Shell Collecting on Southport Sands

Thoughts from a conchologist - the study of shells

Written by Claire Duncan
Photos by Claire Duncan



Fig. 1 Three red whelks. (Photo: Claire Duncan)

In the holidays I tend to spend a lot of time on Southport Beach. Aside from picnicking at me and my fiance’s ‘spot’ on the seawall, using the gym equipment by the lifeboat station and dodging the mass migrations of tourists on Bank Holidays, I’ve also got into conchology. 

Conchology, or the study of shells, taps nicely into both my paddling around in the mud picking up interesting stuff instinct, and my higher, more academic nature, which meticulously researches stuff and jots down the Latin names. When I was small, my dad would take me ‘treasure hunting’, pootling along farm tracks gathering bits of pottery from the hardcore used to mend the potholes. We would then come home, me excited and covered in mud, to piece together our finds and deduce the different types and stories of each piece. Shell collecting’s very like that. It’s amazing what you can find amongst the mud and litter and coal. Although when the tide is out, the sea is famous for needing a half hour walk to see, when it comes in it brings a myriad of things from the surrounding coast, and often further.

One of the main finds at Southport is the edible whelk, Buccinum undatum. This spiral shelled gastropod is found on soft bottomed coasts where it preys on small bivalves. The shells are beautiful- delicately ridged and in a startling array of colours. I’ve lately found out that the colours can come from staining by the various colours of sediment.

Fig. 2 Clockwise from the top: Red whelk, Prickly cockle, Wentletraps, and Auger shells. (Photo: Claire Duncan)

 

In finer sediments (for example, the fringes of the Ribble estuary) lower layers become anoxic, with anaerobic bacteria producing hydrogen sulphide as they feed. Apart from a bit of a pong, this reacts with the iron found in the sand to produce black iron sulphide. So particularly dark shells picked up will have been dead some time, and had prolonged exposure to this iron sulphide rich sediment. On contact with the air, the iron sulphide reverts back to the iron oxide of the original sand, producing gingery orange shells in just a few hours.

Lately, though, the edible whelks seemed smaller, smoother and a more translucent. Odd. What with ocean acidification due to global warming (we’ve already managed to change the pH of the world’s oceans by .1 of a unit.) I was worried that, like many species, these too were struggling to form calcareous shells. With the help of a decent species guide, it turns out they were red whelks, Neptunea antique. These are very similar looking, but a completely different genus. They’re also poisonous. Why they suddenly seem much more common than the edible whelk is anyone’s guess, but it could just be a short term thing with the weather and currents. Or have they supplanted their edible cousins in these waters?

Amongst the smaller shells were periwinkles, cockles, necklace shells and the delightful little wentletraps (Epitoniidae family). From the Dutch for a spiral staircase, wentletraps are characterised by their unusual shells. The whole spiral is covered in ridges which act as protection from other predatory gastropods drilling into them. There are over 600 species worldwide, although I’ve personally only found two or three while out and about. Another personal favourite are the more common auger shells (Terrebridae family), which look like unicorn horns! Or more prosaically augers- spiral drill bits. Although not as common as cockles or the ubiquitous razorshells, they’re always something pleasant to look out for on the sands.

Fig. 3 Beachcombing on Southport beach. (Photo: Claire Duncan)

While most of the shells washed up are fairly easy to identify, I was thrown a bit of a wildcard earlier this week. It was grey, medium sized and was neither a spiral shelled gastropod nor showed any sign of a hinge which would indicate it was a bivalve. The apex was not only to one side, but curled into a little spiral. The closest thing it resembled were the now extinct Devils Toenails (Gryphaea spp.), which haven’t really been a thing since the Jurrasic. But it obviously wasn’t fossilized, and was the wrong shape anyway. I looked at every seashell guide I could find. I went through the Conchological society’s website and googled limpets, gastropods and obscure bivalves. Nothing looked plausible. And absolutely nothing seems to have its apex in a spiral.

The key to this now half solved mystery was the river Ribble. Southport is on the very edge of the Ribble estuary, with saltmarsh giving way to sand just a few hundred yards from the pier. I’m still not sure the exact species, but it seems to be something from the Ancylis genus of freshwater limpets. Apparently they like unpolluted, flowing water where they cling to the rocks to graze. So whatever this odd, lumpy, little grey thing is, it’s a very long way from home. A shellfish out of water, perhaps?