Showing papers in "Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology in 1977"

The rôle of retinula cell types in visual behavior of Drosophila melanogaster

Abstract: We propose that inDrosophila melanogaster the optomotor response to both horizontal and vertical movement is mediated predominantly by the 6 large retinula cells (R1–6) in each facet of the compound eye. Evidence is presented which indicates that this may also be true for most of the other visual responses which at present can be quantitatively studied. These responses include visually controlled landing, pattern-induced orientation of flying and walking animals, the abnormal jump reflex of the mutant Hk1 (Kaplan, 1976) and probably also phototaxis. The only function for which the small retinula cells R7 and/or R8 seem to be required so far is spectral wavelength discrimination in phototaxis at high light intensity. Our hypothesis is based on studies of the receptor deficient mutantssevenless, outer rhabdomeres absent andreceptor degeneration B as well as on results of bleaching experiments by which the retinula cells R1–6 of the eye color mutantwhite can be reversibly blocked. Visual performance of wild typeDrosophila in the optomotor response reflects receptor properties (visual acuity, spectral sensitivity and polarization sensitivity) expected for the R1–6 receptor subsystem. The notion of a ‘high sensitivity’ and a ‘high acuity’ state which was proposed earlier on the basis of experiments on various visual mutants is in agreement with the present results but their interpretation as reflecting properties of different receptor subsystems must be abandoned. Experimental data on wild type also suggest the existence of such an adaptational mechanism; this, however, remains to be demonstrated more conclusively.

Phonotactic Behavior of Crickets

Abstract: Comparative study of phonotactic reactions of females of 5 species of crickets to the calling song (CS) of conspecific males and different sound models in Y-maze experiments showed: 1. InGryllodinus kerkennensis the essential property of the signal is the continuity of the song (Fig 3). 2. InGryllus campestris andG. bimaculatus pulse rate and chirp duration are important, the former having narrow and the latter broad tuning of reaction to chirp duration (Fig. 4). 3. InSpecies 2 (see Methods) chirp rate and pulse duration determine the specific response of females (Figs. 5 and 6). 4. InMelanogryllus desertus the most important parameters are the mean pulse rate and the increase in amplitude of pulses within the chirps (Fig. 7). 6. The spectrum of the CS is not important for the process of recognition as far as it falls into the tuning curve of specialized low-frequency channel of the auditory system. High-frequency sounds outside the range of this channel are not effective even if they have the same amplitude modulation pattern as the CS.

The role of the suprachiasmatic nuclei in the generation of circadian rhythms in the golden hamster, Mesocricetus auratus

Abstract: 1. Neural mechanisms involved in the generation and entrainment of circadian rhythms of behaviour were studied in male golden hamsters,Mesocricetus auratus. 2. Destruction of the suprachiasmatic nuclei (SCN) of the hypothalamus and accompanying interruption of the retino-hypothalamic tract (RHT) modified or eliminated entrainment to lighting cycles. 3. Such lesions also prevented the generation of normal circadian rhythms of both activity and drinking. Some lesioned hamsters generated bimodal (circa 12 h) and trimodal (circa 8 h) activity patterns in constant conditions. 4. Other lesioned hamsters appeared to be arrhythmic under constant conditions; power spectral analysis revealed low amplitude circa 8 h rhythms in the records of many of these hamsters. 5. The records of many lesioned hamsters showed several activity components that dissociated from each other and from the illumination cycle and free ran independently for many cycles. These and other features of the activity records indicate that activity rhythms in hamsters are controlled by a complex of oscillatory units whose mutual coupling produces the features of normal circadian rhythmicity. The SCN are apparently responsible for the maintenance of normal coupling among these oscillators and, thereby, for the generation of circadian behavioural rhythmicity. 6. The presence of residual entrainment after SCN destruction in some hamsters shows that visual pathways other than the RHT can to a limited extent mediate light effects on the circadian system. .

Acuity of compound eyes: Physical limitations and design

Abstract: The two fundamental limitations to resolving power of compound eyes are the wave (diffraction) and particle (photon noise) nature of light. By appreciating their interrelationship we gain insight into the design and limitation of eyes. In particular, we determine the dependence of eye design on the environmental light intensity. 1. The limitations to resolving power include: the intensity of light, angular motion, receptor grain, lens-pupil blur, finite diameter of rhabdom, and neural convergence. 2. Only those animals that are active in bright sunlight and normally have low angular velocity, profit by having some region of their eyes near the diffraction limit, i.e.DΔφ ≅ 0.58λ, whereD is the facet diameter,Δφ the interommatidial angle and λ the wavelength in vacuum. If these conditions are not fulfilled, it is better to have a largerDΔφ. 3. The effect of an animal undergoing angular velocityu is equivalent to a reduction in light intensity by the amount exp−1.78(φtΔφ)2, where φt is the amount the animal turns in one integration time. Taking this into account, we present a possible explanation forMusca havingDΔφ about 4.5 times greater than the diffraction limit. 4. Various strategies for dark-adaptation are considered with the conclusion that neural pooling combined with a widening of the acceptance angle is most effective for coping with reduced intensities.

