Estimated absorbance spectra of the visual pigments of the North Atlantic right whale (Eubalaena glacialis)

To assess the spectral sensitivities of the retinal visual pigments from the North Atlantic right whale (Eubalaena glacialis), we have cloned and sequenced two exons from the rod opsin gene and two exons from the middle‐wavelength sensitive (MWS) cone opsin gene in order to determine the amino acids at positions known to be key regulators of the spectral location of the absorbance maximum (λ_max). Based on previous mutagenesis models we estimate that the right whale possesses a rod visual pigment with a λ_max of 499 nm and a MWS cone visual pigment with a λ_max of 524 nm. Although the MWS cone visual pigment from the right whale is blue‐shifted in its spectral sensitivity like those from odontocetes, the spectral sensitivity of the right whale rod visual pigment is similar to those from terrestrial mammals.     

Interspecific variation in the visual pigments of deep-sea fishes

Summary Visual pigments in the rods of 38 species of deep-sea fish were examined by microspectrophotometry. 33 species were found to have a single rhodopsin with a wavelength of maximum absorbance ( _max) in the range 470–495 nm. Such visual pigments have absorbance maxima close to the wavelengths of maximum spectral transmission of oceanic water. 5 species, however, did not conform to this pattern and visual pigments were found with _max values ranging from 451 nm to 539 nm. In 4 of these species two visual pigments were found located in two types of rod. Some 2-pigment species which have unusual red sensitivity, also have red-emitting photophores. These species have both rhodopsin and porphyropsin pigments in their retinae, which was confirmed by HPLC, and the two pigments are apparently located in separate rods in the same retinal area. In deep-sea fishes the occurrence of unusual visual pigments seems to be correlated with aspects of the species' depth ranges. In addition to ecological influences we present evidence, in the form of _max spectral clustering, that indicates the degree of molecular constraint imposed on the evolution of visual pigments in the deep-sea.     

The photoreceptor system in the retinae of two dogfishes, Scyliorhinus canicula and Galeus melastomus: possible relationship with depth distribution and predatory lifestyle

The small spotted dogfish Scyliorhinus canicula and the blackmouth dogfish Galeus melastomus, whose depth distributions overlap in the upper part of the slope (c. 500 m depth), where they have access to the same prey community, have well‐developed eyes and a pure‐rod retina with a single layer of photoreceptors. Interspecific differences in rod outer segment length (L_ROS) within retinal regions were found. In the periphery and the retinal centre G. melastomus showed a L_ROS 24 and 30% longer, respectively, than S. canicula and, therefore, a potential for increased sensitivity. In both species longer L_ROS were always found in correspondence with the retinal centre where the ganglion cell topography formed a horizontal meridian that allowed for better discrimination of the horizon in the visual field. In this area L_ROS reached 53·4±4·1μm in S. canicula and 77·1±10·5μm in G. melastomus against 46·3±4·2μm and 61·1±10·1μm in the retinal periphery. No significant differences were recorded in L_ROS and rod density during growth. In both species, a rapid increase of theoretical visual acuity was found to be related to an increase in fish L_T and lens size. Visual acuity ranged between 1·7 and 3 cycles degree^‐1 in S. canicula and 2·4 and 4·2 in G. melastomus. The G. melastomus rod visual pigment showed the characteristic spectral adaptation to vision in deep‐water (λ_max of 481 nm), but was also well placed to detect the bioluminescence of some of its main prey species. In S. canicula the visual pigment absorption (λ_max of 496 nm) was more typical of shallow water living fishes. The opsin sequences of the two visual pigments are discussed and key amino acid sites were identified where sequence changes could be responsible for the spectral absorption differences between the two species. The possible relationship between L^ROS, visual acuity, visual pigment absorption, depth distribution and feeding behaviour are discussed.     

