Similar Anatomical Structures Research Articles

Human retinal imaging using visible-light optical coherence tomography guided by scanning laser ophthalmoscopy.

We achieved human retinal imaging using visible-light optical coherence tomography (vis-OCT) guided by an integrated scanning laser ophthalmoscopy (SLO). We adapted a spectral domain OCT configuration and used a supercontinuum laser as the illumating source. The center wavelength was 564 nm and the bandwidth was 115 nm, which provided a 0.97 µm axial resolution measured in air. We characterized the sensitivity to be 86 dB with 226 µW incidence power on the pupil. We also integrated an SLO that shared the same optical path of the vis-OCT sample arm for alignment purposes. We demonstrated the retinal imaging from both systems centered at the fovea and optic nerve head with 20° × 20° and 10° × 10° field of view. We observed similar anatomical structures in vis-OCT and NIR-OCT. The contrast appeared different from vis-OCT to NIR-OCT, including slightly weaker signal from intra-retinal layers, and increased visibility and contrast of anatomical layers in the outer retina.

Abnormal auditory pathways in PHOX2B mutation positive congenital central hypoventilation syndrome.

BackgroundCongenital central hypoventilation syndrome (CCHS) is a rare disease characterized by severe central hypoventilation due to abnormal autonomic control of breathing. The PHOX2B gene, mutations of which define the disease, is expressed in a group of nuclei located in brainstem areas. Pathways controlling breathing and auditory pathways traverse very similar anatomic structures. In the present study, we measure brainstem auditory evoked potentials (BAEP) to assess auditory pathways in CCHS and investigate to which extent brainstem auditory pathways are also affected.MethodsBAEPs were measured in 15 patients with PHOX2B mutations positive CCHS (8 boys and 7 girls. mean age 6.3 yrs ± 5) as part of their regular follow-up in the Centre of reference for central hypoventilation (Robert Debré University Hospital. Paris. France).ResultsBAEP responses were found normal in nine patients (60% of the study group) and abnormal in the other six (40%). Abnormal BAEPs which resulted from brainstem dysfunction were found in three patients (20%).ConclusionDysfunction of brainstem auditory pathways can be observed in CCHS. However, auditory evoked responses can be normal in the disease, therefore suggesting much more complex yet-to-be determined interactions between pathways and functions of central control of breathing and of control of hearing.

Development of Tuberous Cassava Roots under Different Tillage Systems: Descriptive Anatomy

The interaction between the roots of cassava (Manihot esculenta Crantz) and soil physical properties has previously been analyzed. This interaction results in differences in production of plant material and in the physicochemical features of the roots, suggesting that changes in soil physical conditions may be related to changes in root anatomy. This work described the anatomical development of the tuberous cassava roots (cv. IAC 576-70) under different tillage systems. Roots grown under three different tillage systems (minimum, conventional and no tillage) were examined at 15, 30, 60, 90, 120, 150 and 180 days after planting (DAP). The tillage systems did not appear to influence root anatomy during root development; at 15 and 30 DAP roots had early secondary growth; at 60 DAP the process of tuber formation had started; at 90 DAP the secondary xylem had completely differentiated to allow storage of starch; at 120, 150 and 180 DAP roots exhibited a similar anatomical structure to that observed at 90 DAP. From these results we conclude that the anatomical structure of cassava tuberous roots is established by 90 DAP and the sequence of establishment and development of tissues that make up the tuberous roots is not influenced by tillage systems during the first 180 DAP.

Phylogenetic Analysis of Pines Based on Chloroplast trnT-trnL Intergenic Spacer DNA Sequences

This study was conducted to distinguish the pines that are too similar to differentiate using conventional methods. Pinus densiflora and Pinus sylvestris have similar anatomical structure. They both have window-like pits and dentate ray tracheids, so it is not easy to distinguish the plants. We tried to find molecular markers by comparing chloroplast DNA sequences to differentiate the pines growing in Korea. We used P. densiflora, P. densiflora for. multicaulis, P. sylvestris, P. rigida, P. rigitaeda, P. koraiensis, and P. bungeana for this study. We found that the non-coding intergenic region of trnT(UGU) and trnL(UAA) genes have differences among the species. We designed a primer set to amplify the region efficiently and compared the PCR product sequences using CLC Workbench programs to find the polymorphism. We could distinguish the species using the sequences of the amplified region and the sequences were reproducible from the pines collected in Korea.

