Skate Species Given a Name, 100 Years After Its Discovery

For the first time since three mysterious egg sacs caught their gaze in 1904, marine researchers offered a full description on Friday for a heretofore unnamed flat fish.

Near-term male embryo of the newly identified skate species, with a 2cm scale bar. (Image via Courthouse News courtesy of Stehmann et. al.)

(CN) — Some beachgoers know them as “mermaids’ purses.” But the black, rectangular pouches seen lining the shore belong not to sirens of the deep but procreating skate. 

Emptied of the eggs they once contained, the pouches are little more than a passing peculiarity for seafarers who collect or examine the cases among shells and driftwood. For scientists like Simon Weigmann, however, they offer clues to research that has puzzled them for decades. 

Weigmann and colleagues described and named a new type of skate, previously known only from egg cases that were first discovered over a century ago, in a paper published Friday in the journal Marine Biodiversity.

Until now, the dark-mouth skate, known as Raja arctowskii Dollo, had been identified only by three empty egg cases uncovered in Antarctica in 1904. 

Weigmann’s team now explains that Dollo skates are smaller than most other skates in their genus, Bathyraja, which includes more than 50 species. Including its tail, the Dollo skate grows to just 60 centimeters long, half an inch shy of 2 feet.

The skate is also “quite heavily spotted” with white blotches, making it “rather colorful” — at least compared to its relatives, explained Weigmann, a researcher at the University of Hamburg, who primarily studies sharks and skates. 

“Most of the species are black, brown, gray,” Weigmann said in an interview over Skype. Since these skates live in the dark waters of the deep sea, they don’t really need special coloration. But two specimens described in the new paper appear brighter because of the unique markings on their exterior. 

Dollo skates also have fewer thorns on its dorsal side than other species found in Antarctic and sub-Antarctic waters. The bodies are “more or less smooth,” with thorns on the tail, but not in the neck and shoulder area, like the ones their relatives have. 

For Weigmann, piecing together the subtle differences between oceanic creatures is a big reason he is drawn to taxonomy. 

“It’s like doing a puzzle, trying to find missing pieces to connect things — to find links between animals,” Weigmann said. “Sometimes you see that something is different” between animals, he continued, “but you do not even know what is different.” 

To find out, taxonomists dig into the details. 

In the case of the newly named skate, Weigmann’s team examined 11 specimens to characterize its morphology, down to the tiny differences between Dollo and other skates. The researchers detailed the animals’ external appearance, skeletal features, and clasper — an appendage used for mating. 

Lateral view of a Dollo skate tail, with a 2cm scale bar. (Image via Courthouse News courtesy of Stehmann et. al.)

Like other dark-mouth skates, the Dollo skate has a dark grayish pigmented mouth cavity, which appears during its juvenile stage. 

Despite the skate species remaining unnamed for more than a century after its discovery, the skate is not a rare sighting. Researchers say its range includes the Atlantic, Pacific and Indian Ocean sectors of the Southern Ocean. The species seems to be common, at least in the Atlantic sector, and up to 94 specimens have been caught in a single haul. 

The Dollo skate owes its strong number, in part, to its small size. 

“It’s likely to have a rather fast-growing approach, short generation times,” Weigmann explained. “It seems to be not endangered.” 

Still, compiling data about skate distribution can help conservationists better understand the composition of the ocean. 

“For fishery and conservation efforts in the area,” Weigmann said, “it’s important to have a name for these skates.” 
Weigmann is working on a bigger research project studying skates and sharks. Earlier this year, he helped to identify two new sawshark species, so called because of their saw-like snouts. Prior to that discovery, which Weigmann called “astonishing,” only one sawshark had been identified. 

One of the new sawshark species, Kaja’s six-gill sawshark, is named after Weigmann’s daughter, who is now 5 years old. 

Usually, sharks tend to get more attention than skates, Weigmann says. But the marine researcher insists it’s impossible for him to pick a favorite. “I like both,” he said. 

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