Biomedical subjects

D D Yager

Publications and source records attributed to D D Yager.

12 recordsLinked to original sources

PubMed1999

Structure, development, and evolution of insect auditory systems.

This paper provides an overview of insect peripheral auditory systems focusing on tympanate ears (pressure detectors) and emphasizing research during the last 15 years. The theme throughout is the evolution of hearing in insects. Ears have appeared independently no fewer than 19 times in the class Insecta and are located on various thoracic and abdominal body segments, on legs, on wings, and on mouth parts. All have fundamentally similar structures-a tympanum backed by a tracheal sac and a tympanal chordotonal organ-though they vary widely in size, ancillary structures, and number of chordotonal sensilla. Novel ears have recently been discovered in praying mantids, two families of beetles, and two families of flies. The tachinid flies are especially notable because they use a previously unknown mechanism for sound localization. Developmental and comparative studies have identified the evolutionary precursors of the tympanal chordotonal organs in several insects; they are uniformly chordotonal proprioceptors. Tympanate species fall into clusters determined by which of the embryologically defined chordotonal organ groups in each body segment served as precursor for the tympanal organ. This suggests that the many appearances of hearing could arise from changes in a small number of developmental modules. The nature of those developmental changes that lead to a functional insect ear is not yet known.

Animals↗

PubMed1997

Behavioral response to ultrasound by the tiger beetle Cicindela marutha dow combines aerodynamic changes and sound production.

Tethered flying tiger beetles, Cicindela marutha, respond to trains of bat-like ultrasonic pulses with a short-latency, multi-component behavior. The head rolls to one side, the metathoracic legs kick to the opposite side, the elytra swing backwards towards the hindwings and pronate, the hindwings increase their stroke excursion and frequency, and the plane of the hindwing motion tilts forward. In addition, the beetles produce trains of ultrasonic clicks typically containing 100-200 clicks in response to a 1 s stimulus. The clicks average 85-90 dB SPL at 2 cm. The latencies for hindwing changes and elytra swing in response to stimuli more than 10 dB over threshold are 90-110 ms; the latency to clicking is 120-150 ms. Neither the head roll nor the leg kick appears to be directional relative to the sound source. The behavioral response is broadly tuned with greatest sensitivity at 30-60 kHz and mean behavioral thresholds of 75-80 dB SPL. Physiological audiograms from the auditory afferents show substantially greater sensitivity and sharper tuning than the behavioral response, which suggests that tiger beetles may use their hearing in other contexts as well as during flight. The combination of aerodynamic components and arctiid-month-like clicking may provide these insects with a powerful defense against attack by echolocating bats.

Animals↗

PubMed1996

Nymphal development of the auditory system in the praying mantis Hierodula membranacea Burmeister (Dictyoptera, Mantidae).

Like other praying mantises, Hierodula membranacea has a single midline ear on the ventral surface of the metathorax. The ear comprises a deep groove with two tympana forming the walls. A tympanal organ on each side contains 30-40 scolopophorous sensillae with axons that terminate in the metathoracic ganglion in neuropil that does not match the auditory neuropil of other insects. Nymphal development of the mantis ear proceeds in three major stages: 1) The tympanal organ is completely formed with a full complement of sensillae before hatching; 2) the infolding and rotations that form the deep groove are completed primarily over the first half of nymphal development; and 3) over the last five instars (of ten), the tympana thicken and broaden to their adult size and shape, and the impedance-matching tracheal sacs also enlarge and move to become tightly apposed to the inner surfaces of the tympana. Auditory sensitivity gradually increases beginning with the fifth instar and closely parallels tympanum and tracheal sac growth. Late instar nymphs have auditory thresholds of 70-80 dB sound pressure level (SPL). Appropriate connections of afferents to a functional interneuronal system are clearly present by the eighth instar and possibly much earlier. The pattern of auditory system ontogeny in the mantis is similar to that in locusts and in noctuid moths, but it differs from crickets. In evolutionary terms, it is significant that the metathoracic anatomy of newly hatched mantis nymphs matches very closely the anatomy of the homologous regions in adult cockroaches, which are closely related to mantises but are without tympanal hearing, and in mantises that are thought to be primitively deaf.

Acoustic Stimulation↗

PubMed1996

Serially homologous ears perform frequency range fractionation in the praying mantis, Creobroter (Mantodea, Hymenopodidae).

Unlike most praying mantises that have a single region of auditory sensitivity, species in the genus Creobroter have equally sensitive hearing at 2-4 and at 25-50 kHz and and are relatively insensitivity at 10-15 kHz- they have a W-shaped audiogram. Ultrasonic sensitivity originates from an auditory organ in the ventral midline of the metathorax that closely resembles the ear of other mantises. Ablation experiments demonstrate that low frequency sensitivity derives from a serially homologous mesothoracic auditory organ. Extracellular recordings suggest that these two ears operate largely, if not entirely, independently of one another in the thorax. The low frequency response has a longer latency, more action potentials per stimulus, and different patterns of change with increasing SPL than the high frequency response. Separate interneurons mediate responses in the two frequency ranges, but our evidence suggests that they are two serially homologous sets of cells. Neither auditory organ shows any physiological evidence of directional sensitivity. Ultrasound triggers a set of behaviors in flying hymenopodid mantises much like those in other mantises, but the behavioral significance of low frequency hearing in these animals is still unknown.

