A team of marine biologists from Canada has described a new cryptic species of giant file clam, Acesta cryptadelphe, originally collected from the waters off Newfoundland around three decades ago.
In-situ image of giant file clams Acesta cryptadelphe, from the Gully, located approximately 140 miles off Nova Scotia, to the east of Sable Island, on the edge of the Scotian Shelf. Image credit: Jean-Marc Gagnon et al.
“This is the culmination of a story that began decades ago when, as a Ph.D. student, I first observed this clam in an underwater submersible off the coast of Newfoundland,” said Dr Jean-Marc Gagnon from the Canadian Museum of Nature, lead author on the study published in the journal Zootaxa.
“Originally, we assumed it to be a European species (Acesta excavate).”
Recently, more specimens have been collected off the Grand Banks and in a marine protected area about 140 miles (220 km) off the coast of Nova Scotia.
Through DNA analysis coupled with comparative studies of other giant file clams in museum collections, Dr Gagnon and co-authors determined these north Atlantic specimens to be a new species.
Named Acesta cryptadelphe, the newly-discovered clam is about 3.5 to 6 inches (9 – 15 cm) long, 2 – 3 times larger than a regular file clam.
This marine animal attaches to steep, rocky outcrops in canyons that are home to other deepwater species such as cold-water corals.
According to the scientists, the species name cryptadelphe means ‘cryptic sibling,’ which refers to the similarity in shape and structure to the previously described European giant file clam, Acesta excavata.
When Dr Gagnon first discovered the clams in the 1980s, he recognized that they were unusual, with characteristics similar to scallops, but he put them aside to focus on other research.
It was only years later at the museum that he began to look at them more closely.
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Jean-Marc Gagnon et al. 2015. Morphological and genetic variation in North Atlantic giant file clams, Acesta spp. (Bivalvia: Limidae), with description of a new cryptic species in the northwest Atlantic. Zootaxa 4007 (2): 151 – 180; doi: 10.11646/zootaxa.4007.2.1