The visual pigment sensitivity hypothesis: further evidence from fishes of varying habitats

Summary Visual pigments were extracted from the retinas of 8 species of marine teleosts and 4 species of elasmobranchs and a comparison was made of the pigment properties from these fishes, some inhabiting surface waters, others from the mesopelagic zone, and a few migrating vertically between these two environments. An association was found between the spectral position of the absorbance curve and the habitat depth or habitat behavior, with the blue-shifted chrysopsins being the pigments of the twilight zone fishes and the rhodopsins with fishes living near the surface. The retina of the swell shark (Cephaloscyllium ventriosum) yielded extracts with two photopigments; one, a rhodopsin at 498 nm; the second, a chrysopsin at 478 nm. This fish has been reported to practice seasonal vertical migrations between the surface and the mesopelagic waters. In addition to the spectral absorbance, several properties of these visual pigments were examined, including the meta-III product of photic bleaching, regeneration with added 11-cis and 9-cis retinals, and the chromophoric photosensitivity. The chrysopsin properties were found to be fundamentally similar to those of typical vertebrate rhodopsins. Correlating the spectral data with the habitat and habitat behavior of our fishes gives us confidence in the idea that the scotopic pigments have evolved as adaptations to those aspects of their color environment that are critical to the survival of the species.     

Electrophysiological measurements of spectral mechanisms in the retinas of two cervids: white-tailed deer (Odocoileus virginianus) and fallow deer (Dama dama)

Electroretinogram (ERG) flicker photometry was used to study the spectral mechanisms in the retinas of white-tailed deer (Odocoileus virginianus) and fallow deer (Dama dama). In addition to having a rod pigment with maximum sensitivity (_max) of about 497 nm, both species appear to have two classes of photopic receptors. They share in common a short-wavelength-sensitive cone mechanism having _max in the region of 450–460 nm. Each also has a cone having peak sensitivity in the middle wavelengths, but these differ slightly for the two species. In white-tailed deer the _max of this cone is about 537 nm; for the fallow deer the average _max value for this mechanism was 542 nm. Deer resemble other ungulates and many other types of mammal in having two classes of cone pigment and, thus, the requisite retinal basis for dichromatic color vision.Abbreviations ERG electroretinogram - LWS long wavelength sensitive - MWS middle wavelength sensitive - SWS short wavelength sensitive     

Visual pigments of marine carnivores: pinnipeds, polar bear, and sea otter

Rod and cone visual pigments of 11 marine carnivores were evaluated. Rod, middle/long-wavelength sensitive (M/L) cone, and short-wavelength sensitive (S) cone opsin (if present) sequences were obtained from retinal mRNA. Spectral sensitivity was inferred through evaluation of known spectral tuning residues. The rod pigments of all but one of the pinnipeds were similar to those of the sea otter, polar bear, and most other terrestrial carnivores with spectral peak sensitivities (λ_max) of 499 or 501 nm. Similarly, the M/L cone pigments of the pinnipeds, polar bear, and otter had inferred λ_max of 545 to 560 nm. Only the rod opsin sequence of the elephant seal had sensitivity characteristic of adaptation for vision in the marine environment, with an inferred λ_max of 487 nm. No evidence of S cones was found for any of the pinnipeds. The polar bear and otter had S cones with inferred λ_max of ∼440 nm. Flicker-photometric ERG was additionally used to examine the in situ sensitivities of three species of pinniped. Despite the use of conditions previously shown to evoke cone responses in other mammals, no cone responses could be elicited from any of these pinnipeds. Rod photoreceptor responses for all three species were as predicted by the genetic data.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Thermal response of demersal and pelagic juvenile fishes from the surf zone during a heat‐wave simulation

Experimental measurements were collected in the laboratory to evaluate the maximum thermal limit and thermal plasticity of Neotropical juvenile fish with different life habitats (demersal and pelagic) from surf zone in response to a “heat‐wave experiment”. Trials were conducted using two temperature acclimations (T_a), including the current average temperature of Southeastern Brazil (T_a: 14 days at 25°C) and the “heat‐wave experiment” (T_a: 14 days at 30°C), simulating a heat‐wave event that occurs when the daily maximum temperature of more than five consecutive days exceeds the average maximum temperature by 5°C. Typical species of the surf zone were used: the demersal White sea catfish (Genidens barbus) and Gulf kingcroaker (Menticirrhus littoralis), and the pelagic fishes Great pompano (Trachinotus goodei) and Long‐fin mullet (Mugil brevirostris). The thermal range and plasticity values for the both life‐habitats species were verified through current and heat‐wave acclimation. The thermal tolerance at high temperatures (CT_max) of these species differed between T_a, habitat and species. Fish showed a species‐specific response to temperature increase, regardless of their habitat even under similar abiotic conditions. However, at the heat‐wave simulation, the demersal fish presented a greater thermal plasticity in relation to the pelagic fish. Despite the higher thermal tolerance when exposed to heat‐wave simulation, all fish species displayed a lower thermal edge safety that is markedly close to their maximum thermal limits.     

