Tests of Red Sea T. g. elatensis showing the rather smooth appearance of the test. arrows show the paucity of spine tubercles - less than 1 spine for each interambulacral plate (most oceanic Tripneustes
- T. gratilla
, T. depressus
and T. ventricosus
- all show at least one primary spine for each plate). The wide space between the ambulacra is densely covered by pedicellaria, which are poisonous the a certain degree (some people become allergic to it).