Fine structure of the anterior median eyes of the funnel-web spider Agelena labyrinthica (Araneae: Agelenidae)

Only few electron microscopic studies exist on the structure of the main eyes (anterior median eyes, AME) of web spiders. The present paper provides details on the anatomy of the AME in the funnel-web spider Agelena labyrinthica. The retina consists of two separate regions with differently arranged photoreceptor cells. Its central part has sensory cells with rhabdomeres on 2, 3, or 4 sides, whereas those of the ventral retina have only two rhabdomeres on opposite sides. In addition, the rhabdomeres of the ventral retina are arranged in a specific way: Whereas in the most ventral part they form long tangential rows, those towards the center are detached and are arranged radially. All sensory cells are wrapped by unpigmented pigment cell processes. In agelenid spiders the axons of the sensory cells exit from the middle of the cell body; their fine structure and course through the eye cup is described in detail. In the central part of the retina efferent nerve fibres were found forming synapses along the distal region of the receptor cells. A muscle is attached laterally to each eye cup that allows mainly rotational movements of the eyes. The optical performance (image resolution) of these main eyes with relatively few visual cells is discussed.     

The nauplius eye complex in 'conchostracans'(Crustacea, Branchiopoda: Laevicaudata, Spinicaudata, Cyclestherida) and its phylogenetic implications

The nauplius eye in Cyclestherida, Laevicaudata and Spinicaudata (previously collectively termed Conchostraca) consists of four cups of inverse sensory cells separated by a pigment layer and a tapetum layer. There are two lateral and two medial cups, a ventral medial cup and a posterior medial cup. The pigment and tapetum layers contain two different kinds of pigment granules, the inner pigment layer relatively large, dark (and electron dense) granules, and the outer tapetum layer light, reflective pigment granules. The presence of four cups and two different kinds of pigment granules are interpreted as autapomorphies of Phyllopoda. The position and shape of the nauplius eye in Spinicaudata is very distinct and herein interpreted as an autapomorphy of this taxon.Additional frontal eyes might be present dorsally or ventrally in varying proximity to the nauplius eye, but they have separate nerves from their sensory cells to the nauplius eye centre in the protocerebrum. Rhabdomeric structures are present in all these frontal eyes, evidencing their light sensitivity. In Lynceus biformis and L. tatei (Laevicaudata), two pairs of frontal eyes were found. In Cyclestheria hislopi (Cyclestherida), an unpaired ventral frontal eye is present. We did not find additional frontal eyes in Limnadopsis parvispinus and Caenestheriella sp. (Spinicaudata).     

Scanning motion,ocellar morphology and orientation mechanisms in the phototaxis of the nematode Mermis nigrescens

Summary The putative ocellus of Mermis females consists of a hollow cylinder of dense hemoglobin pigmentation located in the anterior tip. The exact location of the photoreceptive nerve endings, however, is unknown. During phototaxis a continual bending or scanning motion of the head (anterior 2 mm) causes the orientation of the tip to swing about the direction of the source. By turning off (shuttering) the light source whenever the tip orientation was to one side of the source direction, the average orientation of the base of the head, and eventually the body orientation, was caused to be biased about 28° to the opposite side. Because the shuttering was synchronized with the scanning motion, the scanning motion must be involved in the maintenance of orientation to light. The direction of the bias rules out a two-signal comparison mechanism of orientation and demonstrates that a deviation of the tip from the source direction must decrease, rather than increase, the illumination of the photoreceptors. These findings, and the ocellar morphology, require that the photoreceptors be located inside the hollow tube of pigmentation where they can be shadowed by the pigment during deviations of the tip. Focusing by the curved anterior end should cause a similar modulation of the illumination at this location. The occasional episodes of transverse phototaxis can be explained by the leakiness of the pigment walls to transverse illumination. Analysis of the motion of the anterior in the presence and absence of shuttering indicates that the orientation of the base of the head, due to the motion of the neck, is controlled by the signals generated during one or more cycles of the scanning motion of the head. The orientation may be regulated by the phase relationship between the photoreceptor signal and putative proprioceptive signals that indicate the bending in the head.     