Colour vision and visual ecology of the blue-spotted maskray, <Emphasis Type="Italic">Dasyatis kuhlii</Emphasis> Müller &; Henle, 1814

Relatively little is known about the physical structure and ecological adaptations of elasmobranch sensory systems. In particular, elasmobranch vision has been poorly studied compared to the other senses. Virtually nothing is known about whether elasmobranchs possess multiple cone types, and therefore the potential for colour vision, or how the spectral tuning of their visual pigments is adapted to their different lifestyles. In this study, we measured the spectral absorption of the rod and cone visual pigments of the blue-spotted maskray, Dasyatis kuhlii, using microspectrophotometry. D. kuhlii possesses a rod visual pigment with a wavelength of maximum absorbance (λ_max) at 497 nm and three spectrally distinct cone types with λ_max values at 476, 498 and 552 nm. Measurements of the spectral transmittance of the ocular media reveal that wavelengths below 380 nm do not reach the retina, indicating that D. kuhlii is relatively insensitive to ultraviolet radiation. Topographic analysis of retinal ganglion cell distribution reveals an area of increased neuronal density in the dorsal retina. Based on peak cell densities and using measurements of lens focal length made using laser ray tracing and sections of frozen eyes, the estimated spatial resolving power of D. kuhlii is 4.10 cycles per degree.     

Visual pigments, oil droplets, ocular media and cone photoreceptor distribution in two species of passerine bird: the blue tit (Parus caeruleus L.) and the blackbird (Turdus merula L.)

The spectral absorption characteristics of the retinal photoreceptors of the blue tit (Parus caeruleus) and blackbird (Turdus merula) were investigated using microspectrophotometry. The retinae of both species contained rods, double cones and four spectrally distinct types of single cone. Whilst the visual pigments and cone oil droplets in the other receptor types are very similar in both species, the wavelength of maximum sensitivity (λ_max) of long-wavelength-sensitive single and double cone visual pigment occurs at a shorter wavelength (557 nm) in the blackbird than in the blue tit (563 nm). Oil droplets located in the long-wavelength-sensitivesingle cones of both species cut off wavelengths below 570–573 nm, theoretically shifting cone peak spectral sensitivity some 40 nm towards the long-wavelength end of the spectrum. This raises the possibility that the precise λ_max of the long-wavelength-sensitive visual pigment is optimised for the visual function of the double cones. The distribution of cone photoreceptors across the retina, determined using conventional light and fluorescence microscopy, also varies between the two species and may reflect differences in their visual ecology. Accepted: 8 January 2000     

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).     

Visual and lenticular pigments in the eyes of demersal deep-sea fishes

We report on the lens pigmentation and visual pigments of 52 species of demersal deep-sea fishes caught at depths ranging from 480 m to 4110 m in the Porcupine Seabight and Goban Spur area of the North-eastern Atlantic. Only one species, caught between 480 and 840 m, had a lens with large amounts of pigment, consistent with the hypothesis that heavily pigmented lenses in deep-sea fish serve to enhance the contrast of bioluminescent signals by removing much of the background radiance, which is only visible to fish living shallower than 1000 m. Low concentrations of lens pigmentation were also observed in a further two species (Rouleina attrita and Micromesisteus poutassou). The retinae of all species except five, contained only a single visual pigment, as determined by microspectrophotometry of individual rods, and/or spectrophotometry of retinal wholemounts and retinal extracts. Those fishes caught between 500 m and 1100 m had wavelengths of peak sensitivity (_max) ranging from 476 nm to 494 nm, while most fish living below 1100 m tended to be more conservative with (_max) values ranging from 475 nm to 485 nm. The only exceptions to this were three deep-living species caught between 1600 m and 2000 m whose retinae contain abnormally short-wave sensitive visual pigments (Cataetyx laticeps — _max 468 nm; Alepocephalus bairdii — _max 467 nm; Narcetes stomias _max 472 nm), suggesting adaptation for the detection of short-wave bioluminescence.     

