<P> The telson is the posterior-most division of the body of an arthropod . It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments . It never carries any appendages, but a forked "tail" called the caudal furca may be present . The shape and composition of the telson differs between arthropod groups . </P> <P> In lobsters, shrimp and other decapods, the telson, along with the uropods forms the tail fan . This is used as a paddle in the caridoid escape reaction ("lobstering"), whereby an alarmed animal rapidly flexes its tail, causing it to dart backwards . Krill can reach speeds of over 60 cm per second by this means . The trigger time to optical stimulus is, in spite of the low temperatures, only 55 milliseconds . </P> <P> In the Isopoda and Tanaidacea (superorder Peracarida), the last abdominal body segment is fused with the telson, forming a "pleotelson". </P>

What is the function of the uropods and telson and what feature indicates this function
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