The 27 Best Deep-Sea Species: #5 Barreleye Fish

#5 Species from the family Opisthoproctidae (Phylum: Chordata, Class: Actinopterygii, Order: Osmeriformes)

These fish are so cool they could be invertebrates.  First is that lovely family name which means behind the anus (opisthe-behind, prokotos-anus), a name whose intent escapes me.

Second, the 12 species in 6 genera are exclusively deep sea. Shallow water species can suck it! Third, all the species except one have tubular eyes that protrude from the skull, always gazing dreamily upwards. In Winteria (image left), the eyes look forward and up. Fourth, those crazy eyes have huge lens (yes size does matter) with an inordinate amoutn of rod cells and rhodopsin.  Fifth, they possess bioluminescent organs on their sides and stomachs that serves a counterillumination from below.


The last and best reason yet, is that all the species have transparent to translucent heads!  You can just look right in there and see all the fish’s thoughts in that tiny little fish brain. The two thoughts so far documented are I am hungry and horny.  Same as Kevin really.  Seriously though, the clear heads presumably allow the fish to collect more light.

Check out the pictures of Opisthoproctus soleatus by Norbert Wu Middle image of Macropinna microstoma from Paul Yancey.

Barreleyes at 5:47

Dr. M (1729 Posts)

Craig McClain is the Assistant Director of Science for the National Evolutionary Synthesis Center, a National Science Foundation supported initiative. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (, a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web. His forthcoming book, Science of the South (, connects cultural icons of South such as pecan pie with the science behind them.

3 comments on “The 27 Best Deep-Sea Species: #5 Barreleye Fish
  1. “First is that lovely family name which means behind the anus (opisthe-behind, prokotos-anus), a name whose intent escapes me.”

    I suspect its latin for “ass-backwards”

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