Responses of Giant Interneurons of the Cockroach Periplaneta americana to Wind Puffs of Different Directions and Velocities

Abstract: 1. Controlled wind puffs of different directions and velocities were delivered to the cerci of cockroaches (Periplaneta americana), while the responses of individually identifiable giant interneurons (GI's) were recorded intracellularly. 2. All fourteen histologically identified GI's (seven bilateral pairs) respond with a burst of action potentials to wind from some or all directions. The directional sensitivity of a given GI is consistent from animal to animal (Fig. 7). 3. Varying the angle of delivery of wind puffs revealed that, in each side of the nerve cord, two GI's (2, 4) show little or no directional selectivity, two GI's (1, 7) have a greater response to wind from the ipsilateral side, two GI's (3, 6) respond primarily to wind from in front of the animal, and one GI (5) responds primarily to wind from the ipsilateral rear quadrant (Fig. 7). These directional properties are independent of wind velocity up to at least 2.6 m/s (Fig. 8). 4. Varying the peak velocity of the wind stimuli (delivered from each GI's maximal response angle) showed that the number of action potentials evoked increases with wind velocity up to at least 2.6 m/s for some GI's (1, 5, 6, 7), while the number does not increase with velocity beyond 0.5 m/s for others (2, 3, 4) (Fig. 9). 5. Covering or removing the cercus contralateral to a given GI reduced the response of each GI without appreciably altering its directional selectivity (Fig. 11 A). Eliminating the ipsilateral cercus also moderately reduced the responses of some GI's (4, 5, 7), but nearly or completely abolished responses in others (GI's 1, 2, 3, 6) (Fig. 11B). 6. The spike frequencies of the GI's in response to “standard wind puffs” (peak velocity 0.6 m/s or 2.6 m/s) are high, with maintained frequencies often over 300 spikes per s (Table 1), and instantaneous frequencies some times over 900 per s (Fig. 10). 7. The directional selectivity, high spike frequency, and rapid conduction velocity of the GI's may be adaptations for mediating the short latency, directional evasive behavior of the cockroach. The results are discussed in terms of the presumed role of the GI's in this behavior and implications for sensory integration.

Neuronal control of locomotion in the lobster,Homarus americanus

Abstract: 1. Lobsters that are tethered in place on a treadmill (Fig. 3) walk against the direction of belt movement (Table 2). Forward and backward locomotion over the full range of step frequencies can be controlled by this method, even in the absence of visual input. The passive traction provided by a moving substrate is therefore an effective stimulus for walking and presumably operates in parallel with previously described optomotor pathways to provide positive feedback reinforcement of locomotory behavior. 2. The movements (Figs. 1, 6) and muscular anatomy (Fig. 2) of a lobster walking leg are described. On the basis of simultaneous extracellular recording from several leg muscles (Fig. 5), and motion picture analysis, the overall patterns of joint movement and muscular coordination underlying forward and backward walking are described (Figs. 5, 6, 7). 3. Some muscles that are synergic for forward walking are antagonistic for backward walking (Figs. 6, 7). Similarly movements that are synergic for lateral walking on the leading side are antagonistic for lateral walking on the trailing side (Fig. 6). 4. Quantitative analysis of leg movements (Fig. 9) and electromyograms (Fig. 10) have shown that the walking muscles can be subdivided into three different functional classes: return stroke muscles, which exhibit bursts of relatively constant duration irrespective of step frequency (Fig. 10A); power stroke muscles in which burst duration varies linearly with step frequency (Fig. 10B); and bifunctional muscles, which exhibit the discharge characteristics of either return or power stroke muscles, depending on the direction of walking (Fig. 10C). 5. Several lines of evidence (Table 3, Figs. 6, 7, 9, 10, 12) suggest that the limb elevator motoneurones (or their central antecedents) function as the central pacemaker of the walking system, and that other cyclic leg movements are appended to the basic elevation/depression cycle as appropriate to the direction of walking. Evidence is presented that proprioceptive inputs provided by passive traction are capable of controlling the direction of locomotion (Table 2), and determining the periodicity of stepping (Fig. 4), by altering the duration of powerstroke bursts (Figs. 9, 10, 15).

