Remora

Image: mentalblock_DMD via Flickr
Remora remora

Do you have a weird suction cup on your head? Wondering if you can get something out of it other than a lifetime of bullying and misery?

Well have no fear! The Remora is here to show you the opportunities granted to you by your horrific, cranial abnormality! Turn the cruelty of nature to your advantage!

You don't have a problem with a little parasitism, do you?

Image: richard ling via Flickr
Echeneis naucrates

Remoras are 8 species in the Echeneidae family, each one reaching somewhere between 30 cm and a metre (1 to 3.3 ft) long and most of them living in tropical oceans.

What they all share in common is a head that looks like it got squished by a giant thumb. I guess Neptune is a right meanie.

Image: mentalblock_DMD via Flickr

It's actually a heavily modified dorsal fin that allows the Remora to attach itself to large sea creatures, almost all of which would rather it didn't. The Remora doesn't care about such feelings; effective freeloading requires a touch of cold-hearted ruthlessness. Just look at your average child.

Image: Albert kok
When cold-hearted ruthlessnesses combine...

And so, the Remora raises the edge of its suction cup against the skin of its host and arranges the thumb print design inside. This opens up a space, a vacuum which keeps the Remora firmly attached. They scarcely need swim ever again! This is good because while Remoras are competent swimmers, their lack of a swim bladder means that it's much more of an effort for them.

In any case, swimming is for suckers! The bad kind. Remoras are the good kind. Or the cold-hearted, ruthless kind anyway.

Image: deErisch via Flickr
Don't worry, turtles always look at least as annoyed as this one does

The strength of the suction disc is really impressive. It's strong enough for some people around the Indian Ocean to use Remoras for hunting turtles! They tie a rope around a Remora's tail and when it seeks safety by attaching itself to a nearby turtle, the hunters can simply haul them both in.

Image: mfmb_bentley via Flickr

Some Remoras would completely shun life on a turtle, though. The Whalesucker, for example, has only ever been found on cetaceans. Adults like whales, while youngsters attach themselves to dolphins. This species has the biggest suction cup of all, taking up half of the animal's entire length. Presumably this keeps them secure on such active, fast moving hosts.

Image source
Phtheirichthys lineatus

The smallest suction cup is found on Phtheirichthys lineatus, where it's only 1 fifth of their length. Of all Remoras this one is least dependant on any host and is often seen swimming on their own or attached to rocks and such.

Image: Saspotato via Flickr
Shipwrecks: not all bad.

Other Remoras are a little more liberal in their host selection, hanging out on sharks, rays, whales, marlin or turtles. Some will even investigate human divers for potential hitch-hiking! That's the cool thing when you can actually swim quite well; there's a whole world of possibilities out there if only you're willing to get off your anal fin and check it out.

This brings us to the question of cuisine. What culinary delights await our hitch-hiking freeloaders? Will it be good, hearty eating laid out on silver platters, smothered in unnecessary extravagance with a soupcon of this and a frisson of that? Or will it be some disgusting slurry slowly dripping through a brown paper bag and bound to give rise to several days of vomiting and diarrhea?

Speaking of vomit and diarrhea... how would you like to eat it?

Image: mentalblock_DMD via Flickr
When the world gives you a gut full of faeces and a head like a plimsoll, smile

I'm afraid so. Dissection reveals that for many Remoras, their host's faeces is a staple part of their diet. They're full of... it. It's not all so terrible, since they also eat the various scraps and crumbs that fall from the master's table when their host chomps on proper food. It must be quite a relief to get to eat stuff that hasn't been digested already.

Oh, and yeah... dolphin vomit. It happens. Actually there's been research into it. A "rich and predictable food source for plankton-eating reef fishes", apparently.

Image: dfinney via Flickr

Some Remoras like the White Suckerfish are more sheltered than most. They reside within the mouth and gills of the Manta Ray, eating the very plankton their host is trying to eat. It's like a cross between one of those living spaceships you get in science fiction and if revolving restaurants actually flew off to take advantage of the local harvest in various parts of the world. Really cool, basically.

And then there's the parasites. This is the only real good Remoras do for their host - eat the itchy, scratchy blood-sucking lice from their skin. The Whalesucker is in for a particular treat here, a "whale of a time" you might say before ducking and running as the audience throws rotten tomatoes at you. Whales are just so huge that they can have anything between lots of massive parasites to thousands of small ones. Either way, that's a lot of good eating! If you're into that kind of thing.

Image: mentalblock_DMD via Flickr

Very little is known about reproduction in Remoras but at least some of them acquire the suction disc when they're around 3 cm (1.2 in) long. Before then I guess they have to fend for themselves like all the other saps.

Image: Steve & Jemma Copley via Flickr

So, life as a reprehensible freeloader is clearly a mixed bag. You get to hang out with a leviathan who will probably scare away anything that would eat you, but then you also get to know their bowel movements in more detail than you'd like.

I guess it depends. If you were buying a house, would a nearby open sewer be a deal breaker?