Statistical iterative reconstruction for streak artefact reduction when using multidetector CT to image the dento-alveolar structures.

When metallic prosthetic appliances and dental fillings exist in the oral cavity, the appearance of metal-induced streak artefacts is not avoidable in CT images. The aim of this study was to develop a method for artefact reduction using the statistical reconstruction on multidetector row CT images. Adjacent CT images often depict similar anatomical structures. Therefore, reconstructed images with weak artefacts were attempted using projection data of an artefact-free image in a neighbouring thin slice. Images with moderate and strong artefacts were continuously processed in sequence by successive iterative restoration where the projection data was generated from the adjacent reconstructed slice. First, the basic maximum likelihood-expectation maximization algorithm was applied. Next, the ordered subset-expectation maximization algorithm was examined. Alternatively, a small region of interest setting was designated. Finally, the general purpose graphic processing unit machine was applied in both situations. The algorithms reduced the metal-induced streak artefacts on multidetector row CT images when the sequential processing method was applied. The ordered subset-expectation maximization and small region of interest reduced the processing duration without apparent detriments. A general-purpose graphic processing unit realized the high performance. A statistical reconstruction method was applied for the streak artefact reduction. The alternative algorithms applied were effective. Both software and hardware tools, such as ordered subset-expectation maximization, small region of interest and general-purpose graphic processing unit achieved fast artefact correction.

Canine Retina Has a Primate Fovea-Like Bouquet of Cone Photoreceptors Which Is Affected by Inherited Macular Degenerations

Retinal areas of specialization confer vertebrates with the ability to scrutinize corresponding regions of their visual field with greater resolution. A highly specialized area found in haplorhine primates (including humans) is the fovea centralis which is defined by a high density of cone photoreceptors connected individually to interneurons, and retinal ganglion cells (RGCs) that are offset to form a pit lacking retinal capillaries and inner retinal neurons at its center. In dogs, a local increase in RGC density is found in a topographically comparable retinal area defined as the area centralis. While the canine retina is devoid of a foveal pit, no detailed examination of the photoreceptors within the area centralis has been reported. Using both in vivo and ex vivo imaging, we identified a retinal region with a primate fovea-like cone photoreceptor density but without the excavation of the inner retina. Similar anatomical structure observed in rare human subjects has been named fovea-plana. In addition, dogs with mutations in two different genes, that cause macular degeneration in humans, developed earliest disease at the newly-identified canine fovea-like area. Our results challenge the dogma that within the phylogenetic tree of mammals, haplorhine primates with a fovea are the sole lineage in which the retina has a central bouquet of cones. Furthermore, a predilection for naturally-occurring retinal degenerations to alter this cone-enriched area fills the void for a clinically-relevant animal model of human macular degenerations.

Content-Based Image Retrieval of Axial Brain Slices Using a Novel LBP with a Ternary Encoding

Retrieval of similar anatomical structures of brain MR images across patients would help the expert in diagnosis of diseases. In this paper, modified local binary pattern with ternary encoding called modified local ternary pattern (MOD-LTP) is introduced, which is more discriminant and less sensitive to noise in near-uniform regions, to locate slices belonging to the same level from the brain MR image database. The ternary encoding depends on a threshold, which is a user-specified one or calculated locally, based on the variance of the pixel intensities in each window. The variancebased local threshold makes the MOD-LTP more robust to noise and global illumination changes. The retrieval performance is shown to improve by taking region-based moment features of MODLTP and iteratively reweighting the moment features of MOD-LTP based on the user’s feedback. The average rank obtained using iterated and weighted moment features of MOD-LTP with a local variance-based threshold, is one to two times better than rotational invariant LBP (Unay, D., Ekin, A. and Jasinschi, R.S. (2010) Local structure-based region-of-interest retrieval in brain MR images. IEEE Trans. Inf. Technol. Biomed., 14, 897‐903.) in retrieving the first 10 relevant images.

