Fish have some of the most amazing retinas in the animal kingdom. Like other fish species that live in environments with little to no light, the elephantnose fish (Gnathonemus petersii) use electrical fields to navigate through dark and murky waters. However, unlike some of those species, the elephantnose fish has not lost its eyes through evolution and uses vision for some functions.
This paper published in Science back in May, 2012 by authors Moritz Kreysing, Roland Pusch, Dorothee Haverkate, Meik Landsberger, Jacob Engelmann, Janina Ruiter, Carlos Mora-Ferrer, Elke Ulbricht, Jens Grosche, Kristian Franze, Stefan Streif, Sarah Schumacher, Felix Makarov, Johannes Kacza, Jochen Guck, Hartwig Wolburg, James K. Bowmaker, Gerhard von der Emde, Stefan Schuster, Hans-Joachim Wagner, Andreas Reichenbach, and Mike Francke shows that the elephantnose fish has absolutely unique and interesting structures that optimize light capture ability and make them insensitive to spatial noise. Also in the mesopic range they match the rod and cone opsin sensitivity curves allowing the use of both rods and cones throughout large ranges of light intensities, but importantly, arrange the cone photoreceptors in functional assemblies that act as photonic reflectors, creating lightwells in a sense that optimize photon capture. The rod photoreceptors meanwhile are positioned *behind* the photonic lightwells or reflectors. The result is that the photonic lightwells or reflectors become wavelength sensitive light intensifiers that functionally match the dynamic range of both rods and cones while boosting sensitivity in the red wavelengths that are the first wavelengths filtered out by water. The thinking is that this allows the elephantnose fish to easily see large predators in murky or turbid environments.
Since Webvision is all about eyes, this was a fun image… Makeup artist Sandra Holmbom is a phenomenal talent, creating impressive illusions with makeup. This time, she created an eyeball with perspective eyelashes, iris and pupil on her lips. The effect is a little discomforting, especially with the teeth. But its fun.
Hat tip to Laughing Squid for pointing this out.
I’ve been doing some reading in plasticity recently and found this paper in the Journal of Neuroscience by Evan Vickers, Mean-Hwan Kim, Jozsef Vigh, and Henrique von Gersdorff published last summer that looks at short term plasticity in the Inner Plexiform Layer mediating light adaptation. Working in goldfish (Carassius auratus auratus) retina (an amazing retina), Vickers et. al. used patch clamp recordings on Mb bipolar cell terminals with paired-pulse light stimulation. The idea was to examine and quantify plasticity in GABAergic lateral IPSCs with findings that show variation in the synaptic strength and latencies which correspond to adaptation and sensitization to surround temporal contrast. The authors found that there are separate retinal circuitry pathways, each with differing mechanisms of plasticity that help to tune temporal response curves with glutamate release from ON bipolar cell terminals. They conclude that “Short-term plasticity of L-IPSCs may thus influence the strength, timing, and spatial extent of amacrine and ganglion cell inhibitory surrounds”.
This Short Communication published in the European Journal of Neuroscience back in 2000 by Lucia Galli-Resta, Elena Novelli, Maila Volpini and Enrica Strettoi was a paper I did not know existed. That said, I ran into it the other day looking for some reference material and found it to be quite useful. This communication represents an analysis of the cholinergic amacrine cell mosaics in the C57Bl6/J murine retina. It served as a useful baseline for cell positioning, and cell mosaicing in both cholinergic arrays of the retina and is a nice analysis that should serve as a reference point for future genetic analysis studies in normal and pathological retinal tissues. Enrica Strettoi’s laboratory has been carefully exploring the functional organization of the retina for some time now in the normal and pathological states and its always a joy to discover her work in the literature, even if it is 13 years old.
This image for the Art of Vision category was made by James Gilman of the Moran Eye Center is an artistic rendering created from a fundoscopic of a normal human retina and retinal vasculature.
This imagery is from a patient with Vogt Koyanagi Harada Syndrome (VKH). VKH is a presumed autoimmune disease that presents with waxing and waning subretinal fluid. There is chromic uveitis with other neurological and dermatological symptoms. The precise mechanism of the disease is unknown, though it is thought that the autoimmune involvement of melanocytes in the uvea, skin, inner ear and CNS is mediated by T helper cells. The fundus photos above show the discoloration of the retina from fluid and the corresponding OCT below, shows the dark areas of fluid infiltration. Fundus photos were made by James Gilman of the Moran Eye Center and taken with a Zeiss FF-450+ and the OCT with with a Zeiss Stratus.