Development and differentiation of the eye in Platynereis dumerilii (Annelida,Polychaeta)

The nereid polychaete, Platynereis dumerilii, possess two pairs of post-trochophoral eyes with one vitreous body each. The development of these eyes has first been observed in 2-day-old larvae. Whether the eye anlagen arise from stem cells or from undifferentiated ectodermal tissue was not determined. At first, the anlagen of the anterior and the posterior eyes adjoin each other. They separate in late 3-day-old larvae. The first separated eye complexes consist each of two supporting and two sensory cells. The supporting cells synthesize two different kinds of granules, the pigment granules of the pigment cup and the prospective tubules of the vitreous body. These tubules accumulate in the distal process of the supporting cell. The vitreous body is formed by compartments of the supporting cells filled with the osmiophilic vitreous body tubules. The short, bulbar photosensory processes bear microvilli that emerge into the ocular cavity. At the apex of each sensory cell process, a single cilium (or occasionally two) arises. The sensory cells contain a different kind of pigment granule within their necks at the level of the pigment cup. The rate of eye development and differentiation varies. New supporting cells are added to the rim of the eye cup. They contribute to the periphery of the vitreous body like onion skins, and sensory cells move between supporting cells. The older the individual compartments of the vitreous body are, the more densely packed is their content of vitreous body tubules. Elongation of the sensory and supporting cell processes of the older cells increases the volume of the eye. The eyespots of the trochophore are briefly described as of the two-celled rhabdomeric type with a single basal body with ciliary rootlet.     

The micromorphology of the nauplius eye of the estuarine calanoid copepod, Sulcanus conflictus Nicholls (Crustacea)

The nauplius eye consists of one median and two lateral ocelli, each within a pigment cup. The three pigment cups are made up from two multi-nucleate pigment cells: each cell forming one lateral cup and half of the median cup. The three cups are lined on the insides by tapetal cells which contain layers of reflectile crystals. Each of the ocelli contains six sensory cells which protrude from the rims of the pigment cups and the protruding parts are sheathed by the conjunctiva cells. The whole eye is enveloped by a thin membrane which also sheaths the proximal parts of the five nerve bundles that leave the eye. All the sensory cells of the lateral ocelli are similar and have rhabdomeric microvilli on the terminal end, and contain phaosomes and a multitude of other organelles and cytoplasmic inclusions. The complex median ocellus contains a superior group of three retinular cells, linked by interdigitating processes, and an inferior group consisting of a large central cell enclosed in two cup-shaped peripheral retinular cells. A two-tiered rhabdome arrangement exists, with a rather complex inferior rhabdome set made up of a central rhabdomere and two hemi-annulate rhabdomeres. The cytoplasm of the retinular cells of the median ocellus lack phaosomes but instead contain double-walled tubular elements, possibly formed by the inpushings of microvilli into adjacent cells. The possible functional significance of the unique arrangement seen in the median ocellus is discussed. The retinular cells are of the inverse type. There are no efferent nerve fibres from the brain nor any nervous connection between the lateral and the median ocelli.     

Components of phototaxis of the nematode Mermis nigrescens

Summary The gravid females of Mermis are positively phototaxic at the time of their migration to egglaying sites in vegetation on which their grasshopper hosts feed. On a horizontal felt surface, segments of the path traced by the tail are oriented approximately towards a source of monochromatic light in the 350–540 nm region, but are not oriented at longer wavelengths and in the dark. The components of this phototaxis include locomotion by the posterior 4/5 of the body, orientational bending of the neck region while the anterior is held above the substrate, and a scanning motion (bending) of the head region (anterior 2 mm). Like other nematodes and snakes, propulsion is associated with posteriorly propagated body waves, but unlike other animals known, the waves tend to lie perpendicular to a felt surface, and unlike other nematodes, contact with the surface is on the female's ventral surface. The body waves are initiated by the motion of the anterior 1/5 (15 mm) of the body, the average orientation of which determines the path of the following 4/5.During phototaxis, the anterior tip is swung both sideways and vertically about the direction towards the light source. The tip motion is a result of a scanning motion of the head and a slower orientational bending of the neck. The base of the head appears to be actively directed towards the source by the bending of the neck. This behavior can resolve two light sources positioned 120° apart but not 90° apart. The scanning motion of the head is independent of neck orientation and appears to enhance the probability of discovering the direction of a new source. Discovery is followed by a directed turn of the base of the head towards the source which is initiated by the bending of the neck. Locomotion of the body follows the path of the anterior through the turn and phototaxis is thus initiated.     

