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.

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 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 ‘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.

Eyes as optical alarm systems in fan worms and ark clams

1994 ◽  
Vol 346 (1316) ◽  
pp. 195-212 ◽  
Keyword(s):  
Visual Motion ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
False Alarms ◽  
Compound Eyes ◽  
Receptor Cells ◽  
Alarm Systems ◽  
Large Numbers ◽  
Mantle Edge ◽  
Higher Sensitivity

Eye structure and optics were investigated in two sabellid polychaetes ( Sabella melanostigma, Dasychone conspersa ) and three arcacean bivalves ( Arca zebra, Barbatia cancellaria, Anadara notabilis ). The polychaetes have numerous compound eyes arranged in pairs along the branchial tentacles. Each ommatidium is composed of three cells: one receptor cell forming a ciliary receptive segment, and two pigment cells forming an extracellular lens (crystalline cone). The ark clams Area and Barbatia possess large numbers of compound eyes arranged along the mantle edge. The ommatidia of these eyes are composed of one or two ciliary receptor cells surrounded by several layers of pigment cells. There are no lenses in the ommatidia of the clam eyes. All three species of ark clam also have many pigment-cup eyes on the mantle edge. The cup eyes lack lenses, and the cavity of the cup is filled with rhabdomeric microvilli from the receptor cells. The crystalline cones in the sabellid compound eyes are powerful lenses that reduce the field of view of the receptor cells to slightly more than 10°. The lensless ommatidia of Barbatia have much larger fields of view (« 30°). This difference correlates with a behavioural response to much finer moving stripes in the fan worms. A comparison of compound eyes and cup eyes in Barbatia reveals a poor resolution in both, but a much higher sensitivity is estimated for the cup eyes. The tentacular eyes of fan worms and the mantle eyes of ark clams trigger protective responses: retraction into the tube and shell closure, respectively. The responses are triggered by visual motion and the eyes work as burglar alarms rather than imaging eyes. For this purpose, the compound eyes may seem to occur in affluent numbers: 240 eyes with a total of 12 000 ommatidia in Sabella and 300 eyes with a total of 39 000 ommatidia in Barbatia . The number of ommatidia that simultaneously monitors any direction in space is, on average, 43 in Sabella and 755 in Barbatia . The large number of eyes is explained as a visual strategy which provides a robust alarm system designed to reliably detect predators without causing false alarms. The literature on tentacular eyes of fan worms and mantle eyes of bivalves is reviewed, and the evolutionary origin of these independently-acquired visual organs is discussed. I suggest the possibility that hyperpolarizing photoreceptor cells (shadow detectors) evolved from chemoreceptors that were inhibited by light.

scholarly journals Brain Sensory Organs of the Ascidian Ciona robusta: Structure, Function and Developmental Mechanisms

2021 ◽  
Vol 9 ◽  
Author(s):  
Paola Olivo ◽  
Antonio Palladino ◽  
Filomena Ristoratore ◽  
Antonietta Spagnuolo
Keyword(s):  
Photoreceptor Cells ◽  
Building Blocks ◽  
Sister Group ◽  
Low Complexity ◽  
Pigment Cells ◽  
Sensory Organs ◽  
Larval Brain ◽  
Gravity Perception ◽  
Good Opportunity ◽  
Simplified Approach

During evolution, new characters are designed by modifying pre-existing structures already present in ancient organisms. In this perspective, the Central Nervous System (CNS) of ascidian larva offers a good opportunity to analyze a complex phenomenon with a simplified approach. As sister group of vertebrates, ascidian tadpole larva exhibits a dorsal CNS, made up of only about 330 cells distributed into the anterior sensory brain vesicle (BV), connected to the motor ganglion (MG) and a caudal nerve cord (CNC) in the tail. Low number of cells does not mean, however, low complexity. The larval brain contains 177 neurons, for which a documented synaptic connectome is now available, and two pigmented organs, the otolith and the ocellus, controlling larval swimming behavior. The otolith is involved in gravity perception and the ocellus in light perception. Here, we specifically review the studies focused on the development of the building blocks of ascidians pigmented sensory organs, namely pigment cells and photoreceptor cells. We focus on what it is known, up to now, on the molecular bases of specification and differentiation of both lineages, on the function of these organs after larval hatching during pre-settlement period, and on the most cutting-edge technologies, like single cell RNAseq and genome editing CRISPR/CAS9, that, adapted and applied to Ciona embryos, are increasingly enhancing the tractability of Ciona for developmental studies, including pigmented organs formation.

scholarly journals Dual Bar homeo box genes of Drosophila required in two photoreceptor cells, R1 and R6, and primary pigment cells for normal eye development.

1992 ◽  
Vol 6 (1) ◽  
pp. 50-60 ◽  
Author(s):  
S Higashijima ◽  
T Kojima ◽  
T Michiue ◽  
S Ishimaru ◽  
Y Emori ◽  
...  
Keyword(s):  
Eye Development ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
Homeo Box

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.

Localization of retinal photoisomerase in the compound eye of the honeybee

1991 ◽  
Vol 7 (3) ◽  
pp. 237-249 ◽  
Author(s):  
W. Clay Smith ◽  
Timothy H. Goldsmith
Keyword(s):  
Immunoelectron Microscopy ◽  
Compound Eye ◽  
Polyclonal Antibodies ◽  
Photoreceptor Cells ◽  
Proximal Portion ◽  
Pigment Cells ◽  
High Concentration ◽  
Peripheral Portion

AbstractThe distribution of honeybee retinal photoisomerase, a soluble light-requiring enzyme that stereospecifically forms W-cis retinal, was investigated by immunoelectron microscopy and by HPLC. Immunolocalization with polyclonal antibodies shows that the highest concentration of retinal photoisomerase is located in the proximal portion of the primary pigment cells in large aggregates (approximately 2 μm diameter).Photoisomerase is also located in the peripheral portion of the photoreceptor cells, laterally displaced from the rhabdom, but in much lower concentration. Because of the larger volume of the photoreceptor cells, about half of the total immunoreactivity is associated with the primary pigment cells.Dissection of the eye with the subsequent use of HPLC to assay for photoisomerase activity showed that most of the photoisomerase activity is associated with tissues near the cornea. The same tissue also supports the reduction of W-cis retinal to W-cis retinol. These biochemical findings are consistent with the immunolocalization of retinal photoisomerase to the high-concentration aggregates in the primary pigment cells that surround the crystalline cones. The major synthesis of W-cis retinol therefore takes place in the primary pigment cells, and the retinoid must be moved into the photoreceptor cells to be available to newly synthesized opsin. The immunoreactivity of the photoreceptor cells appears to reflect the presence of some isomerase without an attached retinoid chromophore.

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