Showing papers in "Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology in 1983"

Landmark learning in bees

Abstract: 1. The experiments described here were undertaken to discover how bees use nearby landmarks to guide their way to a food source. Two major questions are raised. First, what do bees learn about the spatial layout of landmarks and food source? Secondly, how might this information help them reach their destination? 2. Single, marked bees were trained to collect sugar solution from a small and inconspicuous reservoir in a room in which extraneous visual cues had been reduced to a minimum. The position of the reservoir was defined by an array of one or more matt black landmarks. After bees had been trained, their flight path was recorded on videotape when the landmarks were present, but the food source absent. During such tests bees spent most of their time searching where the food source should have been. 3. Thus, if bees were trained to a reservoir whose position was specified by a single cylindrical landmark and tested with the same landmark, they searched at the expected site of the reservoir. However, when the size of the landmark was changed between training and testing, the area in which bees searched was displaced to one where the landmark appeared roughly the same size as the training landmark when viewed from the reservoir. These experiments suggest that bees learn no more than the apparent size and bearing of the landmark as seen from the food source, and that to return there they move to a position where their retinal image matches their remembered image of the landmark. 4. Experiments with more complex arrays of landmarks support the same hypothesis. A simple rule predicts a bee's search area when it is trained to a food source defined by the position of three landmarks and tested either with the same array, or with landmarks of different sizes, or with landmarks placed at different distances from the reservoir. The bee then always searches where the compass bearings of the landmarks on its retina were the same as they had been when it was stationed at the food source. 5. Tests with bees trained to either one or three landmarks suggest that the bearings of landmarks on the retina are learnt with respect to external compass bearings. Thus, a single, cylindrical landmark does not define direction. Nonetheless, bees searched in one location and not in a circle centred on the landmark. Bees trained to three landmarks only learnt the site of the reservoir if the array was kept in a constant orientation during training. 6. Computer models were devised to discover how bees might use a remembered image of the landmark array to direct their flight path to their destination. The models simulated a situation in which a bee takes a 2-dimensional snapshot of its surroundings from the position it wishes to retrieve and continuously compares this with its current retinal image. It then uses the difference between the two to guide its way. Different models of increasing complexity were explored until one was found which closely mimicked the bee's behaviour.

Aerobic diving limits of immature Weddell seals

Abstract: 1. Consistent with previous studies on adult seals, post-dive blood lactic acid (LA) concentrations in immature Weddell seals did not increase above resting levels after short voluntary dives (Fig. 1). 2. Following longer dives, peak blood LA values increased rapidly according to the duration of the dive (Fig. 1). 3. The peak post-dive blood LA concentration relative to dive duration demonstrate that there is a positive relationship between aerobic dive limit (ADL) and body size (Fig. 1 and 3). 4. The ADL for 130 to 145 kg seals was about 10 min, and it was 13 min for 185 to 205 kg seals (Fig. 1). 5. The calculation of the ADL from available oxygen stores correlates well with the lactate/endurance curve intercept, where peak post-dive LA concentration rises rapidly above resting levels as the dive duration increases in adult and immature animals (Table 2 and Fig. 3). 6. Of total dives, 4% of the dive durations exceeded the measured ADL in 130 to 145 kg seals and 8% in the 205 kg seal (Fig. 2). 7. Dive depths of immature seals did not exceed 315 m (Table 1).

A simple method for measuring intestinal solute uptake in vitro

Abstract: We describe a method of measuring intestinal solute uptake that combines the virtues of simplicity, good tissue viability as reflected in high uptake rates, and reduction of unstirred layers comparable to the best reported for chambers. An everted sleeve of intestine is mounted on a grooved rod stationed immediately over a stirring bar rotating at 1,200 rpm. The effect of edge damage is negligible. The coefficient of variation of uptake measurements is 7%. For mouse intestine andd-glucose at high concentrations an incubation time of 1 min represents a suitable compromise among several competing criteria.l-glucose is used to correct actived-glucose uptake simultaneously for adherent fluid and for passive uptake. The technique's general utility is illustrated by its application to intestines of four species representing four classes of vertebrates.

Opsonizing properties of an isolated hemolymph agglutinin and demonstration of lectin-like recognition molecules at the surface of hemocytes fromMytilus edulis

Abstract: Mytilus hemolymph was found to contain an agglutinin which could be inhibited by mucin. The agglutinin was isolated by affinity chromatography using neuraminidase-treated mucin/Sepharose.

Attractiveness of the male Acheta domesticus calling song to females

Abstract: 1. Most crickets first demonstrated positive phonotaxis to 65 dB CSs having a 53–62 ms SP by day 3 following the imaginal molt (Fig. 3B). The onset of copulatory readiness occurred on average at 3.2 days. 2. The attractive range of SPs for most females became progressively broader as they aged (Fig. 4). Three to 4-day-old females were attracted to a smaller number of CS SPs than were 20–21 day old females (Fig. 4). 3. Older, less selective females did not typically respond to the same range of CS SPs (Fig. 6). However, they were more likely to respond to some SPs (especially 50 ms) than to others (Fig. 7). 4. The phonotactic threshold decreased from 95 dB or greater on day 0 to a mean of 55 dB by day 3, during a period of increasing JHIII biosynthesis, and thereafter remained at that level (Fig. 8). 5. During a period of maximal JHIII production, 3–5 day-old females usually responded to 4 of the 7 SPs presented (Fig. 8). Females older than 12 days were unselective for CS SP, and JHIII synthesis remained at a level below the peak production on day 4 (Fig. 8). 6. Older females, that were unselective for CS SP, became as selective as 3 to 5-day-old females within 4 days of topical application of JHIII (Figs. 9–11).

