Biology
The green sea urchin is often found with pieces of algae, bits of seagrass and fragments of mollusc shell on its aboral (upper) surface, holding them in place with its tube feet. It is thought that the urchin is photo-sensitive and that these pieces of debris may provide some protection from strong sunlight and ultraviolet light in the clear shallow waters it favours.
The green sea urchin has a structure called an Aristotle's lantern surrounding its mouth on its oral (under) surface. This has five teeth that can be used to rasp surfaces. It is largely herbivorous, feeding on the seagrass Thalassia. Its tube feet and spines also play a role in feeding, catching and holding bits of debris that float past.
It is sometimes found in aggregations of closely packed individuals. This may be linked to breeding activities but at other times it has no known cause. Breeding takes place at various times of the year in different parts of its range. In Bermuda the spawning period is short and seems to be related to the phase of the moon. Eggs and sperm are liberated into the water column and fertilisation is external. The larvae are planktonic and are known as pluteus larvae. They pass through several developmental stages before undergoing metamorphosis into juvenile urchins.
Read more about this topic: Lytechinus Variegatus
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