Cellular identification of the violet receptor in the crayfish eye

Summary Ten violet receptors in the retinas of crayfish (Procambarus) were injected intracellularly with the fluorescent dye Lucifer Yellow-CH and subsequently identified in histological preparations. All had their cell body located distal to the main rhabdom, in the position of the small, 8th retinular cell. In nine cases it was possible to trace the axon of the violet receptor beyond thelamina ganglionaris, and in four cases, to its termination in themedulla.By contrast, 22 green receptors similarly injected were all found to contribute to the main rhabdom, which is formed by retinular cells 1–7. Their axons synapsed in thelamina ganglionaris.Microspectrophotometry of the 8th cell reveals an absorption peak at 440 nm. As previous microspectrophotometric observations indicated that retinular cells 1–7 all contain a visual pigment with _max at 530 nm, the microspectrophotometric data confirm that the violet receptor is cell 8.This work was supported by USPHS grant EY00222 to Yale University. D.C. is a USPHS predoctoral trainee supported by National Research Service Award 5-T32-GM07527. We are grateful to Dr. W.W. Steward for a gift of Lucifer Yellow-CH and J.D. Collins for technical assistance.     

The Ultrastructure of the Compound Eye of Two Species of Marine Ostracodes (Crustacea: Ostracoda: Cypridinidae)

Ultrastructurally, the compound eyes of the luminescent marine ostracodes Vargula graminkola and V. tsujii are similar. These ostracodes have two lateral compound eyes, with relatively few ommatidia (13 and 20 respectively). They exhibit apposition type compound eyes as seen in many other arthropods. Each ommatidium includes: a flat, ectodermal cuticular covering, corneagen cells, two long cone cells that give rise to a large conspicuous crystalline cone, retinular cells, pigment cells, a microvillar rhabdom and proximal axonal neurons. The axons merge to form an optic nerve that extends into the brain through a short, muscular stalk that is surrounded externally by a cuticle. The number of retinular cells is typically six per ommatidium in V. graminicola and eight per ommatidium in V. tsujii. Screening pigment cells surround each ommatidium forming a layer that is about 5–15 pigment granules thick. In addition to pigment cells, the cytoplasm of the retinular cells includes numerous screening pigment granules. In light/dark adaptation, there are no obvious morphological differences in the orientation of the rhabdom or in the organization of the screening pigments. Both Vargula species studied are nocturnally active and bioluminescent suggesting that these eyes are capable receptors of the bright conspecific luminescence.     

Action spectra of the female's response in the firefly Photinus pyralis (Coleoptera: Lampyridae): evidence for an achromatic detection of the bioluminescent optical signal

Behavioural action spectra of the threshold of the Photinus pyralis female response to light stimuli simulating the bioluminescent optical signal of the conspecific male firefly were determined in the laboratory. The action spectra (Fig. 1) were narrow and peaked in the yellow region of the spectrum. The females responded only to stimuli of wavelengths longer than 480 nm and not to stimuli in the blue (420-460 nm) part of the spectrum. The shape of the function corresponds with (a) the electroretinographic spectral sensitivity function in the long wavelength (520-660 nm) region of the spectrum, (b) the action spectrum of the female response (Fig. 1), (c) the species yellow bioluminescence emission spectrum and (d) the action spectrum of the intracellular response from single retinular cells (Fig. 2) of the compound eyes in the firefly. Such a correspondence suggests that the narrow yellow receptors of the female mediate the detection and processing of the optical signal of the conspecific male. Since the bioluminescent optical signal is processed exclusively by a single receptor class, signal detection is achromatic.     

Compound Eyes of Some Deep-Sea and Fiord Mysid Crustaceans

The compound eyes of the deep-sea mysid Boreomysis scyphops and the two mysid species Amblyops abbreviata and Pseudomma affine, which are indigenous to deep fiords in Norway, have been investigated. The eye stalks are greatly transformed, but contain hypertrophied retinas. The ommatidia of all three species lack a dioptric apparatus, possessing only retinular cells, which are arranged in a cylinder-like fashion. Folds from the retinular cells project into the “cylinder” and are covered with microvilli. The arrangement is explained functionally by an increase in the photopigment-bearing surface as an adaptation to low-light intensities. The orderly arrangement of microvilli in most arthropod compound eyes has been lost, and the arrangement is thus multidirectional in these mysids. With the photopigment dipoles arranged along the microvillar axis, the disorderly arrangement of microvilli signifies a more efficient capture of non-polarized light. It is concluded that the mysid compound eyes show adaptations to low-light intensities probably acquired during the species' evolutionary descent into deep-sea habitats. Amblyops abbreviata and Pseudomma affine, belonging to genera with entirely transformed eyes and with an ultrastructure less “normal” than that of Boreomysis scyphops are believed to be earlier descendants into the deep-sea habitats than the latter species, which belongs to a genus in which most of the species have well-developed eyes.     

