A fovea in the praying mantis eye
01 Mar 1970-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology (Springer-Verlag)-Vol. 67, Iss: 1, pp 58-78
TL;DR: In this article, a special experimental device was employed to study which zones of the eye, the praying mantis uses to "look at" the prey before striking, and the results showed that the mantis can detect the location of the predator's eye.
Abstract: A special experimental device was employed to study which zones of the eye, the praying mantis uses to “look at” the prey before striking.
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01 Mar 1975-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
TL;DR: The visually guided flight behaviour of groups of male and femaleyritta pipiens was filmed at 50 f.p.s. and analysed frame by frame and it was shown that to synchronise the two flies the sideways tracking system must also be operative.
Abstract: 1.
The visually guided flight behaviour of groups of male and femaleSyritta pipiens was filmed at 50 f.p.s. and analysed frame by frame. Sometimes the flies cruise around ignoring each other. At other times males but not females track other flies closely, during which the body axis points accurately towards the leading fly.
2.
The eyes of males but not females have a forward directed region of enlarged facets where the resolution is 2 to 3 times greater than elsewhere. The inter-ommatidial angle in this “fovea” is 0.6°.
3.
Targets outside the fovea are fixated by accurately directed, intermittent, open-loop body saccades. Fixation of moving targets within the fovea is maintained by “continuous” tracking in which the angular position of the target on the retina (Θe) is continuously translated into the angular velocity of the tracking fly (\(\dot \Phi _p \)) with a latency of roughly 20 ms (\(\dot \Phi _p = k \Theta _e \), wherek≏30 s−1).
4.
The tracking fly maintains a roughly constant distance (in the range 5–15 cm) from the target. If the distance between the two flies is more than some set value the fly moves forwards, if it is less the fly moves backwards. The forward or backward velocity (\(\dot F_p \)) increases with the difference (D-D0) between the actual and desired distance (\(\dot F_p = k^\prime (D - D_0 )\)), wherek′=10 to 20 s−1). It is argued that the fly computes distance by measuring the vertical substense of the target image on the retina.
5.
Angular tracking is sometimes, at the tracking fly's choice,supplemented by changes in sideways velocity. The fly predicts a suitable sideways velocity probably on the basis of a running averageΘe, but not its instantaneous value. Alternatively, when the target is almost stationary, angular tracking may bereplaced by sideways tracking. In this case the sideways velocity (\(\dot S\)) is related toΘe about 30 ms earlier (\(\dot S_p = k\prime \prime \Theta _e \), wherek″=2.5 cm · s−1 · deg−1), and the angular tracking system is inoperative.
6.
When the leading fly settles the tracking fly often moves rapidly sideways in an arc centred on the leading fly. During thesevoluntary sideways movements the male continues to point his head at the target. He does this not by correctingΘe, which is usually zero, but by predicting the angular velocity needed to maintain fixation. This prediction requires knowledge of both the distance between the flies and the tracking fly's sideways velocity. It is shown that the fly tends to over-estimate distance by about 20%.
7.
When two males meet head on during tracking the pursuit may be cut short as a result of vigorous sideways oscillations of both flies. These side-to-side movements are synchronised so that the males move in opposite directions, and the oscillations usually grow in size until the males separate. The angular tracking system is active during “wobbling” and it is shown that to synchronise the two flies the sideways tracking system must also be operative. The combined action of both systems in the two flies leads to instability and so provides a simple way of automatically separating two males.
8.
Tracking is probably sexual in function and often culminates in a rapid dart towards the leading fly, after the latter has settled. During these “rapes” the male accelerates continuously at about 500 cm · s−2, turning just before it lands so that it is in the copulatory position. The male rapes flies of either sex indicating that successful copulation involves more trial and error than recognition.
9.
During cruising flight the angular velocity of the fly is zero except for brief saccadic turns. There is often a sideways component to flight which means that the body axis is not necessarily in the direction of flight. Changes in flight direction are made either by means of saccades or by adjusting the ratio of sideways to forward velocity (\(\dot S/\dot F\)). Changes in body axis are frequently made without any change in the direction of flight. On these occasions, when the fly makes an angular saccade, it simultaneously adjusts\(\dot S/\dot F\) by an appropriate amount.
10.
Flies change course when they approach flowers using the same variety of mechanisms: a series of saccades, adjustments to\(\dot S/\dot F\), or by a mixture of the two.
11.
The optomotor response, which tends to prevent rotation except during saccades, is active both during cruising and tracking flight.
484 citations
01 Jan 1979
TL;DR: Invertebrates are the class par excellence where one finds all manner of variations in the structure and arrangement of photoreceptors and their associated light-gathering and processing structures as mentioned in this paper.
Abstract: Invertebrates are the class par excellence where one finds all manner of variations in the structure and arrangement of photoreceptors and their associated light-gathering and processing structures. We are compelled to search for a physiologic explanation of these unique forms. This article offers a highly personalized view of the physics suited to the task.
