‘Life is a beautiful, magnificent thing, even to a jellyfish.’
Charlie Chaplin: Limelight; 1952
Any person who has scuba dived or free dived virtually anywhere in the world’s ocean will have come across swarms of jellyfish. Here in Cape waters they are ubiquitous; both in the warmer Indian Ocean and chilly Atlantic sides, these hordes of little floating parachutes are so dense sometimes that they block the view from your mask. They are fascinatingly beautiful too, their translucent bells tinged with blue or red threads, as they drift seemingly aimlessly as they look for food in the bountiful waters.
But if you happen to be free diving without a wetsuit, and flipper your way through a smack of jellyfish (yes, that is the collective noun for a bunch of jellyfish, and no, we have no idea why), they come with a fairly serious caveat: those tentacles dangling beneath the jelly bells contain a stinging poison that is designed to immobilise prey. All the better to eat you with, Little Red Diving Hood. Those harmless looking parachutes are mostly carnivorous too: the ‘cnidocytes’ on their drifting tentacles contain nematocysts that literally explode on touching something: up to 1500kgs per square centimetre pressure (!), injecting a toxin that stuns prey, which then, somewhat like an octopus, is brought up to the mouth to munch at leisure. Their diet comprises small fish, crustaceans, plankton, fish eggs, larvae and, a little eerily, other jelly fish. Humans have been stung by jellyfish ever since man has engaged with the ocean, ‘with effects ranging from mild discomfort to serious injury or even death’, according to the Smithsonian Institute.
‘Jellyfish’ sounds like a lazily concocted name – but then again their scientific monickers aren’t exactly designed to roll off the tongue: Cnidaria (from Greek, ‘Sea nettle’); with subphyla Medusozoa, scyphozoan, hydrozoan and cubozoan – and ‘jellyfish’ has been in use since 1796. More recently, in these politically correct times, public aquaria have been calling them ‘jellies’ or ‘sea jellies’, as they can’t really be classified as fish, not having a backbone. (Come to think of it, neither do shellfish, cuttlefish and starfish – watch this space.)
Once one starts delving into the whys and wherefores of jellyfish it’s interesting to discover that they are surprisingly mysterious creatures, despite their presence around the aquatic world. Some facts are quite startling once you get into your research: they are among the oldest living animals on the earth, some 600 million years according to fossil records. They come in a wide variety of shapes and sizes too: there are over 10 000 cnidarian species (half of which are coral and sea anemones – close relatives) and they range in size from 5mm and 2 grams in weight – the tiny and highly poisonous Irukandji species – to the 2 metres and 200 kg of the Lion’s Mane jellyfish.
They are extremely simple in construction too; effectively a floating stomach and reproductive system with tentacles. Jellyfish do have muscles, sort of: they are liquid filled sacs in their circular bell that can compress and squirt water out of the bell’s opening to propel it along. It’s called a hydrostatic skeleton, should you want to impress friends who have just been stung. (Earthworms have the identical propulsion unit: who knew?) There is no central nervous system, circulatory or respiratory system; their nearly organless bodies are fully 98% water. And 2% nasty poison, we reckon. Possibly the most dangerous animal on the planet is the ‘box jelly’ chironex fleckeri; its bell is about the size of a football, and its tentacles are over ten metres long. Known nervously as the ‘sea wasp’, this creature floats menacingly off the coasts of Australia and Southeast Asia, and just a passing graze of its tentacles causes excruciating pain; prolonged contact will cause death in as little as two minutes. And, as an aside, all beached toxic jellyfish are equally capable of exploding those pesky nematodes when touched. Don’t be like the Australian Darwin Award winner who put one on his head, draped the tentacles around his body, and said to his mates: ‘Oy mates! D’ya like me floor-length hat?’
Despite their very simple construction, jellyfish have a complex reproduction system. Deciphering the biological terms, the eggs are expelled from the female, fertilized in the water by males, and then sink to the seabed. These hatch into little planula – jelly babies! – which attach themselves to hard surfaces, and grow into a little broccoli shaped creatures like a sea anemone. They hang on for months (or years, for some types) and then one day launch themselves off their perches and become ephyra: a juvenile jellyfish. Off they swim, to eat, grow, and become fully-fledged jellyfish looking for free divers to bother and legs to sting.
There is much more to these fascinating characters, but space dictates we pause here with a suggestion: the safest way to observe a smack of jellyfish is aboard a Waterfront Charters boat. The little ones attract turtles and dolphins too: apparently they are a delicacy in the underwater world. We can’t promise sightings, but we can assure you of a relaxing and informative cruise, with chilled beverages and superb views too; not an exploding nematocyst within range.
