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An
Article by George J. Reclos
Sphaerechinus granularis (Purple-Spined Sea Urchin)
The first moments in captivity. The
animal immediately uses its pedicellariae (those tube feet you can see
protruding from the spines) to "feel" the environment and move around the
tank
The mouth
After spending an hour or so, it
decided it is time for food. And what a grazer it is !!
Sphaerechinus granularis
Probably the most attractive
sea urchin offered to aquarist. It grows to about 2-3 inches (although you
can occasionally find specimens which are almost 4-5 inches in diameter –
spines excluded) and has dark pink spines with white tips on a bright
purple body (see middle photo shot from above). Rarely, the entire spines
are white. Lives commonly with algae, corals and marine plants and at
depths of up to 100 feet. Usually the juveniles live at greater depths and
when grown they migrate in groups for shallower waters. In the course of
this migration many of them are eaten by sea stars like Luidia ciliaris
and Marthasterias glacialis. It does best in aquariums kept at
temperatures of 21oC (70oF) or lower. A temperature
of less than 18oC for the winter months gradually increased to
21oC for the summer months will help it to thrive while at the
same time offering a “seasonal” fluctuation. It is a detritus feeder
(especially in the juvenile stage) and requires fresh vegetable matter to
survive in the home aquarium (from time to time). If your tank has algae
growing on the rocks then you don’t need to do anything. The S.granularis
will easily (and amazingly quickly) move around the tank grazing on the
rocks and eating the algae very efficiently. In fact, so efficiently that
it will leave the rock completely devoid of any algae at all. It will use
its small thin “tentacles” (named pedicellariae) which have special
suckers at the tips (see top photo) to move around its environment or
stick on a rock (or even the glass of the tank if it covered with algae).
It may carry a lot of things on its body (small stones and shells) both in
its natural habitat as well as in the aquarium. This was misinterpreted in
the past as an effort to protect itself from strong light. Collected in
May 2002, at a depth of 5 meters.
All photos by G.Reclos / MCH.
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