Sexy Shrimp

Thor amboinensis is a small shrimp growing to a length of about 13 millimetres (0.5 in). It is an olive brown colour with symmetrically placed white patches edged with thin blue lines. It characteristically carries its abdomen curved upwards with its tail fan above its head.

Though it is named for Ambon or Amboyna Island, one of the Maluku Islands in Indonesia, Thor amboinensis has a pantropical distribution being found in the Red Sea, the Indian Ocean, the Pacific Ocean, the Caribbean Sea, the Gulf of Mexico, Madeira and the Canary Islands.

Thor amboinensis forms a commensal relationship with another invertebrate, usually a shallow water sea anemone or mushroom coral. The species most often used as host in Bermuda include the carpet anemone (Stichodactyla haddoni), the stinging anemone (Lebrunia danae) and the adhesive anemone (Cryptodendrum adhaesivum). One or several shrimps live among the tentacles of their host, feeding on the tentacle tissue and on the mucus-trapped planktonic particles adhering to it. In the Bahamas, Thor amboinensis forms part of an assemblage of symbiotic invertebrates associated with the anemone Lebrunia danae. Each shrimp, crab and brittle star inhabits its own part of the sea anemone and Thor amboinensis is found hidden deep among the pseudotentacles.

The female Thor amboinensis carries the fertilised eggs under her abdomen until they are ready to hatch. The zoea larvae pass through several stages and, before undergoing metamorphosis, are attracted by both chemical cues in the water and visual cues which cause them to settle near potential host anemones. Researchers found that the larvae of Thor amboinensis were generalists, being attracted by and accepting several different species of anemone as hosts. In some experiments they had a preference for the species of anemone from which the parent shrimp had been collected.