Effects of divalent cations and metabolic poisons on the circadian rhythm from the Aplysia eye

Abstract: 1. The isolated eyeof Aplysia has a circadian rhythm of compound optic nerve potentials. An attempt to inhibit entrainment of this rhythm by blocking synaptic transmission led to the discovery that one such inhibitor, manganese, produced phase shifts in the rhythm. Treatments of manganese (10 mM) of 6 h duration at different phases of the rhythm resulted in a phase response curve composed of only delay phase shifts (Fig. 1). 2. Many biological effects of Mn++ involve Ca++ dependent processes and this appears to be the case here since the phase shifting effect of Mn++ was antagonized by increasing external Ca++ concentrations (Fig. 3). 3. Mn++ does not appear to be producing phase shifts by disrupting the flux of Ca++ across the plasma membrane since changing such fluxes by either raising extracellular Ca++ (50 mM) or lowering extracellular Ca++ with EGTA (Ca++ <10−7 M) did not cause phase shifts in the rhythm. 4. A Ca++/Mg++ ionophore, A23187, was used to affect the fluxes of these ions across intracellular membranes. Treatments of A23187 (7.5×10−6 M) produced delay phase shifts in the rhythm whether or not a Ca++ or Mg++ concentration gradient existed across the plasma membrane (Figs. 4, 5). In addition, an all-delay response curve resulted when eyes were treated at different phases with A23187 plus EGTA (Fig. 6). 5. Our results, and the known effects of A23187, led to the hypothesis that phase shifting by A23187 resulted either from the transport of Ca++ and Mg++ out of mitochondria or from oxidative phosphorylation becoming uncoupled as a result of the reuptake of these ions. 6. DNP (0.2 mM) and NaCN (2 mM) which both inhibit oxidative phosphorylation and cause release of Ca++ and Mg++ from mitochondria, also produced phase response curves with only delays (Fig. 9). 7. Mn++, A23187, DNP, and NaCN have a common effect on oxidative phosphorylation and on the ability of mitochondria to regulate Ca++ and Mg++. The correlation between the similar phase response curves of these treatments (Fig. 10) and their common effects on mitochondria suggests that they are all affecting the rhythm by blocking energy production and/or causing the release of mitochondrial Ca++ and Mg++. The manner in which changes in energy production or in the concentrations of Ca++/Mg++ might affect the rhythm is discussed.

The role of the metacerebral giant neuron in the feeding behavior ofPleurobranchaea

Abstract: The metacerebral giant (MCG) neurons of the molluskPleurobranchaea have been analyzed using a wide range of methods (cobalt staining, histochemical, biophysical and electrophysiological) on several types of preparations (isolated nervous systems, semi-intact preparations, and behaving whole-animal preparations). The MCG is serotonergic. The bilaterally-symmetrical neurons have somata in the anterior brain. Each MCG neuron sends an axon out the ipsilateral mouth nerve of the brain and also into the ipsilateral cerebrobuccal connective which descends to the buccal ganglion. The descending axon sends one or more branches out most buccal nerves.

Spatial Information Capacity of Compound Eyes

Abstract: The capacity of the compound eye to perceive its spatial environment is quantified by determining the number of different pictures that can be reconstructed by its array of retinula cells. We can then decide on the best compromise between an animal's capacity for fine detail and contrast sensitivity. The theory accounts for imperfect optics, photon noise, and angular motion limitations to acuity. 1. There is an optimum parameterp = D Δ φ, whereD is the facet diameter andΔ φ is the interommatidial angle, for each mean luminance, angular velocity and mean object contrast. We find that this value ofp is approximately that found by Snyder (1977) for threshold resolution of a sinusoidal grating at the ommatidial sampling frequency. 2. A diffraction limited eye (D Δ φ ≅λ/√¯3) is the optimum design only for those animals that are active in the brightest sunlight, and have a region of their eye that normally experiences low angular velocity, otherwise it is better to have a largerD Δ φ. λ is the wavelength of light in vacuum. 3. The design of the flyMusca is consistent with that of an animal with high angular velocity.

