Papers by Hans-Joachim Wagner
Naturwissenschaften, 1982
Vision Research, 1999
We investigate the processing of chromatic information in the outer retina of a cichlid fish, Aeq... more We investigate the processing of chromatic information in the outer retina of a cichlid fish, Aequidens pulcher. The colour opponent response characteristics of some classes of cone-specific horizontal cells in the fish retina are the result of feedforwardfeedback loops with cone photoreceptors. To interfere with the reciprocal transmissions of signals, animals were reared in monochromatic lights which preferentially stimulated the spectrally different cone types. Here we report the effects on the cones. Their absorbance spectra were largely unaffected, indicating no change in photopigment gene expression. Significant changes were observed in the cone outer segment lengths and the frequencies of spectral cone types. Quantum catch efficiency and survival of cones appear to be controlled in a spectrally selective way. Our results suggest that the retina responds to spectral deprivation in a compensatory fashion aimed at balancing the input from the different cone types to second order neurons.
R/V SONNE Cruise SO258 leg 1 started in Fremantle, close to Perth, which is located at the southw... more R/V SONNE Cruise SO258 leg 1 started in Fremantle, close to Perth, which is located at the southwest coast of Australia. On Monday, June 5th, in the course of an Open Ship event the citizens of Perth and Fremantle had the opportunity to visit the SONNE and get an insight into current research. The vessel, as well as the presentations of the different scientific working groups, attracted 3,200 (!) visitors and received and enthusiastic response by the public and the media. GEOMAR Reports No.
Biological cybernetics, 2014
The aim of this study was to obtain information on the axonal diameters of cortico-cortical fibre... more The aim of this study was to obtain information on the axonal diameters of cortico-cortical fibres in the human brain, connecting distant regions of the same hemisphere via the white matter. Samples for electron microscopy were taken from the region of the superior longitudinal fascicle and from the transitional white matter between temporal and frontal lobe where the uncinate and inferior occipitofrontal fascicle merge. We measured the inner diameter of cross sections of myelinated axons. For comparison with data from the literature on the human corpus callosum, we also took samples from that region. For comparison with well-fixed material, we also included samples from corresponding regions of a monkey brain (Macaca mulatta). Fibre diameters in human brains ranged from 0.16 to 9 μm. Distributions of diameters were similar in the three systems of cortico-cortical fibres investigated, both in humans and the monkey, with most of the average values below 1 μm diameter and a small popu...
Science, 2012
Seeing in the Dark Elephantnose fish are known to use electrosensing to navigate their murky fres... more Seeing in the Dark Elephantnose fish are known to use electrosensing to navigate their murky freshwater environment. However, unlike some other animals from dark environments, they have retained their eyes and some dependence on vision. While most vertebrate vision optimizes either photon catch (for increased light capture) or visual acuity, Kreysing et al. (p. 1700 ) show that the unique structures of the grouped retinae found in the eyes of this species matches rod and cone sensitivity, which allows for the simultaneous use of both types of photoreceptors over a large range of dim light intensities.
Neuroscience Letters, 1993
The teleost retina recieves efferent projections from neurons of the nucleus olfactoretinalis at ... more The teleost retina recieves efferent projections from neurons of the nucleus olfactoretinalis at the base of the olfactory bulbs. These fibres contain gonadotropin-releasing hormone (GnRH) immunoreactive material and are presynaptic to retinal dopaminergic interplexiform cells. We have incubated isolated dark-adapted retinae and eyecup preparations of roach with salmon-GnRH and found an increase in horizontal cell spinule numbers to 70% light-adaptive levels. This effect was blocked by addition of haloperidol to the incubation medium suggesting that GnRH acts via stimulation of the dopaminergic interplexiform cells. We conclude that GnRH containing efferent fibres are capable of inducing light-adaptive changes in the retina and discuss their implication in the control of endogenous rhythms.
Proceedings of the Royal Society B: Biological Sciences, 2014
We describe the bi-directed eyes of a mesopelagic teleost fish, Rhynchohyalus natalensis , that p... more We describe the bi-directed eyes of a mesopelagic teleost fish, Rhynchohyalus natalensis , that possesses an extensive lateral diverticulum to each tubular eye. Each diverticulum contains a mirror that focuses light from the ventro-lateral visual field. This species can thereby visualize both downwelling sunlight and bioluminescence over a wide field of view. Modelling shows that the mirror is very likely to be capable of producing a bright, well focused image. After Dolichopteryx longipes , this is only the second description of an eye in a vertebrate having both reflective and refractive optics. Although superficially similar, the optics of the diverticular eyes of these two species of fish differ in some important respects. Firstly, the reflective crystals in the D. longipes mirror are derived from a tapetum within the retinal pigment epithelium, whereas in R. natalensis they develop from the choroidal argentea. Secondly, in D. longipes the angle of the reflective crystals varies...
