I know octopus are molluscs, but by the title of this post I mean things with external shells – abalone, limpets, whelks, mussels and chitons. Couldn’t find a word that covers all of them!
When I was a child, apart from interfering with innocent sea anemones, I enjoyed everything else that the rocky shore had to offer. I collected shells, tried to pull limpets off the rocks, and admired the tracks left in the sand by plough shells on Fish Hoek Beach. As a scuba divers, the temptation is to dismiss all these creatures as not being that interesting – after all, we dive in order to see BIG things, like rays, sharks, fancy fish, and octopus.
The truth is, however, that during my dives I’ve seen a lot of the shells I used to pick up as a child. With a couple of notable differences. One is that these shells are generally inhabited – and their inhabitants are far more brightly coloured and interesting than I ever imagined they would be. The other difference is that, in general, the specimens I see strolling around on the sea bed are bigger than the empty shells I found in rockpools and on the beach. Much bigger (and it’s not just the magnifying effect of the water).
Take abalone (perlemoen) for example. Prized by sexually insecure foreigners, these gastropods are poached almost into oblivion all along the South African coastline. Most of my diving is done in Marine Protected Areas (MPAs) for which I pay for a permit, but this doesn’t make them immune to poaching. It takes years – up to 30 years – for an abalone to grow to its maximum size of about 18 centimetres in diameter. These are incredibly slow-growing creatures. So when I see a massive specimen clinging to a rock at Fisherman’s Beach, or strolling across the sand with the edges of its mantle waving festively at Long Beach, I feel hugely privileged. He’s almost as old as I am!
A week ago I found an abalone at Long Beach that had gotten flipped over, and his (very beautiful) foot was in the air. I took a picture, righted him, and took another picture. Even though he was not very big (about 13 centimetres) his shell was so encrusted that he was clearly quite old.
We also see many whelks of various kinds. These are voracious predators – they will drill holes in other shells using acid, and then inject digestive juices in order to digest their prey while they are still inside their shell. If you find shells with small holes drilled in them, it’s probably one that met an unlucky end at the hands (foot?) of a whelk.
Chitons are protected by a row of eight overlapping plates – if you find a piece of shell that looks like a little boomerang, that’s a piece of chiton. They come in various sizes from the very small (1 centimetre) to the rather impressive. They can’t see a thing – their heads are completely hidden under their plates. They have a very sharp tongue called a radula that they use to scrape algae and other tasty goods off the rocks for food.
Another regular sighting is the allegedly tasty alikreukel – the biggest snail you’ll ever see. As a child I would pick up the little trapdoors they use to seal their shells – one side is usually gorgeous mother of pearl, and the other has little knobbles. These snails are quite active and we often see them moving about.
There’s a lot to see if you slow down and take your time over small areas of the sand, rocks or reef. You’ll often find a handsome mollusc hiding in amongst the seaweed, or making his way across a sandy patch. They’re little miracles in and of themselves – take a look!
