Jellyfish like small bright jewels littered the strand-lines along the St Peter Port shore in Guernsey last September. At first the bright pink parts in the clear jelly made me think they were immature Moon Jellyfish (Aurelia aurita) but a closer inspection revealed they were very different and not something I had encountered before. They were Mauve Stingers (Pelagia noctiluca) all about 5 centimeters diameter (2 inches) across the bell; mature specimens can reach 10 centimetres in diameter. The pinky-mauve features are the unbranched gastric pouches and the four frilled oral arms surrounding the mouth. There are also numerous tiny purple spots grouped within the transparent jelly.
There are sixteen lobes around the margin of the bell. The bell or umbrella when supported by the water column would look quite deep compared with the flattened stranded examples washed ashore and shown in these photographs. Eight long thin marginal stinging tentacles trailed from the jellyfish and adhered to adjacent pebbles where they lay on the beach. In this species it is not only the tentacles that are dangerous but also the entire outer surface of the bell (exumbrella surface) which has a characteristic bubbly texture created by nematocyst-bearing warts. The projectile stingers within the warts are triggered by touch.
Mauve Stingers are unusual in not having a sessile stage. The adult releases miniature medusae in the autumn, and the size of these increases until the following late summer. They feed on free-floating ascidians (sea squirts) and maybe other small jellyfish.
Hayward, P., Nelson-Smith, T. Shields, C. 1996. Sea Shore of Britain and Europe, Collins Pocket Guide, ISBN 0 00 219955 6, p 48.
Hayward P. J. and Ryland, J. S. 1995 Handbook of the Marine Fauna of North-West Europe, Oxford University Press, ISBN 0 19 854055 8, pp 65-67.