The Fine Structure of the Compound Eyes of Shallow-Water Asellotes,Jaera albifrons Leach and Asellus aquaticus L. (Crustacea: Isopoda)

Abstract Both species have small sessile compound eyes. The dioptric apparatus of J. albifrons consists of a biconvex lens and a pyriform crystalline cone, the latter formed by two principal and two accessory cone cells. A. aquaticus has a reduced lens and a round cone formed by two to four principal cone cells with two to no accessory cone cells. Distal pigment cells and pigmented retinular cells lie between the ommatidia in J. albifrons. A. aquaticus has only the pigmented retinular cells. Both species have a fused, continuous (unhanded) rhabdom formed by eight retinular cells (R1—8), one of which (R8) is situated distally. The retinular cells R1—7 form, in J. albifrons, a cylinder-shaped middle portion with three microvillar directions (60° apart) and a proximal star-shaped portion. The entire rhabdom of A. aquaticus is star-shaped. Distal pigment-cell processes and basal cells form the fenestrated membrane in J. albifrons and “eye-cup cells” in A. aquaticus.     

Solid‐state synthesis and luminescent properties of yellow‐emitting phosphor NaY(MoO4)2:Dy3+ for white light‐emitting diodes

A yellow‐emitting phosphor NaY(MoO₄)₂:Dy³⁺ was synthesized using a solid‐state reaction at 550 °C for 4 h, and its luminescent properties were investigated. Its phase formation was studied using X‐ray powder diffraction analysis, and there were no crystalline phases other than NaY(MoO₄)₂. NaY(MoO₄)₂:Dy³⁺ produced yellow emission under 386 or 453 nm excitation, and the prominent luminescence was yellow (575 nm) due to the ⁴ F_9/2→⁶H_13/2 transition of Dy³⁺. For the 575 nm emission, the excitation spectrum had one broad band and some narrow peaks; the peaks were located at 290, 351, 365, 386, 426, 453 and 474 nm. Emission intensities were influenced by the Dy³⁺ doping content and a concentration quenching effect was observed; the phenomenon was also proved by the decay curves. Moreover, the Commission International de I'Eclairage chromaticity coordinates of NaY(MoO₄)₂:Dy³⁺ showed similar values at different Dy³⁺ concentrations, and were located in the yellow region. Copyright © 2015 John Wiley & Sons, Ltd.     

Retinular fine structure in compound eyes of diurnal and nocturnal sphingid moths

Summary Retinular fine structure has been compared in the superposition compound eyes of three sphingid moths, one nocturnal, Cechenena, and two diurnal, Cephonodes and Macroglossum. Cechenena and Cephonodes have tiered retinas with three kinds of retinular cells: two distal, six regular and one basal. The distal retinular cells in Cechenena are special in having a complex partially intracellular rhabdomere not present in Cephonodes. Macroglossum lacks the distal retinular cell. In Cephonodes a unique rhabdom type, formed by the six regular retinular cells in the middle region of the retinula, is divided into three separate longitudinal plates arranged closely parallel to one another. Their constituent microvilli are consequently all nearly unidirectional. The ratio of rhabdom volume to retinular cell volume in the two diurnal sphingids is 10–27%; this is about the same as that (25%) of skipper butterflies, but significantly smaller than in the nocturnal Cechenena (60%). In the diurnal sphingids retinular cell membranes show elongate meandering profiles with septate junctions between adjacent retinular cells. From the comparative fine structure of their eyes the diurnal sphingids and the skippers would appear to be phylogenetically closely related.Supported in part by grants from Ministry of Education Japan (Special Project Research in Animal Behaviors)     