The larval ocelli of Golfingia misakiana (Sipuncula, Golfingiidae) and of a pelagosphera of another unidentified species

 The inverse cerebral ocelli of the pelagosphera larva of Golfingia misakiana and of another unidentified larva are composed of two or three sensory cells and one supportive pigmented cell. The sensory cells bear an array of microvilli as well as a single cilium with poor undulation of its membrane; the photoreceptive organelles are regarded as the rhabdomeric type. A striking feature of these cells is the cores, which extend within the microvilli from the tip into the midregion of the cell. It is suggested that these structures are identical with the submicrovillar cisternae found in the cerebral inverse eyes of larvae of Polychaeta. The findings allow the conclusion that in the pelagosphera of the Sipuncula, contrary to the teleplanic veliger larvae of Gastropoda, a lengthy pelagic cycle is not correlated with the development of a ciliary photoreceptor. Additionally, it is assumed that the pigment cup ocelli in larvae of Sipuncula are homologous with the cerebral inverted pigment cup ocelli of larvae of Polychaeta. Accepted: 19 March 1997     

Phototaxis in monochromatic light and microspectrophotometry of the cerebral eye of the rotifer Brachionus calyciflorus

The observed wavelength-dependent variations in the phototaxis of the rotifer Brachionus calyciflorus inform us only partially about the spectral characteristics of the sensory pigment of the eye, since these variations are also linked to the absorption spectrum of the accessory pigment(s).

The absence of phototaxis between 420 nm and 500 nm is due to the lack of sensitivity of the sensory pigments at these wavelengths

The absence of response between 650 nm and 700 nm is due to a drop in the absorbance of the accessory pigments, which consequently no longer play a screening role at these wavelengths

The existence of oriented responses between 350 nm and 420 nm and between 500 nm and 650 nm, is due to the joint intervention of the two types of pigments at these wavelengths

     

Immunohistochemical evidence for multiple photosystems in box jellyfish

Cubomedusae (box jellyfish) possess a remarkable visual system with 24 eyes distributed in four sensory structures termed rhopalia. Each rhopalium is equipped with six eyes: two pairs of pigment cup eyes and two unpaired lens eyes. Each eye type probably captures specific features of the visual environment. To investigate whether multiple types of photoreceptor cells are present in the rhopalium, and whether the different eye types possess different types of photoreceptors, we have used immunohistochemistry with a range of vertebrate opsin antibodies to label the photoreceptors, and electroretinograms (ERG) to determine their spectral sensitivity. All photoreceptor cells of the two lens eyes of the box jellyfish Tripedalia cystophora and Carybdea marsupialis displayed immunoreactivity for an antibody directed against the zebrafish ultraviolet (UV) opsin, but not against any of eight other rhodopsin or cone opsin antibodies tested. In neither of the two species were the pigment cup eyes immunoreactive for any of the opsin antibodies. ERG analysis of the Carybdea lower lens eyes demonstrated a single spectral sensitivity maximum at 485 nm suggesting the presence of a single opsin type. Our data demonstrate that the lens eyes of box jellyfish utilize a single opsin and are thus color-blind, and that there is probably a different photopigment in the pigment cup eyes. The results support our hypothesis that the lens eyes and the pigment cup eyes of box jellyfish are involved in different and specific visual tasks.     

First evidence of mitochondrial lensing in two species of the “Typhloplanoida” (Plathelminthes,Rhabdocoela): phylogenetic implications

 Based on electron-microscopical observations the light-sensing organs of Proxenetes deltoides and Ptychopera westbladi, representatives of the ”Typhloplanoida” Trigonostominae, are described. The photoreceptors in both species belong to the type of rhabdomeric pigment cup ocelli. P. deltoides has a single pigment cell and three sensory cells. P. westbladi possesses eyes made up of a single pigmented cup cell and a single sensory cell. The dioptric apparatus in the eyes of P. deltoides is formed by three proliferations of the cup cell containing giant mitochondria. In P. westbladi, the elements focalizing incoming light also consist of modified mitochondria which are arranged in the section of the cup cell covering the eye cavity. With regard to the new findings, mitochondrial lensing is hypothesized as an autapomorphy of a monophylum encompassing distinct taxa or all members of the free-living Rhabdocoela; the Neodermata also belong to this monophylum. Accepted: 21 March 1996     

Ultrastructure of the eyes of the larva of Neoheterocotyle rhinobatidis (Platyhelminthes, Monopisthocotylea), and phylogenetic implications.

