Pulmonates on Port St Mary ledges

Last summer the family and I were visiting the Isle of Man to attend a reunion to mark the end of 114 years of marine science at the Port Erin laboratory. The station was finally, after many threats over the years, succumbing to the inevitable. In many ways it was a sad occasion, a good number of the attendees having spent a number of years there with lots of happy memories, but it was also an opportunity to renew friendships and explore some old haunts.

 

One of the amazing things about travelling with a baby is how something so small can take up so much space in the car. As a result I sadly had to leave all the normal sieves, buckets etc. at home, deciding instead it would give me a good opportunity to concentrate on photography (the camera now accepted as part of the normal baby paraphernalia).

 

The weather, which can be a bit hit and miss on the island, was fantastic and my wife very kindly allowed me a few days off part-time baby duty to explore some of the local beaches. One of these – Port St Mary – is famous within a relatively select community of rocky shore ecologists for the large, more or less, uniform limestone ledges which lend themselves to field experiments. This has resulted in a long line of literature exploring the relationships between the barnacles, limpets and fucoids.

 

The beach has a fairly typical rocky shore molluscan fauna. The upper shore has an abundance of Littorina saxatilis and Melarhaphe neritoides amongst the barnacles and crevices. Below this of course the inimitable limpets – Patella vulgata along with relatively common Gibbula umbilicalis, G. cineraria and Littorina littorea. Lower down there is also evidence of a species burrowing in the limestone but without any means to extract them I couldn’t identify them further. I busied myself primarily experimenting with close-up shots of the common upper shore species and then had a rummage around further down the shore. Nothing particularly interesting appeared until I came across a large lower shore boulder one side of which formed a protected overhang. Here whilst sliding around taking pictures of the sponges I spotted a couple of tiny molluscan specimens on the sponge and amongst the red algae. Both at least looked different from anything else on the beach. I popped both in a tube of alcohol and thought nothing more.

 

Back at home they proved a little more difficult to identify than I expected. After some time leafing through Graham and Thompson & Brown my only conclusion was they were either new to science (which seemed particularly unlikely given how well explored the beaches on the island are!) or Acteon tornatalis (in a very untypical habitat) and Lamellaria perspicua.

 

Some time before, Jan Light had very kindly offered to have a look at anything I was unsure of and some months later I passed my specimens on to her. Depressingly both identifications turned out to be wrong –the identifier having been tricked by the lower shore nature of the boulder. They turned out to be the ‘marine’ pulmonates, Leucophytia bidentata and Otina ovata. Looking back at the boulder (one of the handy things about having a camera on the shore) it did span a relatively large section of the intertidal zone having Fucus spiralis growing on top. Even so, the boulder would definitely be completely submerged at high tide.

 

Excitedly I popped the new names into the NBN Gateway (data.nbn.org.uk) – keen to see whether there were already records of these from the Isle of Man. The Gateway includes most of the Societies computerised records and also a number of other sources. While by no means definitive it does provide a reasonable indication of the currently recorded distributions of species. According to the data on the Gateway, Leucophytia bidentata had been recorded there, but there appeared to be no records of Otina. I also checked the “Marine Fauna of the Isle of Man” last published in 1962. This refers to a single record of Otina at Santan Head (SC3370) recorded in Forbes & Hanley, 1848- 53. This definitely made up for the depression of the misidentifications!

The moral of the story to the less experienced shellers out there (like me) is “Don’t forget the pulmonates!” they can turn up in some unusual places. It also seems even after 114 years of research the Isle of Man still has a few secrets left to discover.

 

I would like to thank Jan Light for help with the identification and my long suffering wife Fiona for putting up with such an odd hobby!

 

Port St Mary ledges (7th July 2006)

SC 200667

Full species list: