scholarly journals Eyes in Staurozoa (Cnidaria): a review

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6693
Author(s):  
Lucília Souza Miranda ◽  
Allen Gilbert Collins
Keyword(s):  
Light Intensity ◽  
Recent Literature ◽  
Image Formation ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
Light Perception ◽  
Dark Pigment ◽  
Single Origin ◽  
Synchronous Spawning ◽  
Shared Ancestry

The presence of dark pigment spots associated with primary tentacles (or structures derived from them, i.e., rhopalioids) in Staurozoa was recently overlooked in a study on the evolution of cnidarian eyes (defined as a “region made of photoreceptor cells adjacent to pigment cells”, irrespective of image formation, i.e., including all photoreceptive organs). Review of old and recent literature on Staurozoa shows that dark pigment spots are present in virtually all species ofManania, as well as some species ofHaliclystus,Stylocoronella, and probablyCalvadosia. The known ultrastructure of ocelli seems to be compatible with light perception, but no immediate response to changes in light intensity have been observed in the behavior of staurozoans. Therefore, although further studies addressing photic behavior are required, we discuss an earlier hypothesis that the dark spots in some stauromedusae may be related to synchronous spawning, as well as the possible sensorial function of rhopalioids. Observations summarized here suggest a possible ninth independent origin of eyes in Cnidaria, within a lineage of benthic medusae. Alternatively, documented similarity across medusae of Cubozoa, Scyphozoa, and Staurozoa—with eyes being topologically associated with primary tentacles in each of these taxa—could indicate shared ancestry and a single origin of eyes in this clade known as Acraspeda. Information on Staurozoa, one of the least studied groups within Cnidaria, is often neglected in the literature, but correctly recognizing the characters of this class is crucial for understanding cnidarian evolution.

scholarly journals Eyes in Staurozoa (Cnidaria): a review

2019 ◽  
Author(s):  
Lucília Souza Miranda ◽  
Allen Gilbert Collins
Keyword(s):  
Light Intensity ◽  
Recent Literature ◽  
Image Formation ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
Light Perception ◽  
Dark Pigment ◽  
Single Origin ◽  
Synchronous Spawning ◽  
Shared Ancestry

The presence of dark pigment spots associated with primary tentacles (or structures derived from them, i.e., rhopalioids) in Staurozoa was recently overlooked in a study on the evolution of cnidarian eyes (defined as a “region made of photoreceptor cells adjacent to pigment cells”, irrespective of image formation, i.e., including all photoreceptive organs). Review of old and recent literature on Staurozoa shows that dark pigment spots are present in virtually all species of Manania, as well as some species of Haliclystus, Stylocoronella, and probably Calvadosia. The known ultrastructure of ocelli seems to be compatible with light perception, but no immediate response to changes in light intensity have been observed in the behavior of staurozoans. Therefore, although further studies addressing photic behavior are required, we discuss an earlier hypothesis that the dark spots in some stauromedusae may be related to synchronous spawning, as well as the possible sensorial function of rhopalioids. Observations summarized here suggest a possible ninth independent origin of eyes in Cnidaria, within a lineage of benthic medusae. Alternatively, documented similarity across medusae of Cubozoa, Scyphozoa, and Staurozoa – with eyes being topologically associated with primary tentacles in each of these taxa – could indicate shared ancestry and a single origin of eyes in this clade known as Acraspeda. Information on Staurozoa, one of the least studied groups within Cnidaria, is often neglected in the literature, but correctly recognizing the characters of this class is crucial for understanding cnidarian evolution.

scholarly journals Eyes in Staurozoa (Cnidaria): a review

2019 ◽  
Author(s):  
Lucília Souza Miranda ◽  
Allen Gilbert Collins
Keyword(s):  
Light Intensity ◽  
Recent Literature ◽  
Image Formation ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
Light Perception ◽  
Dark Pigment ◽  
Single Origin ◽  
Synchronous Spawning ◽  
Shared Ancestry

The presence of dark pigment spots associated with primary tentacles (or structures derived from them, i.e., rhopalioids) in Staurozoa was recently overlooked in a study on the evolution of cnidarian eyes (defined as a “region made of photoreceptor cells adjacent to pigment cells”, irrespective of image formation, i.e., including all photoreceptive organs). Review of old and recent literature on Staurozoa shows that dark pigment spots are present in virtually all species of Manania, as well as some species of Haliclystus, Stylocoronella, and probably Calvadosia. The known ultrastructure of ocelli seems to be compatible with light perception, but no immediate response to changes in light intensity have been observed in the behavior of staurozoans. Therefore, although further studies addressing photic behavior are required, we discuss an earlier hypothesis that the dark spots in some stauromedusae may be related to synchronous spawning, as well as the possible sensorial function of rhopalioids. Observations summarized here suggest a possible ninth independent origin of eyes in Cnidaria, within a lineage of benthic medusae. Alternatively, documented similarity across medusae of Cubozoa, Scyphozoa, and Staurozoa – with eyes being topologically associated with primary tentacles in each of these taxa – could indicate shared ancestry and a single origin of eyes in this clade known as Acraspeda. Information on Staurozoa, one of the least studied groups within Cnidaria, is often neglected in the literature, but correctly recognizing the characters of this class is crucial for understanding cnidarian evolution.

scholarly journals Eyes in Staurozoa (Cnidaria): a review

2018 ◽  
Author(s):  
Lucília Souza Miranda ◽  
Allen Gilbert Collins
Keyword(s):  
Recent Literature ◽  
Image Formation ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
Dark Pigment ◽  
Single Origin ◽  
Independent Origin ◽  
Synchronous Spawning

The presence of dark pigment spots associated with primary tentacles (or structures derived from them, i.e., rhopalioids) in Staurozoa was recently overlooked in a study on the evolution of cnidarian eyes (defined as a “region made of photoreceptor cells adjacent to pigment cells”, irrespective of image formation, i.e., including all photoreceptive organs). Review of old and recent literature on Staurozoa shows that dark pigment spots are present in virtually all species of Manania, as well as some species of Haliclystus, Stylocoronella,and probably Calvadosia. Based on our review, we support the hypothesis that these dark spots may be related to synchronous spawning, and that rhopalioids have both adhesive and sensorial functions. Observations summarized here suggest a possible ninth independent origin of eyes in Cnidaria, within a lineage of benthic medusae. Alternatively, documented similarity across Cubozoa, Scyphozoa, and Staurozoa – with eyes being topologically associated with primary tentacles in each of these taxa – could indicate shared homology and a single origin of eyes in this clade known as Acraspeda. Information on Staurozoa, one of the least studied groups within Cnidaria, is often neglected in the literature, but correctly recognizing the characters of this classis crucial for understanding cnidarian evolution.

Photoreceptors of cnidarians

2002 ◽  
Vol 80 (10) ◽  
pp. 1703-1722 ◽  
Author(s):  
Vicki J Martin
Keyword(s):  
Light Intensity ◽  
Receptor Cell ◽  
Photoreceptor Cells ◽  
Aminobutyric Acid ◽  
Developmental Pathways ◽  
Pigment Cells ◽  
Close Proximity ◽  
Rapid Changes ◽  
Pax Genes ◽  
Behavioral Activities

Cnidarians are the most primitive present-day invertebrates to have multicellular light-detecting organs, called ocelli (eyes). These photodetectors include simple eyespots, pigment cups, complex pigment cups with lenses, and camera-type eyes with a cornea, lens, and retina. Ocelli are composed of sensory photoreceptor cells interspersed among nonsensory pigment cells. The photoreceptor cells are bipolar, the apical end forming a light-receptor process and the basal end forming an axon. These axons synapse with second-order neurons that may form ocular nerves. A cilium with a 9 + 2 arrangement of microtubules projects from the receptor-cell process. Depending on the species, the membrane covering the cilium shows several variations, including evaginating microvilli. In the cubomedusae stacks of membranes fill the apical regions of the photoreceptor cells. Pigment cells are rich in pigment granules, and in some animals the distal regions of these cells form tubular processes that project into the cavity of the ocellus. Microvilli may extend laterally from these tubular processes and interdigitate with the microvilli from the ciliary membranes of photoreceptor cells. Photoreceptor cells respond to changes in light intensity with graded potentials that are directly proportional to the range of the changes in light intensity. In the Hydrozoa these cells may be electrically coupled to each other through gap junctions. Light affects the behavioral activities of cnidarians, including diel vertical migration, responses to rapid changes in light intensity, and reproduction. Medusae with the most highly modified photoreceptors demonstrate the most complex photic behaviors. The sophisticated visual system of the cubomedusan jellyfish Carybdea marsupialis is described. Extraocular photosensitivity is widespread throughout the cnidarians, with neurons, epithelial cells, and muscle cells mediating light detection. Rhodopsin-like and opsin-like proteins are present in the photoreceptor cells of the complex eyes of some cubomedusae and in some neurons of hydras. Neurons expressing glutamate, serotonin, γ-aminobutyric acid, and RFamide (Arg-Phe-amide) are found in close proximity to the complex eyes of cubomedusae; these neurotransmitters may function in the photic system of the jellyfish. Pax genes are expressed in cnidarians; these genes may control many developmental pathways, including eye development. The photobiology of cnidarians is similar in many ways to that of higher multicellular animals.

