A Typical northern Red Sea T.gratilla elatensis. It is unique in several aspects: It is flatter than T.g.gratilla, It has less spines, and many more pedicellaria, covering its interambulacral plates. Coloration variable- spines, tubefeet and pedicellaria coloration each range from pure white to pitch black (in this picture spines are reddish, as well as tubefeet, and pedicellaria are white - all combinations occur in nature), This variety was observed througout the entire north and middle Red Sea. In Eilat, this sea urchin was prone to mass sea pollution that affected the calcification processes as well as the softer collagenous tissues activity, causing extreme deformities. The deformities were of two types - type A exaggerated H/d ratio and showing severe skeletal deformities; and type B, aboral depressions in which the entire aboral part of the test collapsed. These deformities disappeared when the poluting agant were removed.
The two references describe the two deformation types found in the original description populations atcthe northernmost site, at Eilat