282 citations
01 Jan 1979
TL;DR: The aims of this chapter are to show that pseudopupil phenomena provide a direct and deep insight into compound-eye structure and function, and also to indicate possible paths for future research.
Abstract: “I come to the discussion of a remarkable optical phenomenon the unravelling of which has caused me a good deal of worry.” In this way Sigmund Exner (1891, p. 162) begins the chapter on pseudopupils in his invaluable monograph “Die Physiologie der facettirten Augen von Krebsen und Insecten”. His worry has proved worthwhile because his recognition that pseudopupils are optical revelations of the interior of compound eyes has been of longlasting and immense importance. The aims of this chapter are to show that pseudopupil phenomena provide a direct and deep insight, both figuratively and literally, into compound-eye structure and function, and also to indicate possible paths for future research.
224 citations
01 Jul 1985-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
TL;DR: It seems likely that there are two kinds of acute zone in insect eyes, one concerned with forward flight and the other with the detection and capture of other insects.
Abstract: 1.
The directions of the axes of all ommatidia in the frontal eye regions of 2 species of fly (Calliphora erythrocephala andLucilia cuprina, both sexes) were mapped onto the surface of a sphere. This was done by photographing the pseudopupil in white-eyed mutants.
2.
In both sexes of both species there is a region with a high density of ommatidial axes (an acute zone), situated frontally and slightly above the equator. In females the centre of this region is only about 5° above the equator (Lucilia andCalliphora); its location is similar in maleLucilia, but is 15° higher in maleCalliphora. The maximum density of ommatidial axes is about 1 per deg2 inLucilia (both sexes) andCalliphora males; it is lower inCalliphora females (0.7 per deg2). These densities are roughly 3 times higher than at 60° from the front.
3.
We have used the data given by Beersma et al. (1975), to produce a similar map for a maleMusca domestica. The results differ from the other species mainly in that the overall density is lower, the maximum being 0.4 axes per deg2, 20–25° above the equator.
4.
Using these data and others from the literature we arrive at the following conclusions: (i) the regions of highest resolution and highest ommatidial diameter coincide closely, (ii) the region of greatest binocular overlap lies well above the centre of the acute zone, 20° higher in maleCalliphora. (iii) the ‘7r domain’ in maleMusca (Hardie et al. 1981) corresponds closely with the acute zone, (iv) the fields of view of the male-specific lobula interneurones MLG3 and Col D (Hausen and Strausfeld 1980) include the acute zone centre but also most of the dorsal part of the field of view. This is consistent with a function related to chasing.
5.
Differences in function of male and female acute zones are discussed. It seems likely that there are two kinds of acute zone in insect eyes, one concerned with forward flight and the other with the detection and capture of other insects. We also argue that ‘fovea’ should not be used to mean a region of high ommatidial axis density.
149 citations
References
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1,930 citations
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01 Dec 1962
TL;DR: A composite thin film resistor is disclosed, including an electrically inert substrate upon which is deposited a nickel-chromium alloy thin film, and an overlying second thin film - which is initially deposited as metallic tantalum - which provides a very high degree of environmental protection with respect to the Ni-Cr film.
Abstract: A composite thin film resistor is disclosed, including an electrically inert substrate upon which is deposited a nickel-chromium alloy thin film, and an overlying second thin film - which is initially deposited as metallic tantalum. In the final product the tantalum is passivated, as by thermal oxidation, so that the said film is substantially tantalum oxide throughout, except where such film underlies a pair of conductive terminal pads. The terminal pads are spaced on the substrate, so that the resistive path therebetween is defined through the nickel-chromium thin film - via the thin metallic tantalum film interfacing between the nickel-chromium film and conductive pads. The overlying tantalum oxide provides a very high degree of environmental protection with respect to the Ni-Cr film, whereby the product not only displays the desirably low TCR characteristics of Ni-Cr, but is also highly resistant to moisture and other environmental factors. The product also exhibits outstanding resistance to the adverse effects of electrolysis supported by the presence of moisture. The various films, including a gold film from which the terminal pads are derived, may be deposited upon the inert substrate by sequential sputtering during a single evacuation of a vacuum chamber. Desired resistive patterns may then be formed by photo-etching, subsequent to which oxidation of accessible portions of the tantalum film can be effected by heating in an appropriate atmosphere.
1,683 citations
TL;DR: The inhibitory interaction in the eye of Limulus is an integrative process that is important in determining the patterns of nervous activity in the visual system, analogous to the inhibitory component of the interaction that takes place in the vertebrate retina.
