With the help of fishermen in Madagascar and Tanzania, scientists have named two new species of six-gill saw shark.
Floating in the ocean are sharks that look like they have a hedge trimmer attached to their head and a mustache hanging down the middle. These are saw sharks, and they use their formidable shell to cut through schools of fish. The mustache is a sensory device that helps sharks detect prey.
“Hawthorn sharks are something extraordinary,” says Simon Weigmann of the Elasmobranch Research Laboratory in Hamburg, Germany.
Until recently, scientists knew of eight sawshark species, including one that has six gill slits on the side of its body. “This is unusual among sharks,” says Weigmann, as most sharks have five gill slits. With the help of fishermen in Madagascar and Tanzania, two more species of six-gill saw shark were discovered.
Long before Western scientists named them, the six-gill, meter-long saw sharks were known to people in the fishing communities of southwest Madagascar and were called go go go 🇧🇷
In 2017, Malagasy fishermen gave two of the saw-shaped snouts (called rostra) to Ruth Leeney, a visiting biologist at the Natural History Museum in London.
Realizing they were something different, he sent them to Weigmann. He tracked down more preserved specimens that were on the museum shelves and realized they belonged to a different species of six-gill saw shark.
“We used to think we only had one species in South Africa, Mozambique and Madagascar. Now we know that Madagascar has a different species,” says Weigmann.
The name he chose for the scientific literature is kajae plytreme , Kaja’s six-gill saw shark, named after his daughter, who watched with great interest as she examined the shark specimens kept at home. Kaja also means warrior in Frisian, a West Germanic language, which Weigmann deemed appropriate given the sharks’ gun-like snouts.
A specimen of a third species of six-gilled saw shark came to Weigmann after his colleagues visited a fish market on the island of Zanzibar, Tanzania. he called it Pannae, named after Kaya’s cousin A-N-A.
Something that distinguishes these species from the already known sawharks is that their whiskers (technically known as barbels) are located closer to the tip of the snout, but Weigmann still doesn’t know the relevance of this.
Likewise, there is no obvious explanation for why these saw sharks have six gill slits. Of the more than 1,000 species of sharks and rays, only a handful have six or seven gill slits.
The three species of saw sharks live in different parts of the Indian Ocean. the original species, p. warreni , lives off the coast of South Africa and southern Mozambique, up to about 900 meters. Kajas have been found between 200 and 300 meters underwater off Madagascar and on the Mascarene Undersea Plateau, which extends into the Seychelles and Mauritius. So far, Annas have only been found in Zanzibar, in much shallower water, between 20 and 35 meters.
“It’s important to give the species a name, to call attention”, says Weigmann. The next steps will be to determine how endangered the species is and whether it needs protection.
By Helen Scales. Article in English