Mammalian and avian antidiuretic hormone: Studies related to possible species variation in osmoregulatory systems

Abstract: 1. In two representative species of the mammalian and avian classes, the dog and Pekin duck, antidiuretic hormone (ADH) concentrations in the blood were measured by a common radioimmunoassay (RIA) making use of an antiserum raised against the mammalian ADH, arginine vasopressin (AVP) which also cross reacted with the avian ADH, arginine vasotocin (AVT), (Fig. 1). The effects of 24 h dehydration on blood osmolality and ADH concentration and the plasma clearance rates of ADH of conscious dogs and Pekin ducks were compared. 2. An AVP plasma level of 2.37±0.20 pg·ml−1 (2.18±0.18 fmol·ml−1) (mean±SE) was found in normally hydrated dogs at 298.1±1.0 mOsm· kg−1 plasma osmolality; 24 h water deprivation increased plasma AVP to 6.64±0.96 pg·ml−1 (6.12±0.88 fmol·ml−1) and osmolality to 314.2±2.3 mOsm·kg−1 (Fig. 2). In ducks, osmolality and AVT concentration increased from 297.6±1.2 mOsm·kg−1 and 5.80±0.41 pg·ml−1 (5.51±0.39 fmol·ml−1) in normally hydrated animals to 318.6±3.2 mOsm·kg−1 and 14.46±1.45 pg·ml−1 (13.75±1.38 fmol·ml−1) after 24 h water deprivation (Fig. 3). 3. In both species the correlations between plasma osmolality and ADH concentration were highly significant (2 P<0.001) and indicated similar sensitivities of the ADH system to changes in plasma osmolality: 0.24 pg·ml−1 per mOsm·kg−1 in dogs (Fig. 4) and 0.39 pg·ml−1 per mOsm·kg−1 in Pekin ducks (Fig. 5). This interspecies difference in sensitivity was found to be less than the intraspecies variations (Table 1).

Mating call selectivity in the thalamus and midbrain of the leopard frog (Rana p. pipiens): Single and multiunit analyses

Abstract: 1. A single and multiunit survey was made of the tuning properties of auditory neurons in the rostral midbrain and caudal thalamus of the northern leopard frog,Rana p. pipiens. Lesions of the recording sites revealed auditory neurons were located in the rostrolateral torus semicircularis, pretectal gray, pretectal central gray, optic tectum, and posterocentral and posterolateral thalamic nuclei. 2. Single unit analysis of 36 auditory neurons revealed that 10 responded only to specific tone combinations, or responded to single low frequency tones at high intensities (typically greater than 90 dB SPL) but their excitatory thresholds could be decreased as much as 40 dB with the addition of specific tones. All such neurons were similar in that they preferred combinations of low ( 1,200 Hz) frequency tones. They were inhibited or not excited by intermediate frequency tones. 3. The majority of neurons responded to single tones and their excitatory thresholds were not decreased by multiple tone stimulation. They were typically broadly tuned, and in some cases displayed bimodal or trimodal excitatory tuning curves. Some could be inhibited by high intensity tones near the center of their excitatory frequency range. Others were totally unresponsive to these intermediate frequencies, resulting in two discontinuous excitatory tuning curves. 4. The multiunit survey at 26 recording sites examined responses to various single and multiple tone stimuli composed of 300, 750 and 1,750 Hz tones representing the low, mid and high frequency ranges of the three receptor populations. There was considerable variation in the relative excitatory capacities of these stimuli between recording sites. The trend which emerged was that (1) tone combinations were more effective than single tones, (2) combining tones often produced a non-linear summation of the responses to individual tones, (3) the 300+1,750 Hz stimulus (i.e., the low and high frequency combination) was always among the most excitatory stimuli, and (4) the addition of mid frequency tones often reduced the excitatory capacity of a stimulus. 5. A previous evoked potential study of the caudal thalamus (Mudry et al. 1977) reported a non-linear summation of the potential when frequencies within the response ranges of the amphibian (low and mid frequencies) and basilar papillae (high frequencies) were combined. Present single and multiunit analyses extend these results, and suggest that these regions of the anuran auditory system show a particular preference for tone combinations which approximate the spectral energy distribution of the species mating call.

Sensitivity to ultrasound in an identified auditory interneuron in the cricket: a possible neural link to phonotactic behavior

Abstract: 1. In the cricket,Teleogryllus oceanicns, an identified auditory interneuron, interneuron-1 (int-1), is described morphologically and physiologically (Figs. 1,2). There is one such neuron in each hemiganglion of the prothoracic ganglion. The medial dendrites of int-1 overlap part of the terminal field formed by the auditory afferent axons from the ear and int-1's axon ascends to the brain, terminating on the same (ipsilateral) side (Fig- 2). 2. The neuron has a two-part frequency response characteristic: (1) its spontaneous activity is suppressed by low frequencies (3 to 8 kHz) at threshold-to-moderate intensities (Fig. 9 B), and (2) it is strongly excited at high frequencies, especially ultrasonic, from 15–100 kHz (Fig. 3). 3. Int-1 produces more spikes per tone pulse (Fig. 4) and its reponse latency decreases (Fig. 5), with increasing levels of intensity when stimulated by ultrasound. 4. Two-tone inhibition occurs in int-1. When a 30 kHz (normally excitatory) tone is combined with a 5 kHz tone (which suppresses spontaneous activity), the combination tone results in a diminished response, compared to the response to the excitatory tone alone (Fig. 6). 5. The excitation of int-1 shows lateralization. Excitation is stronger in the neuron ipsilateral to the sound source, than in the contralateral int-1 (Fig. 9). 6. Int-1 responds to electronically-generated pulse trains that simulate bat-echolocation signals. The neuron is responsive to a range of ultrasonic frequencies that are contained in the echolocation signals of insectivorous bats (Fig. 11). 7. In light of its response characteristics, we speculate that int-1 plays a role in the detection of ultrasonic signals emitted in the cricket's normal environment by hunting bats.

