麻豆淫院

A published in the Proceedings of the National Academy of Sciences reveals that the Saimaa ringed seal is evolutionarily more differentiated than previously known. In fact, the study suggests that, instead of a subspecies, the Saimaa ringed seal should be acknowledged as a species of its own.

Ringed seals are the most widely distributed Arctic seals. In addition to the Arctic Ocean, they are found in the Sea of Okhotsk, north of Japan, in the Baltic Sea, and in Lake Saimaa and Lake Ladoga. The two lake forms have traditionally been considered close relatives and evolved from seals trapped in inland waters after postglacial rebound.

The history of the Saimaa ringed seal and how it differs from other ringed seals were investigated by an international team of researchers from the Universities of Helsinki, Eastern Finland, Copenhagen, Tokyo Museum of Natural History and the Natural Resources Institute Finland.

In the study, researchers mapped, for the first time, the genetic and morphological characteristics of almost all ringed seal populations in the world. The results show that the Saimaa ringed seal separated from other ringed seals more than 60,000 years ago鈥攖hat is, long before the formation of Lake Saimaa, which took place 10,000 years ago.

"Genetic analyses have long indicated that the Saimaa ringed seal is more different than one might assume from the history of Lake Saimaa. But it was only with the analysis of all the Arctic ringed seals that we could time the separation of the Saimaa lineage," says Ari L枚ytynoja from the University of Helsinki.

Whereas the origin of Baltic and Ladoga ringed seals is in the Atlantic, Saimaa ringed seals have probably spread to Finland from the east, from an area where large glacial lakes existed during the Ice Age. On the way to Saimaa, they admixed with western ringed seals.

"With comprehensive genome analyses, admixture of species is starting to be more the rule than the exception in the history of living organisms. The evolution of our own species shows many examples of intertwining lineages," says Petri Auvinen from the University of Helsinki.

The long evolutionary history of the Saimaa ringed seal prompted researchers to examine the ecological differentiation of the population. The dentition of marine ringed seals is adapted to eating both fish and pelagic crustaceans, such as krill.

Like baleen whales, they suck their prey into their mouths and filter the water out with their teeth and tongue. According to this new study, the dentition of the Saimaa ringed seal is different and specialized for eating fish.

"The measurements of hundreds of individuals showed how unusual the Saimaa ringed seal is in its dentition. These differences support the results of genome analyses and a long independent history for the Saimaa ringed seal," says Jukka Jernvall from the University of Helsinki.

Adaptations to a different diet were also found in the Saimaa ringed seals' tongue and digestive tract. Together, genetic and morphological differences support its species status.

"The Saimaa ringed seal was recognized as clearly different from other ringed seals already in the 19th century. Since then, our understanding of evolutionary processes has deepened, and elevating the Saimaa ringed seal to a species status, Pusa saimensis, best reflects its unique and independent evolutionary trajectory," says Jaakko Pohjoism盲ki from the University of Eastern Finland.

Although the Saimaa ringed seal population has slowly grown to around 500 individuals thanks to active conservation measures, the species is still facing several threats. It is hoped that its status as Finland's only native species will further increase interest in the conservation work.

"Here in Finland lives a truly unique relic, the last representative of the ringed seals of the ancient glacial lakes in the world. It's shocking to think how close we were to losing it forever," says Mervi Kunnasranta from the University of Eastern Finland.