Vision Research, 1996
We have investigated the effects of light and dark adaptation on the overall morphology of bipola... more We have investigated the effects of light and dark adaptation on the overall morphology of bipolar cell (BC) terminals in sublaminae a and b of the inner plexiform layer after labelling with Lucifer Yellow (LY) and PKC immunostaining using confocal laser scanning microscopy and serially sectioned material for electron microscopy. Three-dimensional reconstructed terminals showed marked adaptation-dependent changes of their morphology. Terminals of mixed rod-cone BCs in sublamina a (Ma BC) were irregular and scalloped in light adapted, but smooth and regular in dark-adapted specimens. Terminals from mixed rod-cone BCs in sublamina b (Mb BCs) exhibited an opposite behaviour. At the ultrastructural level, bipolar terminals in both sublaminae showed fingerlike extensions (spinules) invaginating presynaptic amacrine cell (AC) processes. Sixty-two percent of the dark-adapted Mb terminals in sublamina b showed spinules, whereas 21% of the light-adapted terminals had spinules. By contrast, 50.6% of the light-adapted Ma terminals in sublamina a formed spinules, compared to 17.8% of the dark-adapted Ma terminals in this sublamina. These observations reflect the functional subdivision of the inner plexiform layer in an inner ON-and an outer OFF-centre lamina. Our findings suggest that the synaptic plasticity of BC axon terminals may be due to differences of BC membrane potential, or the activity of AC input onto bipolar terminals. They may contribute to processes of fine tuning regulating the efficiency of AC-BC interaction under varying adaptation conditions.
Deep Sea Research Part I: Oceanographic Research Papers, 2011
The inner ear structure of Antimora rostrata and its coupling to the swim bladder were analyzed a... more The inner ear structure of Antimora rostrata and its coupling to the swim bladder were analyzed and compared with the inner ears of several shallow-water species that also have similar coupling. The inner ear of Antimora has a long saccular otolith and sensory epithelium as compared to many other fishes. Some parts of the membranous labyrinth are thick and rigid, while other parts are thinner but attached tightly to the bony capsule. The partially rigid membranous labyrinth, along with its intimate connection to the swim bladder, may help the inner ear follow the sound oscillations from the swim bladder with better precision than would occur in a less rigid inner ear. In addition, the saccular sensory epithelium has an elaborate structure and an anterior enlargement that may be correlated with increased hearing sensitivity. Some of the features in the inner ear of Antimora may reflect the functional specialization of deep-water living and support the hypothesis that there is enhanced inner ear sensitivity in some deep-sea fishes.
Philosophical Transactions of the Royal Society B: Biological Sciences, 2000
To investigate the developmental plasticity of colour vision, we reared fish with a trichromatic ... more To investigate the developmental plasticity of colour vision, we reared fish with a trichromatic cone system ( Aequidens pulcher ) under three near–monochromatic lights, differentially stimulating each spectral cone type from the larval stage to the age of at least one year. Control conditions comprised white lights of two intensities. The treatments did not affect the visual pigments, but led to significant changes in cone outer segment lengths. Furthermore, in the blue–reared group the density of single cones within the retina was reduced by two–thirds after 18 months of exposure, while no changes were observed in the other groups. The connectivity of cone horizontal cells with the single cones was influenced by the intensity and spectral composition of the rearing lights: H1 cells were more sensitive to the spectral component, whereas H2 cells responded to intensity cues. In the blue–light group the dynamics of horizontal cell synaptic spinule formation and degradation were sever...
