The inhuman stain

Natural History, Oct, 2004 by Erin Espelie

Unlike the smear of goo the land snail leaves in its wake, a swath of purple lesions marks the passage of the flamingo tongue snail (Cyphoma gibbosum), as it munches its way across a Gorgonia ventalina sea fan. The carnivorous snail--less than an inch long--masks its plain white shell with a fleshy, leopard-spotted mantle while grazing. Soft corals such as the sea fan are both its feeding ground and its food.

Acting in self-defense, the G. ventalina pictured here responded to the flamingo tongue's attack by making a cocktail of protective compounds. The chemicals turned the sea fan bright violet, and helped fend off a number of fungi and bacteria. But according to Jessica Ward, a marine scientist at Cornell University in Ithaca, New York, the holes and black decay in the center suggest that a fungus, possibly Aspergillus sydowii, might have broken through the coral's barriers.

A. sydowii was once strictly terrestrial, but since the late 1990s the organism has become epidemic at many underwater sites in the Caribbean. Flamingo tongues--not thought to be lethal by themselves--have been found to carry A. sydowii in their gut and, as Ward speculates, may be responsible for spreading the disease.

Photographer Norbert Wu found this ghoulish-looking pair (or trio, if you count the fungus) off the coast of the Caribbean island of Saba.

Photograph by Norbert Wu