Principal Eyes Research Articles

Eye-specific detection and a multi-eye integration model of biological motion perception.

'Biological motion' refers to the distinctive kinematics observed in many living organisms, where visually perceivable points on the animal move at fixed distances from each other. Across the animal kingdom, many species have developed specialized visual circuitry to recognize such biological motion and to discriminate it from other patterns. Recently, this ability has been observed in the distributed visual system of jumping spiders. These eight-eyed animals use six eyes to perceive motion, while the remaining two (the principal anterior medial eyes) are shifted across the visual scene to further inspect detected objects. When presented with a biologically moving stimulus and a random one, jumping spiders turn to face the latter, clearly demonstrating the ability to discriminate between them. However, it remains unclear whether the principal eyes are necessary for this behavior, whether all secondary eyes can perform this discrimination, or whether a single eye-pair is specialized for this task. Here, we systematically tested the ability of jumping spiders to discriminate between biological and random visual stimuli by testing each eye-pair alone. Spiders were able to discriminate stimuli only when the anterior lateral eyes were unblocked, and performed at chance levels in other configurations. Interestingly, spiders showed a preference for biological motion over random stimuli - unlike in past work. We therefore propose a new model describing how specialization of the anterior lateral eyes for detecting biological motion contributes to multi-eye integration in this system. This integration generates more complex behavior through the combination of simple, single-eye responses. We posit that this in-built modularity may be a solution to the limited resources of these invertebrates' brains, constituting a novel approach to visual processing.

When a glimpse is enough: Partial mimicry of jumping spiders by insects

Many flies and moths mimic the frontal appearance of jumping spiders. This type of mimicry, which we term as partial mimicry, can be distinguished from Batesian mimicry since the mimic has spider resembling patterns only in certain parts of the body, and not the entire body. The presence of spider-like patterns is obvious only at certain angles suggesting that the mimic is frequently targeted by its predators from particular angles. We tested this hypothesis using Deep Convolutional Neural Networks (DCNNs). First, we trained the network on images of forward facing jumping spiders, where features such as the large principal eyes, small lateral eyes and outstretched legs were evident. Then we tested the classifier on images of jumping spider mimicking flies and moths. A probability value according to the likelihood of the image being a jumping spider or not was assigned by the classifier. We show that the classifier was more likely to misidentify mimicking flies and moths as jumping spiders, but that this probability varied according to the species tested. We further tested it on images of flies from different angles and by taking into consideration the visual acuity of potential predators. Our results suggest that neural networks can be efficient tools for testing evolutionary hypotheses, and that partial mimicry may be a result of the effect of the signaling angle and orientation of the mimics in combination with the likelihood that predators may depend on cognitive shortcuts to identify insects as prey. Further experiments incorporating the properties of the visual system of predators (such as vision in ultraviolet) would result in a better understanding of the evolution of partial mimicry.

Spatial acuity-sensitivity trade-off in the principal eyes of a jumping spider: possible adaptations to a 'blended' lifestyle.

Jumping spiders (Salticidae) are diurnal visual predators known for elaborate, vision-mediated behaviour achieved through the coordinated work of four pairs of camera-type eyes. One pair ('principal' eyes) is responsible for colour and high spatial acuity vision, while three pairs ('secondary' eyes) are mostly responsible for motion detection. Based on its unusual capacity to visually discriminate specific prey in very low, but also under bright light settings, we investigated the structure of the principal and one pair of secondary eyes (antero-lateral eyes) of Cyrba algerina to determine how these eyes achieve the sensitivity, while maintaining spatial acuity, needed to sustain behaviour in low light. Compared to salticids that live in bright light, the principal eyes of C. algerina have a short focal length, and wide contiguous twin rhabdomeres that support optical pooling, overall favouring sensitivity (0.39 μm2), but without fully compromising acuity (12.4 arc min). The antero-lateral eye retinae have large receptors surrounded by pigment granules, providing effective shielding from scattered light. These adaptations may be beneficial for a xeric salticid species with a 'blended' lifestyle: generally living and hunting under stones in the dark, but sometimes venturing above them, in dramatically different light conditions.

Attention and distraction in the modular visual system of a jumping spider.

