Appearance
A prawn/shrimp of up to 3 cm (1.2 in) in length, appearing in many different colours: red, yellow, brown, green, transparent or blue. The colour can adapt to surroundings. During the night it usually becomes bluish-green. The common name "chameleon shrimp" and specific name varians ("varying, fluctuating") both refer to this colour change. It sometimes matches the seaweed on which it feeds, such as the green Ulva lactuca or the red Palmaria palmata.
The short carapace has a single spine. There is also a spine above each eye, and the telson has two pairs of lateral spines.