Northern koura
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| Paranephrops planifrons A. White, 1842 |
The northern koura (Koura in Māori), Paranephrops planifrons, is a freshwater crayfish of the family Parastacidae found mainly in the North Island of New Zealand but also in Marlborough, Nelson and the West Coast of the South Island. They reach lengths of about 7 cm, and are very similar to the southern koura but have less hairy pincers and are a little smaller.
The northern koura lives in fresh water such as streams, lakes and ponds, and even in swamps, sheltering under stones or logs. They can also burrow into muddy bottoms, and can wait in burrows during dry spells. They are scavengers, feeding on animal or vegetable matter that floats by. Once food is caught in the pincers it is torn up, pushed into its mouth to be ground up and separated by a filter system that lets only fine pieces pass through to the small stomach to be digested.
The northern koura is dark green and mottled, very well camouflaged - often its waving antennae and black beady eyes are all that can be seen because they stay hidden during the day, moving around mostly at night.
For respiration, northern koura draw water in under the thorax where the legs join the body. Water is sucked in, pumped forwards over the gills and out through the mouth. If the gills get clogged they can back-pump to flush out any debris.
When danger threatens they can reverse suddenly by flicking their tail forwards violently. Their first pair of legs, their pincers, are used mainly for catching food, for fighting with invaders, or for waving menacingly at intruders. They are capable of giving a painful nip.
They are predated upon by trout and shags.
Female northern koura produce eggs between April and December, and most in May and June. She carries the berry-like eggs, between 20 and 200, under the side flaps of her abdomen, when she is said to be 'in berry'. Small koura hatch about 3 to 4 months later, looking exactly like their parents in miniature. They cling to their mothers with their pincers until they are nearly 4 mm long, around December of their first year. By their fourth year they are 20 mm long and become adults.
