Spiny Spider Crab

We have new additions to the Aquarium! Well, new to the viewing public, we've been hiding them behind the scenes for about 4 months so they're sort of part of the furniture to me, which doesn't mean I've lost interest in them, in fact, now they're out and can actually be seen by people, my interest has peeked. Let's take a look at them.

The Spiny Spider Crab or the delicious sounding Maja squinado is a hefty sized crab. It's not counted as the largest crab found in British waters, that's the edible crab. But if we go on leg spanning size then the Spiny Spider Crab is longer. The carapace (that's the big middle bit where the legs stick in) of the Spiny Spider Crab can grow up to 20cm across, edible crabs can get to 25cm and edible crabs are heavier.

You may be able to make out green fuzz on the crab in my picture coming off the crabs legs and carapace. Don't worry, it's meant to be there. It's actually algae; you can see it on the walls next to him, as an aquarist I feel slight shame in showing off our algae walls, you may think the algae adds to the tank and not see a green mess and I encourage you to keep thinking that, we can also call it seaweed which makes it look better... Though, the fact the algae is in this tank is actually great, and here's why:

The crab has picked at that algae off the walls and attached it to it's legs and carapace. Why would it do such a thing? To camouflage of course. In the wild they will place seaweed or sponges on their bodies and hide themselves in with their surroundings. I think that's pretty clever.

We've got two of these crabs in each of our modest sized local species tanks. The pictured one is from the "Hilbre tank", which is the tank that looks like it's empty.

It's not actually empty, all the animals in the tank have amazing abilities of avoiding being seen, and the design of the tank also helps them with this. Which we are going to sort out.

This is the same tank taken from above. You may have spotted that rather large common starfish hiding in the corner... there were two more hiding in that corner too, the dogfish on the floor can be seen from the top, but those looking in and down in the tank from outside wouldn't see him, three other dogfish were hiding in the far left hand corner too, and a couple of spiny starfish are- you guessed it- hiding in a corner. There are about 8 goldsinny wrasse and a couple of rock cooks and a male and female cuckoo wrasse (all fishes) living behind the rocky theme.(far right in the photo, behind that barrier) They're fine, they feed well, they just don't get seen other than by us when we look down on the tank. Catching them is pretty difficult. But one day soon we will sort this tank out and I will blog about it.

It may be difficult to spot the spiny spider crabs but trust me, it is worth having a proper look round the tanks, look down into the corners too, you may spot some of our other animals pretending not to exist.

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Common Lobster

Enough about fish, let's pay some attention to a member of the crustacea subphylum (that just means a crustacean). The common Lobster, and you can call them a Homarus gammarus, and I do like to say that out loud several times fast. It's a good word. Onto the animal...

You can eat these, and if you've ate lobster you may have eaten this type. "But it's blue and all gorgeous!" you may say. It is, it goes red and less glamorous when it has been cooked. Our's is a bit small at the minute, so put your forks away, she won't make much of a meal.

My favourite fact about Lobsters involve their claws. Each one has a different function, the larger of the two is the "crusher", think of it like a nutcracker, it crushes its prey, the other is a "cutter", the edges are much sharper and can be used to cut up their prey, think of it like a pair of scissors, they can also just hold onto their prey too. It's not the fact each claw has a different function that is my favourite fact, it's the fact that though usually the left claw will be the "crusher" and the right claw the "cutter" it's not always the case... which means you can get left handed Lobsters, at least that's how I think about it, and it puts a smile on my face.

I took this photo a day after I made up the little rock house for her to place herself in, which she did... but, another day on she's decided that placing herself between the pipe and glass is a better idea than having a house. These animals...

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Common Prawn

Let's take a break from our teleost fish (don't worry, this fancy word is already outdated so I'm not really showing off), and let's head on down to crustacea town.

Crustaceans. There's tons of them, in all shapes and sizes and species. But the one I care about today is the common prawn, known to boffins as Palaemon serratus. 

I take great delight informing people that, that thing by the rock they've pointed at and don't know what it is, is actually a common prawn! or shrimp! depending on which word pops out my mouth first. It doesn't matter really.. I don't think. Prawns and shrimps are sort of the same thing, it just depends on your preference as to what to call it. Even wikipedia refers to it as both in the first sentence. Ahhh, credibility, maybe.

Palaemon serratus, also called the common prawn, is a species of shrimp (source: wikipedia, 31.12.2012 at 13.00.)

So, after I've informed someone it's a prawn or shrimp the next thing I let them know is "It's that pink swirly thing you eat (if you eat prawns)" I've learnt not to be so presumptuous. And I'm usually met with a wide gaped expression of either horror or fascination.

Prawns are transparent when alive, and have faces and legs too, when they've been cooked they turn pink, and their heads and legs and shell is all peeled away.

I don't want to give all the good crustacean stuff away but prawns have exoskeletons, just like all the other crustaceans. This basically means outside skeleton. This is their skin, and also their protection because inside this exoskeleton is the soft body of the animal. They have no bones inside, the bones is the skin outside, which means they moult... but I'm saving that for a crab. Not that the prawn doesn't deserve it, it's just I have better crab moult resources to share.

I've bonded quite well with these prawns over the years, like other shrimp species they're happy to pick away at food with their chelipeds (that's claws to you and me). You can stick your hand in and depending on the sociability of the prawn they may come over to have a nibble at your dry, dead skin. Nom. Most the time though they keep out the way, especially if you're trying to demonstrate that they will come over to "clean" your hand. Can't say I blame them really.

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