Comparative studies of crustacean spectral sensitivity

Summary Spectral sensitivity of the lateral eyes of the isopodPorcellio scaber (wood louse) and the decapodsCallinectes sapidus (blue crab),Palaemonetes paludosus (Everglades prawn),Orconectes virilis, andO. immunis (crayfish) have been measured between 300 and 660 nm by determining the reciprocal number of photons required to evoke a constant size retinal action potential. Porcellio is maximally sensitive at 515 nm andCallinectes at 505 nm. Both species have a single pigment system, as spectral sensitivity is unchanged by red light adaptation. Palaemonetes appears to have a dichromatic color vision. Sensitivity of the dark-adapted eye is dominated by a receptor maximally sensitive at 550–555 nm, but red or yellow adaptation discloses a uv pigment with _max at about 380 nm. Present evidence suggests the 555 and 380 nm pigments are located in different receptor cells. Orconectes has peak sensitivity at 565 nm, but under red light adaptation and close to the electroretinographic threshold a second sensitivity maximum appears at 425 nm. As in the prawn, these peaks seem to indicate the presence of a two-receptor color vision system.The corneas ofOrconectes, Callinectes, andHomarus (lobster) are relatively thick, and microspectrophotometric measurements show near ultraviolet absorption as well as the protein peak at 280 nm. By contrast,Palaemonetes andMusca (housefly), species with near ultraviolet receptors, have thinner corneas which are transparent through the near ultraviolet. The crystalline cone ofPalaemonetes likewise shows no near ultraviolet absorption but a strong protein band at 280 nm.The scarcity of ultraviolet receptors in the compound eyes of crustacea, in contrast to their common occurrence in insects, is thought to be related to the relative absence of ultraviolet wavelengths in most aquatic environments.This work was supported in part by USPHS research grant NB 03333 to Yale University and postdoctoral fellowship NB 22,547 to H.R.F.     

Evolution and mechanism of spectral tuning of blue-absorbing visual pigments in butterflies

The eyes of flower-visiting butterflies are often spectrally highly complex with multiple opsin genes generated by gene duplication, providing an interesting system for a comparative study of color vision. The Small White butterfly, Pieris rapae, has duplicated blue opsins, PrB and PrV, which are expressed in the blue (λ _max = 453 nm) and violet receptors (λ _max = 425 nm), respectively. To reveal accurate absorption profiles and the molecular basis of the spectral tuning of these visual pigments, we successfully modified our honeybee opsin expression system based on HEK293s cells, and expressed PrB and PrV, the first lepidopteran opsins ever expressed in cultured cells. We reconstituted the expressed visual pigments in vitro, and analysed them spectroscopically. Both reconstituted visual pigments had two photointerconvertible states, rhodopsin and metarhodopsin, with absorption peak wavelengths 450 nm and 485 nm for PrB and 420 nm and 482 nm for PrV. We furthermore introduced site-directed mutations to the opsins and found that two amino acid substitutions, at positions 116 and 177, were crucial for the spectral tuning. This tuning mechanism appears to be specific for invertebrates and is partially shared by other pierid and lycaenid butterfly species.     

Effects of environmental colour on growth of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758), maintained individually or in groups

Examined was the influence of different colours of light on the growth of adult Nile tilapia (Oreochromis niloticus) held either individually (initial size 12.8 ± 1.1 cm; 62.9 ± 15.6 g) or in groups (initial size 7.8 ± 0.8 cm; 17.2 ± 6.4 g). Various colours (blue 434.5 nm, violet 430.0 nm, red 609.7 nm, green 525.2 nm and yellow 545.2 nm) did not affect weight gain of fish held individually (initial to final weights: blue 62.5 ± 18.4 to 72.9 ± 16.0 g, violet 63.5 ± 17.8 to 78.0 ± 19.1 g, green 62.1 ± 13.0 to 72.9 ± 15.7 g, and yellow 60.4 ± 20.4 to 71.0 ± 21.1 g); red seemed to restrict growth (initial to final weights: 65.8 ± 13.3 to 71.8 ± 10.8 g). Final weight differences were observed among individuals in groups maintained under blue, violet, red and green light (smaller and larger fish: blue 13.2 ± 5.0 and 18.9 ± 7.0 g, violet 17.3 ± 5.2 and 23.8 ± 4.7 g, red 14.7 ± 3.3 and 23.9 ± 4.7 g, and green 19.4 ± 7.8 and 28.6 ± 8.1 g); however, under the yellow light there were no differences in final weights (smaller fish 19.1 ± 4.8 g; larger fish 26.2 ± 5.2 g). Under the red light, heterogeneity in growth was observed earlier than with the other colours. It is therefore suggested that the red colour might have some harmful effects on Nile tilapia growth, limiting weight gain when fish are individually maintained, and with weight differences increasing when fish are held in groups. On the other hand, the yellow light seems to be positive for Nile tilapia, as it appears not to affect individually‐held fish, but reduces variation in growth of group‐maintained fish, promoting growth homogeneity.     