The photic environment and scotopic visual pigments of the creek chub,Semotilus atromaculatus and white sucker,Catostomus commersoni

Summary Scotopic visual pigments measured in the creek chub and the white sucker are porphyropsins with mean _max values located at 538.3 and 536.5 nm, respectively. There is a shift of the _max towards shorter wavelengths during the winter in both of these species coinciding with similar changes in the quality of downwelling light. _max is significantly correlated to the P₅₀ and spectrum width of the downwelling light and dissolved oxygen. An analysis of variance shows that there are significant differences between the _max values of: fish in the two lakes, fish at different times, the two species at different times and fish in different lakes at different seasons. The offset visual pigments of both species appear to be well adapted to their photic environment in terms of the contrast hypothesis. This improvement of contrast detection is discussed in relation to their feeding habits.Abbreviations _max wavelength at which absorbance is maximum - P₅₀ wavelength which halves the total number of photons between 400 and 700 nm, a measure of spectral quality - PAR photosynthetically active radiation - MSP microspectrophotometric - SE standard error     

Vision in the common bed bug Cimex lectularius L. (Hemiptera: Cimicidae): eye morphology and spectral sensitivity

Bed bugs as pests of public health importance recently experienced a resurgence in populations throughout the U.S. and other countries. Consequently, recent research efforts have focused on improving understanding of bed bug physiology and behaviour to improve management. While few studies have investigated the visual capabilities of bed bugs, the present study focused specifically on eye morphology and spectral sensitivity. A 3‐D imaging technique was used to document bed bug eye morphology from the first instar through adult and revealed morphological characteristics that differentiate the common bed bug from the tropical bed bug as well as sex‐specific differences. Electrophysiological measurements were used to evaluate the spectral sensitivity of adult bed bugs. Male bed bugs were more responsive than females at some wavelengths. Electrophysiological studies provided evidence for at least one photoreceptor with a spectral sensitivity curve peak in the green (λ_max 520 nm) region of the spectrum. The broadened long wavelength portion of the spectral sensitivity curve may potentially indicate another photoreceptor in the yellow–green (λ_max 550 nm) portion of the spectrum or screening pigments. Understanding more about bed bug visual biology is vital for designing traps, which are an important component of integrated bed bug management.     

Wavelength-dependent induction of UV-absorbing mycosporine-like amino acids in the red alga Chondrus crispus under natural solar radiation

Polychromatic response spectra for the induction of UV absorbing mycosporine-like amino acids (MAAs) were calculated after exposing small thalli of the red alga Chondrus crispus under various cut-off filters to natural solar radiation on the North Sea island Helgoland, Germany. The laboratory-grown specimens typically contain only traces of palythine and synthesise five different MAAs rapidly and in high concentrations after being transplanted into shallow water. The resulting qualitative and quantitative patterns of MAA induction differed markedly with respect to spectral distribution. Furthermore, the wavebands effective for MAA induction vary within the MAA. UV-B radiation had a negative effect on the accumulation of the major MAAs shinorine (λ_max=334 nm) and palythine (λ_max=320 nm), while short wavelength UV-A exhibits the highest quantum efficiency on their synthesis. In contrast, the synthesis of asterina-330 (λ_max=330 nm), palythinol (λ_max=332 nm) and palythene (λ_max=360 nm) was mainly induced by UV-B radiation. Whether the synthesis of shinorine and palythine is induced by a photoreceptor with an absorption maximum in the short wavelength UV-A and whether a second photoreceptor absorbing UV-B radiation is responsible for the induction of asterina-330, palythinol and palythene remains to be studied.Our results show that C. crispus has a high capacity to adapt flexibly the qualitative and quantitative MAA concentration to the prevailing spectral distribution of irradiance. On one hand, this is regarded as an important aspect with respect to the acclimation of algae to increasing UV-B irradiance in the context of ongoing depletion of stratospheric ozone. On the other hand, the experiment demonstrates that UV-A irradiance is more important for the induction of the major MAAs shinorine and palythine than UV-B.     

