Friday, March 18, 2011

Creature Feature: Remora.

Watch enough ocean footage and you will eventually notice something very strange: There are slender fish attached to sharks and rays every so often. Whales and other marine mammals may also have these bizarre fish attached to their undersides.  At first, one may wonder if the whales and sharks have taken up body piercing, but these fish are perfectly natural.

Remoras (family Echeneidae) are slender fish often seen attached to larger marine animals. They live in tropical waters and grow anywhere from 1-3 feet in length. Although they can swim perfectly fine by themselves, they are adapted to be the hitchhikers of the ocean.

How does the remora do that? It hitches a ride with a special suction disc on its head. What used to be a dorsal fin has now evolved into a fleshy, ribbed suction cup that creates a small vacuum. This arrangement, combined with the remora's underbite, makes it look like the fish is swimming upside-down. Using this disc, the remora can hitch a ride on larger fish, turtles, humans, and even boats.


Remoras attach to things because they have a different gill structure from most fish. They cannot move water over their gills to get oxygen, so they must be in constant movement. The remora does not harm its host, but gets a free ride, free food, and free protection out of the deal. The host animal gets a non-invasive hitchhiker, and, depending on the remora, maybe a trash can or toilet.

Humans have used remoras to fish for other sea life, particularly turtles. To the ancient Greeks and Romans, the appearance of a remora on a boat's side kept a boat from sailing, thus the name "remora" - "delay." A remora was blamed for Marc Antony's defeat at the Battle of Actium, but there's a good chance Cleopatra had something to do with that, too.

Tomorrow: Speaking of, Egypt has a few interesting cobras.

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