Correlations between behavioral temperature adaptations of goldfish and the viscosity and fatty acid composition of their synaptic membranes

Abstract: 1. Goldfish acclimated either to 5 °C or to 25 °C were transferred to the opposite temperature and the changes in behavioral resistance to high temperature, the fluidity and fatty acid composition of isolated synaptosomal membranes were followed during acclimation to the new temperature with the purpose of establishing some correlation. 2. In 25 °C-acclimated goldfish, hyperexcitability was induced at 34.5 °C, loss of equilibrium at 37.6 °C and coma at 39.0 °C. In 5 °C-acclimated goldfish the corresponding temperatures were 29.2 °C, 32.0 °C and 33.0 °C. Time to attain 75% of the final acclimated state after transfer was approximately 4 days at 25 °C and 28 days at 5 °C. 3. Fluidity of synaptosomal membranes isolated from goldfish brains was estimated by use of the fluorescence polarization technique. Membrane viscosity decreased during acclimation to 5 °C, but increased during acclimation to 25 °C. The early stages of the transitions differed in time course from behavioral resistance acclimation but times to reach the new acclimated state were similar. 4. Fatty acid composition of synaptosomal phospholipids showed increased unsaturation during cold-acclimation and decreased unsaturation during warm-acclimation. 5. It is concluded that during acclimation, behavior shows changes in resistance to heat which are related to synaptic block. These are correlated in direction and overall time course with viscosity of synaptosomes as dictated by changes in the saturation of membrane phospholipids.

The stridulatory movements of acridid grasshoppers recorded with an opto-electronic device

Abstract: (i) The singing movements of acridid grasshoppers are recorded opto-electronically: a small retroflective “Scotchlite” sheeting (O2mm) is attached to the tip of the stridulating femur and illuminated via a semi-transmissive mirror mounted at 45° to the optical axis in front of a photographic object lens. The light retroflected through this mirror is focused by the lens on the surface of a position-sensing photo-detector from which the co-ordinates of the light spot are tapped off instantaneously. Using this principle and having one recording device on each side the stridulatory movements of both hindlegs are monitored simultaneously. (ii) The grasshoppersChorthippus biguttulus (L.) andChorthippus mollis (Charp.) and their hybrids are studied by this method. Each of the two hindlegs performs a different Stridulatory pattern, the movements being considerably phase-shifted. The legs change their patterns from time to time. In the pure species the two patterns are very tightly coupled. Although in the hybrids in principle the same close relationships exist between the two lateral sub-systems, the couplings of the two patterns can be temporarily loosened. In the extreme, one hindleg may stridulate aCh. mollis song-pattern, whereas the other produces aCh. biguttulus pattern.

Sense organs in the femur of the stick insect and their relevance to the control of position of the femur-tibia-joint

Abstract: The sensory innervation pattern is described for the femur of the middle and the hind legs ofCarausius morosus. — In one of the nerves (F121) extracellular recordings show a unit which mirrors the tension of the flexor tibiae muscle (tension receptor). The tension receptor increases the firing rate of the slow extensor tibiae motoneuron. It measures the tension of one or more muscle fibres of the anterior side near the distal end of the muscle. The anatomical basis of this receptor is uncertain. — Another receptor was found on the ventral side of the distal end of the apodeme of the extensor tibiae muscle (apodeme receptor). Recordings from this receptor could not be obtained inCarausius. But inExtatosoma tiaratum it responded to stretching of the nerve. In the natural position it shows a minimum of excitation in the 90°-position of the femur-tibia-joint and an increase in firing rate for both flexion and extension. — Tactile hairs react phasically and have no special sensitivity for one direction. Two receptors at the dorsal side of the femur-tibia-joint (RDAL and RDPL), which are situated in the same position as inSchistocerca hind legs, react phasically to extension movements and fire tonically in the most extended position of the joint. — The influence of these receptors on the position of the femur-tibia-joint is only weak.

Chromatic properties of interneurons in the optic lobes of the bee: II. Narrow band and colour opponent neurons

Abstract: SummaryNarrow band or monochromatic neurons were recorded in the medulla and lobula of the bee optic lobe. The spectral sensitivities of UV, blue and green units were similar to, but narrower than those of the corresponding receptors.Colour opponent cells were recorded in the proximal medulla and were predominantly UV excited and inhibited by blue and green. Green and blue excited neurons which were inhibited by UV were rarely found. All opponent cells showed a maximum sensitivity change in the violet region. The receptive fields of these neurons were homogeneous, each point being excited by the one wavelength and being inhibited by the other.Polychromatic neurons, i.e. those that showed clearly colour dependent responses in several wavelength regions but which showed a dominant response in only one wavelength range were recorded mainly in the lobula. Only UV or green dominated polychromatic cells were found. Their receptive fields show complex colour dependent substructures which are not concentrically arranged.Two neurons showed definite inputs from more than one colour channel but remain narrow band. These neurons respond best in the region of overlap of two receptors, i.e. bluish-green and violet.Colour opponency appears to play a major role in colour integration as in vertebrates, although no evidence supporting the combination of colour with spatial opponency was found.

