The human Retina - Nr. 3 (2019)

With far more than 100 million nerve cells, the retina is the first stage of our visual system and our window to the outside world. The process includes detection of light impulses (photons) by different light receptors, in general called rods (120 million cells) and cones (6 million cells), and the fast and continuous translation, filtration and post-procession into electrical signals (or nerve impulses). These signals are then passed through the optical nerve’s 1.5 million fibres to the visual centre of the brain and reinterpreted into a cohesive image.The flexibility and economy with which retinal cells work together remains beyond our powers of imagination: the eye reports numerous signals to the brain at once, including separate detection of light (light on) and dark (light off), general patterns and finest details, movements and different hues (including: red, green and blue). This literally makes the eye a camera with 10 to 15 different films and despite it appears so naturally to us, the perception of an image is the result of a most complex interaction process involving millions of cells and the electrical signals they produce and pass on to the brain. What you can see on this image is the (1) rods and cones layer. It is located below the pigment epithelia which has been cut away during the preparation and is not visible on this image (black space on top). Below the rods and cones layer you can find the (2) outer nuclear layer (ONL) which contains the nuclei of the rods and cones. The adjacent (3) outer plexiform layer (OPL) is followed by the (4) inner plexiform layer (IPL), which contains numerous cell types, including horizontal cells, bipolar cells and amacrine cells. At the very bottom you can see the (5) inner nuclear layer (INL), followed by the (6) ganglion cell layer with two (7) blood vessels shown at left and (8) nerve fibers (which form the optical nerve).

Beyond our imagination - the retina (of the human eye)

With far more than 100 million nerve cells, the retina is the first stage of our visual system and our window to the outside world. The process includes detection of light impulses (photons) by different light receptors, in general called rods (120 million cells) and cones (6 million cells), and the fast and continuous translation, filtration and post-procession into electrical signals (or nerve impulses). These signals are then passed through the optical nerve’s 1.5 million fibres to the visual centre of the brain and reinterpreted into a cohesive image.The flexibility and economy with which retinal cells work together remains beyond our powers of imagination: the eye reports numerous signals to the brain at once, including separate detection of light (light on) and dark (light off), general patterns and finest details, movements and different hues (including: red, green and blue). This literally makes the eye a camera with 10 to 15 different films and despite it appears so naturally to us, the perception of an image is the result of a most complex interaction process involving millions of cells and the electrical signals they produce and pass on to the brain. What you can see on this image is the (1) rods and cones layer. It is located below the pigment epithelia which has been cut away during the preparation and is not visible on this image (black space on top). Below the rods and cones layer you can find the (2) outer nuclear layer (ONL) which contains the nuclei of the rods and cones. The adjacent (3) outer plexiform layer (OPL) is followed by the (4) inner plexiform layer (IPL), which contains numerous cell types, including horizontal cells, bipolar cells and amacrine cells. At the very bottom you can see the (5) inner nuclear layer (INL), followed by the (6) ganglion cell layer with two (7) blood vessels shown at left and (8) nerve fibers (which form the optical nerve).

Drosophila Eye Development

Coloured scanning electron micrograph (SEM) of two mutant Fruitfly (Drosophila melanogaster) heads. Wildtype (i.e. normal) Fruitflies have two compound eyes (red) - one on either side of the head. Small bristles between the single lenses of the eye make sure it cannot be covered with dust or dirt particles. Genetically manipulated Flies can either lack compound eyes completely (left) or have additional eyes on the antennae, legs and other body areas (right). Fruit flies are widely used in genetic experiments, particularly in mutation experiments, because they reproduce rapidly and their genetic systems are well understood. This image visualizes how easily the results of the genetic modification can be observed in the Fruitfly which is one of the main reasons why it is still the most frequently used model organism in genetics despite more than 100 years of experimental research. left: Sine oculis-1 (so1) variant which lacks the compound eyes completely. right: Eyeless variant with ectopically expressed compound eyes under dpp-promotor in all imaginal discs. Handkoloriertes Raster-Elektronen-Mikroskopiebild zweier Fruchtfliegen-Mutanten. Die Taufliege oder Fruchtfliege (Drosophila melanogaster) ist das klassische Untersuchungsobjekt in der Genetik und Entwicklungsbiologie. Wildtypen, d.h. genetisch unveränderte Fruchtfliegen, besitzen zwei grosse rote Komplexaugen - je eines auf jeder Seite des Kopfes. Die Komplexaugen werden durch Borsten zwischen den winzigen Einzelaugen vor Verschmutzung und Staub geschützt. Die Entwicklung des Auges wird während der Embryonalentwicklung Larve durch bestimmte Gene gesteuert. Durch Veränderungen (Mutation) von Genen lassen sich z.B. Position oder Morphologie der Komplexaugen gezielte beeinflussen. Im Vergleich zu einem Säugetier ist die Fruchtfliege genetisch viel einfacher aufgebaut und weist lediglich vier Paar Chromosomen auf. Diese Tatsache hat, neben der raschen Generationsfolge und einfachen Zucht, wesentlich dazu