Dynamic changes in flow rate and composition of urine during the post-bloodmeal diuresis in Aedes aegypti (L.)

Abstract: 1. The urine of blood-fed mosquitos was collected and analyzed for elemental composition and osmolality. 2. Peak rates of urine flow averaged 4.9 droplets/min at 6 min following the beginning of the bloodmeal; peak flow urine contained, in mM, Na 178, K 4, and Cl 132, and the urine was approximately isosmotic to hemolymph. 3. As urine flow rates fell, the [Na] of the urine decreased and the [K] increased. Urine osmolality declined, measuring less than 100 mOsm/kg in some samples, as compared to 354 mOsm/kg measured in pre-bloodmeal hemolymph. 4. When urine flow rates had fallen to less than 10% of peak flow rates, urine again became approximately isosmotic to hemolymph, still containing Na and K as the principal cations. 5. Approximately 40% each of the water, Na and Cl contained in the plasma fraction of the bloodmeal was excreted during the 1–2h period following the bloodmeal. This excretion represents only 20–30% of the total loads ingested in the bloodmeal. 6. The data are consistent with dynamic changes in the functioning of both the Malpighian tubules and hindgut during the post-bloodmeal diuresis.

Pheromone-triggered flip-flopping interneurons in the ventral nerve cord of the silkworm moth, Bombyx mori

Abstract: 1. A group of extracellularly recorded descending interneurons in the ventral nerve cord of the male silkworm mothBombyx mori share a common flip-flopping input. In response to repeated stimuli these flip-flopping interneurons switch back and forth between long lasting high and low firing rates (Figs. 1, 2). 2. Changes in the level of the female pheromone bombykol in an airstream directed at the antennae were the most effective stimuli in eliciting flip-flopping of the interneurons. Changes in light intensity, up or down, were the only other effective stimuli (Fig. 2, Table 1). 3. The low or high firing frequency states following a single stimulus presentation lasted as long as 4 min, although with some decrement (Fig. 3a). 4. The high and low states corresponded to two different positions of the antennae. Transitions between states were mirrored by changes in antennal position. Immobilizing the antennae did not eliminate flip-flopping (Fig. 5). 5. In intact animals, the two antennal positions corresponded to left and right turning movements of the legs and to left and right ‘ruddering’ of the abdomen (Fig. 6). 6. When bombykol-laden air puffs were presented to a single antenna, the neurons sometimes showed flip-flopping responses, but often remained in a ‘favored’ state between stimuli (Fig. 7). 7. When different concentrations of bombykol were presented to the two antennae, the interneurons assumed a high or low firing rate, consistent with a turn toward the antenna receiving the higher concentration. Different concentrations of bombykal to the two antennae (with equal, constant bombykol levels to the two antennae) elicited the opposite effect, i.e., firing rates consistent with turning away from the higher bombykal concentration (Fig. 8). 8. Most interneurons responded in graded fashion to other stimuli besides those which elicited flip-flopping (Fig. 9). Six response types were discriminated, based upon exclusive combinations of sensory inputs and upon the direction of the correlation between flip-flopping states and animal turning (Table 2). 9. All of the results support the hypothesis that these interneurons carry left and right turning instructions for pheromone-directed turns in the upwind approach of maleBombyx to the female.

Regulation of cryoprotectant metabolism in the overwintering gall fly larva,Eurosta solidaginis: Temperature control of glycerol and sorbitol levels

Abstract: Abrupt temperature change, from 23 to 13 °C, 13 to 3 °C or vice versa, was used to study the metabolic events associated with cryoprotectant polyol synthesis and the reversibility of polyol accumulations in the overwintering, freezing tolerant larvae of the gall fly,Eurosta solidaginis. Sorbitol synthesis was induced when larvae acclimated to 13 °C were abruptly moved to 3 °C. A precursor-product relationship between glucose-6-P, glucose and sorbitol was apparent with elevated levels of the compounds in the larvae first detected after 1, 2 and 24 h at 3 °C, respectively. A negative cross-over (increase in fructose-6-P, decrease in fructose-1,6-P2 levels) at phosphofructokinase at 3 °C demonstrated that inhibition at this locus was responsible for the diversion of carbon flow into sorbitol synthesis. Glycerol synthesis was stimulated when larvae acclimated to 23 °C were chilled to 13 °C, with increased glycerol levels first apparent after 2 days at 13 °C. Synthesis was accomplished via an activation of glycogenolysis coupled with a facilitation of flux through the phosphofructokinase locus and an inhibition (negative cross-over) of flux at the pyruvate kinase reaction resulting in a diversion of triose phosphates into the pathway of glycerol synthesis. Warming of the larvae resulted in a rapid catabolism of sorbitol, with a restoration of glycogen reserves, when larvae were switched from 3 to 13 °C. Glycerol content of the larvae, however, did not respond to warming and remained constant when larvae were moved from 13 to 23 °C. The two cyoprotectants appear to have different roles in the overwintering larvae. Glycerol, once synthesized, provides a constant and permanent cryoprotection throughout the winter. Accumulation of this polyol also appears to be anticipatory occurring in response to chilling at relatively high temperatures, well above those at which cryoprotection is needed. Sorbitol, however, is produced only in direct response to cold when freezing temperatures are imminent. Sorbitol provides a variable cryoprotection, levels of the polyol responding to increases or decreases in ambient temperature.

