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Helmet shell on the move at night at Long Beach
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!
Giant alikreukel at Fisherman's Beach
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.
Kelp limpet at Fisherman's Beach
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).
Ribbed turrid on the move at Long Beach - look at that gorgeous foot!
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!
Abalone on the pipeline at Long Beach
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.
Upside down abalone
Right side up abalone
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.
Deadly (or passionate?) embrace at Long Beach
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.
Tiny chiton in a bivalve at Long Beach
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.
Alikreukel with sealed shell at A Frame
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!
7 Comments
Touch or don’t touch? « Learn to Dive Today
22 Nov 2010 08:11 am
[...] must confess that when I see an upside down starfish, crab, or abalone, I turn them back over. Call it interfering with the natural order of things, but I can’t [...]
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01 Jan 2011 12:01 pm
[...] my post about sea urchins I mentioned how juvenile abalone shelter among urchins. When the rock lobster population gets out of hand, too many urchins (their [...]
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17 Jan 2011 09:01 am
[...] shallows are where I see lots of gorgeous molluscs of various types. Fat plough shells have magnificent large feet, and it’s a pleasure to see [...]
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17 Mar 2011 07:03 am
[...] siphoned whelks (and many other molluscs) have beautiful bodies that you can’t see if you just view their shells from above. Here are [...]
Hitch hikers « Learn to Dive Today
26 Apr 2011 07:04 am
[...] way out at the end of the dive, in the first two metres of water off the beach, I spotted two tiny long-siphoned whelks, clearly juveniles. One was hitching a ride on the back of a hermit crab! Baby long-siphoned whelk [...]
FAQ: Diving in Cape Town « Learn to Dive Today
25 May 2011 07:05 am
[...] sea plants, and extremely diverse invertebrate life such as nudibranchs (colourful sea slugs), molluscs and brightly coloured sea anemones. Diving in Cape Town is colourful and always [...]
Excuse me very much | Learn to Dive Today Blog
29 Apr 2012 07:04 pm
[...] whelks and other molluscs can’t feel things on their hard shells, they seem to be a favourite stepping stone or even a [...]
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