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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