The Exquisite Lamellarias
Shell-less mollusks and those with a reduced or “hidden” shell typically evolved strategies that allow them to stay protected from predators in the absence of that defensive cover. Lamellarias (family Velutinidae) are small (between 5 and 20 mm) marine snails that completely envelop their shells with the mantle. Their shells (see below) are thin, fragile, and hidden, and have obviously lost their protective function. Different species in the genus Lamellaria evolved to resemble distinct marine life. Some take after seaweed, others look like colonial organisms such as sponges, bryozoans, or tunicates. This unidentified species of pink-colored lamellaria photographed by Scott Johnson in Kwajalein, one of the Marshall Islands, looks like the tunicates surrounding it, but with a different hue. In addition to the visual protection afforded by this type of mimetism, lamellarias also rely on chemical protection to avoid being eaten. Instead of banking on a “hard shell” for defense, lamellarias use repugnant compounds to dissuade potential predators. Although secretions from lamellarias, called lamellarins, have been recognized at least since the 19th century, we now know that they are alkaloids that have anti-tumor properties of interest in the search for the cures for different forms of cancer. (I use the common name for the group interchangeably with the formal genus name Lamellaria.) Many thanks to Scott Johnson for use of his great image.