Description
The brine shrimp Artemia comprises a group of eight species very likely to have diverged from an ancestral form living in the Mediterranean area about 5.5 million years ago.
Artemia is a typical primitive arthropod with a segmented body to which is attached broad leaf-like appendages. The body usually consists of 19 segments, the first 11 of which have pairs of appendages, the next two which are often fused together carry the reproductive organs, and the last segments lead to the tail. The total length is usually about 8–10 millimetres (0.31–0.39 in) for the adult male and 10–12 mm (0.39–0.47 in) for the female, but the width of both sexes, including the legs, is about 4 mm (0.16 in).
The body of Artemia is divided into head, thorax, and abdomen. The entire body is covered with a thin, flexible exoskeleton of chitin to which muscles are attached internally and shed periodically. In female Artemia a moult precedes every ovulation.
For brine shrimp, many functions, including swimming, digestion and reproduction are not controlled through the brain; instead, local nervous system ganglia may control some regulation or synchronization of these functions. Autotomy, the voluntary shedding or dropping of parts of the body for defense, is also controlled locally along the nervous system. Artemia have two types of eyes. They have two widely separated compound eyes mounted on flexible stalks. These compound eyes are the main optical sense organ in adult brine shrimps. The median eye, or the naupliar eye, is situated anteriorly in the centre of the head and is the only functional optical sense organ in the nauplii, which is functional until the adult stage.
Read more about this topic: Brine Shrimp
Famous quotes containing the word description:
“As they are not seen on their way down the streams, it is thought by fishermen that they never return, but waste away and die, clinging to rocks and stumps of trees for an indefinite period; a tragic feature in the scenery of the river bottoms worthy to be remembered with Shakespeare’s description of the sea-floor.”
—Henry David Thoreau (1817–1862)
“The type of fig leaf which each culture employs to cover its social taboos offers a twofold description of its morality. It reveals that certain unacknowledged behavior exists and it suggests the form that such behavior takes.”
—Freda Adler (b. 1934)
“God damnit, why must all those journalists be such sticklers for detail? Why, they’d hold you to an accurate description of the first time you ever made love, expecting you to remember the color of the room and the shape of the windows.”
—Lyndon Baines Johnson (1908–1973)