Variation in Stem Anatomical Characteristics of Campanuloideae Species in Relation to Evolutionary History and Ecological Preferences

BackgroundThe detailed knowledge of plant anatomical characters and their variation among closely related taxa is key to understanding their evolution and function. We examined anatomical variation in 46 herbaceous taxa from the subfamily Campanuloideae (Campanulaceae) to link this information with their phylogeny, ecology and comparative material of 56 woody tropical taxa from the subfamily Lobelioideae. The species studied covered major environmental gradients from Mediterranean to Arctic zones, allowing us to test hypotheses on the evolution of anatomical structure in relation to plant competitive ability and ecological preferences.Methodology/Principal FindingsTo understand the evolution of anatomical diversity, we reconstructed the phylogeny of studied species from nucleotide sequences and examined the distribution of anatomical characters on the resulting phylogenetic tree. Redundancy analysis, with phylogenetic corrections, was used to separate the evolutionary inertia from the adaptation to the environment. A large anatomical diversity exists within the Campanuloideae. Traits connected with the quality of fibres were the most congruent with phylogeny, and the Rapunculus 2 (“phyteumoid”) clade was especially distinguished by a number of characters (absence of fibres, pervasive parenchyma, type of rays) from two other clades (Campanula s. str. and Rapunculus 1) characterized by the dominance of fibres and the absence of parenchyma. Septate fibres are an exclusive trait in the Lobelioideae, separating it clearly from the Campanuloideae where annual rings, pervasive parenchyma and crystals in the phellem are characteristic features.Conclusions/SignificanceDespite clear phylogenetic inertia in the anatomical features studied, the ecological attributes and plant height had a significant effect on anatomical divergence. From all three evolutionary clades, the taller species converged towards similar anatomical structure, characterized by a smaller number of early wood vessels of large diameter, thinner cell-walls and alternate intervessel pits, while the opposite trend was found in small Arctic and alpine taxa. This supports the existing generalization that narrower vessels allow plants to grow in colder places where they can avoid freezing-induced embolism, while taller plants have wider vessels to minimize hydraulic resistance with their greater path lengths.

Chronic Inflammation in the Pancreas and Salivary Glands - Lessons from Similarities and Differences in Pathophysiology and Treatment Modalities

The pancreas and salivary glands have similar anatomical structures and physiological functions producing bicarbonate-rich fluid containing digestive enzymes and other components to be delivered into the gut. Despite these similarities, the two organs are also different in numerous respects, especially regarding the inflammatory diseases affecting them. This article will summarize the pathophysiology and current and potential pharmacological treatments of chronic inflammatory diseases such as chronic pancreatitis, autoimmune pancreatitis, Sjögren's syndrome and irradiation-induced salivary gland atrophy. Despite the differences, in both organs the inflammatory process is accompanied by epithelial tissue destruction and fibrosis. Both in pancreatic and in salivary research, an important task is to stop or even reverse this process. The utilization of stem/progenitor cell populations previously identified in these organs and the application of mesenchymal stem cells are very promising for such regenerative purposes. In addition, gene therapy and tissue engineering research progressively advance and have already yielded clinically beneficial preliminary results for salivary gland diseases. For the hard-to-access, hard-to-regenerate pancreas these developments may also offer new solutions, especially since salivary and pancreatic progenitors are very similar in characteristics and may be mutually useful to regenerate the respective other organ as well. These novel developments could be of great significance and may bring new hope for patients since currently used therapeutic protocols in salivary and in pancreatic chronic inflammatory diseases offer primarily symptomatic treatments and limited beneficial outcome.

Characterisation of the effects of leaf galls of Clusiamyia nitida (Cecidomyiidae) on Clusia lanceolata Cambess. (Clusiaceae): Anatomical aspects and chemical analysis of essential oil

Galls develop in different plant organs and are induced by the activity of various organisms. Some studies have investigated the ecological interactions between species of Clusia and gall-inducing insects. The goal of our study is to characterise changes in leaf anatomy caused by the activity of gall insects in Clusia lanceolata. Additionally, we also investigated the chemical composition of volatile compounds of normal leaves and those with galls to detect possible effects on the host plants. For anatomical studies, we used botanical material fixed in FAA50. Transversal sections of the leaf blade were obtained from samples of leaves located on the third and fourth nodes from both male and female individuals. Material was studied from both sexes both with unaffected leaves and leaves containing galls. Fresh leaves of C. lanceolata were used for the extraction of volatile compounds, which were submitted to stem distillation using a modified Clevenger apparatus determining the oil yields subsequently (w/w). The unaffected leaves of female and male individuals of C. lanceolata exhibit similar anatomical structures. However, galls on leaves of both sexes show anatomical differences. The activity of the gall insect Clusiamyia nitida induces several changes in the foliar anatomy and the distribution of metabolic compounds in new tissues during gall development. However, the larvae are not able to induce significant changes in the volatile compounds of inflected leaves from male and female individuals.

