Razorfish

Image: Bernard DUPONT

Can you believe this? There are cut throat razors drifting about in the sea! If you happen to come across an unusually hairy merman on your travels, tell him to be more careful.

Wait... Did they just move? The razor blades are haunted! Run!

Image: Bernard DUPONT

Or maybe it's just a bunch of fish. Razorfish!

You can easily see how they get their name if you look at them head on. They are unbelievably thin! There's barely anything to them at all.

Video: Sadministrator

And speaking of head on, they have a peculiar habit of swimming around with their head pointing straight down. And they don't swim downwards while they're doing it.

They can move forward and turn left and right with surprising speed and agility, all the while maintaining a posture about as aerodynamic as the Homeworld mothership.

Image: Bernard DUPONT

They're also known as Shrimpfish because they look a bit like shrimp. Apparently. I don't really see it, although they do look somewhat like Sawblade Shrimp. Or maybe they just both look like different kinds of blade...

Razorfish can be seen doing their headstands around coral reefs across the Indo-Pacific Ocean. There are two species. One is usually just called the Razorfish and is found mostly in southeast Asia and Australia. The other is the Speckled Razorfish which ranges from South Africa up to the Red Sea. Both reach 15 cm (6 in) long at most.

Video: funseadiving さんのチャンネル

You'll seldom see just one of them, though. Razorfish like to get together in schools, strutting around the place like a Glaswegian razor gang. Or maybe they just appreciate each other's razor sharp wit. Ahem.

Either way, Razorfish frequently hang out among corals that have long, pointy branches or sea urchins that have long, pointy spines. That way, the long, pointy Razorfish can hide quite effectively. They can even change colour, so for example if they're among the long, pointy leaves of sea grass they might turn green to suit.

Video: AE YONG

Some schools of Razorfish are bigger than others. When you get a large number together they do all the crazy gymnastics you see among sardines and the like, except this time with the added flourish of being vertical the whole time.

Or should I say almost the whole time. Razorfish can turn their body horizontal like a normal fish when they just want to get away as quickly as possible. Watching a whole school of them do it at the same time is quite a sight!

Image: Brian Gratwicke

However, just because a Razorfish can speed away quickly it doesn't mean they want to. They'd much rather just, well, keep their heads down. And if you're not careful, you may find that the Razorfish is almost as sharp and spiny as the sea urchin its hiding around...

You see, while Razorfish are stupendously thin, they still make room for some defences against the dangers of the reef. For a start, they're encased in transparent armour plates. So in a way they're even thinner than they look! The plates also join up in such a way as to provide them with a razor sharp belly.

Image: prilfish
Check out all those bendy spikes

Then there's the spike. You know it's dangerous when even the razor blades carry protection. It's situated at the very tip of their... tail, and it has a joint at its base so it's somewhat manoeuvrable.

I'm hesitant to call it their tail because it's actually part of their dorsal fin. A normal fish would have its dorsal fin situated halfway along its back but this is not a normal fish...

Look at how the tail bones curve downwards!

Basically, Razorfish are little bent out of shape. All the better to swim weird with.

Think of it like this:
Take a normal fish that's swimming around like a normal fish.
Twist its tail so the tail fin points down.
Take its dorsal fin, move it past the tail to the very end of its body and twist it so it points down.
Now take the entire fish and turn it so its head points down.

Razorfish!

Image: Tony Shih

Oh, and pull its snout into a long tube and make its mouth really tiny so it can only eat creatures that are virtually microscopic. I guess you need to watch your weight when you're called a Razorfish.

So! It's bent up, covered in bony plates, has a tiny mouth at the end of a tube and swims vertically... sound familiar?

Of course it does! It sounds just like everyone's favourite car crash of a fish, the Seahorse. They are indeed related, it's just that the Razorfish has found a way of being sleek and shiny while still being a bit mangled.