator, and neuroeffector processing and coupling. Synchronic flashing, once thought to occur only in Southeast Asian fireflies, has recently been shown to be a prominent part of the behavior of a North American Photinus and Photuris species. To gain insights into the mechanisms of synchronic timing in fireflies, we compared spontaneous flashing and entrainment flashing in Photuris frontalis LeConte, a synchronic firefly found in Georgia's Coastal Plain, to analogous flashing in Pteroptyx malaccae Olivier, a synchronic firefly found in Malaysia. The timing of spontaneously produced flashes and entrainment flashes was recorded by photometry. Artificially produced, rhythmic stimulus flashes were used to induce a counterfeit synchrony (between subject fireflies and an LED), i.e., flash entrainment. We found that the spontaneously produced interflash intervals were repeated with a high degree of precision in P. frontalis and P. malaccae. However, the pattern of flashing was different during spontaneous flashing and flash entrainment. An isolated P. frontalis flashed intermittently during spontaneously flashing and entrainment flashing. Flash entrainment in P. frontalis started with an initial inhibition and then steady-state entrainment occurred with a fixed delay. In contrast, an isolated P. malaccae flashed continuously during spontaneous flashing and entrainment flashing. No initial inhibition occurred at the start of entrainment, and there was a gradual change in interflash interval until steady-state entrainment occurred at a fixed delay. We think that in-depth studies of the flash activities of different synchronic firefly species, including the locally available P. frontalis, could help our understanding of rhythmic temporal coordination of behavior by the nervous system.

Synchronous flashing occurs in certain species of Southeast Asian and North American fireflies. Most Southeast Asian synchrony involves stationary congregating fireflies, but North American synchrony occurs in flying fireflies that do not congregate. Southeast Asian synchrony is usually continuous, but North American synchrony is interrupted. Photuris frontalis, the only member of the North American genus Photuris to synchronize, shows an intermittent synchrony. This involves synchronization and repeated re-synchronizations while in flight. The precision that occurs at the start of synchrony was studied in Ph. frontalis using caged fireflies and photometry. Barrier experiments (using two fireflies) or flash entrainment experiments (using one LED and one firefly) were performed to measure the temporal precision of the first entrained flash. In both cases, the first entrained flash was close to unison synchrony (phase = 1.0) and showed little variability. The behavioral implications of the ability to synchronize with the first entrained flash are not known, but it might facilitate male-male interactions during brief, transient encounters such as maintaining distance between closely flying males in search of females.

Bioluminescence and Chemiluminescence, pp. 157-160 (2001) No AccessMECHANISMS OF SYNCHRONY IN A COASTAL GEORGIA FIREFLYJONATHAN COPELAND, KELSIE FITZGERALD, and ANDREW MOISEFFJONATHAN COPELANDDepartment of Biology and Applied Coastal Research Laboratory, Georgia Southern University 30460-8042, USA, KELSIE FITZGERALDDepartment of Biology and Applied Coastal Research Laboratory, Georgia Southern University 30460-8042, USA, and ANDREW MOISEFFDepartment of Physiology & Neurobiology, University of Connecticut, 06269-4156, USAhttps://doi.org/10.1142/9789812811158_0039Cited by:0 (Source: Crossref) PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: The following sections are included: INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS Aknowledgements References FiguresReferencesRelatedDetails Recommended Bioluminescence and ChemiluminescenceMetrics History PDF download