Discrimination of surface-structured targets by the echolocating batMyotis myotis during flight

Abstract: 1. Myotis myotis was trained to discriminate a plate with 8 mm deep holes from plates of stepwise varied hole depth. Depth differences in the two plates equal or larger than 1 mm were discriminated by the echolocating bat (Fig. 3). 2. In a second series of experiments a plate with 4 mm deep holes was discriminated from other plates with hole depth differences equal or larger than 0.8 mm (Fig. 3). 3. Echolocation sounds emitted during discrimination are of the same type as those used for catching prey in air or on the ground (Fig. 2). With increasing difficulty of the discrimination task the flight speed of the bat was reduced (Fig. 1). 4. An incidental experiment disclosed the ability to discriminate surface structures with the resolution of roughness produced by 30 μm protrusions in the surface (Fig. 4). 5. We conclude thatMyotis myotis discriminated hole depth differences by spectral, and not by time, cues in the echoes.

Acuity of horizontal angle discrimination by the echolocating bat,Eptesicus fuscus

Abstract: Echolocating bats of the speciesEptesicus fuscus were trained to discriminate between two arrays of vertical rods differing in the size of the angle in the horizontal plane separating the rods in each array. With both two-rod arrays and fiverod arrays the bats were able to distinguish angular differences as small as 1.5 °(75% correct-response threshold). The similarity of the results obtained with both array sizes shows that the angular separation of adjacent rods, and not the width of the array as a whole in the case of five-rod arrays, is the source of cues for the discrimination. Acoustic control experiments were carried out to determine whether echoes reflecting laterally from one rod to another contributed cues to the bat. The results indicate that discrimination was based on the bat's perception of the horizontal angular position of each rod relative to its neighbors, and not upon acoustic interactions among the rods. The acuity of horizontal-angle discrimination measured at 1.5 ° may represent the acuity with which the bat's sonar system processes echoes to display one target's azimuth relative to the azimuth of another target. The results thus may represent the acuity of discrimination of target location by the binaural mechanisms of localization of sound. Although bats are considered to have heads that are too small for producing adequate interaural arrival-time cues for sound localization, the extremely broad bandwidth of FM echolocation signals and echoes may compensate for small interaural separation in bats. It is, therefore, most provocative that the observed performance ofEptesicus fuscus at horizontal-angle discrimination matches the performance to be expected if the 0.5 μs acuity of perception of the time-of-occurrence of sonar echoes measured in echo-jitter experiments can be applied to binaural echo arrivaltime perception. It cannot be ruled out that the FM bat compares the arrival time of echoes at the two ears and reconstructs in some manner the relative phase of these sounds to determine target direction in the horizontal plane.

Ventilatory control of arterial PO2 in the turtleChrysemys picta bellii: Effects of temperature and hypoxia

Abstract: Ventilation, pulmonary O2 uptake, arterial blood gases and pH were measured in fresh water turtles,Chrysemys picta bellii, during voluntary diving and surfacing at temperatures of 10, 20 or 30°C. At each temperature, the animals were also exposed to declining levels of inspired O2 concentration with blood samples taken at various stages of breath holding and during episodes of breathing.

Sexual dimorphism in the visual system of flies: The compound eyes and neural superposition in bibionidae (Diptera)

Abstract: 1. Micro-optical and neuro-anatomical techniques were used to study the retinal organisation of the compound eyes and the receptor terminals in the lamina in Bibionidae (Diptera). 2. Male bibionids have divided compound eyes (Fig. 1). The dorsal eyes have larger facets and longer rhabdomeres than the ventral eyes and the eyes of females (Table 1). Groups of six peripheral retinula cells in six next-but-one ommatidia have parallel optical axes and their terminals in the lamina are shown to pass to next-but-one cartridges (Fig. 6, 7). 3. The retinal organisation of ventral eyes and the eyes of females differs from the one seen in the dorsal eyes of males (Figs. 2, 3). InBibio marci, the rhabdomeres in ventral and female eyes are arranged with the same radial symmetry as in the dorsal eyes, but interrhabdomere angles are smaller than would be expected for ideal neural superposition eyes (Fig. 5d). 4. In the ventral and female eyes ofDilophus febrilis, peripheral rhabdomeres are arranged in a horse-shoe like fashion around the central rhabdomeres (Fig. 2). Groups of four peripheral rhabdomeres in four neighbouring ommatidia have parallel visual axes (Fig. 5b). 5. The terminals of peripheral retinula cells in the ventral and female eye lamina pass to neighbouring and to next-but-one cartridges (Fig. 6). Long visual fibres, originating from the central retinula cells form en passant terminals in the ventral and female lamina. 6. It is shown that in eyes with open rhabdoms where the visual axes are not parallel, neural superposition reduces the amount of overlap between the visual fields of lamina cartridges provided the interrhabdomere angles are larger than 0.876 times the interommatidial angles (Fig. 8). 7. It is suggested that compared with the ventral and female eyes, the dorsal eyes of males are designed to increase the distance at which a small object can be detected against a homogeneous background (Fig. 9).