Animals must selectively attend to relevant stimuli and avoid being distracted by unimportant stimuli. Jumping spiders (Salticidae) do this by coordinating eyes with different capabilities. Objects are examined by a pair of high-acuity principal eyes, whose narrow field of view is compensated for by retinal movements. The principal eyes overlap in field of view with motion-sensitive anterior-lateral eyes (ALEs), which direct their gaze to new stimuli. Using a salticid-specific eyetracker, we monitored the gaze direction of the principal eyes as they examined a primary stimulus. We then presented a distractor stimulus visible only to the ALEs and observed whether the principal eyes reflexively shifted their gaze to it or whether this response was flexible. Whether spiders redirected their gaze to the distractor depended on properties of both the primary and distractor stimuli. This flexibility suggests that higher-order processing occurs in the management of the attention of the principal eyes.

Visual pathways in the brain of the jumping spider Marpissa muscosa.

Some animals have evolved task differentiation among their eyes. A particular example is spiders, where most species have eight eyes, of which two (the principal eyes) are used for object discrimination, whereas the other three pairs (secondary eyes) detect movement. In the ctenid spider Cupiennius salei, these two eye types correspond to two visual pathways in the brain. Each eye is associated with its own first- and second-order visual neuropil. The second-order neuropils of the principal eyes are connected to the arcuate body, whereas the second-order neuropils of the secondary eyes are linked to the mushroom body. We explored the principal- and secondary eye visual pathways of the jumping spider Marpissa muscosa, in which size and visual fields of the two eye types are considerably different. We found that the connectivity of the principal eye pathway is the same as in C. salei, while there are differences in the secondary eye pathways. In M. muscosa, all secondary eyes are connected to their own first-order visual neuropils. The first-order visual neuropils of the anterior lateral and posterior lateral eyes are connected with a second-order visual neuropil each and an additional shared one (L2). In the posterior median eyes, the axons of their first-order visual neuropils project directly to the arcuate body, suggesting that the posterior median eyes do not detect movement. The L2 might function as an upstream integration center enabling faster movement decisions.

Spider eyes inspire compact camera

Jumping spiders are brilliant hunters, accurately leaping relatively large distances to surprise their prey. They can plan these surprise pounces just right thanks to their fantastic depth perception. Each of their two principal eyes has a double-layered retina. Spider behaviorists believe the creatures use their poppy-seed-sized brains to compare the relative sharpness of the two images from the two retinal layers and use that information to estimate distances. “We’re still not 100% sure how spiders actually achieve this because we don’t read spider minds,” says Zhujun Shi, a grad student in physics at Harvard University. Still, she and collaborators Qi Guo and Federico Capasso were inspired by the critters and decided to mimic their retinas to make a simple depth-sensing camera that could lead to simple, low-power sensors for cell phones and robots (Proc. Natl. Acad. Sci. U.S.A. 2019, DOI: 10.1073/pnas.1912154116). Existing systems require an infrared light source or moving

Photoreceptor projection from a four-tiered retina to four distinct regions of the first optic ganglion in a jumping spider.

Jumping spiders have four pairs of eyes (ocelli) of which only the principal eyes (PEs) are used to detect features of objects. Photoreceptors in the retina of the PEs form four layers (PL1-4) and terminate in the first optic ganglion (FOG). Here, we focus on Hasarius adansoni because it has unique depth vision besides color vision and its FOG appears to contribute to the initial processing of these visual modalities. We first investigated the neuroanatomical organization of the FOG. The three-dimensional structure of the FOG revealed by synapsin immunostaining is horseshoe-shaped and consists of four terminal zones (TZ1-4). Then, we traced single photoreceptors through serial sections and found that green-sensitive receptors of PL1 and 2 terminate in TZ1 and 2, respectively, by keeping retinotopic organization. In contrast to TZ1 and 2, TZ3 receives terminals of ultraviolet-sensitive receptors from lateral regions of both PL3 and 4, while photoreceptors of the medial region of PL3 and 4 terminate in TZ4. We further studied details of photoreceptor terminals and the branching pattern of interneurons in the FOG in Golgi stained preparations. Photoreceptors have long lateral processes in each terminal zone. Some photoreceptors terminating in TZ3 have branches innervating TZ1, indicating that TZ1 receives different spectral information. A type of interneuron connects TZ1 and 2, while others have branches within a single terminal zone or in the entire FOG. These results suggest that TZ1 and 2 contribute to color, shape, and depth vision, while TZ3 and 4 have specific roles for UV vision.

