Marine Biologist Discovers Three New Species of Sea Slugs

Posted on
Placida brookae, one of three newly discovered species of sea slugs, named after Brooke Peterson, the diver who collected the specimens from Catalina Island.
Placida brookae, one of three newly discovered species of sea slugs, named after Brooke Peterson, the diver who collected the specimens from Catalina Island.

Ángel A. Valdés, professor of biological sciences, is part of a team that discovered three new species of sea slugs. They named one of the new species Placida barackobamai, to recognize President Barack Obama’s efforts to reduce carbon emissions globally as well as for his proclamation in 2016 extending the Papahānaumokuākea Marine National Monument.

The striking yellow-orange and black sea slugs, Sacoglossa P. cremoniana, were thought to be one species.

“They were found in the Mediterranean in the late 1800s and then in Japan in the 1950’s. It was thought to be the same species,” said Valdés.  “Then a few years later it shows up in the Atlantic and then in California, Australia and the Philippines, all of these different places. So its range was expanding dramatically.

“We were intrigued because a diver found some of these animals off Catalina Island and collected some specimens for us. We sequenced their DNA and those of specimens from the Mediterranean and discovered they were different genetically.”

To confirm their hypothesis that there was an Atlantic species and a Pacific species, Valdes and his research partner, Patrick J. Krug from CSULA, traveled to Maui in summer 2016 with five students to collect more specimens. They collected the algae that the sea slugs eat, took it back to the lab and then waited for the sea slugs to come out of their hiding places. These sea slugs are only about a quarter-inch long.

Pictured left: Placida barackobamai, named for President Barak Obama. Pictured right: Placida kevinleei, named for Kevin Lee, adventurer, naturalist and photographer.
Pictured left: Placida barackobamai, named for President Barak Obama. Pictured right: Placida kevinleei, named for Kevin Lee, adventurer, naturalist and photographer.

In addition to DNA analysis, the team examined the animals’ external coloration and radular tooth morphology. Guided by the molecular data, small differences in color patterns and tooth shape became evident on close examination, confirming that the researchers had in fact found two new species in Hawaii, in addition to the new California species.

The team named the California species Placida brookae after Brooke Peterson, the diver who collected the specimens from Catalina Island. The second Hawaiian species, Placida kevinleei, they named for Kevin Lee, adventurer, naturalist and photographer.

The work was funded by a three-year $700,000 National Science Foundation grant to study Sacoglossa sea slugs. The results were published in the online journal Marine Biodiversity.

“The first author was Jennifer B. McCarthy ’17, who was a master’s student in biology when she worked on the paper.”

Among Valdés’ future projects is a study of a sea slug that has a bivalve shell that makes it resemble a clam. It’s the only snail that has a bivalve shell. It was discovered many years ago as fossils and identified as clams. Then a Japanese colleague found the first live animals in the 1950s and realized they were slugs.

“We’re now working on the evolutionary relationships between living and fossil species of bivalved gastropdos and how they are related to other sea slugs,” said Valdés.