The cercus-to-giant interneuron system of crickets

Abstract: 1. The anatomical and physiological characteristics of filiform hairs, receptor elements on the cerci of the cricketAcheta domesticus, were investigated, with special attention to possible physiological differences between anatomically defined subclasses. 2. Maps of the distribution of hair socket orientations on the cercus show that the filiform hairs can be divided into two main subclasses: those whose sockets are oriented longitudinally and whose hair shafts vibrate transversely (T-hairs), and the reciprocal subclass whose sockets are oriented transversely and whose shafts vibrate longitudinally (L-hairs), with respect to the long axis of the cercus. T-hairs are found on the dorsal and ventral surfaces of the cercus, while the L-hairs are on the medial and lateral surfaces. Obliquely oriented hairs lie primarily at the margins of the well defined T-and L-populations. Hair density is greatest at the base of the cercus. 3. Intracellular cobalt fills of physiologically characterized receptor axons reveal that the processes branch profusely before terminating in the ipsilateral neuropile of the terminal abdominal ganglion. 4. Intracellular recordings from the axons of filiform hairs show that the receptors respond tonically to tones. The receptors studied responded with a phase-locked spike train to tones up to a frequency of about 200 Hz. They showed a preference for sound sources situated either transversely or longitudinally to the longitudinal axis of the cercus. Other than directional preference, no physiological differences were detected between the response properties of T-and L-cells.

The imaginal ecdysis of the cricket ( Teleogryllus oceanicus )

Abstract: 1. The activities of individual motor neurons have been recorded by electromyography from the muscles of unrestrained, successfully ecdysing crickets. 2. As the behavior progresses, each muscle becomes involved in stereotyped patterns of contractions corresponding to a sequence ofmotor programs (Carlson, 1977). For example, muscle 71d participates in 3 programs: (1) Pushups (A1, Fig. 3), (2) Proximal Leg-segment Extrication (B7, Fig. 3), and (3) Distal Leg-segment Extrication (B11, Fig. 3). These motor programs are recruited in tandem, and involve 3 different modes of coordination (Figs. 5A, 7C, 8-bout 55). 3. In this study, 3 motor programs were selected for intensive analysis: (1) Pushups — bilaterally symmetric contractions of front leg muscles; (2) Abdominal Peristalsis (B1, Fig. 3) — longitudinally sequential contractions of abdominal intersegmental muscles; and (3) Proximal Legsegment Extrication — bilaterally alternating contractions of the leg muscles. 4. The entire 4 h period of ecdysis can be recorded bilaterally from right and left muscles 71d, and the motor output underlying all 3 motor programs in which they participate is interrupted by regular interbout intervals (Figs. 4A, 7A, 8, 9). 5. Abdominal peristaltic waves (Fig. 6A, E) occur between bouts of rhythmical contractions by thoracic motor programs (Fig. 9C2), and thus occur at the bout frequency of other programs. 6. During Leg Extrication, the strengths of successive contractions by muscles 71d vary in register with each bout cycle. The strongest contractions occur near the centers of bouts, and are produced by longer bursts of higher frequency impulses (Fig. 7C). Additional motor neurons may be recruited during strong contractions, subject to the “size principle” (see Henneman, 1965). 7. While motor neuron activation varies sinusoidally within each bout cycle, the period of successive burst changes only vary gradually (Fig. 7B, C, 8). This fact implies that the bout generating oscillator does not influence the contraction generating oscillator as it modulates motor neuron activity. The motor neurons must therefore be independent of the oscillator which drives the alternating contractions that extricate the legs. 8. An hypothesis is presented in which “non-spiking interneurons”, are the major components of central oscillators underlying rhythmical contractions, and a series of these, located in each of the segmental ganglia, generate bouts of activity. 9. During a major peak in the intensity of the behavior, which occurs during the Ecdysial Phase, concurrent peaks in bout, burst, and intraburst impulse frequencies of the neurons involved in Proximal Leg-segment Extrication occur (Fig. 10). As interbout intervals shrink, and the burst frequency increases, additional bursts are recruited during each bout, and a second motor neuron is recruited (Fig. 8). 10. Since sensory feedback from areas of newly exposed cuticle are known to accelerate the bout oscillator (Carlson, 1977), it is hypothesized that acceleration of the burst frequency and concurrent increases in average firing rates for motor neurons, which accompany the major intensity peak of the Ecdysial Phase result from sensory feedback. 11. Sensory feedback provides immediate control of the strength of contractions by individual muscles during Pushups (Figs. 5C, 9B1, 9C1), and prolongs motor programs (compare Fig. 9A2 with 9B2, 9C2), without disrupting coordination. 12. It is concluded that a multilayered system of central control which includes more than 48 motor programs, a temporal bout structure, and 4 functionally distinct behavioral phases, cooperates with sensory feedback mechanisms to permit the successful completion of the nearly 4 h of stereotyped behavior which results in the ecdysis of the cricket.

