These close-up photographs of the internal ligament area in an assortment of old Flat Oyster shells remind me of those images of colourful rock strata in Arizona that have been sanded smooth by the wind to reveal curving lines of exposed layers.
In these oyster shells, the lines represent the many layers of shell that have been continually added to the structure over time. The slightly broader bands into which the shell layers are grouped are in many cases the annual growth. There is also a contouring to the surface – with valleys and ridges. The flatter areas show where shell growth was faster in warmer weather and the ridged areas where growth was slower in the cold. The lines are not that easy to count and interpret because other circumstances, such as spawning and storm events, can slow down shell growth rate dramatically.
However, this is the region of the shell that receives most attention from the specialists when it comes to ageing the shell, deciding the season of its death, and looking at the effects of climate. Frequently, the ligament ‘scar’ is sectioned along the axis of growth and examined under the microscope so that the layers and bands can be counted and measured – in a similar way to the analysis of tree growth rings and layering in ice cores.
More about Oyster Variations.
More about Growth Lines.
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Jessica's Nature Blog 
I found the the detail of these shots very interesting and I really enjoy your commentaries. Its lovely to read your blog, there is so much beauty & diversity in coastal habitats. Living in Leeds I couldn’t be further away from the coast, so reading you blog is a fantastic way to stay connected & and learn more about the wonders of the seashore. Best wishes
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Lovely wavy curves and color, Jessica. I tried drawing a couple of shells today. What a challenge for a pencil! Your photographs remind me of growth rings in tree stumps, too.
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Thank you so much for your comments, Linda. I am glad to hear that you enjoy my blog pictures and commentary. Spending so much time writing the blog and sorting out the pictures means that I can relive the enjoyment of my beach trips every day in my living room. I have just spent the week away on another field trip to Gower seashores and must now sort through all the photographs and beachcombing treasures. As I took 1,500 pictures, it could take me some time but there is plenty of material for future postings on the blog!
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Thank you. I thought the ligament scars had a lovely sculptural quality in close-up. Drawing shells is a real challenge. I haven’t tried drawing, myself, for a very long time but I know that it’s quite difficult to get the right perspective and shape with shells. Text-book line drawings of shells frequently mis-represent shell shape – which confuses attempts at identification. Even with taking photographs of shells, it is easy to give a misleading impression of shape – although this can be exploited for artistic purposes.
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hi jessica, i really like the top photo of the growth lines on oyster shell in the blog Growth line patterns in oyster ligament scars. I would like to use a higher res version of that photo in a book i am completing on archaeology where we talk about shell as an important material in many archaeological sites. the book is entitled An Introduction to Archaeological Chemistry. The publisher is springer and i hope it will appear by the end of the year. I would need your permission to use the photo and hopefully a higher res version. Please let me know if that is possible. thanks much
doug
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