The main purpose of t he cruise was to study the perception mechanisms of bioluminescence in the ... more The main purpose of t he cruise was to study the perception mechanisms of bioluminescence in the mesopelagic fauna. Furthermore, the presence of endogenous diel oscillators were investigated as a possible control mechanism for the daily vertical migrations of midwater animals. We conducted 20 trawls between 200 and 700 m depth and collected eyes and brains of mesopelagic fish for immediate experimentation on board or fixation and subsequent investigation in the home laboratories. In addition to these projects, the samples were also used to assess the effect of high pressure on the physiology of muscle fibres, and the toxicity of iatrogenic pollutants (PCBs, DDTs) on the liver metbolism. Another major project involved the study of hadal faunal communities. Five deployments of University of Aberdeen Oceanlab autonomous landers were carried out at depths of 6,000m, 7049m, 8170m, 9,000m and 10,015m. The landers were equipped with baited traps and took time-lapse videos over a period of 12h after which they were recovered. The sighting of the fish at 7100m is possibly the first real scientific observations of a hadal fish species in regard to behaviour and in an in situ context. Furthermore, predation in the hadal zone was aslo recorded for the first time. The collection of amphipods serves to perform population genetic studies, taxonomy and define the zonation of scavenging amphipods through the trench depths. Temperature data were also collected and proved that indeed there is a rise in temperature from 5000 to 10,000m. The 10,000m deployment was a technological milestone that will lead to further investigations and general interest/awareness of the hadal and trench environments. The investigation of the visual pigments in 47 of them myctophids belonging to around 20-25 species will allow for the first time an analysis of the adaptive radiation of deep sea rhodopsins whithout the confounding variables of depth and vertical migration because it is restricted to a single family. An additional and unexspected finding was the occurrence of red shifted visual pigments in Photostomias sp. which is therefore the fourth species of dragonfish with this capability. (R. Douglas, J. Partridge) Morphological investigations of the visual system will focus on three major aspects: We shall investigate the optic tectum of deep sea fish and compare its functional morphology to that of the zebrafish as a current model system. Furthermore, in five speciments of pearleyes the specific role of bundles photoreceptors will be studied because they occur next to randomly arranged rods in the same retina and allow a direct comparison of the cellular basis of signal processing in the inner retina. Finally the visual system of the foureyed fish Dolichopteryx sp. will be studied. (Wagner) For the study of biological rhythms melatonin samples were collected in several species of mesopelagic fish and cell lines established destined at testing the molecular biology of clock genes. In addition, ERG data in crustations prepared by T. Frank show that only species of the shallower depths show an endogenous component of their sensititvity profile whereas species of the deeper water layers do not. 2.3. Affiliation and Addresses of Scientific party
Vision Research, 1996
Blue acaras (Aequidens pulcher, Cichlidae) were reared for 1 yr in white or monochromatic "red", ... more Blue acaras (Aequidens pulcher, Cichlidae) were reared for 1 yr in white or monochromatic "red", "green" and "blue" lights to study the function and control mechanisms of horizontal cell (HC) spinules in the synaptic pedicles of cones. Ratios of spinules per synaptic ribbon (S/R) were determined in tangential sections in both single and double cones. We found that the S/R ratios in light adapted retinae decreased with decreasing wavelength of the rearing light in all cone types. Conversely, there was an increasing number of incompletely formed spinules with the highest frequency in the blue light group. Dark adaptation resulted in the complete degradation of mature spinules. However, significant numbers of incompletely degraded spinules were observed in the group reared in blue light. Fish reared in blue light which were transferred to white light formed mature spinules when light adapted and still had vestigial spinules when dark adapted. The mechanisms of spinule formation and degradation and the control of spinule dynamics appear to be fully developed :in fish reared in monochromatic light. However, long-term chromatic deprivation seems to induce a compensatory modulation of spinule dynamics. A working hypothesis is formulated that interprets the observed effects as manifestations of differences in the activition of dopaminergic interplexiform cells (light adapted) and the sensitivity to glutamate of HCs (dark adapted). Our findings are consistent with the hypothesis that spinules are involved in signinverting feedback transmission from HCs to cones.
Marine Biology
Absolute and relative volumes of four sensory areas (olfactory bulb, optic tectum, octavolateral ... more Absolute and relative volumes of four sensory areas (olfactory bulb, optic tectum, octavolateral area, gustatory area) and two integration centers (telencephalon, cerebellum) were determined in 39 specimens of the demersal grenadier Coryphaenoides armatus from early postmetamorphic stages to adulthood (94-900 mm total length). The relative volume of the optic tectum decreased and the relative volume of the olfactory bulb increased up to a total length of about 500 mm (corresponding to a total weight of about 1 kg) and remained constant subsequently, whereas the relative volumes of the octavolateral and gustatory areas were unchanged during growth. The developmental switch in sensory orientation from vision to olfaction is associated with changes in behavior recorded in lander experiments and feeding strategies based on head morphology and stomach content.
