Promoting Intertidal Sciences blog | Dr Mike Kent | Nov 14th 2018

During Remembrance Week I went searching for inspiration along the strand-line at Polzeath. It was a miserable drizzle-soaked November day, the sort that makes you feel wet from the inside. The only really memorable thing I saw was a moribund jellyfish. Although not in a state of decay nor really ugly, this jellyfish was not a pretty sight. My encounter could be interpreted simply as a timely reminder that not all things found on the shore are bright and beautiful. However, looking at my jellyfish closely, I couldn’t help thinking that this must have been a truly magnificent creature when fully alive. It was no puny specimen, but a fully-grown adult Rhizostoma pulmo, the largest species to be found in Cornish waters; it’s known commonly as the ‘Barrel jellyfish’ or ‘Dust-bin lid’ jellyfish because of its shape and size. It can grow up to 90 cm in width and weigh 30 kg.


Although large and appearing threatening to some bathers, this species is relatively harmless. It has no marginal tentacles. Four pairs of centrally-placed cauliflower-like fused tentacles armed with stinging cells hang down to catch microscopic organisms floating in the sea; the effect of the sting on humans is usually mild, similar to that of a nettle. Nevertheless, beachgoers are advised not to touch Barrel jellyfish as their sting can provoke an allergic reaction in some people.


I’m not certain how my jellyfish became washed up on the beach at Polzeath. Some attribute jellyfish strandings to pollution and climate change, but it is more likely that my stranding was due to natural causes. Generally, jellyfish have a short adult phase and die soon after breeding. Rhizostoma pulmo is known to breed at a phenomenal rate when the seas warm up during the summer. My jellyfish had probably exhausted itself reproducing during the heat wave of the summer after which it was unable to sustain itself: it had given up its life to produce life.


Not surprisingly, my Remembrance Week encounter with the Barrel-jellyfish led me to think of the Parable of the Grain of Wheat:

Very truly, I tell you, unless a grain of wheat falls into the earth and it dies, it remains just a single grain: but if it dies, it bears much fruit. Those who love their life lose it; and those who hate their life in this world will keep it for eternal life. Whoever serves me must follow me; and where I am, there will my servant be also. Whoever serves me, the Father will honour. John 12:24-26