Palaemonid Shrimp are small to moderate-sized shrimps, rarely reaching more than 5 cm, however a few species are large enough to be of commercial value. This family of shrimp have a long toothed beak and the front two legs have claws. The second pair of legs are larger and longer than the first pair.
All species in the juvenile stage, and many species in the adult stage are transparent or nearly transparent,often with dark lines or spots. Large specimens are sometimes more opaque and can be darker coloured.
Many Palaemonid Shrimp are commensal, that is, they live on or inside another host organism such as a sponge, coral or anemone, without causing harm to the host. Some more colourful species are able to alter their colour to match their background or hosts.
Those Palaemonid Shrimp living with a host can often perform cleaning duties both to their host, and to passing marine life, typically advertising their presence by waving their long white antennae to draw attention to their services. These cleaner shrimp, along with cleaner fish such as the Bluestreak Cleaner Wrasse (Labroides dimidiatus) are a hugely important part of a coral reef ecosystem.
Harlequin Shrimp have a white or cream coloured body which is covered with distinctive red, purple and blue spots. This species of shrimp has ten legs, with the first pair being modified with large, flattened claws. The first pair of antennae on the head resemble a flattened leaf which can sense nearby prey using chemical receptors. The eyes are located on stalks.
Harlequin Shrimp are shy animals, usually found in pairs, and prefer to hide during the day and hunt for prey at night. This species feeds on sea urchins and sea stars, particularly the Blue Sea Star (Linckia laevigata). The shrimp may either cut off a section of the sea star arm with their powerful claws and drag it back to their nest to eat, or may work together to turn over a sea star, thus disabling it, and drag the entire animal back to the nest to eat over a period of time, starting at the end of each arm, eating right up to the central disk.
Harlequin Shrimp can grow up to 5 cm, but usually observed slightly smaller than this, often 3 cm - 4 cm. Females are slightly larger than males, and the monogamous pairs are territorial.
Harlequin Shrimp are members of the sub family Hymenoceridae which has only three members in two genus, the Harlequin Shrimp (genus Hymenocera, only one species) and the tiny Tiger Shrimp (genus Phyllognathia, two species).
The Peacock-Tail Anemone Shrimp, sometimes known as the Clown Anemone Shrimp has a translucent body and grows to around 4 cm. The body has several prominent white blotches on the back and tail base. The tail has five black-edged orange spots. The long front legs and claws are transparent with purple bars.
Female Peacock-Tail Anemone Shrimp are often larger and more brightly patterned, with more and larger bright white spots than males. The smaller males may be nearly totally transparent except for the black-edged orange spots on the tail.
The Peacock-Tail Anemone Shrimp lives within anemones and can be found in larger anemones, quite often as a pair.