Crayfish Molt

Have you ever eaten a soft-shell crab? If you haven't, you can try it at the East Coast restaurant in the United States. The soft-shell crab, as the name shows, has the soft-shell. Because the shell is so tender as the meat, you eat it in whole as if you eat the shell-less crab. The whole eating means that there is no nuisance to crack the hard shell and also the crab would be cooked without losing inner juice and crab butter. In another word, it's delicious.

This species doesn't have inherently soft shell but it is a mediocre blue crab similar to what we call "Watarigani". But its shell is soft because it is cooked soon after the molt. The crustacean such as shrimp, crab and crayfish is usually protected by hard shell but pro-molt shell is so floppy and is getting harder and harder as time lapses.

These are the preambles I intend to lead to the crayfish molt story.

The soft-shell crayfish undoubtedly tastes as good as soft-shell crab anyway. The soft-shell rock lobster must be the same. I wish I could eat the molting soft-shell rock lobster in my life.

I have fed a lot of crayfish but I haven't have many chances to face the decisive moment of crayfish molt. He might have been vigilant while I was watching him and refrained from molting, because it was the most vulnerable moment in his life. I was, not once or twice, upset missing the very moment while I left the tank for just a minute.

The molt precursor appears up to two or three days before. As usual appetite declines first, the leftover might be precursor. In this stage, calcium in the shell is being transferred to and accumulated in the gastroliths rapidly. As the calcium in the shell decreases, the shell color fades. This is the sign of molt at hand. If the joint between carapace and tail opens 1 mm, the possibility of the molt is within twenty four hours. I know you cannot keep watching in front of the tank for such a long time. I recommend setting a video camera instead, if you hate missing the molt moment.

Now I would talk about how the molt will proceed.

The joint between the carapace and the tail opens wide up to ninety degree, then the crayfish pops out of it. The body is so soft that "pops out" expression is real. And this happens in only a second.

If a man who wears jeans and a T-shirt bends ninety-degree forward, his lower back opens. The molt is just like, from this position, popping out of his cloths. If his whole body is as soft as gum, it might be possible. And again this happens in only a second.

Pro-molt crayfish is so soft that his eight legs cannot support his body, neither his pincers can be held up. The only thing he can do is to wait until his skin gets hard. In this vulnerable state of octopus-like mollusk, he will run away with utmost effort when a predator comes close.

When I saw crayfish molt as my first experience, it was a kind of " the scales fall from my eyes". I had been wondering why the body gets bigger through molts. Shouldn't it get smaller whenever the shell goes off? But the floppy body makes me understand that it swells after the molt. Actually the floppy body swells and the skin gets hard afterward. This mechanism explains the mystery.

It will take three to four days for the shell to regain the original hardness. During the days, the calcium accumulated in the gastroliths goes back to the new shell. At the same time, the crayfish eats out the old shell, because it is the precious source of calcium. Salt-water lobster or rock lobster, by the way, doesn't eat the old shell, because the seawater is rich with calcium.

When I completed observing the entire scene in front of the tank with curiosity, the pro-molt crayfish was looking up at me with a full amount of fear. Obviously, this was the most vulnerable and dangerous moment for the crayfish and also this was the best chance to eat delicious soft-shell food for me.

Click Picture
3:35 White Crayfish (Procambarus clarkii) Molting. Good Video!
9:58 Blue Redclaw Molting
8:11 Redclaw Molting
6:30 Cajun Dwarf Crayfish Molting
3:25 Redclaw Molting. In danger to be eaten by a fish
0:15 Blue Crayfish Molting
0:44 Blue Crayfish Molting
1:59 Redclaw Molting
1:11 Signal Crayfish Molting. Parasites moving to the new body!
2:00 Blue Crayfish Molting
2:11 Blue Crayfish Molting