Primary spines
Primary spines
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The primary spines are the long, thick spines, what brought the Cidarids their common names: pencil urchins. Their main ecological functions are defense and locomotion.
These spines are attached to the test through the tubercles that act like our joints, allowing a smooth and seamless movement.
They are made of calcite.
Both deep sea sea-urchins, are known to host epibionts living attached to the primary spines. Because these Cidarids are often found on soft substrate like sandy bottoms, they represent islands of shelter and stability.
Primary spines of C. cidaris. Lenght of the longest: 12.5mm
Width of the longest: 1.5mm
A close up view obtained with the SEM, Microspines are made visible with 396x magnification.
Primary spines of S. affinis. Length of the spine from top: 14.7mm
Width of the same spine: 1.2mm
Please note that most of the primary spines were broken.
Intact spines are much longer!
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