11 September: Crayfish

The French Revolutionary Calendar's celebration of a different plant, animal or tool each day brings us today to Ecrevisse (Day of Crayfish). Here are ten facts about crayfish.

1. Crayfish are also known as crawfish, crawdads, freshwater lobsters, mountain lobsters, mudbugs or yabbies. The word crayfish derives from the French word for them, escrevisse. The study of crayfish is called astacology.
2. They are crustaceans, and are the freshwater cousins of the Lobster. Most species are Red, but others are Pink, Yellow, Brown and even Blue.
3. They are found everywhere except Africa and Antarctica. North America has over 330 species and Australia has over 100, including C. tenuimanus, which is critically endangered, and the two largest species, the Tasmanian giant freshwater crayfish Astacopsis gouldi, which can grow to over 5 kilograms (11 lb) and the Murray crayfish Euastacus armatus, which can reach 2 kilograms (4.4 lb).
4. On average, crayfish grow to 17.5 centimetres (6.9 in) in length.
5. In the wild, they can live to be as old as 30, if they can escape being harvested for food. Louisiana supplies 95% of the crayfish harvested in the USA, and Norway is the top producer in Europe. The top consumer is France. They are not kosher, so Jewish people cannot eat them.
6. Crayfish will eat almost anything - plant material, snails, clams, insect larvae, small fish and carrion. A river with crayfish in it is likely to be less polluted because these bottom feeders clear up the crap - but in some parts of the world their tendency to eat anything can be a problem. In China, they've been known to eat the Rice crops.
7. They moult at the end of June, and when they moult they'll eat their old exoskeleton as well, so that they retain the phosphates and calcium. If they lose a limb, it will grow back.
8. Their eyes can move independently of each other and they have good eyesight.
9. They walk forwards and swim backwards.
10. Crayfish sperm don't have tails. They resemble amoebae and crawl towards the eggs.

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