Rapid and step-wise eye growth in molting diving beetle larvae

However complex a visual system is, the size (and growth rate) of all its components-lens, retina and nervous system-must be precisely tuned to each other for the system to be functional. As organisms grow, their eyes must be able to achieve and maintain emmetropia, a state in which photoreceptors receive sharp images of objects that are at infinity. While there has been ample research into how vertebrates coordinate eyes growth, this has never been addressed in arthropods with camera eyes, which tend to grow dramatically and typically in a step-wise manner with each molt (ecdysis). Here, we used histological and optical methods to measure how the larval eyes of Sunburst Diving Beetles (Thermonectus marmoratus, Coleoptera, Dytiscidae) grow, and how well optical and morphological parameters match, during the dramatic growth that occurs between two consecutive larval stages. We find that the eye tubes of the principal eyes of T. marmoratus grow substantially around molt, with the vitreous-like crystalline cone contributing the most to the overall growth. Lenses also reform relatively quickly, undergoing a period of dysfunction and then regaining the ability to project sharp images onto the retina around 8 h post-molt.

Differential expression of retinal determination genes in the principal and secondary eyes of Cupiennius salei Keyserling (1877).

BackgroundTranscription factors that determine retinal development seem to be conserved in different phyla throughout the animal kingdom. In most representatives, however, only a few of the involved transcription factors have been sampled and many animal groups remain understudied. In order to fill in the gaps for the chelicerate group of arthropods, we tested the expression pattern of the candidate genes involved in the eye development in the embryo of the wandering spider Cupiennius salei. One main objective was to profile the molecular development of the eyes and to search for possible variation among eye subtype differentiation. A second aim was to form a basis for comparative studies in order to elucidate evolutionary pathways in eye development.ResultsWe screened the spider embryonic transcriptome for retina determination gene candidates and discovered that all except one of the retinal determination genes have been duplicated. Gene expression analysis shows that the two orthologs of all the genes have different expression patterns. The genes are mainly expressed in the developing optic neuropiles of the eyes (lateral furrow, mushroom body, arcuate body) in earlier stages of development (160 to 220 h after egg laying). Later in development (180 to 280 h after egg laying), there is differential expression of the genes in disparate eye vesicles; for example, Cs-otxa is expressed only in posterior-lateral eye vesicles, Cs-otxb, Cs-six1a, and Cs-six3b in all three secondary eye vesicles, Cs-pax6a only in principal eye vesicles, Cs-six1b in posterior-median, and posterior-lateral eye vesicles, and Cs-six3a in lateral and principal eye vesicles.ConclusionsPrinciple eye development shows pax6a (ey) expression, suggesting pax6 dependence, although secondary eyes develop independently of pax6 genes and show differential expression of several retinal determination genes. Comparing this with the other arthropods suggests that pax6-dependent median eye development is a ground pattern of eye development in this group and that the ocelli of insects, the median eyes of chelicerates, and nauplius eyes can be homologised. The expression pattern of the investigated genes makes it possible to distinguish between secondary eyes and principal eyes. Differences of gene expression among the different lateral eyes indicate disparate function combined with genetic drift.Electronic supplementary materialThe online version of this article (doi:10.1186/s13227-015-0010-x) contains supplementary material, which is available to authorized users.

CNS microstructure in the wandering wolf spider Arctosa kwangreungensis (Araneae: Lycosidae)

AbstractThe supraesophageal ganglion of the wolf spider Arctosa kwangreungensis is made up of a protocerebral and tritocerebral ganglion, whereas the subesophageal ganglionic mass is composed of a single pair of pedipalpal ganglia, four pairs of appendage ganglia, and a fused mass of abdominal neuromeres. In the supraesophageal ganglion, complex neuropile masses are located in the protocerebrum which include optic ganglia, the mushroom bodies, and the central body. Characteristically, the only nerves arising from the protocerebrum are the optic nerves, and the neuropiles of the principal eyes are the most thick and abundant in this wandering spider. The central body which is recognized as an important association center is isolated at the posterior of the protocerebrum and appears as a complex of highly condensed neurons. These cells give off fine parallel bundles of axons arranged in the mushroom bodies. The subesophageal nerve mass can be divided into two main tracts on the basis of direction of the neuropiles. The dorsal tracts are contributed to from the motor or interneurons of each ganglion, whereas the ventral tracts are from incoming sensory axons.