scholarly journals INHERITED RETINAL DYSTROPHY IN THE RAT

1962 ◽  
Vol 14 (1) ◽  
pp. 73-109 ◽  
Author(s):  
John E. Dowling ◽  
Richard L. Sidman
Keyword(s):  
Pigment Epithelium ◽  
Light And Electron Microscopy ◽  
Retinal Dystrophy ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
Membrane Thickness ◽  
Outer Segments ◽  
Progressive Loss ◽  
Retinal Rods ◽  
Microscopy Data

Retinal dystrophies, known in man, dog, mouse, and rat, involve progressive loss of photoreceptor cells with onset during or soon after the developmental period. Functional (electroretinogram), chemical (rhodopsin analyses) and morphological (light and electron microscopy) data obtained in the rat indicated two main processes: (a) overproduction of rhodopsin and an associated abnormal lamellar tissue component, (b) progressive loss of photoreceptor cells. The first abnormality recognized was the appearance of swirling sheets or bundles of extracellular lamellae between normally developing retinal rods and pigment epithelium; membrane thickness and spacing resembled that in normal outer segments. Rhodopsin content reached twice normal values, was present in both rods and extracellular lamellae, and was qualitatively normal, judged by absorption maximum and products of bleaching. Photoreceptors attained virtually adult form and ERG function. Then rod inner segments and nuclei began degenerating; the ERG lost sensitivity and showed selective depression of the a-wave at high luminances. Outer segments and lamellae gradually degenerated and rhodopsin content decreased. No phagocytosis was seen, though pigment cells partially dedifferentiated and many migrated through the outer segment-debris zone toward the retina. Eventually photoreceptor cells and the b-wave of the ERG entirely disappeared. Rats kept in darkness retained electrical activity, rhodopsin content, rod structure, and extracellular lamellae longer than litter mates in light.

scholarly journals The visual system of the genetically tractable crustacean Parhyale hawaiensis: diversification of eyes and visual circuits associated with low-resolution vision

2019 ◽  
Author(s):  
Ana Patricia Ramos ◽  
Ola Gustafsson ◽  
Nicolas Labert ◽  
Iris Salecker ◽  
Dan-Eric Nilsson ◽  
...  
Keyword(s):  
Light Intensity ◽  
Visual System ◽  
Photoreceptor Cell ◽  
Optic Lobe ◽  
Photoreceptor Cells ◽  
Single Species ◽  
Low Resolution ◽  
Parhyale Hawaiensis ◽  
Visual Tasks ◽  
Significant Divergence

AbstractBackgroundArthropod eyes have diversified during evolution to serve multiple needs, such as finding mates, hunting prey, and navigating in complex surroundings under varying light conditions. This diversity is reflected in the optical apparatus, photoreceptors and neural circuits that underpin vision. While this diversity has been extensively documented, our ability to genetically manipulate the visual system to investigate its function is largely limited to a single species, the fruitfly Drosophila melanogaster. Here, we describe the visual system of Parhyale hawaiensis, an amphipod crustacean for which we have established tailored genetic tools.ResultsAdult Parhyale have apposition-type compound eyes made up of ∼50 ommatidia. Each ommatidium contains four photoreceptor cells with large rhabdomeres (R1-4), expected to be sensitive to the polarisation of light, and one photoreceptor cell with a smaller rhabdomere (R5). The two types of photoreceptors express different opsins, belonging to families with distinct wavelength sensitivities. Using the cis.-regulatory regions of opsin genes, we established transgenic reporters expressed in each photoreceptor cell type. Based on these reporters, we show that R1-4 and R5 photoreceptors extend axons to the first optic lobe neuropil, revealing striking differences compared with the photoreceptor projections found in related crustaceans and insects. Investigating visual function, we show that Parhyale has a positive phototactic response and is capable of adapting its eyes to different levels of light intensity.ConclusionsWe propose that the visual system of Parhyale serves low-resolution visual tasks, such as orientation and navigation, based on broad gradients of light intensity and polarisation. Optic lobe structure and photoreceptor projections point to significant divergence from the conserved visual circuits found in other malacostracan crustaceans and insects, which could be associated with a shift to low-resolution vision. Our study provides the foundation for research in the visual system of this genetically tractable species.

scholarly journals Mathematical Analysis of Electrical Responses in Photoreceptor Cells Reveals Distinct Chemical Control of Visual Signal Transduction in Rods and Cones.

