Freshwater Shrimp

Paratya is New Zealand's most common freshwater shrimp. These shrimps are often found in streams near the sea because they spend part of their lives in seawater. They graze algae and other microscopic life growing on stream or river beds.

Shrimps cannot swim very fast, so they are best suited to slow waters and can be found, as here in the Waipapa River, drifting amongst weed beds. Some shrimps use the legs under the abdomen for swimming. However, like all crayfish some shrimp can only swim backwards using their tails. They are also used to fan freshwater to the gills (and may even bear gills themselves), food to the mouth and to carry their eggs.

The antennae and atennules in front of the mouth are are a shrimp's sensory organs and also aid swimming and feeding in their larvae forms. The smaller pair of antennae contain fluid sacks used to orientate the animal. The large pair of antenna are very mobile and sensitive, and enable them to move safely through even the darkest waters. Their sense of touch is further enhanced by fine bristles situated on their limbs, allowing them to sense even the slightest movement.

Like crabs and crayfish, their compound eyes are located on stalks. There are between 7,000 and 30,000 individual eyes on each eyestalk. Even with compound eyes, shrimp orientate themselves primarily by touch.

Paratya is a crustacean, like the crab and the crayfish. A shrimp's body is covered with a solid shell which is held together by an underlying layer of skin (called the endoskeleton), and together forms the crustacean's exoskeleton. Its muscles are also attached to this outer shell. Like the crayfish, the freshwater shrimp also moults.

Did you know? When paratya migrate into fresh waters, they are able to climb waterfalls and dams using their claws to grasp rough surfaces.

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© 2006 Puketi Forest Trust