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How Giant Oarfish Work

Physical Traits of Giant Oarfish
R. glesne gets vertical in waters nears the Bahamas. This photo is rare because giant oarfish aren't usually photographed alive.
R. glesne gets vertical in waters nears the Bahamas. This photo is rare because giant oarfish aren't usually photographed alive.
Jonathan Bird/Photolibrary/Getty Images

Undoubtedly, the giant oarfish's physical credits are what make it most interesting to us, at the offset. But it's important to dive a little deeper into the physicality of this fish, because it's not just a pretty face. If you looked at the shiny, silvery body of Regalecus glesne you might assume that they have scales, much like a trout or most other "bony fish." (Giant oarfish are the biggest of the bony fish, which have bone -- as opposed to cartilage -- skeletons.) But R. glesne actually has soft skin covered with guanine, the crystals that add a lovely pearlescent sheen. So in reality, giant oarfish skin is fairly delicate and easily damaged when these animals aren't in their high-pressure, deep-sea surroundings. Also referred to as "ribbonfish," giant oarfish are flat too, more like an eel than a snake [source: National Marine Fisheries].

The dorsal fin also provides a bit of visual va-va-voom to R. glesne. (Remember that the dorsal fin is located where we think of as the spine or "back" of the fish.) On the dorsal are thin, red or coral-colored fins that stretch from end to end, including a sprightly crest of red over its head. The giant oarfish also has pelvic fins that fan out at the ends, resembling -- aha! -- oars [source: Burton]. Interestingly, these fins and rays are apparently easily broken off and often aren't intact on giant oarfish that have washed up; it's still not known if they signify the sex of the giant oarfish, or are for any other purpose [source: Whittaker].

The sheer size of this bony fish could preclude many predators from harassing it, although no one is quite sure who those predators are, aside from the usual shark suspects. They must have some though because a lot of giant oarfish that have been studied seem to have previous wounds on their lower half or have lost part of their tail. That's not as problematic as it might sound. While the oarfish has an extremely long body, most of its organs are crowded into its front-most quarter. That could mean that if a shark or some other predator attacks the fish away from its organs, it has some protection from fatal wounds [source: Burton].

One other cool thing: While we imagine our serpentinelike friends slithering gracefully through the water like snakes, we know that the fish spends at least some time in a face-to-the-surface vertical position. A solitary sort, it can quickly swim up or down in that position, maintaining that verticality. That ability would help to hide it from predators that look for lateral shadows. The flattened, upright body of the oarfish would be hard to spot from either above or below if it was just a narrow, shadowy line in the water as the rays on the dorsal fin undulate [source: Whittaker].