How aquatic water-beetle larvae with small chambered eyes overcome challenges of hunting under water.

A particularly unusual visual system exists in the visually guided aquatic predator, the Sunburst Diving Beetle, Thermonectus marmoratus (Coleoptera: Dytiscidae). The question arises: how does this peculiar visual system function? A series of experiments suggests that their principal eyes (E1 and E2) are highly specialized for hunting. These eyes are tubular and have relatively long focal lengths leading to high image magnification. Their retinae are linear, and are divided into distinct green-sensitive distal and UV and polarization-sensitive proximal portions. Each distal retina, moreover, has many tiers of photoreceptors with rhabdomeres the long axis of which are peculiarly oriented perpendicular to the light path. Based on detailed optical investigations, the lenses of these eyes are bifocal and project focused images onto specific retinal tiers. Behavioral experiments suggest that these larvae approach prey within their eyes' near-fields, and that they can correctly gauge prey distances even when conventional distance-vision mechanisms are unavailable. In the near-field of these eyes object distance determines which of the many retinal layers receive the best-focused images. This retinal organization could facilitate an unusual distance-vision mechanism. We here summarize past findings and discuss how these eyes allow Thermonectus larvae to be such successful predators.

A scanning retina with a narrow field of view: Do jumping spiders examine entire objects or only parts?

Event Abstract Back to Event A scanning retina with a narrow field of view: Do jumping spiders examine entire objects or only parts? Cynthia Tedore1* and Sönke Johnsen2 1 Lund University, Biology, Sweden 2 Duke University, Biology, United States Jumping spiders (Salticidae) are famous for their principal eyes’ high visual acuity and bizarre retinal morphology. The field of view subtended by the retinae of the principal eyes is roughly 0.6 degrees horizontally by 21 degrees vertically. The retinae are capable of significant movement, presumably allowing an individual to scan and mentally piece together features of entire objects. In high-stakes situations requiring rapid reaction times, it is unclear whether salticids’ unusual retinal morphology might affect visual processing speed and/or the amount of information gathered. Because various salticid species (which prey upon each other) live in close proximity, we hypothesized that, when a male encounters another salticid and endeavors to identify it, he should minimize the time spent visually scanning over it, and in turn, his risk of being predated upon, by searching for species-specific features on the first body part he spots (i.e. either the face or the legs), and making a recognition decision based on that body part, or a small group of body parts, alone. In the presence of conspecific pheromones, which provide an additional clue as to the identity of a spider, we would expect males to be even more likely to use this visual shortcut. To test our hypotheses, we showed male Lyssomanes viridis jumping spiders animated images of conspecifics and composite images which combined the facial coloration and morphology of one sex or species with the leg coloration of another. Males’ courtship versus threat displays indicated whether a stimulus was perceived as a potential mate or threat. By comparing males’ display types and visual inspection times (as an index of confusion) in response to the various images in the presence versus absence of female pheromones, we were able to deduce whether males tend to inspect both the face and legs, or just one or the other, and whether this changes in the presence of pheromones. Counter to our predictions, we discovered that males examine features on both the face and legs before coming to a decision as to the identity of a spider, and that they continue to do so in the presence of pheromones. This suggests that salticids do take the time to visually scan over entire objects to identify them, despite the fact that quick reaction times in high-stakes encounters with other salticids would seem to be adaptive. Keywords: Vision, Chemoreception, jumping spider, Retina, field of view Conference: International Conference on Invertebrate Vision, Fjälkinge, Sweden, 1 Aug - 8 Aug, 2013. Presentation Type: Oral presentation preferred Topic: Eye design, optics and spatial vision Citation: Tedore C and Johnsen S (2019). A scanning retina with a narrow field of view: Do jumping spiders examine entire objects or only parts?. Front. Physiol. Conference Abstract: International Conference on Invertebrate Vision. doi: 10.3389/conf.fphys.2013.25.00115 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 28 Feb 2013; Published Online: 09 Dec 2019. * Correspondence: Dr. Cynthia Tedore, Lund University, Biology, Lund, SE-221 00, Sweden, cynthia.tedore@uni-hamburg.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Cynthia Tedore Sönke Johnsen Google Cynthia Tedore Sönke Johnsen Google Scholar Cynthia Tedore Sönke Johnsen PubMed Cynthia Tedore Sönke Johnsen Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Secondary eyes mediate the response to looming objects in jumping spiders ( Phidippus audax , Salticidae)