Gustatory responses of the rainbow trout (Salmo gairdneri) palate to amino acids and derivatives

Abstract: 1. Gustatory responses to amino acids and derivatives obtained from the palatine nerve (VIIth cranial nerve) of rainbow trout (Salmogairdneri) were studied. 2. The response to an amino acid was characterized by its fast-adapting, phasic nature that returned to baseline within 5 s during continuous stimulation. 3. Complete recovery of the response took place 120 s after stimulation when tested with two identical stimuli given successively (Figs. 2, 3). 4. Among common amino acids tested, onlyL-isomers of proline, hydroxyproline, alanine, leucine, and phenylalanine were stimulatory (Table 1), demonstrating that the facial taste system is more narrowly-tuned to amino acid stimuli than the olfactory system. The arginine derivative,L-α-amino-β-guanidinopropionic acid (L-AGPA) andL-argininic acid, and betaine were also effective. 5. Concentration-response relations, when plotted semi-logarithmically, were generally sigmoidal, saturating at higher concentrations (>1 mM) (Fig. 5). The threshold concentration forL-proline, the most effective amino acid tested, was estimated to be 50 nM. The thresholds for other stimulatory chemicals ranged between 1 and 100 μM. 6. L-AGPA, though having higher threshold (10 μM), could induce responses three times the magnitude of that ofL-proline at 1 mM. 7. The stimulatory activity of heterocyclic-imino acids having 4-, 5-, and 6-membered rings and also of thioproline and hydroxyproline suggests that the receptor recognizes primarily the imino acid region (Fig. 6). 8. Taste responses to amino acids were independent of pH, except that arginine analogues were only active at basic pHs (Fig. 7 and Table 3). larginine was active only at pHs higher than 8.5. The palatal chemoreceptors were stimulated by waters with pHs below 7.0, suggesting the existence of receptors for pH and/or CO2 (Fig. 7).

The tritocerebral commissure giant (TCG) wind-sensitive interneurone in the locust

Abstract: 1. The TCG interneurone of the locust integrates information from the wind-sensitive head hairs and the antennae. The cell is rhythmically active in tethered flight and is sensitive to a yaw imposed on the animal in a laminar stream of air — the left TCG is more sensitive to a yaw to the left and vice versa (Figs. 1, 5). 2. Successively waxing over the different windhair fields (fields 1...5) and immobilising the antennae reveals that all these sense organs contribute to the sensitivity of the neurone to the angle of yaw (Figs. 2, 3). There is no mutual inhibition between the right and left TCG (Fig. 4). 3. The cell shows a phasic-tonic reaction when either the resting or the flying animal is subjected to a stepwise yaw. However, the tonic component is stronger when the animal is flying (Fig. 7). 4. During flight the TCG fires rhythmically in bursts synchronised with depressor muscle potentials, i.e., at about the time when the wing is in its top position. Yaw angle is coded by the number of spikes per burst and their timing within the wing-beat cycle. An increase of the TCG activity is correlated with an earlier beginning of the burst (Figs. 8, 9). There is no change in the interspike interval within the TCG burst during a yaw stimulus: the 1st and 2nd interspike intervals remain at an average of about 4 ms (Fig. 9). 5. In straight flight, electric stimulation applied to the right TCG neurone (thus mimicking a yaw to the right) evokes antagonistic time shifts in downstroke muscles, equivalent to those observed in response to an actual right yaw being imposed on the animal (Figs. 10, 11). The results suggest that the TCG is an important pathway in mediating yaw-correcting behaviour. 6. A small resetting of the flight rhythm is produced when the TCG is electrically stimulated during flight (Fig. 13).

Digestion and metabolism of a natural foliar diet (Eucalyptus punctata) by an arboreal marsupial the koala (Phascolarctos cinereus)

Abstract: Digestion and energy metabolism in an arboreal marsupial, the koalaPhascolarctos cinereus, fed mature foliage from a common food tree, the grey gumEucalyptus punctata, were investigated. Six feeding (balance) experiments, at various times of year, and one slaughter experiment were performed and average daily oxygen consumption was measured. The average apparent digestibilities of dietary constituents were: dry matter 54%; total cell-contents 69%; available carbohydrate 92%; crude lipid 43%; total nitrogen 45%; total phenolics 91%; total cell walls 25%; hemicellulose 24%; acid-detergent fibre 25%; cellulose 31%; lignin 19%. Average digestible and metabolizable energy intakes were 0.50 and 0.43 MJ kg−0.75 d−1 respectively of which only 0.28 MJ kg−0.75 d−1 was expended in oxidative metabolism. The digestible energy intake required for maintenance was estimated to be 0.33 MJ kg−0.75 d−1, which is lower than that of eutherian and of other marsupial herbivores. The principal sources of metabolizable energy were non-structural carbohydrate and lipid. It is postulated that the ability of koalas to utilizeEucalyptus foliage as a sole source of nutrients is facilitated by their low requirement for energy and their ability to maximize intake of non cell-wall constituents.E. punctata foliage has a high digestible energy content compared with the foliage of many other trees and this may be a factor in its selection by koalas.

