There is a new Explorer special based on an article in the latest issue of National Geographic with Michael Stevens (@tweetsauce), Unlocking The Eyes that is well worth checking out. In the video above, Michael interviews Marty Banks and William Sprague about why many prey animals like goats have the eye anatomy they do. i.e., why are their eyes have horizontal pupils and why their eyes are positioned on the sides of their heads?
There is a short video from National Geographic that is a companion to an article by Ed Yong (@edyong209) in National Geographic here. The photography is wonderful as is typical of National Geographic and is well worth your time.
The extinct Neanderthals had orbital eye sockets that are much larger than ours. Recently, there has been an discussion covered in a fascinating article linked the other day on the BBC discussing the large orbital eye sockets of the Neanderthals and whether these eye represented a reason for the Neanderthals’ demise or not.
There is an interesting paper from an evo devo perspective out of the Jékely laboratory, looking at the connectomics of some of the earliest of organized visual systems in the Platynereis dumerilii larva. They have described a visual circuit consisting of 71 neurons and 1,106 “connections”. The cool thing about this study was that they were also able to combine behavioral experiments with ablations revealing the ability to detect spatial light, directing movement or taxis in the direction of the light.
Its too bad I did not visit with them last time I was in Tübingen as it would have been good to talk connectomics and techniques with them. I am encouraged that they used serial section transmission electron microscopy to perform circuit level analysis as we think its the right approach for circuit level analysis, though I worry that the resolution was too low to image gap junctions, though they did mention looking for them. Regardless, I would have loved to see their setup and talked with them.
There is a great TED-Ed video on “The Evolution of the Human Eye” with some very clever animation. The video itself is short and geared towards the college level, and while some of the conjecture at the end contains some far out statements, it is a fun few minutes.
Photographer Suren Manvelyan has produced an amazing collection of photographs of eyes over the last couple of years. He started with a phenomenal set of images from human eyes and has now expanded his collections to include 3 sets of animal eyes. Part 1, Part 2 and now Part 3.
Spending some time looking through them is a good investment, particularly if you consider the evolution that has shaped the biology as looking at the different structures of the outer eyes gives you clues as to the environments these organisms live in.
There are species of shark that are bioluminescent and have evolved ocular structures designed to detect faint light patterns in the deep ocean produced by other bioluminescent sharks that live at depths from 600 to 3,000 feet in the mesopelagic zone where very little sunlight reaches.
These eyes as expected, have visual adaptations optimized for this environment. Julien Claes, the lead authors of a new study notes that “There are about 50 different shark species that are able to produce light”. Given that there are 50 separate bioluminescent species of shark, one might expect some visual system specializations and indeed there are. Everything from higher rod densities to descriptions of bioluminescent specializations used for communication and specialized transparencies in the upper socket of the eye to help adjust illumination. Continue reading “Glowing Sharks Have Unusual Eyes”
We at Webvision have a fascination with the evolution of the eye and are always looking for interesting papers that help describe from where, how and when vision came. This paper, Molecular analysis of the amphioxus frontal eye unravels the evolutionary origin of the retina and pigment cells of the vertebrate eye by Pavel Vopalenskya, Jiri Pergnera, Michaela Liegertova, Elia Benito-Gutierrez, Detlev Arendt, and Zbynek Kozmika attempts to answer the question of where the vertebrate eye came from. While the amphioxus has for many years been recognized as a viable candidate for the earliest vertebrate eye, the retinal structure is different from that of other vertebrates. Specifically, the photoreceptors of amphioxus are simple ciliated cells as opposed to the more sophisticated elaborations of structures on top of cillia in other vertebrate retinas. This paper describes in molecular terms, gene coexpression and structural features the different cell types of amphioxus in an attempt to define neuronal circuitry. Its a very cool paper that provides additional detail into the evolutionary origins of vision and we encourage you to have a look.