Drosophila Eye Development

Coloured scanning electron micrograph (SEM) of two mutant Fruitfly (Drosophila melanogaster) heads. Wildtype (i.e. normal) Fruitflies have two compound eyes (red) - one on either side of the head. Small bristles between the single lenses of the eye make sure it cannot be covered with dust or dirt particles. Genetically manipulated Flies can either lack compound eyes completely (left) or have additional eyes on the antennae, legs and other body areas (right). Fruit flies are widely used in genetic experiments, particularly in mutation experiments, because they reproduce rapidly and their genetic systems are well understood. This image visualizes how easily the results of the genetic modification can be observed in the Fruitfly which is one of the main reasons why it is still the most frequently used model organism in genetics despite more than 100 years of experimental research. left: Sine oculis-1 (so1) variant which lacks the compound eyes completely. right: Eyeless variant with ectopically expressed compound eyes under dpp-promotor in all imaginal discs. Handkoloriertes Raster-Elektronen-Mikroskopiebild zweier Fruchtfliegen-Mutanten. Die Taufliege oder Fruchtfliege (Drosophila melanogaster) ist das klassische Untersuchungsobjekt in der Genetik und Entwicklungsbiologie. Wildtypen, d.h. genetisch unveränderte Fruchtfliegen, besitzen zwei grosse rote Komplexaugen - je eines auf jeder Seite des Kopfes. Die Komplexaugen werden durch Borsten zwischen den winzigen Einzelaugen vor Verschmutzung und Staub geschützt. Die Entwicklung des Auges wird während der Embryonalentwicklung Larve durch bestimmte Gene gesteuert. Durch Veränderungen (Mutation) von Genen lassen sich z.B. Position oder Morphologie der Komplexaugen gezielte beeinflussen. Im Vergleich zu einem Säugetier ist die Fruchtfliege genetisch viel einfacher aufgebaut und weist lediglich vier Paar Chromosomen auf. Diese Tatsache hat, neben der raschen Generationsfolge und einfachen Zucht, wesentlich dazu

Drosophila Eye Development

Coloured scanning electron micrograph (SEM) of two mutant Fruitfly (Drosophila melanogaster) heads. Wildtype (i.e. normal) Fruitflies have two compound eyes (red) - one on either side of the head. Small bristles between the single lenses of the eye make sure it cannot be covered with dust or dirt particles. Genetically manipulated Flies can either lack compound eyes completely (left) or have additional eyes on the antennae, legs and other body areas (right). Fruit flies are widely used in genetic experiments, particularly in mutation experiments, because they reproduce rapidly and their genetic systems are well understood. This image visualizes how easily the results of the genetic modification can be observed in the Fruitfly which is one of the main reasons why it is still the most frequently used model organism in genetics despite more than 100 years of experimental research. left: Sine oculis-1 (so1) variant which lacks the compound eyes completely. right: Eyeless variant with ectopically expressed compound eyes under dpp-promotor in all imaginal discs. Handkoloriertes Raster-Elektronen-Mikroskopiebild zweier Fruchtfliegen-Mutanten. Die Taufliege oder Fruchtfliege (Drosophila melanogaster) ist das klassische Untersuchungsobjekt in der Genetik und Entwicklungsbiologie. Wildtypen, d.h. genetisch unveränderte Fruchtfliegen, besitzen zwei grosse rote Komplexaugen - je eines auf jeder Seite des Kopfes. Die Komplexaugen werden durch Borsten zwischen den winzigen Einzelaugen vor Verschmutzung und Staub geschützt. Die Entwicklung des Auges wird während der Embryonalentwicklung Larve durch bestimmte Gene gesteuert. Durch Veränderungen (Mutation) von Genen lassen sich z.B. Position oder Morphologie der Komplexaugen gezielte beeinflussen. Im Vergleich zu einem Säugetier ist die Fruchtfliege genetisch viel einfacher aufgebaut und weist lediglich vier Paar Chromosomen auf. Diese Tatsache hat, neben der raschen Generationsfolge und einfachen Zucht, wesentlich dazu

Calcitic Microlens

"In a clever twist of nature, the sea has eyes in its stars." John Roach, National Geographic. Scientists have discovered a species of brittle star, Ophiocoma wendtii, with crystalline microlens plates in its skeleton that have exceptional optical performance: according to Gordon Hendler and Joanna Aizenberg, the scientists that made the discovery, the microlens plates in the brittle stars outer skeleton are even compensated for physical effects that bother us when we fabricate lenses in the laboratory (birefringence and spherical aberration). From the microlenses the light is focused onto nerve bundles located beneath which transmit the optical information to the rest of the body. Although yet unproven, the whole photoreceptive system of the brittle star is thought to function like a compound eye, allowing the detection of predators or seeking out hiding places. The study of creatures such as O. wendtii has important implications for science. How the brittle star's visual system works may be useful, for example, in developing technologies for chip design in optical networks and better lithographic techniques. Thereby, the microlens arrays of the brittle star O. wendtii proofs that nature is often a step ahead of people and foreshadows technical developments.