Sexual dimorphism in the visual system of flies: The free flight behaviour of male bibionidae (Diptera)

Abstract: 1. The free flight behaviour of swarming male Bibionidae (Diptera) has been filmed in the field with two cameras simultaneously at 50 frames/s. A method is described which allows the reconstruction of the three-dimensional trajectories of flies from the two films. 2. Males track other flies and dummy targets from below and from downwind (Figs. 5–8; 10a). They keep pointing into the wind and control flight direction and their position relative to the target by way of translational movements (forward, side-ways and vertical movements) (Fig. 9; Fig. 16b–d). Angular tracking is minimal, there is evidence, however, that the flies roll and pitch. 3. When interacting with a target, the flies keep the target's image close to and within the zone of binocular vision of their dorsal compound eyes (Figs. 3; 10c). There is some evidence that the flies' sideways acceleration is determined by the error angle velocity with a delay of 90 ms (Fig. 12). Underneath the target the flies perform sideways oscillations at 3–5 Hz (Fig. 13). 4. The flies repeatedly home in on and retreat from a target. At close range (0–20 cm) their vertical and forward velocity is linearily related to the target distance (Figs. 14a, 15a). Switches from ascending to descending flight occur whenever the target is lost from the visual field of the dorsal eyes. 5. Both forward and vertical velocity are to some extent dependent on the altitude of the target above the horizon of the fly (Figs. 14b, 15b). 6. Rotational body movements in response to rotating striped patterns can only be elicited by stimulating the ventral eyes, the dorsal eyes do not mediate the optomotor response (Fig. 17). 7. In bibionids, male-specific visually guided behaviour is mediated through the dorsal eyes only. The visual tasks of swarming males are discussed. The complex behaviour seen in males interacting with a dummy target might reflect their need to distinguish other males in a swarm from females and to keep the surrounding airspace clear of unwanted targets.

Vibratory signals and spider behavior: How do the sensory inputs from the eight legs interact in orientation?

Abstract: When the wandering spiderCupiennius salei is standing with one or several of its legs on a platform that begins to vibrate, it turns toward the platform if the stimulus resembles prey-generated vibration With application of simultaneous, uniformly intense substrate vibration, the turning angle depends on the combination of legs stimulated

Intensity discrimination and the precision of call timing in two species of neotropical treefrogs

Abstract: 1. Field acoustic playback experiments were conducted with maleEleutherodactylus coqui andE. portoricensis. Periodic tone bursts of intensities similar to natural sounds in the habitat of the frogs were used to create sonic interference. The period between tone bursts, the ‘time window’, was varied in duration and in intensity relative to the tone burst. 2. Males of both species suppressed vocalizations during the stimulus tone bursts. The amount of suppression decreased as the tone burst was lengthened. 3. Males of bothE. coqui andE. portoricensis suppressed calling in response to tone bursts of 0.40 to 2.0 kHz, a range which encompasses the principal frequency components present in their vocalizations. 4. BothE. coqui andE. portoricensis initiated significantly (P<0.01) more calls within the time windows between stimulus tone bursts than would be expected by chance when the window duration was as short as 0.25 s and 0.10 s, respectively. These durations are approximately 10% of the spontaneous call repetition periods for each species. 5. E. coqui initiated significantly (P<0.01) more calls than would be expected by chance in tone-filled time ‘windows’ which were only 4 to 6 dB less intense than the tone bursts. This ability of intensity discrimination under sonically adverse natural field conditions indicates a level of performance in the same range as that of mammals. 6. The ability of frogs to call preferentially during very brief silent periods or during periods of slight intensity reductions is viewed as an adaptation for avoiding acoustic interference, and thus improves the efficiency of acoustic communication in an intense and complex sonic environment.

Discrimination by the cod of sounds from opposing directions

Abstract: 1. The ability of cod (Gadus morhua L.) to discriminate between sound waves coming from opposing directions was studied by means of cardiac conditioning in approximately free field conditions under a raft in a Scottish sea loch. The sound sources were positioned at 0° (frontal), 60° or 120° in the fish's median vertical plane, or at 60° or 90° in the transverse plane, other sources occupying diametrically opposed locations. Radial distances varied between 3.05 m and 4.20 m. 2. Switching a continually pulsed 120 Hz pure tone stimulus from a reference source to an opposing source was detected under all conditions. 3. Discrimination was absent when a standing wave was added to the opposing source, locally inverting the phase of sound pressure with respect to the acoustic particle motion without influencing the direction of propagation. 4. Switching to a completely synthesized standing wave field, simulating the phase relations of the reference source, was not detected. Switching to a simulation of the opposite source was detected. 5. It is concluded that the detection of sound propagation direction is based on the characteristic phase relationship between particle motion and sound pressure. Cues resulting from sound propagation itself are irrelevant, and do not appear to be perceived. 6. It appears that the 180° ambiguity in determining sound propagation direction by means of acoustic particle oscillation alone can be eliminated by the cod. This ability seems to hold for all stimulus directions, thus providing a basis for truly three-dimensional directional hearing.

Visual pattern discrimination through interactions of neural networks: a combined electrical brain stimulation, brain lesion, and extracellular recording study inSalamandra salamandra

Abstract: In freely movingSalamandra salamandra various brain sites (n = 33) were stimulated monopolarly via chronically implanted electrodes. Stimulation of the optic tectum mainly elicited prey-catching behavior (mean lower current threshold Ilt = 9 μA) and sometimes predator-avoidance behavior (Ilt = 28 μA). Stimulation of the caudal dorsal (Ilt = 27 μA) or rostral dorsal thalamus (Ilt = 26 μA) exclusively released avoidance movements, such as ipsiversive turning, running, or moving backward. Telencephalic stimulation (Ilt = 66 μA) activated backward-creeping, trunk-raising, or jaw-opening/closing. Brain lesions were produced inn = 64 fire salamanders either by anodal DC current, radiofrequency current, Kainic acid micro-injections, or micro-knife cuts. After ablation of the optic tectum, both visually guided prey-catching and predator-avoidance behaviors failed to occur. Unilateral lesions in the following prosencephalic brain areas caused a strong deficit of configurational prey-selection (‘disinhibition of prey-catching behavior’) and a failure of visual predator-avoidance behavior in response to stimuli moving in certain areas of the visual field: (i) caudal dorsal thalamus (entire contralateral visual field), (ii) rostral dorsal thalamus (frontal visual field of both eyes), and (iii) medial pallium (entire visual field of both eyes). Lesions in the lateral pallium led to a decrease in the threshold of visually guided predator-avoidance behavior. Action potentials were extracellularly recorded from single tectal T5 neurons in intact animals and following various prosencephalic lesions (i), (ii), or (iii). In all of then = 14 investigated neurons the same alteration of response properties was obtained, corresponding to the change in behavior. Recordings from a single prey-selective class T5(1) neuron pre and post DC coagulation in the ipsilateral caudal dorsal thalamus produced: an increase in the diameter of the excitatory receptive field (ERF) from ≈30 ° to ≈50 ° and a strong deficit in selectivity with regard to moving configurational visual stimuli.

