Environment – A particular cuteness

A recent photo from The Forest Bridge Trust was of one of the most beautiful-ugly creatures I’d seen for a while. It was a panephrops planefrons (kōura or freshwater crayfish).

It was grey-brown, with a hard, scaly, jointed body, long rigid feelers, black beady eyes, and was as big as a person’s hand. Though, in the online photo, it was perched on a brave and lucky person’s arm.

Kōura are crustaceans, so as they grow, they moult their scaly exoskeleton shells, and by the looks of this one, she’d changed shells a few times. They can also grow back any legs they lose through moulting.

Panephrops planefrons are found in the North Island, Marlborough and the West Coast of the South Island, and are one of two species in New Zealand. They grow to around 70mm maximum, a bit smaller (with less hairy feelers) than their Paranephrops zealandicus southern South Island and Rakiura cousins.

Kōura are freshwater denizens, mostly active at night, and as their stream and swampy habitats have been degraded, so have their numbers. They burrow into gravels and substrates and can bed down to endure summers even when waters dry up to re-emerge when conditions allow.

They breathe by drawing in water, which passes over their gills where the legs join the body under their thorax, and out through the mouth. If their gills get blocked with mud, they can back-flush them clean.

They have four pairs of walking legs and their front legs (their chelae) are used for fetching food (old leaves, small insects) passing by in the water column, ‘scavenging’ rather than actively hunting. Those front legs are also used for fighting or as a defence or alarm posture, and they can also nip.

To breed, male kōura attach a package of sperm to the underside of the female. The female kōura lay their eggs between April and December, maybe across two seasons a year, mostly between March and May, and the eggs move through into the sperm package and become fertilised. She then carries between 20 and 300 berry-like eggs around under flaps on her abdomen, and at that stage she’s called ‘in-berry’.

The babies hatch three to four months later and hang on to her with their rear legs until they’re about four millimetres long, between four and 14 months after that, depending on water temperature, or when they’re old enough to live independently and alone. They’re adults at about 20mm around four years old.

Kōura are threatened by land and water changes affecting their habitat quality and quantity, and also pollution and introduced fish. Shags eat them, and historically they were important mahinga kai or a food source for Māori. Apparently even today they are sometimes harvested for food by non-Māori.

When there are lots of them, they also sometimes eat each other.

They’re not the most cuddly creatures on the planet, but only found here, and are special all the same.