"Margaritaville" in Jimmy Buffett's famous song isn't a real place, but it has long been associated with the Florida Keys. This chain of tropical islands is home to the only living coral barrier reef in the continental United States and many animals found nowhere else in the world. Among them is a newly discovered bright yellow snail named in honor of Margaritaville.
This lemon-colored (or "key lime") snail, and its lime-green cousin from Belize, are the subject of a study published in the journal PeerJ.
These marine snails are distant relatives of land-dwelling gastropods, and you may find the slimy trails they leave behind in your garden. Nicknamed "worm snails," they spend most of their lives in one place.
"I think they're particularly cool because they're related to regular free-living snails," said Rüdiger Bieler, curator of invertebrates at the Field Museum in Chicago and lead author of the study. "But when the larvae find a suitable living spot, they huddle up, anchor their shells to the substrate, and never move again. Their shells continue to grow into irregular tubes around the snail's body, and the animals hunt by laying down a web of mucus to catch plankton and debris."
Bieler has been studying invertebrates living in the western Atlantic for the past four decades, but these particular snails "are so small and well hidden that we have never encountered them before in diving surveys. We had to look closely," he said. The new species belongs to the same family of marine snails as the invasive "Spider-Man" snail described by the same research team in 2017 on the wreck of the USS Vandenberg near the Florida Keys.
He and his colleagues, including fellow Field Museum director Petra Sierwald, discovered the lemon-yellow snail in the Florida Keys National Marine Sanctuary, and they also found a similar lime-gray snail in Belize. "Many snails are polychromatic -- within the same species, you'll see different colors. Within a population, even in a small group, one might be orange and one might be gray," Beeler said. "I think they do it to confuse the fish and not give them a clear target, and some fish have warning colors. At first, when I saw the lime green and the lemon yellow, I thought they were the same species. But when we sequenced their DNA, they were completely different."
Based on these molecular data, Bieler, Sierwald and their co-authors Timothy Collins, Rosemary Golding, Camila Granados-Cifuentes, John Healy and Timothy Rawlings placed the snails in a new genus, Cayo, which is Spanish for a low island. The yellow snail is named "Cayomargarita" after the citrus drink in Jimmy Buffet's "Margaritaville". The lime snail's name Cayogalbinus means "yellow-green".
Cayo snails share a key feature with another snail genus, Thylacodes, and a research team has described a new species in Bermuda and named it Thylacodes bermudensis. Although only distantly related, these snails all have brightly colored heads poking out of their tubular shells. "We think it's a warning coloration," Buehler said. "They have some nasty metabolites in their mucus. That would also explain why their heads can stick out -- on a coral reef, everyone wants to eat you, and if you don't have any defense mechanisms, you're going to be swamped by corals, anemones and everything around you. It seems like the mucus may be helping to stop neighbors from getting too close."
Beeler said the research is important because it helps shed light on the biodiversity of coral reefs, which are under serious threat from climate change. Global water temperatures have been rising, and some species are better suited to these temperatures than others. Cayo snails tend to live on dead coral fragments, and as more and more coral is killed, the snail population may continue to spread.
Furthermore, Buehler said: "This shows once again that there are undescribed species right under our noses. This is snorkeling depth in a heavily visited area, and we are still discovering new things around us."