of the Month
Bob Goemans photograph by the author
Common Name(s): Mine urchin,
club urchin, pencil urchin, slate
urchin, rock-boring urchin
Range: Tropical Western Atlantic
Ocean: North Carolina to Brazil,
including the Caribbean
Natural Environment: Inhabits
somewhat shallow coastal environments
usually no deeper than about 150 feet.
They are most often found in seagrass
beds, under rocks, coral crevices, and
where algae-encrusted rubble exists.
Captive Care: This is a small,
slow-moving animal with a test/body
measuring 2 to 3 inches featuring short, thick spines that usually measure no longer than 5 inches. Body color varies from brown to
reddish brown, and its primary spines are arranged vertically in 10 rows. Secondary rows of very short spines are arranged between
the longer spines. The spines can be regenerated if broken or lost, and their color depends upon the amount of encrustation covering
them, usually coralline algae.
Though their main diet is algae, they are omnivorous creatures that will feed upon small invertebrates such as bivalves, gastropods,
bryozoans, and sponges, along with detritus. In fact, urchins have a desire for calcium carbonate (there goes the coralline algae!) and
therefore can be given pieces of cuttlebone to graze upon, which may help satisfy this need and possibly save some valuable coralline
algae. If the aquarium is somewhat devoid of algae, various frozen foods will also be accepted, as would those small plaster-of-Paris
feeding stones that contain seaweed and algae.
This is a very hardy, long-lived species that is fairly reef safe, though it may knock over small animals not securely attached to
some form of substrate. Nevertheless, it’s probably better suited for fish-only systems with lots of algae-covered live rock. In fact, in
situations where undesirable forms of algae are a major problem, these urchins can quickly help reduce their content. But it should be
remembered that any large consumer of algae also produces copious amounts of waste, so additional filtration and vacuuming of the
sandbed might be required.
Water Quality Requirements: Calcium 380 to 430 ppm, alkalinity 2. 5 meq/l, pH 8. 1 to 8. 2, specific gravity 1.024 to 1.026, nitrate
< 40 ppm, and a temperature range of 72° to 83°F.
Note: Urchins are part of the class Echinoidea, and these spherical, multi-spined, nocturnal members are mostly excellent herbivores.
In fact, lance urchins, those in this order, belong to a group that came about 450 million years ago. They were around when dinosaurs
first appeared, and they survived the mass extinction that eliminated the dinosaurs and many other forms of animal life about 65
million years ago. Hardy would be an understatement for these urchins, and they are more primitive in their physical appearance than
others; e.g., their constantly growing teeth (magnesium-bearing calcite) are not keeled, nor do their spines have a skin covering.
For what its worth, there’s a look-alike to the above described species that hails from the Eastern Pacific Ocean/Galapagos Islands,
E. galapagensis. It not only grazes on algae but also live corals, with Pocillopora apparently one of its favorites. Fortunately, this is a
cooler-water species that is not seen in the trade.