The oncomiracidium of Neoheterocotyle rhinobatidis (Monogenea, Monopisthocotylea, Monocotylidae) has two pairs of eyes, each eye with a lens and pigment cup. The anterior eyes have a single rhadomere; the posterior ones, two rhadomeres. Lenses are part of the pigment cup cells, as indicated by cytoplasmic connections between them and the pigment cups, and they are of mitochondrial origin because mitochondrial cristae are present in the periphery of the lenses. This is the first time that mitochondrial lenses have been shown to exist in a neodermatan. Such lenses may be a synapomorphy of a large taxon comprising the Neodermata and its turbellarian sister groups, or they may have evolved convergently in several not closely related groups as a result of strong selection pressure to find a suitable habitat or host.     

Formation of the function of the photosensing system in early development

The function of simple eyes in two planarian species, two-eyed Girardia tigrina and multi-eyed Polycelis tenuis, has been studied. When exposed to light, planarians display a light avoidance reaction known as negative phototaxis. This reaction has been investigated in intact animals and in head and tail fragments in the course of eye regeneration after their section. Specific features of the phototaxis reaction have been described in all groups of animals. The differences in light response recovery were shown between two planarian species and two regenerating fragments. No correlation has been found between phototactic reactions and restoration of eye structure, the number of eyes, maturation of the ganglion, growth of regenerative blastema, and motor system. The phototactic response occurred two days after the recovery of the morphology of eyes and their connection with the brain. The participation of conserved and novel genes in early development of the eye function is discussed.     

Formation of the photosensing system function in early development

The function of simple prototypic eyes in two planarian species, the two ocular Girardia tigrina and the multiocular Polycelis tenuis, has been studied. When exposed to light, planarians display the light avoidance reaction known as negative phototaxis. This reaction has been investigated in intact animals and in head and tail fragments after their section in the course of eye regeneration. Specific features of the phototaxis reaction have been described in all groups of animals. The differences in light response recovery were shown between two planarian species and two regenerating fragments. No correlation between phototaxic reactions and the restoration of the eye structure, the number of eyes, the maturation of ganglion, the growth of regenerative blastema, and motor system has been found. The phototaxic response occurred two days after the recovery of the morphology of eyes and their connection with the brain. The participation of conserved and novel genes in early development of the eye function is discussed.     

Fine structural description of the lateral ocellus of Craterostigmus tasmanianus Pocock, 1902 (Chilopoda: Craterostigmomorpha) and phylogenetic considerations

The lateral lens eye of adult Craterostigmus tasmanianus Pocock, 1902 (a centipede from Australia and New Zealand) was examined by light and electron microscopy. An elliptical, bipartite eye is located frontolaterally on either side of the head. The nearly circular posterior part of the eye is characterized by a plano-convex cornea, whereas no corneal elevation is visible in the crescentic anterior part. The so-called lateral ocellus appears cup-shaped in longitudinal section and includes a flattened corneal lens comprising a homogeneous and pigmentless epithelium of cornea-secreting cells. The retinula consists of two kinds of photoreceptive cells. The distribution of the distal retinula cells is highly irregular. Variable numbers of cells are grouped together in multilayered, thread-like unions extending from the ventral and dorsal margins into the center of the eye. Around their knob-like or bilobed apices the distal retinula cells give rise to fused polymorphic rhabdomeres. Both everse and inverse cells occur in the distal retinula. Smaller, club-shaped proximal retinula cells are present in the second (limited to the peripheral region) and proximal third of the eye, where they are arranged in dual cell units. In its apical region each unit produces a small, unidirectional rhabdom of interdigitating microvilli. All retinula cells are surrounded by numerous sheath cells. A thin basal lamina covers the whole eye cup, which, together with the distal part of the optic nerve, is wrapped by external pigment cells filled with granules of varying osmiophily. The eye of C. tasmanianus seemingly displays very high complexity compared to many other hitherto studied euarthropod eyes. Besides the complex arrangement of the entire retinula, the presence of a bipartite eye cup, intraocellar exocrine glands, inverse retinula cells, distal retinula cells with bilobed apices, separated pairs of proximal retinula cells, medio-retinal axon bundles, and the formation of a vertically partitioned, antler-like distal rhabdom represent apomorphies of the craterostigmomorph eye. These characters therefore collectively underline the separate position of the Craterostigmomorpha among pleurostigmophoran centipedes. The remaining retinal features of C. tasmanianus agree with those known from other chilopod eyes and, thus, may be considered plesiomorphies. Characters like the unicorneal eye cup, sheath cells, and proximal rhabdomeres with interdigitating microvilli were already present in the ground pattern of the Pleurostigmophora. Other retinal features were developed in the ancestral lineage of the Phylactometria (e.g., large elliptical eyes, external pigment cells, polygonal sculpturations on the corneal surface). The homology of all chilopod eyes (including Notostigmophora) is based principally on the possession of a dual type retinula.     

