Found on the 160m-long missile-tracking ship USNS Gen Hoyt S Vandenberg, a popular diver attraction since it was sunk off Key West in 2009, the worm-snail has been named Thylacodes vandyensis – but informally dubbed the 'Spiderman' snail, because of its habit of shooting a web of mucus to trap prey. 

Worm-snails are known to threaten the growth and composition of corals, and the invasion of Thylacodes vandyensis, possibly a recent arrival from the Pacific Ocean, has caused concern among marine biologists.

There is growing evidence that artificial reefs can become “sentinels” for such new species of marine invertebrate, say the authors of a report based on scuba-diving surveys of five Keys wrecks, including the Vandenberg.

The scientists say that wrecks can act as “permanent way-stations for arriving non-natives, providing nurseries within which populations may grow in an environment with reduced competition compared to native habitats”. 

The worm-snails come in various colour-combinations, and unusually the females brood stalked egg-capsules attached to their shell within their mantle cavity. The juveniles later crawl away, which results in rapid colonisation.

The report recommends continued monitoring of mollusc populations on the wrecks so that new invasions can be spotted and if necessary eradicated to maintain the health of the natural barrier reef within the Florida Keys National Marine Sanctuary .

Other species noted colonising the wrecks in the survey include an invasive orange tube coral (Tubastraea coccinea), a non-native giant foam oyster (Hyotissa hyotis), the sea-snail Cyclothyca pacei and another oyster, Hyotissa mcgintyi.

The report, written by Rüdiger Bieler, Camila Granados-Cifuentes, Timothy Rawlings, Petra Sierwald and Timothy M Collins and published in PeerJ, can be read here

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