gramandy's picture

Common Limpet

Observed: 2nd June 2013 By: gramandy
Kent Wildlife TrustThanet Coast ProjectWildwood Trust
gramandy’s reputation in Invertebratesgramandy’s reputation in Invertebratesgramandy’s reputation in Invertebratesgramandy’s reputation in Invertebrates
Common Limpet

Made a home in a Crassostrea gigas shell, see other postings to come.

Species interactions

No interactions present.


dejayM's picture


Have you yet worked out why so few people can recognize a limpet?
I am becoming more and more frustrated by these common shells. No two descriptions are the same, the large number of illustration in Google do nothing to help me!
I have three posts - few have agreements, few show definitive features - the two (vulgata and ulyssiponensis) are not easy to separate. See my most recent and read my comment.
Otherwise gooð wishes

dejayM's picture

Coming back

Ordinarily and not long ago I would have agreed to Common limpet. But they are really quite difficult to tell apart via just a top-view. Personally I would rather see these titled Limpet but with notes suggesting that they might be one of, perhaps, three.
I have been through this several times with an expert, including having empty shells to hand, to the conclusion that it really IS hard to tell them apart unless one can see the animal or at least the underside - which usually means killing it.
That it is common and that other examples can be seen as close lookalike, is no proper evidence. This is really VERY unfortunate.
I feel like a spoilsport because I have agreed to a few Commons in my quite short time here - though there probably is no harm in that..
I have read and read, talked to experts, posted a few and STILL believe it might be impossible to tell.
There are a good number of limpet Observations, is one of mine. Despite me making it easy for people to agree, there are still none.
And here is my only slightly more educated post in which I have written -

"It is very difficult to find definitive information which allows correct separation of the three most common ones and a huge overlap in descriptions of each. Book illustrations are somewhat vague and the internet is loaded with pictures which do nothing for separation."
Jan Light's "straightforward" Guide is here She writes "With practice it is possible to discern these differences and make accurate judgements based on exterior appearance but it is not foolproof even for the ‘experts’" Oh dear then!

gramandy's picture

History Derek... has to take into account the historic evidence and experience thrown up by this, of regular visits to this area. The fact that zoologists of the past have recorded vulgata in this area and ONLY vulgata - plus the evidence of the dead animals around which show the white interior leads me to fairly good evidential reasoning that this is vulgata. I have no evidence of any other spp here - so sorry am sticking to my guns on this. P.vulgata for me based on the historic records of the area and my own experience of never having found another sp here - despite the fact that the picture cannot show the interior for this individual.

I also think my confidence shows my intent "It's likely to be this, but I can't be certain" - is a pretty good assessment. I don't necessarily believe that you need a complete certainty for an ID of a picture and I think that just putting family doesn't help anyone when visiting the area. They are most likely to come across vulgata and their own ID is helped by pictures from the area.



dejayM's picture

A spade's a spade..

yes Graham, that's cool and I agree entirely about area-experience and appreciate your Icon-status but the suggestion that nothing else might occur there might be a claim too far as, to be fair, there are so few records of Patella in the general area, maybe as few as six, that one HAS to suspect they are difficult to separate (proving my general point). There are certainly not enough to be certain about anything!
You also write above " the evidence of the dead animals around which show the white interior.." Most of the good descriptions state (of vulgata) that the "Inner surface greenish-bluish nacre, may be yellowish in older shells..." (Fish & Fish) or again typically "Inner surfaces grey-green" (H&R); a white interior 'suggests' P.ulyssiponensus. I wrote that to emphasise that it is VERY difficult to tell!
A problem, nowadays, is that iSpot posts and pictures are appearing via Search engines and, given that some have expert agreement, without comment, they might be taken as definitive.
I have put up a lot of similar notes recently, not just in Marines, to express a little caution (I happen to hit Patella this week because I wanted to post another of my own). You will know that fairly inexperienced people are becoming powerfully 'iconed' (no fault of theirs) and it's tempting to assume they really know what they are 'talking' about.
I'm with you Graham - honest (calling a spade a spade). But I really think that, in the case of a limpet with one picture, no ID notes and no evidence that the sighting is explored a little, say with links, the post is lacking (is meant to be constructive!). I don't think we, you and I should cop-out with "I can't be certain" unless we give reasons. I have to ask, WHY aren't you certain?
Few people (no-one?) will come here to argue either way, so this is 'tween you and me I guess. This sort of dialogue helps me greatly to understand how iSpot works and sometimes fails.
Now take a look at the trouble we are going to here Such good example of education, education, education.