Evolution of cerebral vesicles and their sensory organs in an ascidian larva

Sorrentino M., Manni L., Lane N. J. and Burighel P. 2000. Evolution of cerebral vesicles and their sensory organs in an ascidian larva. —Acta Zoologica (Stockholm) 81 : 243–258 The ascidian larval nervous system consists of the brain (comprising the visceral ganglion and the sensory vesicle), and, continuous with it, a caudal nerve cord. In most species two organs, a statocyst and an ocellus with ciliary photoreceptors, are contained in the sensory vesicle. A third presumptive sensory organ was sometimes found in an ‘auxiliary’ ganglionic vesicle. The development and morphology of the sensory and auxiliary ganglionic vesicles in Botryllus schlosseri and their associated organs was studied. The sensory vesicle contains a unique organ, the photolith, responding to both gravity and light. It consists of a unicellular statocyst, in the form of an expanded pigment cup receiving six photoreceptor cell extensions. Presumptive mechano‐receptor cells (S1 cells), send ciliary and microvillar protrusions to contact the pigment cup. A second group of distinctive cells (S2), slightly dorsal to the S1 cells, have characteristic microvillar extensions, resembling photoreceptor. We concur with the idea that the photolith is new and derived from a primitive statocyst and the S2 cells are the remnant of a primitive ocellus. In the ganglionic vesicle some cells contain modified cilia and microvillar extensions, which resemble the photoreceptor endings of the photolith. Our results are discussed in the light of two possible scenarios regarding the evolution of the nervous system of protochordates.     

Ultrastructural and immunocytochemical observations of the nervous systems of three macrodasyidan gastrotrichs

The nervous systems of three macrodasyidan gastrotrichs, Dactylopodola baltica, Macrodasys caudatus and Dolichodasys elongatus, were investigated using immunocytochemistry and electron microscopy. Labelling of neural structures against serotonin revealed the presence of two pairs of cerebral cells, a dorsal cerebral connective, and paired ventral nerve cords in D. baltica. In M. caudatus and D. elongatus serotonin immunoreactivity was present in a single pair of dorsal cerebral cells and the ventral nerve cords; the dorsal connective of D. elongatus was also immunoreactive to serotonin and acetylated α‐tubulin. The presence of paired, serotonin‐like immunoreactive cells in D. baltica and other species may represent the plesiomorphic condition in Macrodasyida. The fine structure of the photoreceptors in D. baltica was also investigated to explore the potential ground pattern for eyes in the Macrodasyida. The pigmented photoreceptors of D. baltica contain a unicellular pigment cup, sheath cell and sensory receptor. The pigment cup contains numerous osmiophilic granules that presumably function to shield the eyes from downwelling light in the red part of the spectrum. Projecting into the pigment cup and sheath cell are numerous microvilli from a bipolar sensory cell. A single sensory cell may represent the plesiomorphic condition in Macrodasyida, with multiplication of sensory cells representative of more derived taxa.     