Chromatic properties of interneurons in the optic lobes of the bee

Abstract: The chromatic properties of single units in the optic medulla and lobula of the worker bee were examined. This paper describes the spectral sensitivity, S (λ) and the receptive fields of “broad band” units, ie. those neurons which receive qualitatively similar inputs from 2 or 3 colour receptor types.

The anaerobic oyster heart: Coupling of glucose and aspartate fermentation

Abstract: The interrelationships of carbohydrate and amino acid metabolism during anaerobiosis were investigated in the ventricle of the intertidal oyster,Crassostrea gigas. While the ventricle accumulates alanine and succinate in a 2∶1 ratio during anoxia, these end products appear to arise from different precursors. Thus glucose-14C is metabolized mainly to alanine-14C (55% of glucose carbon appears in alanineversus 3% in succinate) by the anoxic ventriclein vitro while succinate-14C is the principle end product of aspartate-14C catabolism. Glutamate-14C is poorly metabolized by the anoxic ventricle, and correspondingly, while ventricular aspartate concentrations drop during anoxia, those of other amino acids do not. A metabolic scheme coupling glucose and aspartate catabolism in this facultative anaerobe is proposed. The detection of a third, as yet incompletely identified, anaerobic end product produced by the ventricle is reported.

Single photon signals and transduction in an insect eye

Abstract: 1. Under very weak illumination, photoreceptors of the darkadapted locust compound eye produce large (in the range 0.5 to 10 mV) discrete depolarising potentials called bumps. 2. By eliminating all sources of stray light it was shown that spontaneous bumps are very rare (less than 10 per h). 3. Statistical analysis of the occurrence of bumps following brief flashes of light and during continuous light exposure shows that an absorbed photon triggers the production of only one bump with a probability greater than 0.59+-0.19 (S.D.). 4. As a consequence of the extremely low rate of spontaneous activity and the invariability of the number of bumps elicited by an effectively captured photon, two potential sources of transducer noise in the photoreceptor are minimized.

Colour vision in Drosophila melanogaster

Abstract: Using a fully automatized procedure and a training scheme symmetrical with respect to the visual stimuli as well as to the aversive stimulus,Drosophila could be conditioned to blue and yellow lights. With constant test conditions and variation of the light intensities during the training procedure, it could be shown that the flies respond primarily to the colour of the light.

Directional sensitivity of echolocation in the horseshoe bat, Rhinolophus ferrumequinum

Abstract: The directionality of sound emission by a horseshoe bat (Rhinolophus ferrumequinum) has been determined for the constant frequency component of its orientation sounds. The bat was fixed in the center of an acoustic perimeter and the SPL of the orientation sounds measured with a scanning microphone at different angles compared with the SPL measured by another microphone located in the direction perpendicular to the plane of the horseshoe-like structure of the nose-leaf. The maximum SPL was always found in this direction which also corresponds to the flight direction of a bat in horizontal flight. Above and lateral to this direction the SPL decreases steadily with -6 dB-points at 24 ‡ above and 23 ‡ lateral. Below the flight direction we found a prominent side lobe with a -6 dB-point at 64 ‡.

Der Einfluß des Erdmagnetfeldes auf die Schwereorientierung der Honigbiene (Apis mellifica)

Abstract: The misdirection (“Misweisung”) which indicates a definite direction in the bee's dance is correlated to daily variations of the total intensity (ΔF) of the earth's magnetic field (EMF). It depends on the orientation of the dancing place with regard to the EMF coordinates. The distance of the feeding place, however, is insignificant. There exists a positive correlation between the efficiency ofΔF and a progressive tilting of the comb toward the horizontal position. No difference is observed in the intensity and exactness of the bees' dancing whether they are dancing on the lower side of the oblique comb in a somewhat ‘hanging’ attitude or on the upper side. The efficiency ofΔF is comparable on both sides of the comb. Bees dancing on a horizontal comb orient primarily to the main first-order directions of the EMF and, to a lesser extent, to the second-order directions regardless of the direction of the feeding place.

