Researchers describe four new shark species

The new species are dogfishes belonging to the genus Squalus. They are roughly 70 cm long and weigh about 4 kg. Their habitat begins where the continental shelf ends and extends into the abyssal depths of the ocean.

By Peter Moon  |  Agência FAPESP – If a zoologist were to announce the simultaneous discovery of not one but four new species of medium-sized mammals in Brazil, it would be celebrated by the scientific community. The recent discovery of four new dogfish shark species occurring off the Brazilian coast deserves just such a response.

The new species are described in an article recently published in Zootaxa and written by Sarah Tházia Viana, Marcelo Rodrigues de Carvalho and Ulisses Gomes.

The study was part of Viana’s Master’s and PhD research, supported by FAPESP with a doctoral scholarship and a research internship abroad. Her supervisor was Carvalho, a professor at the University of São Paulo’s Bioscience Institute (IB-USP) and an expert on the systematics, morphology and evolution of cartilaginous fish species, which include rays and chimeras as well as sharks. Gomes, the other co-author of the article, is affiliated with Rio de Janeiro State University (UERJ).

“The study was only feasible thanks to FAPESP, which enabled me to visit the world’s major collections,” Viana said. “It wouldn’t have been possible to identify the new species otherwise.”

According to Carvalho, evidence has been cropping up repeatedly since the 1980s that certain specimens of the genus Squalus captured off the Brazilian coast did not exactly match the morphology of the species to which they were thought to belong. One reason for this, he explained, is that Squalus is found in all of the world’s oceans, and many descriptions have been based on old, poorly conserved type specimens belonging to collections in Europe, the United States, Japan and Oceania. Another reason is that the differences among the known species are very slight.

Squalus was the first shark genus described by Linnaeus, in 1758. Until the Brazilian researchers published their article, there were 26 recognized species of Squalus in the planet’s oceans. The new species – S. albicaudus, S. bahiensis, S. lobularis and S. quasimodo – bring this number to 30.

“Squalids are small compared with the sharks you so often see in movies, like the great white shark, Carcharodon carcharias, or the tiger shark, Galeocerdo cuvier, both of which are over 5 m long,” Viana said. The new species are about 70 cm long and weigh about 4 kg.

The four new species are not found in the waters above Brazil’s continental shelf. Their habitat begins where the continental shelf ends and extends into the abyssal depths of the open ocean. “They live at depths of 300 m and more,” Viana said. “Little is known of their biology. The available specimens were caught in nets by oceangoing fishing vessels or collected by oceanographers more than 20 years ago.”

Blue Amazon

To describe the new species, Viana visited several Brazilian collections during her Master’s research, traveling up and down the coast from South to Northeast. None of the collections had enough specimens for serious scientific study, with a few exceptions, such as the collections held by the University of São Paulo’s Zoology Museum, the National Museum in Rio de Janeiro, the Pontifical Catholic University of Rio Grande do Sul and the Federal University of Paraíba.

In the United States, Viana was able to evaluate a larger number of specimens from the South Atlantic belonging to collections housed in New York, Washington, San Francisco, and Florida and at Harvard University.

However, none of these collections could be used for diagnosis of the new species, and during her PhD research, Viana had to travel far and wide in search of specimens of Squalus, including type specimens. She went first to South Africa and then visited Australia and New Zealand, followed by Sweden, where she analyzed the same specimens studied by Linnaeus. Her research proceeded in London, Berlin, Hamburg and Vienna. Finally, she went to Hokkaido and Tokyo in Japan. Currently, she is in South Africa.

Viana and her fellow researchers succeeded in confirming the validity of the four new species by means of a detailed comparative analysis of the Brazilian specimens with the external morphology (morphometrics, dentition and color patterns) and skeletal morphology of the type specimens.

“The next step, perhaps as postdoc research, could be to study the molecular biology of these species of Squalus from our own region,” Viana said.

The description of four new species from offshore Brazil can be seen as the tip of an unknown marine biology iceberg inhabiting the Blue Amazon, as the navy calls its territorial waters, an area of roughly 3.6 million square km along 8,500 km of coastline.

“What we know of our marine fauna is limited to the species that live near the coast,” Carvalho said. Research in the open ocean calls for appropriate vessels and equipment, especially remotely operated marine robots. In Brazil, only Petrobras has these.

“Although research in biology and evolution requires relatively little funding, the work done on Squalus shows how much is still unknown about our biodiversity and resources,” Carvalho added. “It highlights the importance of investing in the training of qualified systematists.”

The article “Taxonomy and morphology of species of the genus Squalus Linnaeus, 1758 from the Southwestern Atlantic Ocean (Chondrichthyes: Squaliformes: Squalidae)” by Sarah T. de F. Viana, Marcelo R. de Carvalho and Ulisses L. Gomes, published in Zootaxa (doi: 10.11646/zootaxa.4133.1.1.) can be retrieved from mapress.com/j/zt/article/view/zootaxa.4133.1.1.