Cytoskeleton of retinular cells from the stomatopod,Gonodactylus oerstedii: possible roles in pigment granule migration

Retinular cells of the compound eyes of stomatopods (mantis shrimps) contain screening pigment granules that migrate radially in response to light. To clarify the role of the cytoskeleton in these movements, we have performed light microscopy and ultrastructural analyses of cytoskeletal organelles in retinular cells. Rhodamine phalloidin staining indicates that filamentous actin is a component of microvillar rhabdomeres and zonula adherens between retinular cells. Ultrastructural studies reveal three populations of microtubules in retinular cells that differ in their orientations and labilities to fixation. Two of these populations are oriented longitudinally in cells: the soma microtubules, found primarily in a column in the cell soma, and the more labile palisade microtubules, which extend alongside the palisade vacuole near the rhabdomere. The third, most labile microtubule population, and filaments 9–30 nm in diameter, are oriented radially in retinular cells, some within cytoplasmic bridges that span the palisade. The radial microtubules and filaments are appropriately oriented for participating in pigment granule migration. Determination of microtubule polarities in retinular cells by decoration with endogenous tubulin indicates that palisade and soma microtubules contain subpopulations having opposite polarity orientations, as has been observed in neuronal dendrites. In contrast, neighboring pigment cells contain microtubules uniformly oriented with minus ends towards the nucleus, as has been observed in most cell types studied.     

The Spectral Sensitivities of Single Receptor Cells in the Lateral, Median, and Ventral Eyes of Normal and White-Eyed Limulus

Spectral sensitivity curves can be distorted by screening pigments. We have determined whether this is true for Limulus polyphemus by determining, from receptor potentials recorded using intracellular microelectrodes, spectral sensitivity curves for normal animals and for white-eyed animals (which lack screening pigment). Our results show: (a) In median ocelli, the curve for UV-sensitive receptor cells peaks at 360 nm and does not depend on the presence of screening pigment, (b) The curve for ventral eye photoreceptors is identical to that for retinular cells from the lateral eyes of white-eyed animals and peaks at 520–525 nm. (c) In normal lateral eyes, when the stimulating light passes through screening pigment, the curve indicates relatively more sensitivity in the red region of the spectrum than does the curve for white-eyed animals. Therefore, the screening pigment is probably red-transmitting, (d) In median ocelli, the curve for visible-sensitive cells peaks at 525 nm and is approximately the same whether the ocelli are from normal or white-eyed animals. However, the curve is significantly broader than that for ventral eyes and for lateral eyes from white-eyed animals.     

Vision in the fireflyPhoturis lucicrescens (Coleoptera: Lampyridae): Spectral sensitivity and selective adaptation in the compound eye

Summary The waveform of the electroretinograms (ERGs) recorded from the compound eyes in the dark-active fireflyPhoturis lucicrescens was different in the short (near-UV and violet) and long (green-yellow) wavelengths (Fig. 1). The spectral sensitivity curves in the dark and chromatic adaptation conditions suggested the presence of receptor types in the short (near-UV, Fig. 4, and violet, Fig. 5) and long wavelength (green; max 550 nm, Figs. 3–5) regions of the spectrum. The green peak is in correspondence with the species' bioluminescence emission peak at 554 nm (Fig. 3c).Abbreviations DA dark-adapted - ERG electroretinogram - VP visual pigment Contribution No. 1112 of the McCollum-Pratt Institute and Department of Biology, The Johns Hopkins University     

The ontogeny of facultative superposition optics in a shrimp eye: hatching through metamorphosis

Summary Compound eyes of larval and first postlarval grass shrimp (Palaemonetes pugio Holthuis) were studied with light and electron microscopy following adaptation to darkness or bright light. Larvae have well-developed apposition eyes, including 3 main types of accessory screening and reflecting pigments and a fourth class of putatively reflective granules recently described in adult shrimps. Rhabdoms contain orthogonally layered microvilli, and by the last larval stage, 8 retinular cells. Ocular accessory pigments in both light- and dark-adapted larvae are distributed much like those of light-adapted adults, but the distal mass of reflecting pigment is concentrated dorsally in larvae and ventrally in adults. Since larvae swim upside-down, reflecting pigment is oriented downward in all developmental stages and may function for countershading. Light and dark adaptational migrations of all 3 major accessory pigments commence abruptly at metamorphosis to the first postlarva. Upon dark adaptation in postlarvae, superposition optics remain impossible because (1) distal screening pigment migrates only slightly, (2) no clear zone has developed, and (3) the crystalline cones remain circular in cross section. Nevertheless, a slight improvement in photon catch is expected due to extensive redistributions of reflecting pigment and retinular cell screening pigment granules.