Calcitic Microlens

"In a clever twist of nature, the sea has eyes in its stars." John Roach, National Geographic. Scientists have discovered a species of brittle star, Ophiocoma wendtii, with crystalline microlens plates in its skeleton that have exceptional optical performance: according to Gordon Hendler and Joanna Aizenberg, the scientists that made the discovery, the microlens plates in the brittle stars outer skeleton are even compensated for physical effects that bother us when we fabricate lenses in the laboratory (birefringence and spherical aberration). From the microlenses the light is focused onto nerve bundles located beneath which transmit the optical information to the rest of the body. Although yet unproven, the whole photoreceptive system of the brittle star is thought to function like a compound eye, allowing the detection of predators or seeking out hiding places. The study of creatures such as O. wendtii has important implications for science. How the brittle star's visual system works may be useful, for example, in developing technologies for chip design in optical networks and better lithographic techniques. Thereby, the microlens arrays of the brittle star O. wendtii proofs that nature is often a step ahead of people and foreshadows technical developments.

Euglena

Euglena is a genus of unicellular flagellate protists. It is the best known and most widely studied member of the phylum Euglenozoa, a diverse group containing some 44 genera and at least 800 species. Most species of Euglena have photosynthesizing chloroplasts within the body of the cell, which enable them to feed by autotrophy, like plants. However, they can also take nourishment heterotrophically, like animals. Euglena possess a red eyespot, an organelle composed of carotenoid pigment granules. The red spot itself is not thought to be photosensitive. Rather, it filters the sunlight that falls on a light-detecting structure at the base of the flagellum (a swelling, known as the paraflagellar body), allowing only certain wavelengths of light to reach it. As the cell rotates with respect to the light source, the eyespot partially blocks the source, permitting the Euglena to find the light and move toward it (a process known as phototaxis). Euglena lacks a cell wall. Instead, it has a pellicle made up of a protein layer supported by a substructure of microtubules, arranged in strips spiraling around the cell. The action of these pellicle strips sliding over one another gives Euglena its exceptional flexibility and contractility.

Jumping Spider

Often fuzzy and measuring less than a half inch in body length, Jumping spiders (Salticids) can run, climb, and - jump! Thereby the small predators can achieve stunning distances of more than 50 times its body size. Surprisingly, the extreme jumps are not the result of very strong or muscular legs. Instead, Jumping spiders quickly increase the blood pressure to their legs, which causes the legs to extend and propel the spider through the air. Prior to jumping, whatsoever, the spider glues silk threads to the surface beneath, to allow a quick and safe return to the perch, if required. Interestingly, Salticids rely on an excellent visual system. Like most other spiders, they have eight eyes on their face. An enormous pair in the center facing towards the front, and one adjacent pair of eyes to both sides give them an almost alien appearance. The remaining smaller eyes are located on the dorsal surface of the cephalothorax and allow almost 360° angle panoramic view. In general, animals have developed several different visual systems to accurately and reliably judge distance and depth. Humans, for example, have binocular stereovision. Because our eyes are spaced apart, they receive visual information from different angles, which our brains use to automatically triangulate distances. Other animals, such as insects, adjust the focal length of the lenses in their eyes, or move their heads side to side to create an effect called motion parallax — nearer objects will move across their field of vision more quickly than objects farther away. However, Jumping spiders have eyes that are too close together for binocular stereovision and don’t appear to use motion parallax while hunting. So how are these creatures able to perceive depth? In fact, these amazing creatures have developed a way of gauging distances that appears to be unique in the animal kingdom: rather than having a single layer of photoreceptor cells, as in our case, the spider's retina of the principal e

Turban Eye

Mayflies produce eggs that are laid on the surface of lakes or streams where they sink to the bottom. Naiads moult 20-30 times over a period of few months up to one year or even more. They live primarily on algae or diatoms, but some species are also predatory. The lifespan of adult mayflies is very short and varies between hours and 2-3 weeks. Since the primary function of the adult is reproduction, the mouthparts are non-functional and the digestive tract is filled with air. Adults have short flexible antennae, usually three ocelli and relatively large compound eyes. In most species, males additionally feature very large turban-shaped dorsal eyes, i.e. greatly enlarged compound eyes that are located on top of the head. The dorsal turban-eyes are especially designed to boost light sensitivity and allow vision at low light. At dawn, male mayflies fly close to the water surface in search of females, trying to detect females against the dim background of the sky. The turban-eyes are only capable of detecting ultra-violet (UV) light. In some species (e.g. European Mayfly) the turban-eye of the male is divided: The upper portion is for seeing movement, and the lower portion is specialized for seeing details. The females have smaller eyes.