Some species have sensory systems divided into subsystems with morphologically different sense organs that acquire different types of information within the same modality. Jumping spiders (family Salticidae) have eight eyes. Four eyes are directed anteriorly to view objects in front of the spider: a pair of principal eyes track targets with their movable retinae, while the immobile anterior lateral (AL) eyes have a larger field of view and lower resolution. To test whether the principal eyes, the AL eyes, or both together mediate the response to looming stimuli, we presented spiders with a video of a solid black circle that rapidly expanded (loomed) or contracted (receded). Control spiders and spiders with their principal eyes masked were significantly more likely to back away from the looming stimulus than were spiders with their AL eyes masked. Almost no individuals backed away from the receding stimulus. Our results show that the AL eyes alone mediate the loom response to objects anterior to the spider.

Hyperacute motion detection by the lateral eyes of jumping spiders

Jumping spiders (Salticidae) are renowned for their high performing visual system. In addition to their prominent forward-facing telescope-like principal eyes, salticids possess two or three pairs of secondary eyes used for wide-angle motion detection. Salticids orient towards relevant sources of motion detected by the secondary eyes, enabling them to inspect the stimulus with their spatially acute principal eyes. The anteriormost pair of secondary eyes, the anterior lateral (AL) eyes, also faces forward and has higher spatial acuity than the other, laterally-facing, secondary eyes. We used small computer-generated targets to elicit orienting saccades from tethered jumping spiders in order to examine the perceptual limits of the AL eyes. We describe the contrast thresholds of male and female spiders, investigate the reaction time between stimulus appearance and initiation of orientation, as well as the minimum distance a stimulus must travel before eliciting a saccade. Our results show that female spiders react to lower contrast stimuli than males and demonstrate that the secondary eyes can detect stimulus displacements considerably smaller than the inter-receptor angle.

Visual fields and eye morphology support color vision in a color-changing crab-spider

Vision plays a major role in many spiders, being involved in prey hunting, orientation or substrate choice, among others. In Misumena vatia, which experiences morphological color changes, vision has been reported to be involved in substrate color matching. Electrophysiological evidence reveals that at least two types of photoreceptors are present in this species, but these data are not backed up by morphological evidence. This work analyzes the functional structure of the eyes of this spider and relates it to its color-changing abilities. A broad superposition of the visual field of the different eyes was observed, even between binocular regions of principal and secondary eyes. The frontal space is simultaneously analyzed by four eyes. This superposition supports the integration of the visual information provided by the different eye types. The mobile retina of the principal eyes of this spider is organized in three layers of three different types of rhabdoms. The third and deepest layer is composed by just one large rhabdom surrounded by dark screening pigments that limit the light entry. The three pairs of secondary eyes have all a single layer of rhabdoms. Our findings provide strong support for an involvement of the visual system in color matching in this spider.

'Don’t eat me!' – Trade-offs between recognition speed and accuracy in a jumping spider