Metal-induced streak artifact reduction using iterative reconstruction algorithms in x-ray computed tomography image of the dentoalveolar region

The objective of this study was to reduce metal-induced streak artifact on oral and maxillofacial x-ray computed tomography (CT) images by developing the fast statistical image reconstruction system using iterative reconstruction algorithms. Adjacent CT images often depict similar anatomical structures in thin slices. So, first, images were reconstructed using the same projection data of an artifact-free image. Second, images were processed by the successive iterative restoration method where projection data were generated from reconstructed image in sequence. Besides the maximum likelihood-expectation maximization algorithm, the ordered subset-expectation maximization algorithm (OS-EM) was examined. Also, small region of interest (ROI) setting and reverse processing were applied for improving performance. Both algorithms reduced artifacts instead of slightly decreasing gray levels. The OS-EM and small ROI reduced the processing duration without apparent detriments. Sequential and reverse processing did not show apparent effects. Two alternatives in iterative reconstruction methods were effective for artifact reduction. The OS-EM algorithm and small ROI setting improved the performance.

Successive iterative restoration applied to streak artifact reduction in X-ray CT image of dento-alveolar region

X-ray computed tomography (CT) images in the dento-alveolar region are sometimes rendered unusable for diagnostic purposes due to the appearance of streak artifacts. The purpose of the study is to reduce streak artifacts appeared on dental and maxillofacial X-ray CT images by the application of modified iterative restoration method. We took advantage of the aspect that adjacent CT images often depict very similar anatomical structures within the resulting collection of thin-slice images. CT images having streak artifacts were processed using the projection data of adjacent CT images. A modified iterative correction, the maximum likelihood-expectation maximization (ML-EM) reconstruction algorithm, was employed to reduce the streak artifact caused by metallic materials in the oral cavity. It approximates between the processed image and the original projection data. First, the projection data of an intact image were obtained, and then, the next image that had streak artifacts was processed. The projection data of the processed image were obtained, and the ML-EM method was applied to the next image again. Then, the successive iterative restoration was carried out. Twelve adjacent images were processed. Each iterative restoration was carried out fifty times. Streak artifacts were observed on processed images at the initial stage, but some of them either suppressed or disappeared as the iteration progressed. The modified ML-EM method was effective to reduce streak artifacts in X-ray CT images in dento-alveolar region.

Subtraction lung image for evaluating pulmonary ventilation in xenon‐enhanced CT

The goal of this work was to develop a method of transforming a xenon-enhanced CT (Xe-CT) image of the lung, so as to overlap well with its baseline CT image, and creating a subtraction image (enhanced image minus baseline image), and to demonstrate the possibility of evaluating pulmonary ventilation using the subtraction image. Eight healthy men (37.1 +/- 10.1 yr) underwent Xe-CT lung studies. In protocol 1 for five subjects, 30% nonradioactive xenon (Xe) was inhaled for 2 min (washin) followed by air breathing for 4 min (washout). In protocol 2 for three subjects, only washin (30% Xe) for 2 min was applied. In each study, a specific range of the thorax (30 mm) in the supine position was scanned cranio-caudally three times in the helical mode: At the start and end of washin and at the end of washout in protocol 1 and at 1 min intervals from the start to end of washin in protocol 2. After each study, 10-mm-thick CT images were reconstructed to have similar anatomical structures throughout the study. Two-dimensional geometrical warping was performed on enhanced CT images so that they could geometrically overlap with the baseline CT image. Second to eighth degree polynomials were applied to the warping functions. It was derived from the Kety model that subtraction images during washin would directly reflect pulmonary ventilation. Geometrical warping achieved an increase of 0.3%-22.0% in the area, for which ventilation could be evaluated in the subtraction image. In the cases in protocol 2 where the initial lung volume was well retained throughout the study, the ratios of the specific ventilation from the subtraction image to that from the specific ventilation map were 0.88 +/- 0.06 and 0.96 +/- 0.10 for the right and left lungs, respectively. A subtraction lung image during washin would provide quantitative information on pulmonary ventilation when the baseline and enhanced images could have close lung volume and these two images could overlap well. Image subtraction requires only two scans and therefore less radiation exposure compared to ordinary protocols in Xe-CT. The proposed Xe-CT subtraction method with the geometrical warping technique could be clinically utilized for evaluating pulmonary ventilation.

