The deep-sea fish with a see-through head!

Wednesday, September 2, 2015 by Caroline Casals

Credit: (c) 2004 MBARI

The scientists at the Monterey Bay Aquarium Research Insitute (MBARI) discovered an amazing adaptation of a very unusual animal: the barreleye fish (Macropinna microstoma). This fish has very unusual tubular eyes inside its head - which look like green marbles! In the past scientists thought that these eyes only looked in one direction, but now researchers have watched this fish in the wild, and discovered something different.

Credit: (c) 2004 MBARI

The MBARI researchers discovered that the marble-like tubular eyes can move around inside the fish's head. The barreleye fish lurks motionless underneath its prey - when it turns upwards to eat - so do the eyes. The clear dome "shield" protects the delicate eyes which are can detect tiny amounts of light. Thanks to use of ROVs and a lot of patience, we know a little more about this rare fish. You can learn more about this research here.

Credit: (c) 2006 MBARI

The barreleye (Macropinna microstoma) has extremely light-sensitive eyes that can rotate within a transparent, fluid-filled shield on its head. The fish's tubular eyes are capped by bright green lenses. The eyes point upward (as shown here) when the fish is looking for food overhead. They point forward when the fish is feeding. The two spots above the fish's mouth are are olfactory organs called nares, which are analogous to human nostrils.

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