Pineal organs of deep-sea fish: photopigments and structure.
TL;DR: The morphology and photopigments of the pineal organs from a number of mesopelagic fish, including representatives of the hatchet fish, scaly dragon-fish and bristlemouths, were examined, and two spectral classes of pinealocyte were identified, both spectrally distinct from the retinal rodphotopigment.
Abstract: We have examined the morphology and photopigments of the pineal organs from a number of mesopelagic fish, including representatives of the hatchet fish (Sternoptychidae), scaly dragon-fish (Chauliodontidae) and bristlemouths (Gonostomidae). Although these fish were caught at depths of between 500 and 1000 m, the morphological organisation of their pineal organs is remarkably similar to that of surface-dwelling fish. Photoreceptor inner and outer segments protrude into the lumen of the pineal vesicle, and the outer segment is composed of a stack of up to 20 curved disks that form a cap-like cover over the inner segment. In all species, the pineal photopigment was spectrally distinct from the retinal rod pigment, with lambdamax displaced to longer wavelengths, between approximately 485 and 503 nm. We also investigated the pineal organ of the deep demersal eel, Synaphobranchus kaupi, caught at depths below 2000 m, which possesses a rod visual pigment with lambdamax at 478 nm, but the pineal pigment has lambdamax at approximately 515 nm. In one species of hatchet fish, Argyropelecus affinis, two spectral classes of pinealocyte were identified, both spectrally distinct from the retinal rod photopigment.
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TL;DR: Pineal glands, which regulate circadian rhythms in response to light levels by releasing melatonin, are usually located on top of the brain just beneath the skull, which is an ideal position for deep-sea fish exposed to weak downwelling.
Abstract: James Bowmaker is fascinated by pineal glands. These photosensitive glands, which regulate circadian rhythms in response to light levels by releasing melatonin, are usually located on top of the brain just beneath the skull. Which is an ideal position for deep-sea fish exposed to weak downwelling
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Journal Article•
8,559 citations
"Pineal organs of deep-sea fish: pho..." refers methods in this paper
...2381Pineal organs of deep-sea fish Histology Pineal glands were isolated, preferably with parts of the cranium attached, and fixed in a mixture of 4% paraformaldehyde, 2% glutaraldehyde in 0.1·mol·l–1 cacodylate buffer (Karnovsky, 1965)....
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Journal Article•
5,201 citations
TL;DR: In this paper, the authors investigated the accuracy limits of putative universal templates for visual pigment absorbance spectra, and if possible to amend the templates to overcome the limitations, and concluded that the idea of universal templates remains valid and useful at the present level of accuracy of data on photoreceptor absorbance.
Abstract: Absorbance spectra were recorded by microspectrophotometry from 39 different rod and cone types representing amphibians, reptiles, and fishes, with A1- or A2-based visual pigments and λmax ranging from 357 to 620 nm. The purpose was to investigate accuracy limits of putative universal templates for visual pigment absorbance spectra, and if possible to amend the templates to overcome the limitations. It was found that (1) the absorbance spectrum of frog rhodopsin extract very precisely parallels that of rod outer segments from the same individual, with only a slight hypsochromic shift in λmax, hence templates based on extracts are valid for absorbance in situ; (2) a template based on the bovine rhodopsin extract data of Partridge and De Grip (1991) describes the absorbance of amphibian rod outer segments excellently, contrary to recent electrophysiological results; (3) the λmax/λ invariance of spectral shape fails for A1 pigments with small λmax and for A2 pigments with large λmax, but the deviations are systematic and can be readily incorporated into, for example, the Lamb (1995) template. We thus propose modified templates for the main “α-band” of A1 and A2 pigments and show that these describe both absorbance and spectral sensitivities of photoreceptors over the whole range of λmax. Subtraction of the α-band from the full absorbance spectrum leaves a “β-band” described by a λmax-dependent Gaussian. We conclude that the idea of universal templates (one for A1- and one for A2-based visual pigments) remains valid and useful at the present level of accuracy of data on photoreceptor absorbance and sensitivity. The sum of our expressions for the α- and β-band gives a good description for visual pigment spectra with λmax > 350 nm.
985 citations
"Pineal organs of deep-sea fish: pho..." refers background in this paper
...The visual pigment templates are ‘Govardovskii’ spectra (Govardovskii et al., 2000)....