2021 ◽  
Author(s):  
Yukari Takeda ◽  
Kazuma Sato ◽  
Yukari Hosoki ◽  
Shuji Tachibanaki ◽  
Chieko Koike ◽  
...  
Keyword(s):  
Light Intensity ◽  
Current Model ◽  
Photoreceptor Cells ◽  
Light Sensitivity ◽  
Visual Signal ◽  
Visual Transduction ◽  
Rods And Cones ◽  
Experimental Systems ◽  
Lower Light

Abstract Retinal photoreceptor cells, rods and cones, convert photons of light into chemical and electrical signals as the first step of the visual transduction cascade. Although the chemical processes in the phototransduction system are very similar to each other in these photoreceptors, the light sensitivity and time resolution of the photoresponse in rods are functionally different than those in the photoresponses of cones. To systematically investigate how photoresponses are divergently regulated in rods and cones, we have developed a detailed mathematical model on the basis of the Hamer model. The current model successfully reconstructed light intensity-, ATP- and GTP-dependent changes in concentrations of phosphorylated visual pigments (VPs), activated transducins (Tr*s) and phosphodiesterases (PDEs), as well as cyclic nucleotide-gated currents (ICNG) in rods and cones. In comparison to rods, the lower light sensitivity of cones was attributed not only to the lower affinity of activated VPs for Trs but also to the faster desensitization of the VPs. The assumption of an intermediate inactive state, MIIi, in the thermal decay of activated VPs was pivotal for inducing faster inactivation of VPs. In addition to the faster inactivation of VPs, calculating a faster rate of RGS9 intervention for PDE-induced Tr* inactivation in cones was indispensable for simulating the electrical waveforms of the light intensity-dependent ICNG at higher temporal resolution in experimental systems in vivo.

scholarly journals The ‘division of labour’ model of eye evolution

2009 ◽  
Vol 364 (1531) ◽  
pp. 2809-2817 ◽  
Author(s):  
Detlev Arendt ◽  
Harald Hausen ◽  
Günter Purschke
Keyword(s):  
Visual Information ◽  
Photoreceptor Cells ◽  
Cell Types ◽  
Division Of Labour ◽  
Pigment Cells ◽  
Sensory Cells ◽  
Cell Type ◽  
Eye Evolution ◽  
Residual Functions ◽  
Light Shading

The ‘division of labour’ model of eye evolution is elaborated here. We propose that the evolution of complex, multicellular animal eyes started from a single, multi-functional cell type that existed in metazoan ancestors. This ancient cell type had at least three functions: light detection via a photoreceptive organelle, light shading by means of pigment granules and steering through locomotor cilia. Located around the circumference of swimming ciliated zooplankton larvae, these ancient cells were able to mediate phototaxis in the absence of a nervous system. This precursor then diversified, by cell-type functional segregation, into sister cell types that specialized in different subfunctions, evolving into separate photoreceptor cells, shading pigment cells (SPCs) or ciliated locomotor cells. Photoreceptor sensory cells and ciliated locomotor cells remained interconnected by newly evolving axons, giving rise to an early axonal circuit. In some evolutionary lines, residual functions prevailed in the specialized cell types that mirror the ancient multi-functionality, for instance, SPCs expressing an opsin as well as possessing rhabdomer-like microvilli, vestigial cilia and an axon. Functional segregation of cell types in eye evolution also explains the emergence of more elaborate photosensory–motor axonal circuits, with interneurons relaying the visual information.

The receptive fields of cells in the retina of the housefly (Musca domestica)

1966 ◽  
Vol 164 (997) ◽  
pp. 552-576 ◽  
Keyword(s):  
Light Intensity ◽  
Receptive Field ◽  
Musca Domestica ◽  
Dark Adaptation ◽  
Gaussian Function ◽  
Light Flux ◽  
Pigment Cells ◽  
Focal Region ◽  
Generator Potential ◽  
The Relationship

A theory of movement perception has been proposed to explain the optomotor responses of the housefly ( Musca domestica ), and this has been tested by McCann & Maginitie (1965). The present study was made in order to ascertain if the anatomical and physiological properties of the compound eye are commensurate with those postulated by the model. The three properties studied were the inter-ommatidial angle, the receptive field of the retinula cells, and the relationship between light intensity and the magnitude of the generator potential. The angle between the axes of adjacent ommatidia was measured anatomically. This varies with the position in the eye but has a mean value of 3.9° in the horizontal plane and 2.4° in the vertical. During dark adaptation the secondary pigment cells contract by about 5 pm at either end, moving the pigment back away from the lenses and also exposing the focal region of the ommatidium. The receptive field of single retinula cells was measured electrophysiologically. The light flux curve for a single unit is a Gaussian function with a width at half the maximum light flux of 3.2° in the horizontal and 2.5° in the vertical plane when light adapted. After 15 min dark adaptation these increase to 8.5° and 4.5°. These values agree well with those predicted by the optomotor model. The increase in field width during dark adaptation should change the relative acuity for spatial wavelengths of striped patterns, and this also was found in the optomotor experiments. The relationship between the magnitude of the generator potential and the light intensity was logarithmic over the intensity range used.

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