Iterative correction applied to streak artifact reduction in an X-ray computed tomography image of the dento-alveolar region

Objectives Streak artifacts that appear on dental and maxillofacial X-ray computed tomography (CT) images are mainly caused by the presence of metallic prosthetic appliances. Because of the design of common CT hardware, the thin slice thickness method is routinely used in CT examinations of the dento-alveolar region. Thus, within the resulting collection of thin slice images, adjacent CT images will often depict very similar anatomical structures. We took advantage of this aspect and employed iterative correction to reduce the streak artifact caused by metallic materials.

Theories of impaired consciousness in epilepsy.

Although the precise mechanisms for control of consciousness are not fully understood, emerging data show that conscious information processing depends on the activation of certain networks in the brain and that the impairment of consciousness is related to abnormal activity in these systems. Epilepsy can lead to transient impairment of consciousness, providing a window into the mechanisms necessary for normal consciousness. Thus, despite differences in behavioral manifestations, cause, and electrophysiology, generalized tonic-clonic, absence, and partial seizures engage similar anatomical structures and pathways. We review prior concepts of impaired consciousness in epilepsy, focusing especially on temporal lobe complex partial seizures, which are a common and debilitating form of epileptic unconsciousness. We discuss a "network inhibition hypothesis" in which focal temporal lobe seizure activity disrupts normal cortical-subcortical interactions, leading to depressed neocortical function and impaired consciousness. This review of the major prior theories of impaired consciousness in epilepsy allows us to put more recent data into context and to reach a better understanding of the mechanisms important for normal consciousness.

Estudo farmacobotânico de duas espécies de Anileira (Indigofera suffruticosa e Indigofera truxillensis, Leguminosae) com propriedades farmacológicas

The Leguminosae genus Indigofera has two important pharmacological species, Indigofera suffruticosa and I. truxillensis. The present work aims to establish a morphological quality control for vegetal drugs obtained from these two species through the analyses of surface and organoleptic features in leaflet powder, and also through anatomical and histochemical studies in leaflet, shoot and root. Powder analyses evidenced that shape and ornamentation of the simple trichomes are good diagnostic characters for the sprayed drug, with particles bigger than 53 µm; moreover, odor was strong and awkward, with non-persistent, weakly bitter taste in I. suffruticosa, and weak and pleasant, with more persistent, bitter taste in I. truxillensis. Similar anatomical structures were found in leaflets, cauline internodes and lateral roots in both species, except for papillose epidermic cells that occurred in both leaflet sides in I. truxillensis, and only on the adaxial side in I. suffruticosa. Phenolic compounds were found in leaflets, and alkaloids in shoots and roots (greater amount) of both studied species. The occurrence of alkaloids in roots of I. suffruticosa and I. truxillensis seems to be similar to that observed in ichthyotoxic legume species that belong to the so-called timbo complex, whose roots are toxic due to rotenoids.

Is sclerophylly of Mediterranean evergreens an adaptation to drought?

SUMMARYThe potential role of sclerophylly (leaf hardness and rigidity) in the control of leaf dehydration and rehydration was investigated in two sclerophylls (Viburnum tinus and Ilex aquifolium) and two non‐sclerophylls (Hedera helix ssp. helix and Sambucus nigra). After leaves were dehydrated in the pressure chamber, water transport from the apoplast (mainly consisting of xylem conduits and mechanical cells) to symplast was detected 15 min from pressure release, in terms of a spontaneous increase in leaf water potential (ϕ1). This ϕ1 increase was much larger in sclerophylls than in non‐sclerophylls.Positive pressures applied to leaves simulated the tensions developing in the leaf apoplast under water stress conditions, causing water to be expelled from leaf xylem conduits and mechanical cells and transferred to the leaf symplast, thus leading to symplast rehydration and to the consequent ϕ1 increase.No correlation was found between the leaf modulus of elasticity at full turgor or the degree of sclerophylly (in terms of the ratio of leaf d. wt to surface area) and the characteristic rehydration time of the leaves, i.e. between the two main parameters expressing the rigidity of the leaf blade and the rate of leaf rehydration. However, when changes in ϕ1 were measured as a function of leaf water deficit (RWD), equal ϕ1s corresponded with larger RWDs during leaf rehydration than during leaf dehydration in the two non‐sclerophylls. In particular, the two sclerophylls showed rehydration of their leaf apoplast and symplast completely and simultaneously. By contrast, the two non‐sclerophylls showed a persisting water loss, localized, it is likely, in their xylem conduits and mechanical cells.In other words, the two sclerophylls did not recover from water loss more rapidly than non‐sclerophylls but they recovered from xylem cavitation more completely. The major elasticity of the cavitation strain shown by the two sclerophylls studied was interpreted as of advantage to plants subjected to diurnal large drops in ϕ1 followed by nocturnal recovery. This is the case in Mediterranean sclerophylls growing in areas characterized by high humidity of the air condensing on the soil at night. The same mechanism of cavitation recovery, however, would be useless in very xeric areas.The hypothesis is advanced that sclerophylly of Mediterranean species may derive from similar anatomical structures developed in species formerly adapted to more humid environments which later migrated to more arid zones.