Temperate macroalgae impacts tropical fish recruitment at forefronts of range expansion

Warming waters and changing ocean currents are increasing the supply of tropical fish larvae to temperature regions where they are exposed to novel habitats, namely temperate macroalgae and barren reefs. Here, we use underwater surveys on the temperate reefs of south-eastern (SE) Australia and western Japan (~33.5°N and S, respectively) to investigate how temperate macroalgal and non-macroalgal habitats influence recruitment success of a range of tropical fishes. We show that temperate macroalgae strongly affected recruitment of many tropical fish species in both regions and across three recruitment seasons in SE Australia. Densities and richness of recruiting tropical fishes, primarily planktivores and herbivores, were over seven times greater in non-macroalgal than macroalgal reef habitat. Species and trophic diversity (K-dominance) were also greater in non-macroalgal habitat. Temperate macroalgal cover was a stronger predictor of tropical fish assemblages than temperate fish assemblages, reef rugosities or wave exposure. Tropical fish richness, diversity and density were greater on barren reef than on reef dominated by turfing algae. One common species, the neon damselfish (Pomacentrus coelestis), chose non-macroalgal habitat over temperate macroalgae for settlement in an aquarium experiment. This study highlights that temperate macroalgae may partly account for spatial variation in recruitment success of many tropical fishes into higher latitudes. Hence, habitat composition of temperate reefs may need to be considered to accurately predict the geographic responses of many tropical fishes to climate change.

     

Sequence and localization of an ultraviolet (sws1) opsin in the retina of the Japanese sardine Sardinops melanostictus (Teleostei: Clupeiformes)

A full‐length complementary (c)DNA encoding ultraviolet (UV)‐sensitive opsin (sws1) was isolated from the retina of the Japanese sardine Sardinops melanostictus. The sws1 phylogenetic tree showed a sister group relationship with the Cypriniformes, following the ray‐finned fish phylogeny. By expressing reconstituted opsin in vitro, it was determined that the maximum absorbance spectrum (λ_max) of sws1 is around 382 nm, being intermediate in position between two subtypes of sws1 pigment that are UV sensitive (λ_max = 355–380 nm) and violet sensitive (λ_max = 388–455 nm), which have been reported to date. The ocular media transmitted >20% transmittance of light in the range of 360–600 nm. In situ hybridization analyses revealed that sws1 messenger (m)RNA is localized in a central single cone surrounded by four double cones in a square mosaic. The square mosaic occupies the ventro‐temporal quadrant of the retina and the in situ hybridization signals were dominant in this area suggesting that the fish may use UV vision when looking upward. Based on these results, considerable significances of potential UV sensitivity, in relation to characteristic habits of S. melanostictus, are discussed.     

The Molecular Evolution of Visual Pigments of Freshwater Crayfishes (Decapoda: Cambaridae)

This study examines the diverse maximum wavelength absorption (λ_max) found in crayfishes (Decapoda: Cambaridae and Parastacidae) and the associated genetic variation in their opsin locus. We measured the wavelength absorption in the photoreceptors of six species that inhabit environments of different light intensities (i.e., burrows, streams, standing waters, and subterranean waters). Our results indicate that there is relatively little variation in λ_max (522–530 nm) among species from different genera and families. The existing variation did not correlate with the habitat differences of the crayfishes studied. We simultaneously sequenced the rhodopsin gene to identify the amino acid replacements that affect shifts in maximum wavelength absorption. We then related these to changes that correlated with shifts in λ_max by reconstructing ancestral character states using a maximum-likelihood approach. Using amino acid sequences obtained from five species (all were 301 amino acids in length), we identified a number of candidates for producing shifts of 4 to 8 nm in λ_max. These amino acid replacements occurred in similar regions to those involved in spectral shifts in vertebrates. Received: 12 March 1997 / Accepted: 3 June 1997     