昆虫趋光性及其机理的研究进展

依据目前已有资料 ,从行为学、生理学及田间应用调查等方面概述了近几十年昆虫趋光性的国内外研究进展。其中 ,行为学与生理学研究较多 ,且两者结果基本一致 ,相互补充 ,为趋光性机制的假说提供了可靠的依据。关于昆虫趋光性机制的假说较多 ,其中报道较多的是光干扰假说、光定向行为假说和生物天线假说 3种 ,现在较为普遍接受的是前两者。光干扰假说是指刺眼作用干扰昆虫的正常活动导致趋光 ,而光定向行为假说则指昆虫趋光是由于光定向行为所致     

Structure and ultrastructure of eyes and brains of Thalia democratica (Thaliacea,Tunicata, Chordata)

Salps are marine planktonic chordates that possess an obligatory alternation of reproductive modes in subsequent generations. Within tunicates, salps represent a derived life cycle and are of interest in considerations of the evolutionary origin of complex anatomical structures and life history strategies. In the present study, the eyes and brains of both the sexual, aggregate blastozooid and the asexual, solitary oozooid stage of Thalia democratica (Forskål, 1775 ) were digitally reconstructed in detail based on serial sectioning for light and transmission electron microscopy. The blastozooid stage of T. democratica possesses three pigment cup eyes, situated in the anterior ventral part of the brain. The eyes are arranged in a way that the optical axes of each eye point toward different directions. Each eye is an inverse eye that consists of two different cell types: pigment cells (pigc) and rhabdomeric photoreceptor cells (prcs). The oozooid stage of T. democratica is equipped with a single horseshoe‐shaped eye, positioned in the anterior dorsal part of the brain. The opening of the horseshoe‐shaped eye points anteriorly. Similar to the eyes of the blastozooid, the eye of the oozooid consists of pigment cells and rhabdomeric photoreceptor cells. The rhabdomeric photoreceptor cells possess apical microvilli that form a densely packed presumably photosensitive receptor part adjacent to the concave side of the pigc. We suggest correspondences of the individual eyes in the blastozooid stage to respective parts of the single horseshoe‐shaped eye in the oozooid stage and hypothesize that the differences in visual structures and brain anatomies evolved as a result of the aggregate life style of the blastozooid as opposed to the solitary life style of the oozooid.     

First evidence of unpigmented rhabdomeric photoreceptors in a Microstomum species (Plathelminthes, Macrostomorpha, Microstomidae) and ultrastructure of photoreceptor-like ciliary aggregations

Microstomum spiculifer possesses a pair of intracerebral photoreceptors each consisting of a single rhabdomeric sensory cell and two cup or mantle cells. The mantle cells are devoid of pigment. In addition, four so-called ciliary aggregations, presumed to have a light-sensing function, are present. Each ciliary aggregation represents a specialized cell with an internal cavity filled with axonemes of modified cilia. Rhabdomeric photoreceptors consisting of one to three sensory cells and a single pigmented or unpigmented mantle cell are widespread within taxa of the Plathelminthes Rhabditophora. On the contrary, the existence of two mantle cells forming the eye cup is only known for M. spiculifer and a few other species of the Macrostomida. Therefore, at least two hypotheses are possible: (1) two cup cells are a basic characteristic of the Rhabditophora and a reduction from two to one cup cell has occurred secondarily or (2) the stem species of the Rhabditophora possessed rhabdomeric eyes with one cup cell, and two mantle cells have evolved within the Macrostomorpha. The existence of ciliary aggregates has been documented for several taxa of the Plathelminthes Rhabditophora. From their distribution it can not be concluded whether these differentiations are either a basic feature of the Rhabditophora or have evolved several times convergently. Accepted: 26 September 1999     

Fine structure of light- and dark-adapted eyes of desert ants,Cataglyphis bicolor (Formicidae,Hymenoptera)

Among ants, Cataglyphis bicolor shows the best performance in optical orientation. Its eye is of the apposition type with a fused rhabdom. Morphological studies on the general struture of the eye as well as the effect of light have been carried out with transmission and scanning electron microscopy. An ommatidium is composed of a dioptric apparatus, consisting of a cornea, corneal process and a crystalline cone, the sensory retinula, which is made up of eight retinula cells in the distal half and of an additional ninth one in the proximal half. The ommatidia are separated from each other by two primary pigment cells, which surround the crystalline cone and an average of 12 secondary pigment cells, which reach from cornea to the basement membrane. The eye of Cataglyphis bicolor possesses a light intensity dependent adaptation mechanism, which causes a radial and distal movement of the pigment granules within the retinula cells and a dilatation of cisternae of the ER along the rhabdom. Until now, no overall order in arrangement of retinula cells or direction of microvilli has been found from ommatidium to ommatidium. Such an order, however, must exist, either on the retina or the lamina level, since we have proven the ant's capacity for polarized light analysis.