Acoustic Stimulation↗

PubMed1995

Characterization of auditory afferents in the tiger beetle, Cicindela marutha Dow.

We have identified a nerve carrying auditory afferents and characterized their physiological responses in the tiger beetle, Cicindela marutha. 1. The tympana are located at the lateral margins of the first abdominal tergum. The nerve carrying the tympanal afferents is a branch of the dorsal root from the first abdominal ganglion. 2. Both male and female auditory afferent responses are sharply tuned to 30 kHz with sensitivities of 50-55 dB SPL. 3. The auditory afferents show little adaptation and accurately code the temporal characteristics of the stimulus with the limit of a resolution of 6-10 ms. 4. The difference in threshold between contralateral and ipsilateral afferents for lateral stimuli is greatest at 30 kHz and is at least 10-15 dB. 5. Ablation studies indicate that the floppy membrane in the anterolateral corner of the tympanum is crucial for transduction while the medial portion of the tympanum is less important. 6. The tiger beetle and acridid (locust and grasshopper) ears have evolved independently from homologous peripheral structures. The neural precursor of the tympanal organs in both animals is likely the pleural chordotonal organ of the first abdominal segment.

Acoustic Stimulation↗

PubMed1993

Directional characteristics of tuberous electroreceptors in the weakly electric fish, Hypopomus (Gymnotiformes).

This paper is an electrophysiological study of the directionality of the tuberous electroreceptors of weakly electric fish. We recorded from two classes of tuberous electroreceptors known for pulse gymnotiforms: Burst Duration Coders (BDCs), and Pulse Markers (PMs). Both code for stimulus amplitude, although the dynamic range for BDCs is greater, and both exhibit strong directional preferences. Polar plots of spike number (for BDCs) or spike threshold (for PMs) versus electric field azimuth, are figure-8 shaped with two asymmetrical, elliptical lobes separated by 180 degrees. The best azimuth of these two types of receptors from a given body region correlate with each other and with measures of best azimuth for transepidermal current flow. The shape and asymmetry of the directionality profiles appear to be caused by filter dynamics of the receptors. Pulse Markers are located on the anterior part of the body surface while Burst Duration Coders are located all over. The best directions of receptors in the anterior third of the body vary systematically with location from 0 degrees to 180 degrees. This region is probably critical for determining the direction of local electric fields. Together these receptors provide the CNS with sufficient information to construct a map of horizontal plane electric field directions.

Adaptation, Physiological↗

PubMed1993

Directional sensitivity of tuberous electroreceptors: polarity preferences and frequency tuning.

This paper examines the directionality of tuberous electroreceptor responses and relates them to a polarity bias seen for passive electrolocation by electric fish (Hypopomus). We recorded from Burst Duration Coders (BDCs) while stimulating with 1 kHz single period sine waves with electric fields oriented horizontally in different directions. Electroreceptors have figure-8 directional sensitivity profiles with two, usually unequal lobes of sensitivity separated by 180 degrees. For most units the larger lobe points inward, while for a few, the lobes are symmetrical or the larger lobe points outward. The differences correlate with differences in frequency tuning of the receptors. We can alter, and even reverse, the directional asymmetry of a single unit by changing the frequency of the stimulus. Two general response profiles results, with two corresponding classes of tuning curves. The degree of asymmetries and the effects of stimulus frequency and of tuning can be modeled with a linear/non-linear/linear cascade filter. The behavioral preference for approaching the head end (+) of an electrode is difficult to understand in light of the asymmetry of responses we report for amplitude-coding BDCs but can be understood by reference to the time-coding Pulse Marker (PM) receptors.

Animals↗

PubMed1990

Ultrasound-triggered, flight-gated evasive maneuvers in the praying mantis Parasphendale agrionina. I. Free flight.

Free-flying male praying mantises Parasphendale agrionina (Gerst.) perform evasive maneuvers when stimulated by ultrasound and when attacked by hunting, echolocating bats. They do not, however, respond in any way when standing on a substratum. The maneuvers are graded in intensity with distance from the sound source: far from the source they are simple turns, whereas close to the source they are steep diving turns or spirals. The maneuvers are made under power, and the male's velocity doubles to almost 4 m s-1 by the end of a steep dive. The mantis does not show any directional preference. The behavioral threshold of 64 dB SPL and minimum latency to course change of 125 ms indicate that these mantises should have adequate time to evade bats using calls of greater than 85-90 dB SPL (at 10 cm). In field experiments with wild, hunting bats, P. agrionina successfully evaded capture in all five attacks to which they responded with evasive maneuvers. Out of three attacks on P. aeruginosa and three on a normally non-responding mantis, Miomantis paykullii Stål, in which there were no evasive maneuvers, the mantis was captured in five cases.