Scientific reports, Dec 20, 2016
Most deep-sea fish have a single visual pigment maximally sensitive at short wavelengths, approxi... more Most deep-sea fish have a single visual pigment maximally sensitive at short wavelengths, approximately matching the spectrum of both downwelling sunlight and bioluminescence. However, Malcosteus niger produces far-red bioluminescence and its longwave retinal sensitivity is enhanced by red-shifted visual pigments, a longwave reflecting tapetum and, uniquely, a bacteriochlorophyll-derived photosensitizer. The origin of the photosensitizer, however, remains unclear. We investigated whether the bacteriochlorophyll was produced by endosymbiotic bacteria within unusual structures adjacent to the photoreceptors that had previously been described in this species. However, microscopy, elemental analysis and SYTOX green staining provided no evidence for such localised retinal bacteria, instead the photosensitizer was shown to be distributed throughout the retina. Furthermore, comparison of mRNA from the retina of Malacosteus to that of the closely related Pachystomias microdon (which does no...
Investigative Ophthalmology & Visual Science
Light adaptive morphologic changes in the teleost retina, such as movements of rods, cones, and e... more Light adaptive morphologic changes in the teleost retina, such as movements of rods, cones, and epithelial pigment and spinule formation on horizontal cell terminals, are normally associated with continual exposure to light. Depending on a variety of factors these processes are generally completed within 30-60 min. In this report we show that a brief exposure to light (1-2 min) preceded and followed by darkness is sufficient to elicit these changes in four species of teleost; the trout (Salmo gairdneri), the tench (Tinca tinca), the carp (Cyprinus carpio), and the goldfish (Carassius auratus). A brief pulse is as effective in causing cone migration and an increase in the number of spinules as continual exposure; however, it is sometimes less effective in causing pigment migration. The photomechanical changes following a brief period of light are always completed more quickly and show greater species variability than the formation of spinules. These results show that the various morphologic manifestations of light adaptation are autonomous processes that need only a short pulse of light to trigger the whole sequence of events. This is of interest when considering their control mechanisms and may have consequences for physiologic work involving experiments on dark-adapted eyes.
The Journal of experimental biology, Jan 23, 2015
Using immunohistochemistry and Western blot analysis we demonstrate that melanospin is localised ... more Using immunohistochemistry and Western blot analysis we demonstrate that melanospin is localised in cells around the central pore of lateral line neuromasts in the African clawed frog, Xenopus laevis. Since melanopsin is a known photoreceptor pigment with diverse functions in vertebrates, we suggest that the lateral line of Xenopus laevis, which is primarily a mechanorecptor, may also be light sensitive. Potential functions of such photosensitivity are discussed, including its role in mediating locomotor responses following dermal illumination.
Anatomical record (Hoboken, N.J. : 2007), 2013
Inner ear structures are compared among three major genera of the deep-sea fish family Melamphaid... more Inner ear structures are compared among three major genera of the deep-sea fish family Melamphaidae (bigscales and ridgeheads). Substantial interspecific variation is found in the saccular otoliths, including the presence of a unique otolithic "spur" in the genera Melamphaes and Poromitra. The variation in the saccular otolith is correlated with an increase in the number of hair bundle orientation groups on the sensory epithelia from the genera Scopelogadus to Poromitra to Melamphaes. The diverse structural variations found in the saccule may reflect the evolutionary history of these species. The sensory hair cell bundles in this family have the most variable shapes yet encountered in fish ears. In the saccule, most of the hair bundles are 15-20 μm high, an exceptional height for fish otolithic end organs. These bundles have large numbers of stereovilli, including some that reach the length of the kinocilium. In the utricle, the striolar region separates into two unusually...
Vision research, 1995
In a sample of 37 species of deep-sea fish species from the sea floor of the Porcupine Seabight a... more In a sample of 37 species of deep-sea fish species from the sea floor of the Porcupine Seabight and the Gobal spur (North Atlantic) we investigated the overall structure of the retina with special respect for the organization of rods, their length and their arrangement in multiple banks. Using an immunocytochemical marker for cell proliferation (PCNA) we studied the mechanisms of rod proliferation, and, by means of serial section reconstruction followed their integration into the existing population of rods. Furthermore, in three different species we have observed growth related changes in retinal thickness, rod density and proliferation activity. We found evidence for two different principles for the organization of rods in these deep-sea fish retinae. In the first group of species represented by Nematonurus armatus and Coryphaenoides guentheri we found rods to be rather short (20-30 microns) and arranged in three and more banks. In these species rod proliferation occurred in a sin...
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Papers by Hans-Joachim Wagner