Sea urchins are one of beautiful marine creatures that come in many sizes and colors. They are non-aggressive and may be found all over the world in the shallow, rocky bottoms, or between the sea grasses. Sea urchins are also infamous for their venomous spines that often accidentally injured people on the beach. But the fact is most of sea urchins are not venomous. The venomous urchins are characterized by the long sharp spine such in the family Diadematidae or the bright fiery color as present in the fire urchin.
On my trip to Nusa Dua, Bali, I encountered several species of urchins. Some look dangerous, but some are so pretty.
Cake urchins or collector urchins (Tripneustes gratilla) are not venomous. They are edible and in some part of the world their gonads (mistakenly known as “urchin’s roe”) are considered as delicacy. This urchin is also exploited in Bali. Scientific reports from Indonesian Scientific Institusion (LIPI) stated that the cake urchins population in Bali is declining.
|Cake urchins feed on algae and seagrass, thus they could be easily found between the seagrass|
|Cake urchins come in many colors. However this color disappears when the individual dies and is difficult to preserve|
This Echinometra mathaei urchin is also not venomous and the spines have smooth rubbery texture. I wore rubber glove just for protection since I was observing the venomous urchins also.
This long-spined urchin is mildly venomous. Special characteristic of the species is the presence of a bright, orange ring around the urchin's periproctal cone (anus).
This is another urchin species which is mildly venomous. The characteristic of a Diadema savignyi is its long spines are predominately black with light blue lines around its periproctal cone .
The light blue lines around the periproctal cone and long thin spines of the urchin pictured below suggest this species is a Diadema savignyi. However, banded/ striped pattern of echinothrix character also present. This suggest that this species might be a hybrid between the two species, which is common.
Another venomous urchin is the Echinothrix calamaris. It has two sets of spines, the shorter spines which are dark in color and venomous, and the longer spines that are often banded/ striped in color.
So those are the types of urchins you can find in Nusa Dua Beach, Bali. Sea urchins are amazing creature. If you are careful in your observation trip, you shall not suffer from any puncture injury from the venomous ones.