I really like to look at shells and have them around me. I often discover the odd shell in my pocket as a souvenir of a trip to the beach. Sometimes I will collect empty shells in larger numbers where this is permitted. The pictures in this post show different assortments and arrangements of common British seashells that have decorated my home from time to time over the last couple of years.
There are many posts on Jessica’s Nature Blog about seashells – sometimes just showing pretty pictures (like here) but often also describing their identifying features and other information. Click here if you would like to browse through more than 60 SEASHELL POSTS.
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The pottery bowls are very pretty too – the perfect display!
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Thank you, Jody.
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Hi Jessica,
I realize it has been years since you took the photos of the black and white bivalves.
I have just collected about 50 of this exact shell on the beach of Port Aransas, Texas. I have been searching to identify them and your photos keep popping up. I have still not found a name for this particular shell. Were you able to identify or even find a common name for the bivalve?
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I no longer have the shells and I seem to rember that they were not all the same species. However, I think that most of the shells were Thick Trough Shells – Spisula solida (Linnaeus) – and they were found on the beach at Studland in Dorset, England. I am uncertain whether this species occurs on Texas coasts, so your fifty specimens may be a related species perhaps within the same family (Mactridae).
The black stripes or bands are not typical of the family; they are not genetic. It seems possible that the discolouration of the shell edges may occur during the period of slower shell growth in winter time when the living mollusc has been buried deeper down in the sediments where the conditions are anoxic. The anaerobic bacteria that inhabit this layer of the sediments produce hydrogen sulphide, ammonia, and methane, which make the sand black and smelly. The hydrogen sulphide reacts with iron in the sand to give black iron sulphides that not only colour the sand grains and sediment particles but also stain the occupied and unoccupied shells of molluscs. The method of uptake of the staining by shells is not clearly understood but it is initially preferential and some parts of the shell take up the colouring more readily than others. This means that some parts rarely become black even after prolonged burial, for example the adductor muscle scar area inside flat oyster shells, but most areas will blacken entirely given a long enough time in the black layer. In the instance of the “striped” trough shells, the new and very slowly growing shell margin in winter is probably more susceptible to the process than the older parts of shell during the brief period of winter burial in deeper sediments before the return to more superficial sediments in warmer weather.
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Jessica,
Thank you for the information about the black and white bivalves you collected.
It has helped me narrow down my search and understand the nature of the striped patterns. I have also learned some surprising things. I now know that the shells I have been finding are fossils of fresh water clam shells that were deposited into the Gulf of Mexico at a very specific area where there was once a river emptying into the gulf. I love that story! And I am looking forward to learning more.
I appreciate your thoughtful response to my inquiry.
Suzanne
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It seems that you have come across some very interesting specimens and I am glad that you have found out something of their history.
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