The neural control of alternate heartbeat coordination states in the leech,Hirudo medicinalis

Abstract: The bilateral paired hearts of the medicinal leech are controlled by a set of segmental heart motor neurons (HE cells) which are in turn controlled, via inhibitory synapses, by a set of segmental heart interneurons (HN cells). The HE cells fire in rhythmic impulse bursts because their steady discharge is periodically inhibited by the HN cells. 1) With the identification of an additional pair of HN cells in segmental ganglion 1 and the elucidation of several synaptic connections between HN cells a more complete heart control circuit diagram is now available. This circuit diagram accounts for the observed activity cycles of the various HN and HE cells and consequently for the behavior of the hearts themselves. 2) The bilaterally paired HE cells are coordinated by the HN cells such that the segmental heart tube sections on one side constrict in a caudorostral sequence to produce a rear-to-front peristalsis, while the segmental heart tube sections on the other side constrict nearly synchronously (non-peristaltically). This difference in the coordination modes of the two hearts is not permanent, and reciprocal coordination mode transitions occur every 10–50 heartbeat cycles. Cell HN(5) is phasically active on the side of the non-peristaltic heart tube and completely inactive on the side of the peristaltic heart tube. Reciprocal changes in the activity-inactivity pattern of the HN (5) cell pair are responsible for the observed spontaneous reciprocal changes in coordination mode. When cell HN (5) is made to be active or inactive, by intracellularly injected current, similar but unilateral changes, in coordination mode occur.

Neuronal organization of escape swimming inTritonia

Abstract: 1 Escape swimming behavior inTritonia diomedea consists of two major components: an initial reflexive withdrawal followed by a series of alternating ventral and dorsal flexions The basic mechanism of generating motor neuron activity, therefore, switches from reflexive to centrally programmed 2 Three classes of cerebral interneurons and some of their synaptic connections have been identified 3 Reflexive withdrawal interneurons (RWI) receive direct input from sensory afferents and synapse with motoneurons in the pedal ganglion (DFN, VFN) This class of interneuron is excited during reflexive withdrawals and inhibited during the swim phase 4 Swim interneurons (SI) are excited during reflexive withdrawals and burst during the swim phase 5 The third set of interneurons (C2) are shown to be necessary for the normal initiation and maintenance of the cyclical swim phase Activity in C2 neurons appears to retrigger the swim oscillator network cycle-by-cycle 6 C2 neurons inhibit the RWI neurons during swimming thus freeing motoneurons to respond predominantly to inputs from the SI and C2 neurons The switch from reflexive to programmed motor output is, therefore, mediated centrally by two identified C2 neurons

The visual pigment and visual cycle of the lobster, Homarus

Abstract: The visual pigment of the American lobster,Homarus americanus, has been studied in individual isolated rhabdoms by microspectrophotometry. Lobster rhodopsin has λmax at 515 nm and is converted by light to a stable metarhodopsin with λmax at 490 nm. These figures are in good agreement with corresponding values obtained by Wald and Hubbard (1957) in digitonin extracts. Photoregeneration of rhodopsin to metarhodopsin is also observed. The absorbance spectrum of lobster metarhodopsin is invariant with pH in the range 5.4–9, indicating that even after isomerization of the chromophore fromcis totrans, the binding site of the chromophore remains sequestered from the solvent environment. Total axial density of the lobster rhabdom to unpolarized light is about 0.7. As described for several other Crustacea, aldehyde fixation renders the metarhodopsin susceptible to photobleaching, a process that is faster at alkaline than at neutral or acid pH. Small amounts of a photoproduct with λmax at 370 nm are occasionally seen. A slower dark bleaching of lobster rhabdoms (τ1/2−2 h) also occurs, frequently through intermediates with absorption similar to metarhodopsin. The molar extinction coefficient of metarhodopsin is about 1.2 times greater than that of rhodopsin, each measured at their respective λmax. Isomerization of the chromophore fromcis totrans is accompanied by a change in the orientation of the absorption vector of about 3°. The absorption vector of metarhodopsin is either tilted more steeply into the membrane or is less tightly oriented with respect to the microvillar axes. When living lobsters are kept at room temperature, light adaptation does not result in an accumulation of metarhodopsin. At 4 °C, however, the same adapting lights cause a reduction of rhodopsin and an increase in metarhodopsin. There is thus a temperature-sensitive regeneration mechanism that supplements photoregeneration. Following 1 ms, 0.1 joule xenon flashes that convert about 70% of the rhodopsin to metarhodopsin in vivo, dark regeneration occurs in the living eye with half-times of about 25 and 55 min at 22 °C and 15 °C respectively.

