The Caulerpa Slug is the ‘little green Martian’ of the Sea Slug World

Habitat: Saint Thomas, U.S. Virgin Islands
Status: Not Listed

This massive creature (hah) is the Caulerpa slug (Oxynoe antillarum), a marine gastropod mollusk also known as a sea slug or bubble snail.

As you can see, this tiny green Martian-looking creature is well-suited to blending in with its environment. You’ve got to have keen eyes to spot this little guy which only has a shell height of 6-6.25 mm and a width of 4.5 mm. If you’re looking for the shell – don’t. It’s an internal shell so you won’t be able to see it; only the folds that encompass it.

The guy holding this small slug had better watch out! When disturbed, the Caulerpa slug will exude a thick, milky white substance that contains unpleasant chemicals to fend off predators. Those chemicals are derived from the algae the creature feeds off of.

An interesting thing to note, too, is that the algae stays in the slug’s system for a while where it provides not only sustenance but also provides continued nutrients through the absorbed photosynthetic pigments, which in the presence of sunlight, continue to carry out photosynthesis secreting by-products directly into the slugs tissue. That’s right, this slug is photosynthetic! Hm… not only does it look like a little green space man, but it also has some pretty nifty tricks up its sleeve. Maybe it is a tiny sluggy visitor from another planet! … Or not.