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...Solid lines are pigment templates with λmax at 486·nm and 498·nm (Govardovskii et al., 2000)....
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TL;DR: How the interplay between the mechanisms that contribute to amplification and those that govern termination of G protein activity determine the speed and the sensitivity of the cellular response to light is examined.
Abstract: Phototransduction is the process by which a photon of light captured by a molecule of visual pigment generates an electrical response in a photoreceptor cell. Vertebrate rod phototransduction is one of the best-studied G protein signaling pathways. In this pathway the photoreceptor-specific G protein, transducin, mediates between the visual pigment, rhodopsin, and the effector enzyme, cGMP phosphodiesterase. This review focuses on two quantitative features of G protein signaling in phototransduction: signal amplification and response timing. We examine how the interplay between the mechanisms that contribute to amplification and those that govern termination of G protein activity determine the speed and the sensitivity of the cellular response to light.
608 citations
TL;DR: Good quantitative agreement was found when the microspectrophoto-metrically measured absorbance spectra were used to predict the behavioural sensitivity of individual animals to long wavelengths and suggests that the behavioural variation arises from variation in the retinal photopigments.
Abstract: The squirrel monkey (Saimiri sciureus) exhibits a polymorphism of colour vision: some animals are dichromatic, some trichromatic, and within each of these classes there are subtypes that resemble the protan and deutan variants of human colour vision. For each of ten individual monkeys we have obtained (i) behavioural measurements of colour vision and (ii) microspectrophotometric measurements of retinal photopigments. The behavioural tests, carried out in Santa Barbara, included wavelength discrimination, Rayleigh matches, and increment sensitivity at 540 and 640 nm. The microspectrophotometric measurements were made in London, using samples of fresh retinal tissue and a modified Liebman microspectrophotometer: the absorbance spectra for single retinal cells were obtained by passing a monochromatic measuring beam through the outer segments of individual rods and cones. The two types of data, behavioural and microspectrophotometric, were obtained independently and were handed to a third party before being interchanged between experimenters. From all ten animals, a rod pigment was recorded with $\lambda \_{\max}$ (wavelength of peak absorbance) close to 500 nm. In several animals, receptors were found that contained a short-wave pigment (mean $\lambda \_{\max}$ = 433.5 nm): these violet-sensitive receptors were rare, as in man and other primate species. In the middle- to long-wave part of the spectrum, there appear to be at least three possible Saimiri photopigments (with $\lambda \_{\max}$ values at about 537, 550 and 565 nm) and individual animals draw either one or two pigments from this set, giving dichromatic or trichromatic colour vision. Thus, those animals that behaviourally resembled human protanopes exhibited only one pigment in the red--green range, with $\lambda \_{\max}$ = 537 nm; other behaviourally dichromatic animals had single pigments lying at longer wavelengths and these were the animals that behaviourally had higher sensitivity to long wavelengths. Four of the monkeys were behaviourally judged to be trichromatic. None of the latter animals exhibited the two widely separated pigments (close to 535 and 567 nm) that are found in the middle- and long-wave cones of macaque monkeys. But the spread of $\lambda \_{\max}$ values for individual cones was greater in the trichromatic squirrel monkeys than in the dichromats; than in the case of three, behaviourally deuteranomalous, trichromats there was clear evidence that the distribution of $\lambda \_{\max}$ values was bimodal, suggesting photopigments at approximately 552 and 565 nm. The fourth, behaviourally protanomalous, trichromat exhibited a spread of individual $\lambda _{\max}$ values that ranged between 530 and 550 nm. Good quantitative agreement was found when the microspectrophotometrically measured absorbance spectra were used to predict the behavioural sensitivity of individual animals to long wavelengths. The concordance of the two sets of measurements places beyond question the existence of a polymorphism of colour vision in Saimiri sciureus and suggests that the behavioural variation arises from variation in the retinal photopigments. Heterozygous advantage may explain the polymorphism.
350 citations
"Pineal organs of deep-sea fish: pho..." refers methods in this paper
...The λmax of both the absorbance spectra and difference spectra were determined by a standard computer programme that best fits a visual pigment template to the right-hand limb of the spectra (Bowmaker et al., 1991; Mollon et al., 1984)....
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...Microspectrophotometric recordings were made in the conventional manner using a Liebman dual-beam microspectrophotometer (Bowmaker et al., 1991; Liebman and Entine, 1964; Mollon et al., 1984)....
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