Sunday 10 March 2013

Sea Hare

Image: asbjorn.hansen

Bunnies of the sea!

They really shouldn't have bothered...

Sea Hares are several dozen species in the Aplysiidae family. They're marine sea slugs, with a tiny, internal shell, a round body and long rabbit ears.

Rabbit ears?

Image: Nuytsia@Tas
Alright no, not rabbit ears. All that fur would just get damp and horrible all the time, anyway. And then the Sea Hare would get a cold and if there's one thing a slug doesn't need, it's a nose clogged up with even more mucus.

Image: marylkayoe
Rhinophores and oral tentacles
Can you see the tiny eye below the rhinophore? Looks like a rocking-horse sneezing!
What they do need is some kind of organ to help them figure out what's going on around them. Their eyes are tiny and can only tell light from dark, so instead they use a pair of rhinophores atop their head and a pair of oral tentacles either side of their mouth.

These are sensitive to touch and smell and happen to look like delicately rolled lettuce leaves. They say "you are what you eat", so maybe it's not a complete surprise to learn that Sea Hares are herbivores, munching on all sorts of algae. They certainly don't eat rabbits or hares, that's for sure.

Image: bibliomaniac15
Black Sea Hare and egg mass.
Or black pudding and noodles?
This vegetable diet is all the Californian Black Sea Hare needs to reach almost a metre (3.3 feet) long when fully extended. That makes it the biggest slug in the world, and a strong contender for biggest of all gastropods.

Image: eclectic echoes
Taylor's Sea Hare
Others are a little more humble in size, some as tiny as 2 cm (an inch) long. Taylor's Sea Hare can reach about 8 cm (3 in) and has stripy markings on its bright green body. It's the kind of pattern you might see when they try to brighten up an airport departure lounge.

Image: BabyDinosaur
Sea Hare on the run, er... swim
Speaking of which, Sea Hares have wings! Sort of.

Image: Adam Gerritsma
If you look at your average Sea Hare's round back, you'll see what looks like a kind of wrinkly crest running all along it. This is actually where their parapodia meet. When fully opened out, the parapodia reveal themselves to be a large pair of wings or swimming fins, much like the Sea Butterfly's.

Its pretty weird to see a great, big slug flapping its flabby fins through the sea, but there it is.

Image: Baki Yokeş
Some smaller Sea Hares have their parapodia almost completely fused together above their body, but they don't let a little thing like that stop them.

Sea Hares of the genus Petalifera are less than 8 cm (3 in) long, they swim by repeatedly coiling and uncoiling their body.

Image: Baki Yokeş
Notarchus Sea Hares are more like 5 cm (2 in) long. They can suck water into a cavity between their parapodia and the rest of the body. Then they squirt it all out through a tiny gap in the mostly fused parapodia. This sends them flying off... it's jet propulsion!

All this unsluglike flying and zooming around is probably a great way of finding new algal pastures once they've eaten everything in the immediate vicinity. It is, however, also a cool way of escaping predators. "Leaving the area" is pretty much what actual hares do as well, but many Sea Hares have another trick up their sleeve. Up their mantle, actually...

Clouds of ink! You know how octopods squirt out a load of ink and disappear amid the confusion with remarkable speed like a ninja with a smoke bomb? Sea Hares do that! Only without disappearing amid the confusion. They just kind of sit there. Like a slug.

Image: colin.brown
The Sea Hare acquires these inky pigments from some of the algae it eats (sure, you are what you eat, but you also squirt out what you eat. They aren't so keen on mentioning that bit, are they). This is common stuff among sea slugs; they can get all kinds of stuff from their food, from pigments to toxins to symbiotic algae.

In the case of the Sea Hare it looks like they can do a bit of chemical jiggery-pokery to make that ink deter predators. At least one has been found to be a strong crab deterrent, so it isn't actually a visual thing.

Oh, and at least one Sea Hare is incredibly poisonous. Aplysia gigantea comes from Australia (of course), and has been known to kill dogs who lick it. Curiosity killed the dog, it seems. Wait... what's that noise? Is that the sound of a thousand land hares cheering their aquatic namesakes onward? Have at you, carnivore!

These poisonous Sea Hares are dangerous even when they wash up on shore, whereupon local Australian ragamuffins and whippersnappers call them "beach blobbies". You can see why...

Image: m. s. coleman
Most ineffective cannon ball, ever
The Sea Hare retracts its body as much as possible to retain water for as long as possible and ends up looking like a blob on a beach.

Of course, that isn't what they want. Want they really want is...

Image: Nuytsia@Tas rabbits...
To make babies.

Sea Hares are hermaphrodite, but due to the position of their sexual organs they can't make a one on one sperm swap. They can, however, line themselves up into an obscene conga line where each one simultaneously acts as a male for the one in front, and a female for the one behind. "Liberated", I think they call it.

Also they have their penis on the right hand side of their head. I don't want to be crude, so I won't say anything. Except that...

Image: Castaway in Scotland
Not all Sea Hares are beach blobbies.


natsukah said...

Here in Portugal is normal to see dozens of them swimming on the shore. Normally Aplysia fasciata, which is one of the most beautiful animals I've ever seen.
One morning I was in a field trip on the beach and caught a small A.fasciata, my teacher told me to "pet it" and sure enough I had purple ink all over my hands in few seconds.
Funny thing is, the name old folks give to them is Xôxa-de-velha, which means "Old woman's fanny"

TexWisGirl said...

kinda lost my appetite for breakfast on some of those pics. that last one, however... :)

Joseph JG said...

@natsukah: Dozens of them! Wow! That must look really weird. Cool!

Xôxa-de-velha... I must remember that and save it for the most inappropriate opportunity I can find.

@TexWisGirl: Ironic, since some of them look a lot like breakfast!

Christy said...

This is the best creature! I enjoy the goo ball concept. Is there a reason we can't post the picture of the actual creature to Facebook any more? It just shows the site logo. I find that very disappointing.

At any rate, thank you for this wonderful site!

Anna said...

WOW! this is the REAL MASTER in deep sea. i really amazed it!
waiting for your response :)

Joseph JG said...

@ Christy: "Goo ball", yes! It looks like you could bounce it around all over the place!

The Facebook pictures should work! It looks like it does when I look at it. I've fiddled about with it a little so maybe something went wrong somehow. I hope you'll come back to say whether it works or not tomorrow!

Glad you're enjoying the site!

@anna lou secoya: I'm sure the Sea Hares would blush at you saying that, they look very humble to me!

I had a quick glance at your site, keep it up! I'll look properly a little later, I'm just about ready for bed right now!

Anna said...

@Joseph Jameson-Gould: Thank you! keep posting because i really love to see it! :)

Anna said...

I love surfing amazing Animals