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Evolutionswege zum Larvalauge der Insekten -Die Stemmata der höheren Dipteren und ihre Abwandlung zum Bolwig-Organ

Evolutionary pathways to the larval eyes of insects. Higher Dipteran stemmata and the evolutionary development of Bolwig's organ 1. A cornrehensive morphological study of the photoreceptors in the so-called hemi — Institut für Biologie I (Zoologie) der Albert-Ludwigs-Universität, Albertstr. 21a, D-7800 Freiburg i. Brsg., FRGand acephalic lrvae of Brachycera was undertaken. In Brachyceran larvae the head casule originally is more or less retracted into the thorax. The larval hotoreceptor in Musca and Drosophila, here called Bolwig's organ, is situated on the outer side of the cephalopharyngeal apparatus, well below the surface. The aim of this study is to elucidate the homology of Bolwig's organ, i. e. whether Bolwig's organ originated from typical stemmata during the evolution of Cyclor-rhaphan larval organlsation or whether it represents a unique type of hotoreceptor. Larval photoreceptors and the anatomy of the head capsules of representative Erachycerans were examined by means of light and electron microscopy. In particular, the site and the structure of the photofecetors of Stratiomys (Stratiomyidae, Solva (Solvidae), Atherix ibis (Athericidae), Rhagio (Rhagionidae), Thereva (derevidae), Lonchoptera (Lonchoteridae), Epistrohe balteata, Volu-cella bombylans, Eristalis tenax (Syrphidae), Drosophila (f;rosophilidae), jannia and Musca domestica (Muscidae) were investigated. 2. Brachyceran stemmata are either situated on the ocular plates of the free remnant of the head (Stratiomyidae, Therevidae), or on the inner wall of an epidermal invaination, which includes epithelia of the head as well as of the thorax (Tabaniformia). In adfition, they can be found on the outer side of the tentorial phragmata (Cyclorrhapha). In all taxa studied, stemmata keep contact directly with the epithelium or through short processes of eithelial cells. 3. Ancestral Brachycera have fused stemmata that correspond with typical larval eyes of other holometabolan insects. 4. A cornea is found solely in Stratiomyidae and Xylophagidae, in contrast to all other taxa, where no dioptric apparatus is found. 5. In “Orthorrapha” and in “Aschiza”, rhabdomeric photoreceptors occur, forming a fused, star-shaped or Ktticed rhabdom. In Schizophoran larvae, retinular cells are distinguished by a different type of surface enlargement of the photoreceptor cell membrane. Here, the membrane forms flat ramella. The latter originate from transformed and/or rudimentary rhabdomeric microvilli. 6. In the primitive “Orthorrhapha”, pigment cups can be found, that are composed of retinular pirnent, whereas in derived Brachycera, pigment grains are absent. In Cyclorrhapha, tentorial piramata and their optic deressions operate as external and functional piment cups 7. In Therevidae and in Syrphidae, a tracheal tapetum lucidum can be founfi which la, been evolved independently in both families. The tapetum is always found together with inversely orientated retinular cells. 8. The homology of Brachceran stemmata is shown by a transformation series of stem-mata's site and fine structure. The homology is corroborated by the identical innervation in primitive and derived taxa, the identical site within Cyclorrhaha, and structural similarities of “Orthorrhaphan” and primitive Cylorrhaphan stemmata. Although transformations of the fine structure appear as a sequence or reductions, particular adaptations such as multilication of retinular celfs (Epistrophe), or deepening of the pigment cup (Musca) have evolved separately. Despite the fact that in Brachyceran larvae the head has been reorganized, the eyes still keep contact with the epithelium of the frontal sacks and/or tentorial phragmata. 9. The transformation series given shows that Bolwig's organ represents a highly modified stemma.     

Electrophysiology of the visual system in the cricket Gryllus firmus (Orthoptera: Gryllidae): Spectral sensitivity of the compound eyes

The electroretinographic spectral sensitivity of the cricket compound eyes shows the presence of two receptor types, a dominant one at 520 nm and another in the near-u.v. (λ_max 355 ± 5 nm) under dark- and intense chromatic adaptation conditions (Fig. 3). The waveform of the electrical responses elicited by short-wavelength stimuli differ from those elicited by long wavelength stimuli (Fig. 1).     