Abstract: In the compound lateral eye of Limulus each ommatidium functions as a single receptor unit in the discharge of impulses in the optic nerve. Impulses originate in the eccentric cell of each ommatidium and are conducted in its axon, which runs without interruption through an extensive plexus of nerve fibers to become a fiber of the optic nerve. The plexus makes interconnections among the ommatidia, but its exact organization is not understood. The ability of an ommatidium to discharge impulses in the axon of its eccentric cell is reduced by illumination of other ommatidia in its neighborhood: the threshold to light is raised, the number of impulses discharged in response to a suprathreshold flash of light is diminished, and the frequency with which impulses are discharged during steady illumination is decreased. Also, the activity that can be elicited under certain conditions when an ommatidium is in darkness can be inhibited similarly. There is no evidence for the spread of excitatory influences in the eye of Limulus. The inhibitory influence exerted upon an ommatidium that is discharging impulses at a steady rate begins, shortly after the onset of the illumination on neighboring ommatidia, with a sudden deep minimum in the frequency of discharge. After partial recovery, the frequency is maintained at a depressed level until the illumination on the neighboring receptors is turned off, following which there is prompt, though not instantaneous recovery to the original frequency. The inhibition is exerted directly upon the sensitive structure within the ommatidium: it has been observed when the impulses were recorded by a microelectrode thrust into an ommatidium, as well as when they were recorded more proximally in single fibers dissected from the optic nerve. Receptor units of the eye often inhibit one another mutually. This has been observed by recording the activity of two optic nerve fibers simultaneously. The mediation of the inhibitory influence appears to depend upon the integrity of nervous interconnections in the plexus: cutting the lateral connections to an ommatidium abolishes the inhibition exerted upon it. The nature of the influence that is mediated by the plexus and the mechanism whereby it exerts its inhibitory action on the receptor units are not known. The depression of the frequency of the discharge of nerve impulses from an ommatidium increases approximately linearly with the logarithm of the intensity of illumination on receptors in its vicinity. Inhibition of the discharge from an ommatidium is greater the larger the area of the eye illuminated in its vicinity. However, equal increments of area become less effective as the total area is increased. The response of an ommatidium is most effectively inhibited by the illumination of ommatidia that are close to it; the effectiveness diminishes with increasing distance, but may extend for several millimeters. Illumination of a fixed region of the eye at constant intensity produces a depression of the frequency of discharge of impulses from a nearby ommatidium that is approximately constant, irrespective of the level of excitation of the ommatidium. The inhibitory interaction in the eye of Limulus is an integrative process that is important in determining the patterns of nervous activity in the visual system. It is analogous to the inhibitory component of the interaction that takes place in the vertebrate retina. Inhibitory interaction results in the exaggeration of differences in sensory activity from different regions of the eye illuminated at different intensities, thus enhancing visual contrast.
436 citations
TL;DR: In each compound eye of the fly, about 3200 ommatidia are arranged in a peculiarly distorted hexagonal array as mentioned in this paper, and the pattern of projection can be explained by the simple principle that all the fibers carrying information from the same point of the optical environment are united into one synaptic site of the lamina ganglionaris.
Abstract: In each compound eye of the fly about 3200 ommatidia are arranged in a peculiarly distorted hexagonal array. Each ommatidium contains 7+1 rhabdomeres arranged in the asymmetrical pattern of the retinula. 7 fibers leaving each ommatidium are distributed onto 7 synaptic sites in the first optic ganglion (lamina ganglionaris), again arranged asymmetrically around the axis of the ommatidium. Taking into account the distortion of the macroscopical array and considering Kirschfeld's findings on the optical properties of the ommatidial lens, this complicated pattern of projection can be explained by the simple principle that all the fibers carrying information from the same point of the optical environment are united into one synaptic site of the lamina ganglionaris.
424 citations
TL;DR: It is shown that the unfused rhabdomeric structure of the Musca ommatidium increases the effective entrance pupil of the eye by a factor of seven compared to the classical apposition eye.
Abstract: The dioptrics of the Musca ommatidium acts as an inverting lens system. The distal endings of the rhabdomeres at the basis of the dioptric apparatus are separated and arranged in a typical asymmetric pattern. The optical axes of the individual rhabdomeres of one ommatidium are the geometric projections of the distal rhabdomere endings into the environment, inverted by 180° by the dioptric apparatus. The divergence angles between the optical axes of the rhabdomeres of one ommatidium correspond to divergence angles between the appropriate set of ommatidia in such a way, that seven rhabdomeres of seven ommatidia are looking at one point in the environment (in the intermediate region between dorsal and ventral part of the eye: eight to nine rhabdomeres of a set of eight to nine ommatidia). These facts were established from sections of living eyes and confirmed by using special optical methods in the intact animal. The pattern of the decussation of individual retinulacell axons between retina and lamina was predicted adopting the hypothesis that the fibres of retinulacells number one to six, whose rhabdomers are looking at one point in the environment, project into a single “cartridge” in the lamina. These predicted connections were confirmed by other investigators. We have therefore a one to one correspondence between a lattice of points in the environment and the lattice of “cartridges” in the lamina. It is shown that the unfused rhabdomeric structure of the Musca ommatidium increases the effective entrance pupil of the eye by a factor of seven (resp. eight to nine in the intermediate region between dorsal and ventral part of the eye) compared to the classical apposition eye. —The Musca compound eye can be regarded as a “neural superposition eye”.
363 citations