Intraspecific variation of spectral sensitivity in threespine stickleback (Gasterosteus aculeatus) from different photic regimes

To examine the influence of the spectral characteristics of underwater light on spectral sensitivity of the ON and OFF visual pathways, compound action potential recordings were made from retinal ganglion cells of threespine stickleback from different photic regimes. In fish from a red-shifted photic regime (P₅₀ 680 nm for downwelling light at 1m), peak sensitivity of both the ON and OFF pathways was limited to long wavelength light (_max 600–620). In contrast, the ON pathway of fish from a comparatively blue-shifted (P₅₀ 566 nm) photic regime exhibited sensitivity to medium (_max 540–560) and long (_max 600 nm) wavelengths, while the OFF pathway exhibited peak sensitivity to only medium (_max 540 nm) wavelength light. In a third population, where the the ambient light is moderately red-shifted (P₅₀ 629 nm), the ON pathway once again exhibited only a long wavelength sensitivity peak at 620 nm, while the OFF pathway exhibited sensitivity to both medium (_max 560 nm) and long (_max 600–620 nm) wavelength light. These findings suggest that the photic environment plays an integral role in shaping spectral sensitivity of the ON and OFF pathways.     

Visual pigments and spectral sensitivity of the diurnal gecko Gonatodes albogularis

The visual pigments and oil droplets in the retina of the diurnal gecko Gonatodes albogularis were examined microspectrophotometrically, and the spectral sensitivity under various adapting conditions was recorded using electrophysiological responses. Three classes of visual pigments were identified, with _max at about 542, 475, and 362 nm. Spectral sensitivity functions revealed a broad range of sensitivity, with a peak at approximately 530–540 nm. The cornea and oil droplets were found to be transparent across a range from 350–700 nm, but the lens absorbed short wavelength light below 450 nm. Despite the filtering effect of the lens, a secondary peak in spectral sensitivity to ultraviolet wavelengths was found. These results suggest that G. albogularis does possess the visual mechanisms for discrimination of the color pattern of conspecifics based on either hue or brightness. These findings are discussed in terms of the variation in coloration and social behavior of Gonatodes.Abbreviations ERG electroretinogram - MSP microspectrophotometry - UV ultraviolet - _max wavelength of maximum absorbance     

Action Spectra and Adaptation Properties of Carp Photoreceptors

The mass photoreceptor response of the isolated carp retina was studied after immersing the tissue in aspartate-Ringer solution. Two electro-retinogram components were isolated by differential depth recording: a fast cornea-negative wave, arising in the receptor layer, and a slow, cornea-negative wave arising at some level proximal to the photoreceptors. Only the fast component was investigated further. In complete dark adaptation, its action spectrum peaked near 540 nm and indicated input from both porphyropsin-containing rods (λ_max ≈ 525 nm) and cones with longer wavelength sensitivity. Under photopic conditions a broad action spectrum, λ_max ≈ 580 nm was seen. In the presence of chromatic backgrounds, the photopic curve could be fractionated into three components whose action spectra agreed reasonably well with the spectral characteristics of blue, green, and red cone pigments of the goldfish. In parallel studies, the carp rod pigment was studied in situ by transmission densitometry. The reduction in optical density after a full bleach averaged 0.28 at its λ_max 525 nm. In the isolated retina no regeneration of rod pigment occurred within 2 h after bleaching. The bleaching power of background fields used in adaptation experiments was determined directly. Both rods and cones generated increment threshold functions with slopes of +1 on log-log coordinates over a 3–4 log range of background intensities. Background fields which bleached less than 0.5% rod pigment nevertheless diminished photoreceptor sensitivity. The degree and rate of recovery of receptor sensitivity after exposure to a background field was a function of the total flux (I x t) of the field. Rod saturation, i.e. the abolition of rod voltages, occurred after ≈12% of rod pigment was bleached. In light-adapted retinas bathed in normal Ringer solution, a small test flash elicited a larger response in the presence of an annular background field than when it fell upon a dark retina. The enhancement was not observed in aspartate-treated retinas.