Orientation of homing pigeons: compass orientation vs piloting by familiar landmarks

Abstract: To study the relative importance of piloting by familiar landmarks compared to navigation using a ‘map’ and a compass at familiar sites, 6 h slow shifted pigeons were released under sun at locations from which they had homed more than 60 times before. They showed the typical ca. 90 ° clockwise deviation from the mean of the controls indicating the use of the sun compass. These findings show that even at very familiar sites the home direction is determined as a compass direction. There is no evidence for piloting, i.e. following chains of familiar landmarks. Another use of landmarks, however, namely their use to recognize a location where the home course is known from previous experience, appears possible.

Differential effects of secretagogues on Na and K secretion in the Malpighian tubules ofAedes aegypti (L.)

Abstract: 1. Rates of fluid secretion were measured in isolated Malpighian tubules from adult female mosquitoes and the concentrations of Na, K and Cl in the secreted fluid were measured by electron probe analysis under control conditions and in the presence of the secretagogues dibutyryl cAMP or head extract. 2. Under control conditions tubules secreted fluid at an average rate of 0.8 nl/min. The principal solutes in secreted fluid were Na at 94 mM, K at 91 mM and Cl at 161 mM. 3. Dibutyryl cAMP (1 mM) stimulated the rate of fluid secretion ∼250% (to 2.9 nl/min), increased the [Na] of secreted fluid to 178 mM, decreased the [K] to 17 mM, and did not change the [Cl]. Consequently, the net effect of dibutyryl cAMP was a highly significant stimulation of Na, Cl, and water secretion with no significant change in the secretion of K. 4. An aqueous extract of mosquito heads (0.1 head/μl) also stimulated the rate of fluid secretion ∼250% (to 2.8 nl/min), but introduced no major changes in the composition of secreted fluid with the exception of a slight, though significant decrease in the [K] from 91 to 73 mM. Consequently, the net effect of the head extract was the highly significant stimulation of Na, K, Cl, and water secretion. 5. The different effects of dibutyryl cAMP and head extract on the secretion of cations suggest that Na secretion and K secretion can be regulated independently of one another. In vivo, such a separate regulation of Na and K secretion might be important in the maintenance of hemolymph Na and K concentrations, especially following a blood meal.

How stalk-eyed flies eye stalk-eyed flies: Observations and measurements of the eyes of Cyrtodiopsis whitei (Diopsidae, Diptera)

Abstract: 1. The Malayan stalk-eyed flyCyrtodiopsis whitei, of the family Diopsidae, exhibits sexual dimorphism in that the eyestalk span of the males exceeds the length of the body, whereas that of the females, which have shorter bodies on the average, is smaller than the body length. The ratio of the sexes in a population departs significantly from 1∶1; in samples of newly emerged imagines there are twice as many females as males. 2. The behaviour ofCyrtodiopsis is very much determined by vision. During the day, temporary territories may be defended by threat behaviour. At dusk the animals gather in small groups on selected threadlike structures, returning to the same site each day. When males of about equal size encounter one another within such a group they may engage in ritualized fights (or occasionally contact fights). Competitors are driven away by the dominant male. Conspecifics are most likely to elicit a threat or flight reaction when they are at a distance of about 50 mm, and reactions to model flies and reflections in a mirror also occur at about this critical distance. 3. Body length is closely correlated with both eyestalk span and the number of ommatidia in the compound eyes (cf. Results, Sect. 2, Table 1 and Figs. 2, 3, 7 and 8). The largest animals have about 2,600 ommatidia in each eye; the number of optic nerve fibres in the eyestalk is about 6,600. 4. Each compound eye sees a region of space extending over more than a hemisphere in all directions, so that there is extensive binocular overlap; about 70% of the ommatidia of each eye have binocular partner ommatidia in the opposite eye viewing in the same direction. The binocular field is most extensive in the frontoventral quadrant, where it reaches over 135 °, and is smallest in the dorsal region. 5. In large animals the size of the binocular field increases because of the greater number of ommatidia. This increase affects chiefly the frontoventral quadrant. As a result, the blind region immediately ahead of and below the head is independent of body size, extending to a distance of only 3 mm in the median plane. 6. The divergence angles of adjacent ommatidia are ca. 3 ° in most parts of the eye. In the foveal region this angle is reduced to just over 1 °. The optical axes of the foveal ommatidia point forward in the horizontal plane; the foveal zone is above and adjacent to the region of greatest binocular overlap. In a small part of the lateral monocular region the divergence angles increase to 5 °. 7. Optomotor experiments show that the head can be moved actively by ca. ±25 ° about the vertical and longitudinal axes, and 20 ° upward and 35 ° downward about the eyestalk axis. Conspecifics are fixated by turning the head and body about the vertical and transverse axes, so as to center the object in the binocular field, either in the horizontal plane or in the adjacent region of greatest binocular overlap. During a ritualized fight the opponents keep their eyestalks parallel and position themselves such that each animal sees the other in a region between the horizontal plane (fovea) and a plane inclined frontoventrad (in the region of greatest binocular overlap), at a distance equal to or smaller than the eyestalk span. 8. The way conspecifics of various sizes at various distances are imaged in the ommatidial array is calculated for the horizontal plane and a plane tilted downward in front by 20 °. Each combination of size and distance generates a different pattern in the array. 9. The pattern constellations on the ommatidial array, like the behavioural observations, indicate that the size and distance of a conspecific can be detected over a relatively extensive region, from a few millimeters to a meter away from the viewing animal. The high foveal resolution, the wide separation of the eyes and the large binocular field make this possible. 10. The eyestalks are probably intraspecific sign stimuli by which a conspecific is recognized and its size (and hence the strength of a potential opponent) is determined.