Pseudoscorpion

Pseudoscorpions are small arachnids with a flat, segmented, pear-shaped body. Despite being harmless and inoffensive creatures, this individual was able to move very quickly to escape. Pseudoscorpions got their name from a pair of huge pincers (pedipalps), resembling those of scorpions. But unlike true Scorpions they have a rounded abdomen that does not extend into a segmented tail with a stinger. The small creatures usually range from 2 to 8 millimetres (0.08 to 0.31 in) in length, with yellowish to red or dark brown colors. Pseudoscorpions are generally beneficial to humans and prey on clothes moth larvae, carpet beetle larvae, booklice, ants, mites, and small flies. Chelifer cancroides is the most commonly found species in homes, where they are often observed in rooms with dusty books. A venom gland and duct are located in the mobile finger of the pincers. The venom is used to capture and immobilize prey. During digestion, a mildly corrosive fluid is poured over the prey to liquify the remains externally before they are ingested. They enter homes by "riding along" attached to insects (known as phoresy). The jaws (chelicera; have a look at the beautiful structure in the center) are used to spin silk which is used to make disk-shaped cocoons for mating, molting, or waiting out cold weather. A comb-like structure (serrula externa), which can be seen on the left side of the chelicera in a close-up picture, is used for grooming. In the center of the chelicera is a membrane called serrula interna. It helps to prevent food and fluids from escaping. Also, two pairs of sensory setae can be found on the chelicera and additional structures which resemble plant pores are located on the cephalothorax (above the eyes in the overview picture). Scientists believe that the latter detect bending and stress on the cuticule and call them lyrifissures. Pseudoscorpions breathe through spiracles on their abdomen (not shown), a trait they share with the insects. Most species have o

Divided Eye of a Whirligig Beetle

Portrait of a Whirligig Beetle (Gyrinus substriatus). The most interesting insect compound eyes are those of whirligig beetles (Family Gyrinidae). You've probably seen groups of these lively little metallic beetles on ponds and slow streams. They have two sets of compound eyes. One pair of eyes is on top of the head to see what's going on above, i.e. to watch for predators. The other pair of eyes is located below the water surface to look out for smaller aquatic insects on which they prey on themselves. The antennae are also divided which is very unusual among beetles: the short and plump part is placed about at water level while the hairy lower part remains permanently submerged. The long bristles are used to detect vibrations of struggling insects that have fallen in and float with the current.

Juvenile Bug (Pentatomidae)

An insect's compound eye is an engineering marvel: high resolution, wide field of view, and incredible sensitivity to motion, all in a compact package. Immature insects without metamorphosis, like this juvenile bug (Pentatomidae), are called nymphs. Examples are dragonflies, grasshoppers, or bugs. Nymphs do have compound eyes and look like adults, though more ommatidia (single lenses) are added each time the nymphs shed their skins. Each single lens does not see the entire picture. Instead, it only sees a small proportion and what the insect finally sees looks similar to a jigsaw puzzle. In general, compound eyes are fairly large in proportion to an insect's head. They are smallest in insects that spend their lives on the ground while flying insects have the largest compound eyes. Flying predatory insects have the very largest. A dragonfly's head is made up almost entirely of eyes and can see 360°. Each eye may have more than 20'000 single lenses (ommatidia). Male flying insects have larger eyes than females because they spend much of their time to flying around looking for females. It would be difficult to find mates if both sexes would search actively, so females usually stay still and let the males search for them. The most interesting insect eyes are those of whirlagig beetles (Family Gyrinidae). You've probably seen groups of these lively little black beetles on ponds and slow streams. They have two sets of compound eyes. One pair of eyes is on top of the head to see what's going on above, i.e. to watch for predators. The other pair of eyes is located below the water surface to look out for smaller aquatic insects on which they prey on themselves. Finally, insects to not necessarily see the same colors that we do. Many can see ultra-violet (UV) wavelenghts but do not see red (e.g. ants) at the other end of the spectrum. Other insects do not see yellow which is why yellow outside lights do not attract flying insects. Many flowers attract bees to pollinate

Cat Flea (Ctenocephalides felis)

Frontansicht eines Katzenflohs. Parasiten sind normalerweise auf einen bestimmten Wirt spezialisiert. Katzenflöhe auf Katzen, nur ausnahmsweise werden auch Menschen gestochen (wenn keine Katze in der nähe ist). Portrait of a cat flea (Ctenocephalides felis). The cat flea's primary host is the domestic cat, but this is also the primary flea infesting dogs in most of the world. Cat fleas can transmit other parasites and infections to dogs and cats and also to humans. The most prominent of these are Bartonella, murine typhus, and apedermatitis. The tapeworm Dipylidium caninum can be transmitted when a flea is swallowed by pets or humans. In addition, cat fleas have been found to carry Borrelia burgdorferi, the etiologic agent of Lyme disease, but their ability to transmit the disease is unclear.

