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: The results of the present study provide the first evidence that melatonin enhances TH expression in specific brain regions in a non‐mammalian species, and could represent one pathway by which environmental factors could modulate reproductive function in the eel.
Abstract: In the eel, a deficit in gonadotrophin-releasing hormone (GnRH) and a strong dopaminergic (DA) inhibition are responsible for the blockade of gonad development if silver eels are prevented from their reproductive migration. Environmental factors that eels encounter during their oceanic reproductive migration are thought to play an important role in the stimulation of eel pubertal development. We investigated the potential role of melatonin, a known mediator of the effects of external factors on reproductive function in vertebrates. We demonstrated that a long-term melatonin treatment increased brain tyrosine hydroxylase (TH, the rate limiting enzyme of DA synthesis) mRNA expression in a region-dependent way. Melatonin stimulated the dopaminergic system of the preoptic area, which is involved in the inhibitory control of gonadotrophin [luteinising hormone (LH) and follicle-stimulating hormone (FSH)] synthesis and release. Moreover, we showed that the increased TH expression appeared to be consistent with melatonin binding site distribution as shown by 2[(125)I]-melatonin labelling studies. On the other hand, melatonin had no effects on the two eel native forms of GnRH (mGnRH and cGnRH-II) mRNA expression. Concerning the pituitary-gonad axis, we showed that melatonin treatment decreased both gonadotrophin beta-subunit (LHbeta, FSHbeta) mRNA expression and reduced sexual steroid (11-ketotestosterone, oestradiol) plasma levels. This indicates that melatonin treatment had a negative effect on eel reproductive function. To our knowledge, the results of the present study provide the first evidence that melatonin enhances TH expression in specific brain regions in a non-mammalian species. By this mechanism melatonin could represent one pathway by which environmental factors could modulate reproductive function in the eel.
83 citations
TL;DR: The first evidence of relative photoreception in teleosts was obtained in cod suggesting that the definition of illuminance thresholds (day/night perception) would depend on the day intensity, and a single order of magnitude increase or decrease in day intensity was shown to elicit a significant shift in the intensity response curve of night-time melatonin suppression.
74 citations
TL;DR: This review will focus on the behavioural rhythms of crustacean decapods inhabiting depths where the sun light is absent, and potential scenarios for future research on deep-sea decapod behaviour are suggested by new in situ observation technologies.
Abstract: Ocean waters deeper than 200 m cover 70% of the Earth's surface. Light intensity gets progressively weaker with increasing depth and internal tides or inertial currents may be the only remaining zeitgebers regulating biorhythms in deep-sea decapods. Benthopelagic coupling, exemplified by vertically moving shrimps within the water column, may also act as a source of indirect synchronisation to the day-night cycle for species living in permanently dark areas. At the same time, seasonal rhythms in growth and reproduction may be an exogenous response to spring-summer changes in upper layer productivity (via phytoplankton) or, alternatively, may be provoked by the synchronisation mediated by an endogenous controlling mechanism (via melatonin). In our review, we will focus on the behavioural rhythms of crustacean decapods inhabiting depths where the sun light is absent. Potential scenarios for future research on deep-sea decapod behaviour are suggested by new in situ observation technologies. Permanent video observatories are, to date, one of the most important tools for marine chronobiology in terms of species recognition and animals' movement tracking.
61 citations
TL;DR: A morphometry-based protocol for automated video-image analysis where animal movement tracking (by frame subtraction) is accompanied by species identification from animals' outlines by Fourier Descriptors and Standard K-Nearest Neighbours methods is elaborated.
Abstract: The understanding of ecosystem dynamics in deep-sea areas is to date limited by technical constraints on sampling repetition. We have elaborated a morphometry-based protocol for automated video-image analysis where animal movement tracking (by frame subtraction) is accompanied by species identification from animals' outlines by Fourier Descriptors and Standard K-Nearest Neighbours methods. One-week footage from a permanent video-station located at 1,100 m depth in Sagami Bay (Central Japan) was analysed. Out of 150,000 frames (1 per 4 s), a subset of 10.000 was analyzed by a trained operator to increase the efficiency of the automated procedure. Error estimation of the automated and trained operator procedure was computed as a measure of protocol performance. Three displacing species were identified as the most recurrent: Zoarcid fishes (eelpouts), red crabs (Paralomis multispina), and snails (Buccinum soyomaruae). Species identification with KNN thresholding produced better results in automated motion detection. Results were discussed assuming that the technological bottleneck is to date deeply conditioning the exploration of the deep-sea.
56 citations
Cites background from "Pineal organs of deep-sea fish: pho..."
...The physiological and behavioural response of deep-sea fishes and crustaceans to rhythmic changes in bottom currents was already characterized in the Atlantic [5,29-31]....
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01 Nov 2007
TL;DR: Observations strongly suggest that biological rhythms are present in demersal fish, the melatonin metabolism shows signs of periodicity, and tidal currents may act as zeitgeber at the bottom of the deep sea.
Abstract: We have studied physical and biological rhythms in the deep demersal habitat of the Northeastern Atlantic. Current velocity and direction changes occurred at intervals of 12.4 h, demonstrating that they could have an impact of tidal activity, and also showed indications of other seasonal changes. As an indicator of biological rhythms, we measured the content of pineal and retinal melatonin in the grenadier Coryphaenoides armatus and the deep-sea eel Synaphobranchus kaupii, and determined the spontaneous release of melatonin in long-term (52 h minimum) cultures of isolated pineal organs and retinae in S. kaupii. The results of the release experiments show statistically significant signs of synchronicity and periodicity suggesting the presence of an endogenous clock. The melatonin content data show large error bars typical of cross-sectional population studies. When the data are plotted according to a lunar cycle, taken as indication of a tidal rhythm, both species show peak values at the beginning of the lunar day and night and lower values during the second half of lunar day and night and during moonrise and moonset. Statistical analysis, however, shows that the periodicity of the melatonin content is not significant. Taken together these observations strongly suggest that (1) biological rhythms are present in demersal fish, (2) the melatonin metabolism shows signs of periodicity, and (3) tidal currents may act as zeitgeber at the bottom of the deep sea.
54 citations
References
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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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