Event Abstract Back to Event 'Don’t eat me!' – Trade-offs between recognition speed and accuracy in a jumping spider Cynthia Tedore1* and Sönke Johnsen1 1 Duke University, Biology, United States Jumping spiders’ principal eyes, specialized for analysis of shape and pattern, have unusually narrow fields of view subtending a small fraction of the angle subtended by a conspecific at normal viewing distances. This should theoretically retard visual processing time. Encounters with other predaceous arthropods, including other jumping spiders, can be dangerous. Quick and accurate reactions can make the difference between life and death. We therefore hypothesized: 1) Selection should favor precise visual templates for multiple conspecific features so that multiple features need not be evaluated in order for spiders to make quick and accurate identifications, and 2) When pheromones are present, males should allocate less time to visual inspection, and, as a result, make more recognition errors when challenged with unnatural combinations of visual features. We tested our hypotheses by presenting male Lyssomanes viridis with computer-animated images of conspecifics, heterospecifics, and artificial combinations of features, in the presence versus absence of female pheromones. Subjects’ courtship versus threat responses indicated whether an image was perceived as a potential mate or threat. Males demonstrated only coarse visual templates for conspecific features, and were more likely to respond appropriately to images when pheromones were absent. When pheromones were present, males spent less time examining images, and frequently approached heterospecific and composite images with courtship displays. This suggests males reconstruct complete mental representations of objects when visual cues are the only ones available. When chemical cues are also available, males seem to be inspecting a subset of visual features and, as a result, are liable to make potentially fatal recognition errors. Figure 1 Keywords: Chemoreception, jumping spider, multimodal communication, recognition, Vision, Visual Field Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster (but consider for Participant Symposium) Topic: Sensory: Vision Citation: Tedore C and Johnsen S (2012). 'Don’t eat me!' – Trade-offs between recognition speed and accuracy in a jumping spider. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00295 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Apr 2012; Published Online: 07 Jul 2012. * Correspondence: Ms. Cynthia Tedore, Duke University, Biology, Durham, North Carolina, 27708, United States, cynthia.tedore@uni-hamburg.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract Supplemental Data The Authors in Frontiers Cynthia Tedore Sönke Johnsen Google Cynthia Tedore Sönke Johnsen Google Scholar Cynthia Tedore Sönke Johnsen PubMed Cynthia Tedore Sönke Johnsen Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

What do Sunburst Diving beetle larvae see? The role of polarization sensitivity

Event Abstract Back to Event What do Sunburst Diving beetle larvae see? The role of polarization sensitivity Annette Stowasser1* and Elke K. Buschbeck1 1 University of Cincinnati, Department of Biological Sciences, United States Although polarization sensitivity has been studied fairly well in adult insects, little is known about it in larvae. Nevertheless it is likely that at least some larvae, such as Thermonectus marmoratus, could substantially benefit from it. In previous work, the possibility of polarization sensitivity in one of their retinas had been raised based on the ultrastructure. However, because light travels through more distal photoreceptors (that potentially could influence polarization) before reaching this region, the polarization sensitivity remained unclear. We used electrophysiological methods and single-cell staining to confirm polarization sensitivity in the proximal retina of eyes E1 and E2. Larvae of the aquatic beetle T. marmoratus are highly successful visually guided predators. Their principal eyes E1 and E2 each have a single lens, are tubular in shape, and have at least two distinct retinas: the distal and proximal retinas. The former is sensitive to green light, whereas, the latter is sensitive to UV light. Based on transmission electron microscopy the proximal retina of E1 and E2 is composed of three distinct cell types: T1, T2, and T3. These cells are arranged in an alternating pattern. Cells of type T1 and T2 are somewhat larger, and have vertically and horizontally aligned microvilli, respectively. T3 is organized similar to T1, but it’s rhabdomeric portion is much smaller. As expected from the ultrastructure, cells of the type T1 are most sensitive to vertically polarized light, while cells of the type T2 are most sensitive to horizontally polarized light. While we could not directly confirm the polarization sensitivity of T3 cells, there is evidence that we recorded from all three morphologically distinct cell types. Two cell populations were most sensitive to vertically polarized light, with polarization sensitivity (PS) values of 13.9 (± 7.5 s.d., n = 16) and 3.1 (± 0.4 s.d., n = 4) respectively. Cells most sensitive to horizontally polarized light showed a PS value of 9.3 (± 3.2 s.d., n = 14). Compared to other insects these values are relatively high, suggesting that polarization sensitivity likely plays an important role in the visual system of these larvae. Based on their natural history and behavior, possible functions are: (1) finding water after hatching, (2) finding the shore before pupation, and (3) making prey more visible, by filtering out horizontally polarized haze, and/or by using polarization features for prey detection. Behavioral experiments will be necessary to determine for which of these behaviors polarization sensitivity might be important. Acknowledgements We thank John E. Layne for lending us his rotating arm. We thank Shannon Werner for helping with beetle care and Randy Morgan and the Cincinnati Zoo & Botanical Garden for providing Sunburst Diving Beetles. This work was supported by the NSF (IOS0545978 and IOS1050754). Keywords: coleoptera, Dytiscidae, stemmata Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster Presentation (see alternatives below as well) Topic: Sensory: Vision Citation: Stowasser A and Buschbeck EK (2012). What do Sunburst Diving beetle larvae see? The role of polarization sensitivity . Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00172 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Apr 2012; Published Online: 07 Jul 2012. * Correspondence: Ms. Annette Stowasser, University of Cincinnati, Department of Biological Sciences, Cincinnati, United States, annette.stowasser@uc.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Annette Stowasser Elke K Buschbeck Google Annette Stowasser Elke K Buschbeck Google Scholar Annette Stowasser Elke K Buschbeck PubMed Annette Stowasser Elke K Buschbeck Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Electrophysiological evidence for polarization sensitivity in the camera-type eyes of the aquatic predacious insect larva,Thermonectus marmoratus(Coleoptera: Dytiscidae)