Pupae of malaria carrying mosquito (Anopheles gambiae)

Mosquito larvae have well developed mouthparts, which are used to induce a current and feed from algae and bacteria. Mosquitos go through four stages of their life cycle: egg, larvae, pupae and imago (adult insect). Adult females lay their eggs in standing water. The first three stages are aquatic and last 5–14 days, depending on the species and temperature. The pupa is comma-shaped, as in Anopheles when viewed from the side, and is commonly called a "tumbler". As with the larvae, pupae must come to the surface frequently to breathe, which they do through a pair of respiratory trumpets on the cephalothorax. After a few days, the pupa rises to the water surface, the dorsal surface of the cephalothorax splits and the adult mosquito emerges.

Fruitfly Head FIB

Fruitfly head cut with Focused Ion Beam Microscope (FIB)

Stalk-Eyed Fly (Diasemopsis meigenii)

Among the true flies (Diptera) there are many examples of species with bizarre head projections, including eyes that are located on stalks. In the Diopsid family, the exaggeration of eye-stalks can be extreme, with males having an eyespan greater than their body length. Many stalk-eyed flies exhibit sexual dimorphism for eyespan, with males having much greater eyespan than females. Stalk-eyed flies are a well-documented example of sexual selection, because of the strong female preference for males with large eyespans.

Stalk-Eyed Fly, Teleopsis whitei, male

Head of a stalk-eyed fly females and males. Stalk-eyed flies are distinguished by the possession of eyestalks: projections from the sides of the head with the eyes at the end. Males generally have more elongated eyestalks than females. This family (Diopsidae) of flies has been subject to a considerable amount of research due to their unique morphology to find out how it arises through forces of sexual selection and natural selection. Though the evolution of exaggerated male traits due to female mate choice was at one point considered rather controversial, stalk-eyed flies are now regarded as a classic example of animals that exhibit sexually selected traits.

Stalk-Eyed Fly, Teleopsis whitei, female

Head of a stalk-eyed fly females and males. Stalk-eyed flies are distinguished by the possession of eyestalks: projections from the sides of the head with the eyes at the end. Males generally have more elongated eyestalks than females. This family (Diopsidae) of flies has been subject to a considerable amount of research due to their unique morphology to find out how it arises through forces of sexual selection and natural selection. Though the evolution of exaggerated male traits due to female mate choice was at one point considered rather controversial, stalk-eyed flies are now regarded as a classic example of animals that exhibit sexually selected traits.

Stalk-Eyed Fly (Teleopsis thaii)

Head of a stalk-eyed fly females and males. Stalk-eyed flies are distinguished by the possession of eyestalks: projections from the sides of the head with the eyes at the end. Males generally have more elongated eyestalks than females. This family (Diopsidae) of flies has been subject to a considerable amount of research due to their unique morphology to find out how it arises through forces of sexual selection and natural selection. Though the evolution of exaggerated male traits due to female mate choice was at one point considered rather controversial, stalk-eyed flies are now regarded as a classic example of animals that exhibit sexually selected traits.

Stalk-Eyed Fly (Diasemopsis meigenii)

Head of a stalk-eyed fly females and males. Stalk-eyed flies are distinguished by the possession of eyestalks: projections from the sides of the head with the eyes at the end. Males generally have more elongated eyestalks than females. This family (Diopsidae) of flies has been subject to a considerable amount of research due to their unique morphology to find out how it arises through forces of sexual selection and natural selection. Though the evolution of exaggerated male traits due to female mate choice was at one point considered rather controversial, stalk-eyed flies are now regarded as a classic example of animals that exhibit sexually selected traits.

Stalk-Eyed Fly, Diasemopsis thaii, male

Head of a stalk-eyed fly females and males. Stalk-eyed flies are distinguished by the possession of eyestalks: projections from the sides of the head with the eyes at the end. Males generally have more elongated eyestalks than females. This family (Diopsidae) of flies has been subject to a considerable amount of research due to their unique morphology to find out how it arises through forces of sexual selection and natural selection. Though the evolution of exaggerated male traits due to female mate choice was at one point considered rather controversial, stalk-eyed flies are now regarded as a classic example of animals that exhibit sexually selected traits.