Effects of site and menstrual cycle on barrier function and stratum corneum water-holding capacity.

Areas of the skin with similar anatomical structure may have different functional behaviour. In vivo barrier function and stratum corneum water-holding capacity during the menstrual cycle on two sites of the volar forearm (upper and lower) and on the anterior aspect of the thigh were evaluated using the plastic occlusion stress test (POST). 13 healthy women (age 31 ± 4) with regular menses entered the study. POST was performed by applying a plastic chamber (1.8 cm diameter) on the skin for 24 h. After removal the skin surface water loss (SSWL) was measured using an evaporimeter (EP1-Servomed, Sweden) every 5 min for 30 min. Measurements were taken on the 10th and 25th day of the menstrual cycle. Statistical analysis was performed using one-factor Anova for repeated measures. Free and bound water compartments of evaporation were also analysed. Higher hydration and SSWL were detectable on the 25th day of the cycle. However, no significant influence of menstrual cycle was found. Significant differences between the upper and lower volar foream were detected (P < 0.001). The differences observed were mainly related to the evaporation of bound water, confirming a different barrier function at the sites investigated; therefore, it must be taken into account that adjacent skin sites with equal structure may have different functional behaviour.

Registration error quantification of a surface-based multimodality image fusion system.

This paper presents a new reference data set and associated quantification methodology to assess the accuracy of registration of computerized tomography (CT) and magnetic-resonance (MR) images. Also described is a new semiautomatic surface-based system for registering and visualizing CT and MR images. The registration error of the system was determined using a reference data set that was obtained from a cadaver in which rigid fiducial tubes were inserted prior to imaging. Registration error was measured as the distance between an analytic expression for each fiducial tube in one image set and transformed samples of the corresponding tube obtained from the other. Registration was accomplished by first identifying surfaces of similar anatomic structures in each image set. A transformation that best registered these structures was determined using a nonlinear optimization procedure. Even though the root-mean-square (rms) distance at the registered surfaces was similar to that reported by other groups, it was found that rms distances for the tubes were significantly larger than the final rms distances between the registered surfaces. It was also found that minimizing rms distance at the surface did not minimize rms distance for the tubes.

Microanatomy of the anterior median eyes and its possible relation to polarized‐light reception inLycosa tarentula(Araneae, Lycosidae)

Abstract Microanatomy of the anterior median eyes (AME) of a lycosid spider (Lycosa tarentula) shows two classes of photoreceptors in the retina: dorsal and median visual cells (A) are polygonal in cross‐section and bear rhabdomeres on all their faces; ventral visual cells (B), rectangular in section, bear rhabdomeres only on two opposite faces; rhabdomes are aligned in parallel series and successive lines of rhabdoms are oriented orthogonally to each other. Receptor A cells are wider than ? cells, and about twice as numerous. In AME optic nerve, axons are also of two types, large and small, and the optic centre shows thick and narrow fibres, from the second order neurons, being separated by connective and glial cells. Anterior median eyes of second stage juveniles already present the same structure as those of adults. A similar anatomical structure was previously described in the AME of an agelenid spider by Schröer (1974). Since the detection and analysis of polarized light by agelenid and lycosid AME have also been demonstrated, it is suggested that the analysers of the e‐vector of sky‐polarized light are in the receptor ? cells and that the analysis is a successive process using a twisting of the retina due to the action of two muscles.