Clathrus confused - notes on some Epitonidae records

I first encountered Epitonidae (the wentletraps) in the early 1950s. Two were given to me by an elderly lady who had found them on the beach at St Ives and I found another on sand flats at the Naze end of Walton-on-the-Naze. The Cornish shells were small but chunky dove grey shells with white ribs and the other was a conventional adult Clathrus clathrus (Linne, 1758). In days of innocence, the shape was a thing of wonder. In later years I bought and traded specimens and found living material in drift lines and dredgings. I read the available literature and, as time went on, fell prey to the illusion that I had a reasonable understanding of the more frequent species.

In the mid 1980s I lived by Portland Harbour and discovered that just once a year, usually during the weekend before the BSCC Show, then in Spring, a live ‘Clathrus’ could be found in the vicinity of the old torpedo pier. A couple of times I brought them along as live exhibits. The animals were highly distinctive and the upper surface of the foot was decorated with a bright violet outline of a spear head on a white background. I have found no reference to this in any description of the animal. This was observed on three torpedo pier specimens and one from nearer the Naval Air Station. A more recent specimen was dredged off the Lulworth Banks but this had an orange and black animal. The four shells were within normal range of variation of conventional C. clathrus but the offshore specimen, while of a similar size and shape, was a more robust shell with wide varices and rich dark colours (figure 2). At the time I speculated on whether this could be a clathrus/turtonis hybrid.

There is a short stretch of rocky beach on the Portland causeway where another form of Clathrus washes ashore (figure 3). These are all bigger and heavier than any of the live specimens. When fresh, they are more colourful. They do not compare well with C. turtonis yet neither do they seem to be the usual race of C.clathrus though of course, as members of the same genus, there are naturally common characteristics. The latest shell found is presumably part of this population but it is a big, wide, heavy shell with thirteen varices on the body whorl. If I saw it in isolation without the data, I would automatically assume it to be exotic as we just do not have anything that should look like this so this is the point where I must re-evaluate all my opinions.

Several authorities assume that European Epitonids change sex with age and there is evidence that some do. Some exotic Epitonids appear not to change and are sexually di-morphic. The sexes have different shell shapes from an early stage. It is not just a matter of size though males are smaller and more numerous. Can we have a situation where pollutants arrest the change of sex, leaving an adult to grow large in an unnatural shell shape? This raises more questions than it answers.

Are we sure that C. clathrus (Linne, 1758) is a valid recognisable species? Some Continental authorities have discarded the taxa on the grounds that it is a composite species and are using plain Epitonium commune (Lamarck, 1822) for our population! Other authorities believe they can perceive consistent differences between Atlantic and Mediterranean populations. Based on personal observation I find this implausible (one specimen from Newport Wales and one from Ston Croatia both look the same to me), but I retain serious doubt that all the shells I have assumed to be C. clathrus are all one and the same species. Are there two or more? Alternatively, it may be that none of the experts who have published on the family actually had access to enough data and specimens to enable them to appreciate the potential range of shape size and colour within one species.

There may be someone out there who knows all the answers but has not published. Genuine experts are thin on the ground and the task is limitless. Your observations are more important than the actual shells you collect so if you see something of interest, please please record and report it, if possible with photographs. This does not just apply to Epitonidae!

_{figure 1: C. clathrus, intact but dead shell buried in beach Portland Harbour side of causeway. Height 33 mm.              Photo: Alan Fell}

_{figure 2: C. clathrus, dredged offshore in maerl. Height 26 mm.  Photo: Alan Fell}

_{figure 3: C. clathrus, fresh dead, 60 m south of figure 1 specimen. Height 33 mm (protoconch missing).                   Photo: Alan Fell}