Stalk-Eyed Fly, Diasemopsis thaii, female

Head of a stalk-eyed fly females and males. Stalk-eyed flies are distinguished by the possession of eyestalks: projections from the sides of the head with the eyes at the end. Males generally have more elongated eyestalks than females. This family (Diopsidae) of flies has been subject to a considerable amount of research due to their unique morphology to find out how it arises through forces of sexual selection and natural selection. Though the evolution of exaggerated male traits due to female mate choice was at one point considered rather controversial, stalk-eyed flies are now regarded as a classic example of animals that exhibit sexually selected traits.

The human Retina - Nr. 3 (2019)

With far more than 100 million nerve cells, the retina is the first stage of our visual system and our window to the outside world. The process includes detection of light impulses (photons) by different light receptors, in general called rods (120 million cells) and cones (6 million cells), and the fast and continuous translation, filtration and post-procession into electrical signals (or nerve impulses). These signals are then passed through the optical nerve’s 1.5 million fibres to the visual centre of the brain and reinterpreted into a cohesive image.The flexibility and economy with which retinal cells work together remains beyond our powers of imagination: the eye reports numerous signals to the brain at once, including separate detection of light (light on) and dark (light off), general patterns and finest details, movements and different hues (including: red, green and blue). This literally makes the eye a camera with 10 to 15 different films and despite it appears so naturally to us, the perception of an image is the result of a most complex interaction process involving millions of cells and the electrical signals they produce and pass on to the brain. What you can see on this image is the (1) rods and cones layer. It is located below the pigment epithelia which has been cut away during the preparation and is not visible on this image (black space on top). Below the rods and cones layer you can find the (2) outer nuclear layer (ONL) which contains the nuclei of the rods and cones. The adjacent (3) outer plexiform layer (OPL) is followed by the (4) inner plexiform layer (IPL), which contains numerous cell types, including horizontal cells, bipolar cells and amacrine cells. At the very bottom you can see the (5) inner nuclear layer (INL), followed by the (6) ganglion cell layer with two (7) blood vessels shown at left and (8) nerve fibers (which form the optical nerve).

FHNW_LensQuer448_mini_bl

FHNW_LensQuer447_mini_Hellblau

acherontia atropos

Compound eye of acherontia atropos

FHNW_ChrysisIgnita_001a340_mini2

spider mite eye

Most if not all Acari react to optical stimuli and thus demonstrate photosensitivity, yet not much is known about mite vision. Spider mites have two pairs of relatively large eyes. They can be used for color vision and to detect near-ultraviolet light waves.The pair of eyes on each side of Tetranychus urticae consists of fifteen retinular cells, six pigment cells, six corneal cells, and one vitreous cell. Responses of the summer form of adult females placed in near-ultraviolet and green light have shown that two separate photoreceptor systems are present and are able to discriminate between upper and lower leaf surface. Spider mites rely on vision to locate the preferred habitate, avoid deleterious UV-radiation, and to find a place to hide.

FliegenEye57256_H_mini

WhiteflyEye56871mini

Evolution of Eyes

Sunlight was and still is one of the most important selective forces for the evolution of living organisms. As a consequence, catching photons and obtain high quality vision is under strong selection pressure which has lead to the evolution of many different types of eyes under various environmental conditions, over the last 5 billion years. In this image the surface (lens) area of a crustacean compound eye is shown. In general, each unit, or ommatidium, consists of a lens that forms an image onto a small number of receptor cells (which are called 'rhabdom') and the resolving power of compound eyes depends on the size and number of facets. In contrast to insects, whatsoever, shrimps and lobsters have compound eyes with square, homogeneous box-like structures. This has caused considerable confusion in the 1950s and 1960s because no optical function could be ascribed to square lens elements and for more than 20 years shrimps were believed to be blind. However, in these animals ray-bending is not done by the lens but by mirror in the wall of each omatidia and the mirror-box design only works with right-angle corners and not hexagons, which accounts for the square facets. Clearly, the resultant image as seen by insects and crustaceans is of comparable quality.

Drosophila compound eye

Coloured scanning electron micrograph (SEM) of a small area from the left eye from the common Fruitfly (Drosophila melanogaster). These small insects are widely used in genetic experiments, particularly in mutation experiments, because they reproduce rapidly and their genetic systems are well understood. Wildtype (i.e. normal) Fruitflies have two compound eyes (red) – one on each side of the head. Each eye is a regular structure built up with 750 repeating units, or single lenses. Each single lens sends signals to the fly’s brain where they are combined and arranged into a mosaic map of the visual “outside world”. Tiny bristles between the lenses make sure it cannot be covered with dust or dirt particles.

