Fire Urchin growth? ?

I have had a fire urchin for 8 months, it started out yellow, then turned beautiful red.
I guessed it was part of its growth cycle.
The question: How does it get a larger body/shell?
Do they molt?
 
That's a good question. I couldn't find anything in the subject but now I need to know how it grows too

Sent from my SAMSUNG-SM-N920A using Tapatalk
 
The internal skeleton of a sea urchin, or test, is made up of many hexagonally shaped calcareous plates known as ossicles. Each ossicle is a single crystal of calcium carbonate in a form known as calcite. The ossicles are fenestrated (have holes) which, remarkably, increases their relative strength. The adjoining plates or ossicles in a sea-urchin test are not fused; rather, they are separated by tissue sutures within which crystalline calcium carbonate is secreted for growth. A newly metamorphosed sea urchin Strongylocentrotus purpuratus has 10 interambulacral plates (5 in each column). The number of interambulacral plates increases wtih age/size from 10 to over 40 in 70-80mm diameter individuals.
 
Back
Top