Polarization sensitivity has most often been studied in mature insects, yet it is likely that larvae also make use of this visual modality. The aquatic larvae of the predacious diving beetle Thermonectus marmoratus are highly successful visually guided predators, with a UV-sensitive proximal retina that, according to its ultrastructure, has three distinct cell types with anatomical attributes that are consistent with polarization sensitivity. In the present study we used electrophysiological methods and single-cell staining to confirm polarization sensitivity in the proximal retinas of both principal eyes of these larvae. As expected from their microvillar orientation, cells of type T1 are most sensitive to vertically polarized light, while cells of type T2 are most sensitive to horizontally polarized light. In addition, T3 cells probably constitute a second population of cells that are most sensitive to light with vertical e-vector orientation, characterized by shallower polarization modulations, and smaller polarization sensitivity (PS) values than are typical for T1 cells. The level of PS values found in this study suggests that polarization sensitivity probably plays an important role in the visual system of these larvae. Based on their natural history and behavior, possible functions are: (1) finding water after hatching, (2) finding the shore before pupation, and (3) making prey more visible, by filtering out horizontally polarized haze, and/or using polarization features for prey detection.

Flicker-induced eye movements and the behavioural temporal cut-off frequency in a nocturnal spider

We investigated changes in the eye muscle activity in the spider Cupiennius salei as a response to temporal intensity modulations. These spiders are known to enhance eye muscle activity in their principal eyes when moving stimuli are detected in the secondary eyes. We measured the activity of the dorsal eye muscle using a small telemetric unit attached to the spiders' prosoma and confronted the animals to flicker stimuli presented on a cathode ray tube monitor. We registered a significant increase in eye muscle activity as response to temporal light intensity modulations, which implies that no directed motion is required to trigger the spiders' response. This allowed the determination of the behavioural temporal cut-off frequency. None of the frequencies higher than 8.6 cycles s(-1) and all of the frequencies lower than 4.3 cycles s(-1) elicited a significant increase in eye muscle activity. A behavioural cut-off frequency of only a few cycles per second is well in line with the temporal properties of the photoreceptor cells determined using intracellular recordings. A relatively low temporal resolution and a relatively high spatial resolution suit well C. salei's lifestyle as a nocturnal sit-and-wait hunter.

Spectral sensitivity of the principal eyes of sunburst diving beetle, Thermonectus marmoratus (Coleoptera: Dytiscidae), larvae

The principal eyes of sunburst diving beetle, Thermonectus marmoratus, larvae are among the most unusual eyes in the animal kingdom. They are composed of long tubes connecting bifocal lenses with two retinas: a distal retina situated a few hundred micrometers behind the lens, and a proximal retina that is situated directly beneath. A recent molecular study on first instar larvae suggests that the distal retina expresses a long-wavelength-sensitive opsin (TmLW), whereas the proximal retina predominantly expresses an ultraviolet-sensitive opsin (TmUV II). Using cloning and in situ hybridization we here confirm that this opsin distribution is, for the most part, maintained in third instar larvae (with the exception of the TmUV I that is weakly expressed only in proximal retinas of first instar larvae). We furthermore use intracellular electrophysiological recordings and neurobiotin injections to determine the spectral sensitivity of individual photoreceptor cells. We find that photoreceptors of the proximal retina have a sensitivity curve that peaks at 374-375 nm. The shape of the curve is consistent with the predicted absorbance of a single-opsin template. The spectral response of photoreceptors from the distal retina confirms their maximum sensitivity to green light with the dominant λ-peak between 520 and 540 nm, and the secondary β-peak between 340 and 360 nm. These physiological measurements support molecular predictions and represent important steps towards understanding the functional organization of the unusual stemmata of T. marmoratus larvae.