Corneal Nipple-Array or Moth Eye-Array

Antireflective Coating – ‘Corneal Nipple Arrays’ in Insect EyesEyes naturally possess a refracting surface - without it, image formation would be impossible. But if the transition in the refractive index is sharp, reflections might be produced which can impair image quality. Moreover, the bright glare from an animal's eye can alert predators. Therefore, some insects have evolved fascinating nanoscale anti-reflection devices in the surface of their compound eyes.The compound eye of the Old Lady (Mormo maura) moth reveals highly ordered nano-structured conical protrusions on the corneal cuticle. It has been shown that this so-called ‘corneal nipple array’ or ‘moth-eye array’ has almost perfect anti-reflection properties. The crucial factor to reduce reflection of light is the nipple height. Only nipples with a height of > 50-200nm are anti-reflective. Corneal nipple arrays best known from nocturnal moths and butterflies (Lepidoptera), however they are widespread among insects and have probably evolved more than once. The nipples of the Old Lady moth are arranged in a hexagonal, almost crystalline fashion. In parallel to their anti-reflective function, the nipples also increase the surface area and thereby enhance the light sensitivity of the moth, though light transmittance increase may only be of minor importance compared to the potentially life-saving ability of the anti-reflective coating.Studying nano-structured corneal nipple arrays of insect eye facets helps to design better amorphous silicon thin film solar cells and improves the antireflective coating on notebooks and smartphones.

Corneal Nipple-Array or Moth Eye-Array

Antireflective Coating – ‘Corneal Nipple Arrays’ in Insect EyesEyes naturally possess a refracting surface - without it, image formation would be impossible. But if the transition in the refractive index is sharp, reflections might be produced which can impair image quality. Moreover, the bright glare from an animal's eye can alert predators. Therefore, some insects have evolved fascinating nanoscale anti-reflection devices in the surface of their compound eyes.The compound eye of the Old Lady (Mormo maura) moth reveals highly ordered nano-structured conical protrusions on the corneal cuticle. It has been shown that this so-called ‘corneal nipple array’ or ‘moth-eye array’ has almost perfect anti-reflection properties. The crucial factor to reduce reflection of light is the nipple height. Only nipples with a height of > 50-200nm are anti-reflective. Corneal nipple arrays best known from nocturnal moths and butterflies (Lepidoptera), however they are widespread among insects and have probably evolved more than once. The nipples of the Old Lady moth are arranged in a hexagonal, almost crystalline fashion. In parallel to their anti-reflective function, the nipples also increase the surface area and thereby enhance the light sensitivity of the moth, though light transmittance increase may only be of minor importance compared to the potentially life-saving ability of the anti-reflective coating.Studying nano-structured corneal nipple arrays of insect eye facets helps to design better amorphous silicon thin film solar cells and improves the antireflective coating on notebooks and smartphones.

Corneal Nipple-Array or Moth Eye-Array

Antireflective Coating – ‘Corneal Nipple Arrays’ in Insect EyesEyes naturally possess a refracting surface - without it, image formation would be impossible. But if the transition in the refractive index is sharp, reflections might be produced which can impair image quality. Moreover, the bright glare from an animal's eye can alert predators. Therefore, some insects have evolved fascinating nanoscale anti-reflection devices in the surface of their compound eyes.The compound eye of the Old Lady (Mormo maura) moth reveals highly ordered nano-structured conical protrusions on the corneal cuticle. It has been shown that this so-called ‘corneal nipple array’ or ‘moth-eye array’ has almost perfect anti-reflection properties. The crucial factor to reduce reflection of light is the nipple height. Only nipples with a height of > 50-200nm are anti-reflective. Corneal nipple arrays best known from nocturnal moths and butterflies (Lepidoptera), however they are widespread among insects and have probably evolved more than once. The nipples of the Old Lady moth are arranged in a hexagonal, almost crystalline fashion. In parallel to their anti-reflective function, the nipples also increase the surface area and thereby enhance the light sensitivity of the moth, though light transmittance increase may only be of minor importance compared to the potentially life-saving ability of the anti-reflective coating.Studying nano-structured corneal nipple arrays of insect eye facets helps to design better amorphous silicon thin film solar cells and improves the antireflective coating on notebooks and smartphones.