Characterization of the Muscle Electrical Properties in Low Back Pain Patients by Electrical Impedance Myography

Objectives

This study aims to investigate the electrical properties of lumbar paraspinal muscles (LPM) of patients with acute lower back pain (LBP) and to study a new approach, namely Electrical Impedance Myography (EIM), for reliable, low-cost, non-invasive, and real-time assessment of muscle-strained acute LBP.

Design

Patients with muscle-strained acute LBP (n = 30) are compared to a healthy reference group (n = 30). Electrical properties of LPM are studied.

Background

EIM is a novel technique under development for the assessment of neuromuscular disease. Therefore, it is speculated that EIM can be employed for the assessment of muscle-strained acute LBP.

Methods

Surface electrodes, in 2-electrode configurations, was used to measure the electrical properties of patient''s and healthy subject''s LPM at six different frequencies (0.02, 25.02, 50.02, 1000.02, 3000.02, and 5000.02 kHz), with the amplitude of the applied voltage limited to 200 mV. Parameters of impedance (Z), extracellular resistance (R_e), intracellular resistance (R_i), and the ratio of extracellular resistance to intracellular resistance (R_e/R_i) of LBP patient''s and healthy subject''s LPM were assessed to see if significant difference in values obtained in muscle-strained acute LBP patients existed.

Results

Intraclass correlation coefficient (ICC) showed that all measurements (ICC>0.96 for all studying parameters: Z, R_e, R_i, and R_e/R_i) had good reliability and validity. Significant differences were found on Z between LBP patient''s and healthy subject''s LPM at all studying frequencies, with p<0.05 for all frequencies. It was also found that R_e (p<0.05) and R_e/R_i (p<0.05) of LBP patient''s LPM was significant smaller than that of healthy subjects while R_i (p<0.05) of LBP patient''s LPM was significant greater than that of healthy subjects. No statistical significant difference was found between the left and right LPM of LBP patients and healthy subjects on the four studying parameters.

Conclusion

EIM is a promising technique for assessing muscle-strained acute LBP.     

Electroretinogram and the spectral sensitivity of the compound eyes in the firefly Photuris versicolor (Coleoptera-Lampyridae): A correspondence between green sensitivity and species bioluminescence emission

ERGs were recorded from the dorsal sector of dark- and chromatic-adapted compound eyes in the dark-active firefly Photuris versicolor ♀ and ♂ at different wavelengths across the spectrum ranging from 320 nm to 700 nm over 4.5 log units of change in the stimulus intensity. ERG elicited by white light stimulus was an on-negative monophasic wave typical of scotopic eyes. ERGs elicited by chromatic stimuli differed in their waveform characteristics in the short (near-u.v. and violet) and long (green-yellow) wavelengths. The slope of the intensity-response curves at different stimulus wavelengths were similar for phasic response and differed for the plateau component of the ERG. The spectral sensitivity curves obtained under dark- and chromatic-adapted conditions revealed peaks in the near-u.v. (λ_max, 380 nm) and in the green (λ_max 550 nm), suggesting the presence of at least two receptor types in the dorsal sector of the compound eyes of P. versicolor. The green (550 nm) peak corresponds with the species bioluminescence emission peak (552 nm).     

The effect of light-dark adaptation on the ultrastructure ofLimulus lateral eye retinular cells

Summary The fine structure of retinular cells within lateral eyes ofLimulus polyphemus which had been dark or light adapted for 12 h in vivo was studied via electron microscopy. The ommatidium to ommatidium and retinular cell to retinular cell variability observed in light microscope studies was confirmed. The rhabdomeric microvilli were longer and narrower, the area of contiguous microvillar membranes greater, the endoplasmic reticulum less abundant and the mitochondrial granules (? calcium containing) more numerous in well dark adapted than in well light adapted retinular cells (Figs. 1, 3, 4, 7, 8) and membrane whorls or vacuoles were present in the peripheral cytoplasm of very well light adapted retinular cells (Fig. 6). Phagocytotic vesicles, multivesicular bodies and lysosomes were present in the interrhabdomeral cytoplasm of partially light adapted retinular cells (Figs. 1, 2, 3, 10). The number of retinular cell microvilli in contact with the eccentric cell dendrite was smaller in very well light adapted than in well dark adapted ommatidia (Fig. 9). The possible functional significance of these light-dependent structural changes is discussed.This investigation was supported in part by Grant 2 RO1 EY 00236 National Eye Institute, National Institutes of HealthMember of the SFB 160 of the Deutsche Forschungsgemeinschaft