Visitors to beaches in South Wales have been warned to keep Dogs on leads and avoid walking barefoot after a number of Portuguese Man 'o War, Physalia physalis, have been found on beaches in Pembrokeshire and Carmarthenshire this week. The planktonic Animals die rapidly after being exposed on beaches, but remain capable of delivering a powerful and unpleasant sting for some time afterwards, and in extreme circumstances these can prove fatal to both Humans and Dogs. Detatched tentacles, which are harder to spot than their brightly coloured floats, also present a risk. The venemous Cnidarians have been seen on beaches at Cefn Sidan, Llansteffan, Broadhaven, Manorbier, Newton, Freshwater West, and Newgale. They have also been reported at Tywyn, Barmouth and Harlech on the coast of Gwynedd in North Wales, though in lower numbers.
Portuguese Man o' War are colonial Siphonophores only distantly related to true Jellyfish, Scyphozoa, though commonly referred to as such. Their bodies are made up of thousands of individual zooids, each with their own sting, tentacles and digestive system. New zooids are formed by budding from other members of the colony, but remain attached to these to form a single colony. Each year a generation of specialist sexual zooids (gonozoids) is produced which produce eggs and sperm, with fertilised eggs going on to form new colonies. These animals are anchored to the sea surface by a highly modified zooid which forms an air sack, filled with a mixture of carbon monoxide defused from the zooid and nitrogen, oxygen and argon from the atmosphere, which are brought into the sack through osmosis. Portuguese Man o' War produce an extremely strong venom, for both capturing food and defending the colony, and which is capable of causing extremely painful stings, and sometimes death, in Humans, for which reason people are advised to be extremely cautious on beaches where these animals wash up, not just of entire animals but also detached tentacles, which are less visible but still capable of stinging.
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