Researching the Age of Lobster
by Sandra Dinsmore
Five years ago in Portland, at a US-Canada Science Symposium on The American Lobster in a Changing Ecosystem, Raouf Kilada, Ph.D., of Canada’s University of New Brunswick, presented the results of his research on determining the age of snow crab, sculptured shrimp, northern shrimp, and American lobster.
Kilada worked with two other biologists, Rémy Rochette and Neill Davis from the University of New Brunswick, Bernard Sainte-Marie and C. Vanier from the Maurice Lamontagne Institute of Fisheries and Oceans Canada, in Quebec, and S. Campana from the Bedford Institute of Oceanography, in Nova Scotia. The six researchers had detected growth bands in the eyestalk and in the ossicle of the gastric mill of these decapods. They found that comparing the number of growth bands with other measures of age indicated that the bands form annually and provide an accurate indicator of age.
Two years later, the University of Maine’s Richard Wahle, Ph.D., with Dr. Kilada as a partner and collaborator, set out to build on Kilada’s work of 2012.
Until 2012, there was no way to tell the age of crustaceans.
Wahle explained that the gastric mill or the “foregut” is like a chicken gizzard in that “It crunches shells in food. These hard ossicles are like molars,” he said. Therefore when the researchers take a histological section, which Wahle compared to taking a slice of salami, they can look at the cross section and count the number of growth bands.
Kilada’s work to date suggests the growth rings are annual rings, much like tree rings. “But we haven’t entirely ruled out the possibility that the bands could be added with each molt,” Wahle said, which is more complicated because lobsters may molt more or less than once a year depending on age and size.
Wahle’s research team plans to compare growth bands in lobsters across regions with contrasting temperatures from southern New England to the Bay of Fundy. He explained, “If we compare lobsters of the same size from the two locations, we’d expect to see fewer growth bands in lobsters from Long Island Sound than those from the Bay of Fundy because they grow faster in the warmer south.”
To do this, the research team will dip lobsters in a stain called calcein. Calcein fluoresces under ultraviolet light, Wahle explained. It shows up in the hard, molar-like parts. It adheres to calcium. Wahle said, “We’re looking for bands to accumulate beyond that marker.”
Although they started on this project in 2014, Wahle’s team has not yet reached any conclusions. “Within the next year,” he said, “We hope to have a better indication of the link between band-counts and age.”