Nov 14, 2012 8:12 PM

I have a blue tuxedo urchin in my marine tank. It appears to have 4 or 5 'lice' close to its mouth. Unfortunately due to their small size I cannot provide pictures though I will try next time it comes onto the glass. They are 3 to 4mm long, black with an apparent white stripe along the top edge, you can just about make out some legs and antenna. I believe they have eaten spines from the urchin and are starting to eat into the skeleton hence my concern.

I know very little about sea urchins, let alone looking after them, but looked around and found this:

"Little is reported on diseases of west-coast sea urchins. However, a parasitic amphipod inhabiting the tips of spines of red urchins Strongylocentrotus franciscanus is seen quite commonly, at least in British Columbia. Little if anything is known of the biology of the amphipod, or of its effects on its host. The photographs show spine degradation in a specimen of red urchin. The crustaceans appear to crawl over the surface of the spine, rather than burrow into it, and their activities may kill the skin covering the spine, thus leading to degradation of the underlying calcium carbonate. The inset photos show crustaceans on the spine tips, but it's difficult to make out much detail. The inset photo on the Left appears to show some juveniles lined up along the spine distally, with one or more adults clustered proximally. The inset photo on the Right shows one (or perhaps two) crustaceans of uncertain identification."

Little is reported on diseases of west-coast sea urchins. However, a parasitic amphipod inhabiting the tips of spines of red urchins Strongylocentrotus franciscanus is seen quite commonly, at least in British Columbia. Little if anything is known of the biology of the amphipod, or of its effects on its host. The photographs show spine degradation in a specimen of red urchin. The crustaceans appear to crawl over the surface of the spine, rather than burrow into it, and their activities may kill the skin covering the spine, thus leading to degradation of the underlying calcium carbonate. The inset photos show crustaceans on the spine tips, but it's difficult to make out much detail. The inset photo on the Left appears to show some juveniles lined up along the spine distally, with one or more adults clustered proximally."