Steroid influences upon the discharge frequencies of a weakly electric fish

Abstract: Sternopygus dariensis, a weakly electric gymnotiform fish, possesses sexually different electric organ discharges (EODs), with females emitting EODs at higher frequencies than males. This difference can be accounted for by the effects of gonadal steroids: laboratory experiments indicate that daily injections (0.25 to 20 μg/g body weight) of androgens lower discharge frequencies while injections of estrogens raise discharge frequencies. Clear changes in discharge frequencies can be noted over the course of days, and persist until several days after injections are terminated. These effects are noted irrespective of age or sex, and can be seen in both intact and gonadectomized animals. The discharge frequencies of these animals are established by a neuronal oscillator, the medullary pacemaker nucleus. Thus, the steroid-elicited changes in discharge frequencies are indicative of changes in the activity of the pacemaker nucleus. Steroids may be exerting their effects either through indirect effects upon those neurons which provide input to the pacemaker, or through direct effects upon the spontaneous depolarizations of the pacemaker itself.

Detection of oscillating target movements by echolocation in the greater horseshoe bat

Abstract: The abilities of 11 Greater Horseshoe bats (Rhinolophus ferrumequinum) to discriminate an oscillating from a stationary target by evaluating Doppler shifts in the echoes were studied in a two-alternative forced-choice procedure. At oscillation frequencies (f osc) from 5–30 Hz the best performing bat reached the threshold of 75% correct choices at approximately constant modulation depths of 60 Hz. Atf osc above 30 Hz the threshold modulation depths decreased with increasingf osc down to only 12 Hz at af osc of 200 Hz whereas the thresholds of the maximal sweep rate stayed constant at about 6 Hz/ms. The results demonstrate that Greater Horseshoe bats evaluate frequency modulations caused by oscillating target movements. They suggest the existence of two separate mechanisms for the detection of modulations forf osc between 5–30 Hz and forf osc above 30 Hz.

Coordination of lateral giant and non-giant systems in crayfish escape behavior

Abstract: 1 The modal escape response of a wellrested crayfish to a tap on the abdomen consists of an initial lateral giant-mediated flexion, a movement-triggered reflex extension, and then a series of centrally patterned, non-giant mediated, extension-flexion cycles (Figs 1 and 2) 2 We investigated three models to explain how the non-giant system is triggered (Fig 3) Direct stimulation of the giant axons in unrestrained animals showed that neither their central activity nor the sensory consequences of the tailflip they produce are sufficient to trigger the non-giant system (Fig 4) 3 In well-rested animals, weak taps often triggered the non-giant system alone, ie, without activating the giant axons (Fig 5) This may have occurred rarely in earlier studies since the non-giant system habituates more rapidly than the lateral giant system (Fig 6) 4 Although firing the giant axons does not trigger the non-giant system, the giant axons do cause subthreshold excitation which can summate with sensory input to trigger the non-giant system (Fig 7) 5 The combined results show that the giant and non-giant systems are usually activated in parallel The orderly transition from giant to non-giant escape behavior is in large part the result of marked differences in the latencies of each system: the median latency for the lateral giant axon response is 6 ms compared to approximately 140 ms for the non-giant response (Fig 8) 6 The long latency of the non-giant system may be inherent to the processing time required to set up the nervous system for an optimal response Direct observations establish that the non-giant system uses at least one bit of information that the giant axon system ignores: it reacts to the laterality of the stimulus as well as to its anterior-posterior location (Fig 9)

Splitting in a Circadian Activity Rhythm: The Expression of Bilaterally Paired Oscillators *

Abstract: Circadian stridulation rhythms of the male Australian field cricketTeleogryllus commodus (Walker) recorded in continuous light (LL) and constant temperature sometimes split spontaneously or after a pulse of low temperature into two activity components per cycle. Both components exhibited different free-running periods longer than 24 h, referring to separate oscillatory control mechanisms. One of the components disappeared when an optic lobe was removed. Two activity components per circadian cycle with different periods were also found after the ommatidial nerves between retina and optic lobe had been cut on one side during the last larval instar. In LL, one period was then longer, the other shorter than 24 h; these periods correspond to the freerunning rhythms of intact crickets in LL and constant darkness (DD) (Loher 1972), and indicate that they can be simultaneously expressed in the same cricket. The two underlying pacemakers are only weakly coupled, they jointly or alternatingly influence the overt rhythm causing a spectrum of different patterns. Additional removal of the optic lobe on the intact side eliminated the LL-component (>24 h) while the DD-component (<24 h) continued. Removal of the de-afferented optic lobe had the reverse effect. Each component of the split activity rhythm can therefore be attributed to either side of the brain. The circadian control mechanism of the calling song inT. commodus is interpreted as being composed of two bilaterally organized subunits.