Animals↗

PubMed1990

Ultrasound-triggered, flight-gated evasive maneuvers in the praying mantis Parasphendale agrionina. II. Tethered flight.

In tethered flight, Parasphendale agrionina (Gerst.) males respond to ultrasonic stimuli with a unique suite of behaviors that includes full extension of the forelegs, strong dorsiflexion of the abdomen, a head roll, a 5% decrease in wingbeat frequency and a 33% increase in forewing excursion. Latency for the foreleg extension averages 66 ms while the latency to onset of yaw is 174 ms. The direction of the turn is unrelated to the location of the speaker. Yaw magnitude and latency are only weakly related to sound pressure level, and variability in these and other parameters is high. The behavior shows moderately sharp tuning to 40-60 kHz with a lowest mean threshold of 60 dB SPL. A male will not respond to ultrasound unless in flight, and the context-gating is independent of sensory input from the tarsi. Several components of the in-flight evasive behavior resemble defensive displays on the ground, and we suggest that this mantis has responded to predation pressure from bats with both flight-derived maneuvers and an aerial deimatic display.

Animals↗

PubMed1989

Audition in the praying mantis, Mantis religiosa L.: identification of an interneuron mediating ultrasonic hearing.

1. The praying mantis possesses a single ear located in the ventral midline of the metathorax. We have studied the mantis' auditory nervous system using both extracellular and intracellular techniques and have identified anatomically and physiologically a mirror-image pair of interneurons (MR-501-T3) in the metathoracic ganglion that mediates ultrasonic hearing. 2. MR-501-T3 is tuned broadly to ultrasound with best sensitivity (55-60 dB SPL) between 25 and 45 kHz. Its tuning matches closely that of the whole tympanal nerve. 3. The physiological responses of MR-501-T3 are characterized by: (1) a phasic-tonic firing pattern with a distinctive initial burst at 500-800 spikes/s; (2) minimum latencies of 8-12 ms; (3) no spontaneous activity; (4) sigmoid intensity response curves with a small (10 dB) dynamic range; (5) accurate coding of stimulus duration and of repetition rates up to 60 pps. 4. The ascending axon of MR-501-T3 conducts action potentials at 4 m/s, a rate comparable with some giant fiber systems. 5. MR-501-T3 shows no directional capability. Sound from right and left produce identical responses in both cells of the pair. Neither cutting one tympanal nerve nor removing one hemi-ear leads to different responses in the two cells indicating that they must receive a common input, either from the auditory afferents or from interneurons. We present evidence that the two cells are not directly connected. 6. MR-501-T3 is a large, symmetrical cell with its processes primarily in the intermediate neuropil (lateral ring tract). Its integration segment crosses the midline in the supramedian commissure, and the cell body lies dorsally near the entrance of the leg nerve. The axon travels in the dorsal lateral tract and is one of the largest (17 microns) in the connective. 7. Given the strong anatomical similarities between MR-501-T3 and the G and B cells of the locust, these cells may be homologous. 8. We present arguments based on our physiological results and existing behavioral data that MR-501-T3 is part of an ultrasonic warning/escape system in the mantis. As in moths, lacewings, and crickets, this system may provide a defense against nocturnally foraging bats.

Acoustic Stimulation↗

PubMed1987

The midline metathoracic ear of the praying mantis, Mantis religiosa.

The praying mantis, Mantis religiosa, is unique in possessing a single, tympanal auditory organ located in the ventral midline of its body between the metathoracic coxae. The ear is in a deep groove and consists of two tympana facing each other and backed by large air sacs. Neural transduction takes place in a structure at the anterior end of the groove. This tympanal organ contains 32 chordotonal sensilla organized into three groups, two of which are 180 degrees out of line with the one attaching directly to the tympanum. Innervation is provided by Nerve root 7 from the metathoracic ganglion. Cobalt backfills show that the auditory neuropile is a series of finger-like projections terminating ipsilaterally near the midline, primarily near DC III and SMC. The auditory neuropile thus differs from the pattern common to all other insects previously studied.

Animals↗

PubMed1986

The cyclopean ear: a new sense for the praying mantis.

The praying mantis, thought to be deaf, possesses a sensitive and specialized acoustic sense. Neural recordings show that the auditory system responds primarily to ultrasound between 25 and 45 kilohertz with thresholds of 55 to 60 decibels. Other insects with auditory tympana possess paired, laterally placed ears; the mantis has only a single ear that is located in the ventral midline between the metathoracic legs. Some species of mantis abruptly and dramatically alter their flight path when stimulated with ultrasonic pulses, suggesting a behavioral response to insectivorous echo-locating bats.

Animals↗