The role of macromolecular antifreeze in the darkling beetle, Meracantha contracta

Abstract: Macromolecular antifreeze solutes are present in the hemolymph of the overwintering larvae of the darkling beetle,Meracantha contracta. These antifreeze solutes produce a thermal hysteresis in the hemolymph of overwinteringMeracantha larvae whereby the freezing point of the hemolymph may be 3–4 °C below the melting point. This thermal hysteresis is very similar to that produced by proteinaceous and glycoproteinaceous antifreezes which are used by many cold water, marine teleost fishes to prevent freezing. One function of the macromolecular antifreeze inMeracantha may be to hinder inoculative freezing which might otherwise occur because of the dampness of the hibernaculae. A probably more important function is to depress the supercooling point of the frost susceptibleMeracantha larvae, thereby preventing lethal ice formation in the larvae's body fluids down to temperatures of approximately −11 °C.

Auditory sensitivity of the diencephalon of the leopard frogRana p. pipiens

Abstract: Evoked potentials were recorded from the posterocentral nucleus in the dorsal diencephalon of leopard frogs (Rana p. pipiens) in response to acoustic stimulation. This electrophysiological study confirms the anatomical study by Neary (1974) of the existence of an auditory area within this nucleus.

Directional hearing in the median vertical plane by the cod

Abstract: The ability of cod (Gadus morhua) to discriminate between sound sources in the median vertical plane was studied using a cardiac conditioning technique. Masked auditory thresholds were obtained by transmitting tone and noise from separate projectors. There was a significant decrease in masking as the angular separation between tone and noise sources increased, confirming that cod is able to perform an auditory discrimination based on directional cues (Fig. 2). The power of angular resolution was studied using a directional change of a pulsed tone as the conditioning stimulus. The limit for angular discrimination was close to 16°, as compared to 20° previously reported for the horizontal plane (Fig. 4). Humans are unable to discriminate between pure tones from different directions in the median vertical plane. This difference in auditory ability between fish and humans may be attributed to the difference in habitat; the fish living in a three dimensional medium while humans are restricted to a surface.

Auditory interneurons in the cricketTeleogryllus oceanicus: Physiological and anatomical properties

Abstract: 1. The morphology and physiology of two acoustic interneurons in the prothoracic ganglion have been studied by the use of extracellular microelectrodes filled with cobalt chloride. 2. Interneuron 1 is inhibited by 5 kHz tones (Fig. 1) and does not reliably code the temporal pattern of the calling song (Fig. 2). It is unique in each half of the prothoracic ganglion, sends dendrites unilaterally into the acoustic neuropile, and sends its axon to the brain (Figs. 3, 4). 3. Interneuron 2 is excited tonically by 5 kHz tones (Figs. 5, 6) and accurately codes the temporal structure of song (Fig. 7). One pair of these neurons is present in the prothoracic ganglion. Each interneuron 2 projects to both left and right acoustic neuropiles, but has no process leaving the ganglion (Figs. 8, 9); it is an intra-ganglionic interneuron. 4. The reliability of the relatively new extracellular cobalt staining procedure is discussed.

Sensitivity to frequency and direction of sound in the auditory system of crickets (Gryllidae)

Abstract: The ears of crickets (Teleogryllus commodus and an undescribed species) are sharply tuned to the frequency of the species' communication signal. The auditory tympanum is vibrated by sound simultaneously acting on its external surface and on its internal surface after entering the prothoracic tracheal system. The sensitivity and frequency of the hearing optimum of the ear ipsilateral to incident sound, however, does not depend on the interaction of the external and internal sound pressures at the tympanum. The tuned response of the ear does not depend on acoustic properties of the prothoracic leg trachea, but on unknown mechanisms at the ear itself.

Some responses of the shore crab,Carcinus maenas (L.) to progressive hypoxia at different acclimation temperatures and salinities

Abstract: 1. TheP IO2 at which crabs emerged from shallow seawater during progressive hypoxia (Table 1), as well as theP c levels for\(\dot V_{O_2 }\) (Fig. 2) and\(\dot V_g \) (Fig. 4) of submerged crabs, increased with acclimation temperature and following exposure to 50% seawater at low temperatures (Fig. 6). This pattern of variation resembles the changes in relative oxygen demand with temperature and salinity. 2. TheP c levels for heart rate increased with acclimation temperature but were unaffected by dilution (Fig. 6). 3. Percentage extraction of oxygen from the respired water (Table 2) as well as the levels of motor activity (Fig. 5) were not affected by exposure to hypoxia. 4. Lactic acid concentration in the blood of submerged crabs increased markedly during hypoxia and there was an enhanced\(\dot V_{O_2 }\) on recovery in normoxia (Fig. 2), which apparently served to completely repay an accumulated oxygen debt. 5. It was concluded that when exposed to environmental hypoxiaCarcinus can adopt the alternative strategies of either accumulating an oxygen debt when in deep water or emerging into air from shallow water to aerate the branchial chambers.