Ghost Jelly

The medusa stage of Cyanea nozakii has a distinctive flat-topped bell which can grow to a diameter of 50 centimetres (20 in). The bell is usually cream or pale yellow in colour with a dark centre and a translucent rim. It has eight large marginal lobes and eight bundles of thread-like marginal tentacles. There may be a hundred or more tentacles in each bundle which are either translucent or a reddish colour, and can extend for 10 metres (33 ft). Under the centre of the bell is the manubrium, the mouth being surrounded by a tangled mass of rusty-brown or orange oral tentacles.

Cyanea nozakii is found around the coasts of China and Japan. Since the beginning of this century, Cyanea nozakii has become more common, with mass aggregations occurring. In 2004 this happened in Liaodong Bay in Northeast China and it was noticed that commercial catches of the edible jellyfish Rhopilema esculentum were adversely affected.

A number of species of juvenile fish associate with this jellyfish, making use of the protection provided by its stinging tentacles. The razorbelly scad (Alepes kleinii) and Malabar trevally (Carangoides malabaricus) are two such fish; large numbers of tiny fish congregate around and among the fine tentacles. Each fish either avoids touching the tentacles or is relatively unaffected by their mild sting, and if the jellyfish is netted, the little fish stay with it and may get more heavily stung, and consequently die. As they get larger, the fish leave the jellyfish and live independently.