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Tale of a tube worm—a new species from the Gulf of St. Lawrence

(left) Jenna Moore © University of Florida (right) Luc Beaudin © Fisheries and Oceans Canada

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(left): Microscopic view of the new species, C. bruneli. The scale represents 5 mm. (right): Closeup of sediment from the lab showing live specimens of C. bruneli. The red arrows indicate the openings of burrows created by the worms.


 

November 16, 2020

A tiny and elusive marine worm from the St. Lawrence Estuary has a new identity—thanks to the persistence of the museum’s Curator of Invertebrates, Dr. Jean-Marc Gagnon.

The new species, named Chaetopterus bruneli, was recently described by Dr. Jenna Moore from the University of Florida and Dr. Gagnon in the European Journal of Taxonomy. It represents the northernmost record for this group of marine invertebrates known as parchment tube worms. These worms rest on the ocean floor inside their protective tube made of mucous and sediment, and filter water for food.

The species honours Dr. Pierre Brunel, a researcher in Quebec that greatly contributed to the study of marine invertebrates living on the seafloor in the St. Lawrence maritime system.

The tale of this new species began almost 30 years ago, in 1991, when Gagnon was a post-doctoral fellow in the lab of his supervisor, Dr. Norman Silverberg, at Fisheries and  Oceans Canada. He was studying biodiversity of the benthos (seafloor) associated with sediment samples collected at 345 metres depth from a research site in the St. Lawrence Estuary.

Luc Beaudin © Fisheries and Oceans Canada

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From 1991, Dr. Jean-Marc Gagnon (left) stands with Dr. Norman Silverberg behind a mesocosm basin (called a benthocosm), which is used to preserve and study sediment samples collected from the ocean floor.

Scientists had collected at that same station for many years, and had never observed the species. But Gagnon benefitted from a special experimental setup—Silverberg’s lab kept the sediment samples intact in special basins that replicated the temperature and salinity of the deep-ocean habitat. 

“This lab experiment allowed us to keep things alive and to study their behaviour,” says Gagnon. Upon inspection, along with seastars, echinoderms and other marine invertebrates, Gagnon found the tiny worms (measuring 1.5 to 2 cm) that would be ultimately named Chaetopterus bruneli.

To help identify the species, Gagnon originally sought the expertise of Dr. Mary Petersen (the third author on the publication, posthumous), a world authority on this group of marine worms. But the samples remained unexamined as Petersen moved labs and focussed on other priorities. Following her death in 2014, Gagnon retrieved the samples and sent them to Dr. Moore who joined Gagnon on the project.

As with much taxonomic research, the tiniest details often distinguish one species from another. It was initially thought the St. Lawrence species might be one known from the northeast Atlantic waters, C. norvegicus. But close examination showed the new species had some significant differences—notably with the neuropodial structures that anchor the worm to its protective tube.

The Canadian Museum of Nature now has 18 specimens of C. bruneli in its national collections, but the species remains elusive. Gagnon notes that sampling efforts from the same St. Lawrence collecting site in 2015 and 2020 have failed to turn up other specimens.

Anne Mauviel © Institut des sciences de la mer de Rimouski

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View of the benthos (seafloor) from the sampling site in the St. Lawrence. Some of the animals present include an anemone (top left), many brittlestars, and a few seapens. The big holes are made by a burrowing shrimp. There are no signs of the tube worm, C. bruneli.

He says it could be that the tiny, brittle animals do not survive the trip to the surface, and traditional extraction methods. But environmental changes may also be causing a decrease in the species’ abundance. Gagnon refers to the reduction in oxygen concentration levels that is taking place in the deep waters of the St. Lawrence Estuary and Gulf, as is also the case off the West Coast of Canada.

“This raises a question for further study – whether the population density of C. bruneli has gone down as a result of this decrease in oxygen,” he says. As such, it might be counted among species that can be considered as indicators of environmental change.