They can “walk” with the help of fins and for a long time do without water.
Indo-Australian cat sharks (Hemiscyllium) are the last evolutionary branch of their species. Unlike their neighbors, they use fins to move along reefs and sand, even without water. This is stated in a study by the California Academy of Sciences, published in the journal Marine and Freshwater Research.
The essence of the work was a phylogenetic analysis of nine recognized species of Indo-Australian cat sharks. Researchers sequenced DNA and established kinship relations between sharks.
It turned out that the “walking” sharks are the freshest branch of the evolution of sharks that first appeared on Earth about 450 million years ago. As Motherboard co-author Mark Erdmann explained to Motherboard, Indo-Australian cat sharks separated from their closest ancestor about nine million years ago and have been actively developing since then.
Of course, by human standards, it seems that it was a long time ago, but for sharks, as for the species as a whole, this [appearance of a new genus] happened recently.Mark Erdmannco-author of walking sharks
According to Erdmann, the time of the appearance of “walking” sharks coincides with major geological changes when the Australian continental plate crashed into a relief in the north. This process was accompanied by volcanic eruptions that changed the region for millions of years.
Indo-Australian cat sharks survived these geological incidents while on shallow reefs. There they gained the ability to wriggle along the earth to get to remote tidal pools and adapt to oxygen starvation.
If such a shark appears in shallow water, it slows down breathing and palpitations, as well as the flow of oxygen to the brain. This allows the fish to survive at least an hour without water: during this time it is able to “reach” it on the fins.
As scientists noted, despite the ability to adapt, “walking” sharks are extremely vulnerable to natural disasters like the tsunami. The problem is that the reefs in which they were born and are “couch potatoes” do not leave.
In addition to natural hazards, Indo-Australian cat sharks face anthropogenic impact. They like to be placed in artificial aquariums, and habitats are destroyed during the arrangement of the coastline. Because of this, conservationists are trying to achieve the inclusion of three of the nine species in the international red book.
Erdmann and his colleagues plan to conduct more expeditions to the Indo-Pacific reefs to learn more about these sharks. They expect to find several new species that are still unknown to humans.
Genetics confirms that this is a very young species that is still actively developing, so we hope for good chances of the existence of several more species of “walking” sharks in this region. This shows us that sharks are still an active part of our evolving planet and this is really good news.Mark Erdmann