Hornet58587mini

PTU_Motte_001_mini

Drosophila Eye Development

Coloured scanning electron micrograph (SEM) of two mutant Fruitfly (Drosophila melanogaster) heads. Wildtype (i.e. normal) Fruitflies have two compound eyes (red) - one on either side of the head. Small bristles between the single lenses of the eye make sure it cannot be covered with dust or dirt particles. Genetically manipulated Flies can either lack compound eyes completely (left) or have additional eyes on the antennae, legs and other body areas (right). Fruit flies are widely used in genetic experiments, particularly in mutation experiments, because they reproduce rapidly and their genetic systems are well understood. This image visualizes how easily the results of the genetic modification can be observed in the Fruitfly which is one of the main reasons why it is still the most frequently used model organism in genetics despite more than 100 years of experimental research. left: Sine oculis-1 (so1) variant which lacks the compound eyes completely. right: Eyeless variant with ectopically expressed compound eyes under dpp-promotor in all imaginal discs. Handkoloriertes Raster-Elektronen-Mikroskopiebild zweier Fruchtfliegen-Mutanten. Die Taufliege oder Fruchtfliege (Drosophila melanogaster) ist das klassische Untersuchungsobjekt in der Genetik und Entwicklungsbiologie. Wildtypen, d.h. genetisch unveränderte Fruchtfliegen, besitzen zwei grosse rote Komplexaugen - je eines auf jeder Seite des Kopfes. Die Komplexaugen werden durch Borsten zwischen den winzigen Einzelaugen vor Verschmutzung und Staub geschützt. Die Entwicklung des Auges wird während der Embryonalentwicklung Larve durch bestimmte Gene gesteuert. Durch Veränderungen (Mutation) von Genen lassen sich z.B. Position oder Morphologie der Komplexaugen gezielte beeinflussen. Im Vergleich zu einem Säugetier ist die Fruchtfliege genetisch viel einfacher aufgebaut und weist lediglich vier Paar Chromosomen auf. Diese Tatsache hat, neben der raschen Generationsfolge und einfachen Zucht, wesentlich dazu

Drosophila Eye Development

Coloured scanning electron micrograph (SEM) of two mutant Fruitfly (Drosophila melanogaster) heads. Wildtype (i.e. normal) Fruitflies have two compound eyes (red) - one on either side of the head. Small bristles between the single lenses of the eye make sure it cannot be covered with dust or dirt particles. Genetically manipulated Flies can either lack compound eyes completely (left) or have additional eyes on the antennae, legs and other body areas (right). Fruit flies are widely used in genetic experiments, particularly in mutation experiments, because they reproduce rapidly and their genetic systems are well understood. This image visualizes how easily the results of the genetic modification can be observed in the Fruitfly which is one of the main reasons why it is still the most frequently used model organism in genetics despite more than 100 years of experimental research. left: Sine oculis-1 (so1) variant which lacks the compound eyes completely. right: Eyeless variant with ectopically expressed compound eyes under dpp-promotor in all imaginal discs. Handkoloriertes Raster-Elektronen-Mikroskopiebild zweier Fruchtfliegen-Mutanten. Die Taufliege oder Fruchtfliege (Drosophila melanogaster) ist das klassische Untersuchungsobjekt in der Genetik und Entwicklungsbiologie. Wildtypen, d.h. genetisch unveränderte Fruchtfliegen, besitzen zwei grosse rote Komplexaugen - je eines auf jeder Seite des Kopfes. Die Komplexaugen werden durch Borsten zwischen den winzigen Einzelaugen vor Verschmutzung und Staub geschützt. Die Entwicklung des Auges wird während der Embryonalentwicklung Larve durch bestimmte Gene gesteuert. Durch Veränderungen (Mutation) von Genen lassen sich z.B. Position oder Morphologie der Komplexaugen gezielte beeinflussen. Im Vergleich zu einem Säugetier ist die Fruchtfliege genetisch viel einfacher aufgebaut und weist lediglich vier Paar Chromosomen auf. Diese Tatsache hat, neben der raschen Generationsfolge und einfachen Zucht, wesentlich dazu

Turban Eye

Mayflies produce eggs that are laid on the surface of lakes or streams where they sink to the bottom. Naiads moult 20-30 times over a period of few months up to one year or even more. They live primarily on algae or diatoms, but some species are also predatory. The lifespan of adult mayflies is very short and varies between hours and 2-3 weeks. Since the primary function of the adult is reproduction, the mouthparts are non-functional and the digestive tract is filled with air. Adults have short flexible antennae, usually three ocelli and relatively large compound eyes. In most species, males additionally feature very large turban-shaped dorsal eyes, i.e. greatly enlarged compound eyes that are located on top of the head. The dorsal turban-eyes are especially designed to boost light sensitivity and allow vision at low light. At dawn, male mayflies fly close to the water surface in search of females, trying to detect females against the dim background of the sky. The turban-eyes are only capable of detecting ultra-violet (UV) light. In some species (e.g. European Mayfly) the turban-eye of the male is divided: The upper portion is for seeing movement, and the lower portion is specialized for seeing details. The females have smaller eyes.

Spruce & Timber Beetle, Trypodendron lineatum (?)

Portrait of a Bark Beetle (Spruce & Timber Beetle; Trypodendron lineatum). Bark beetles are a subfamily of the Snout beetles ('Weevils'). 154 species exist within Europe and between 4'000-5'000 worldwide. As primary destruents, they play an essential role in forrest ecosystems, living on dead wood or on dying trees. However, other species are known as notorious pests and are attacking (also) healthy trees. Trypodendron lineatum has a divided compound eye and is a monogamous species and shows brood care. The parents for example clean