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
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TL;DR: Differences between day and night values and between autumn and spring suggest that pineal melatonin acts as neurochemical signal mediating rhythmic processes and behaviour.
Abstract: We studied ten species of demersal fish from depths of 1500-4800 m, i.e. regions of the abyss outside the reach of sunlight. A pineal window in the skin and/or the skull, often found in mesopelagic fish, was never observed in demersal specimens. Nine species had a well-developed pineal organ, with light- and electron-microscopic features, well known in other teleosts living in surface waters, including photoreceptor cells with inner and outer segments, synaptic ribbons, neuronal perikarya, and (radial) glial cells. One species ( Bathypterois dubius) showed signs of regression; it also had reduced eyes. We observed considerable morphological variation in location, size, microscopic structure and ultrastructural organisation, including the frequency of photoreceptor cells, size of outer segments and the number of myelinated and unmyelinated axons. No systematic trend in the sense of an increase of sensitivity with greater depths was observed. Melatonin contents varied between 4 pg and 92 pg per pineal in the grenadier Coryphaenoides ( Nematonurus) armatus and between 2 pg and 70 pg per pineal in the eel Synaphobranchus kaupi. Differences between day and night values and between autumn and spring suggest that pineal melatonin acts as neurochemical signal mediating rhythmic processes and behaviour. The role of an alternative non-solar zeitgeber in the demersal environment is discussed.
16 citations
"Pineal organs of deep-sea fish: pho..." refers background in this paper
...We also investigated the pineal of the deep demersal eel, Synaphobranchus kaupi(Wagner and Mattheus, 2002)....
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...Interestingly, among the demersal population, the differentiation of the pineal cells was much more correlated with the differentiation of the retina than with the depth that the fish inhabited (Wagner and Mattheus, 2002)....
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...…level have shown photoreceptors with varying numbers of discs in their outer segments, along with other typical attributes such as synaptic ribbons and other cell types, some of which contain dense bundles of intermediate filaments (McNulty and Nafpaktitis, 1976, 1977; Wagner and Mattheus, 2002)....
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...Bin size is 2·nm. 2385Pineal organs of deep-sea fish the previous morphological studies (Wagner and Mattheus, 2002) are bottom dwellers and have been caught between ~1000 and 2000·m....
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Journal Article•
TL;DR: The pineal organ and retina of the rat-fish Chimaera monstrosa were compared by electron microscopy and immunocytochemistry using antisera against colour-specific opsins and paying special attention to pineal CSF-contacting neurons and retinal Landolt's clubs, finding them to be principally similar in cytology.
Abstract: The pineal organ and retina of the rat-fish Chimaera monstrosa were compared by electron microscopy and immunocytochemistry using antisera against colour-specific opsins and paying special attention to pineal CSF-contacting neurons and retinal Landolt's clubs. In the retina, a large number of Landolt's clubs and two types of rod-like photoreceptors were found. The outer segments of the numerous electron-dense "tall rods" displayed strong immunoreactivity with the monoclonal OS-2 antibodies--first of all detecting green- and blue-sensitive pigments. These results point out the presence of a chrysopsin-like photopigment. A weak cross-reactivity with the COS-1 and rhodopsin antisera indicates that the photopigment in question has certain amino acid sequence homologies with red and green photopigments. The outer segments of the few electron-lucent "broad rods" reacted with the OS-2 antiserum intensely but weakly with the COS-1 antiserum, a result suggesting the presence of a (blue?) photopigment differing from that of the tall rods. Since in the pineal organ the outer segments of the photoreceptor cells were opsin-immunonegative with all four antisera used, it is suggested that they contain an essentially different (UV-blue?) pigment. The pineal CSF-contacting neurons and retinal Landolt's bipolars were found to be principally similar in cytology. Their ciliated (receptor) dendrite terminals protruding into the photoreceptor space lacked photoreceptor membranes and were opsin-immunonegative. They are supposed to perceive information (on ionic properties?) from the fluid of the pineal lumen and retinal photoreceptor space. On the other hand, by their synaptic connections the CSF-contacting neurons and Landolt's bipolars are considered to be secondary neurons of the light-perceiving pathway of both organs.
12 citations
"Pineal organs of deep-sea fish: pho..." refers background in this paper
...…of pineal photoreceptors, employing a range of antibodies (e.g. COS and OS) raised against retinal opsins (Forsell et al., 2001; Garcia-Fernandez et al., 1997; Tamotsu et al., 1994; Vigh-Teichmann et al., 1990, 1992), which again indicate that both rod-like and cone-like opsins may be present....
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TL;DR: Both the retina and pineal organ appear to be suitably differentiated to detect light in the larval and embryonic charr and cisco, and may be involved in negative phototaxic behavior.
Abstract: The pineal organ and retina were compared in developing charr and cisco, further in adult cisco, eel, creek chub, dace, zebrafish and black moli by opsin immunocytochemistry. In prehatching charr embryos, retinal rods and cones and pinealocytes displayed well-developed outer segments and formed synapses. Differentiation of the retina started centrally but was more advanced in the dorso-caudal retina than rostroventrally. The pineal organ differentiated earlier distally than proximally. In the cisco, the pineal organ and retina differentiated around hatching. In charr embryos, further in the larval and adult species studied, opsin immunoreactivity was found in retinal rods, accessory cones and many "rod-like" pinealocytes, a result indicating the presence of rhodopsin and/or porphyropsin. Retinal principle cones, long and short cones and some "cone-like" pinealocytes were opsin-immunonegative; they are thought to represent red- and/or u.v./violet-sensitive elements. The pineal organ may be involved in negative phototaxic behavior. Both the retina and pineal organ appear to be suitably differentiated to detect light in the larval and embryonic charr.
10 citations
"Pineal organs of deep-sea fish: pho..." refers background in this paper
...…of pineal photoreceptors, employing a range of antibodies (e.g. COS and OS) raised against retinal opsins (Forsell et al., 2001; Garcia-Fernandez et al., 1997; Tamotsu et al., 1994; Vigh-Teichmann et al., 1990, 1992), which again indicate that both rod-like and cone-like opsins may be present....
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