Dolphins, Sharks, and Whales: Adventures in BiodiversityPosted: March 4, 2014
“Space is the last great frontier.” Space is indeed spectacular, but maybe not the last frontier of discovery, especially when completely new species pop up with some regularity on your own planet. Due to an inability to grow gills, humans have yet to sprawl into the ocean, so many of these new species are water-dwelling, surprisingly big, and good at hiding. A few of these new species we are newly distinguishing from their neighbors, and others we’ve just gotten to know. But these sharks and squids and jellyfish have been here all along, and are now rolling their eyes at the uninformed humans. Here are some quick introductions to our newly-identified global neighbors.
The half snake, half two-ducks-in-a-costume creature you see waddling around in the video above is a new species of walking shark, also known as carpet sharks. Named Hemiscyllium halmahera, it was discovered off the coast of the eastern Indonesian island of Ternate, the 16th member of the Hemiscyllium walking shark genus. This species is a mini version of its relations- on average 12 cm smaller than the 40 cm length of other species- and has distinctive snake-like dark bands running down its back. The nocturnal members of the genus Hemiscyllium prefer shallow, warm tidal pools, which have one major drawback as a habitat. As the pools are cut off from the ocean at high tide, any resident Hemiscyllium gradually use up the available oxygen, leaving them in a state of extreme oxygen depletion, known as hypoxia. They have evolved to survive until the tide comes in by carefully regulating blood flow, even ‘turning off’ – reducing the metabolism – of some areas of its brain. For an animal that looks like a cartoon creature come to life, that’s quite a talent.
Only two specimens of Hemiscyllium halmahera were caught before researchers started to realize they were looking at an entirely new species. In the case of Sphyrna gilberti, however, it has taken more than 40 years to officially recognize this species of hammerhead shark. Carter Gilbert (it was named after him) first noted in 1967 that some specimens of the common scalloped hammerhead shark of the South Carolina coast (Sphyrna lewini) had ten fewer vertebrae than normal. At first glance, and even second and third, this group looked identical to the scalloped hammerhead. But a professor at the University of South Carolina, Joe Quattro, recently examined the genetics of the (slightly) novel shark, and found them to be a distinct species. Unfortunately, that’s about all that is known about S. gilberti. S. lewini, its doppelganger, is endangered thanks to commercial and sport overfishing, meaning our new friend S. gilberti probably is too.
Speaking of near-endangered species, there a new species of river dolphin was discovered about a month ago, the first new species found since 1918. Known as botos, river dolphins face death at the hands of competitive fishermen and pollution, and can die out when dams cut off populations from each other, reducing reproductive possibilities. But the newly discovered species of river dolphin diverged from nearby populations of botos more than two million years ago, making their home in the Araguaia River Basin, when their relatives live in the Amazon Basin. The species’ home waters are close, but only linked by a series of rapids, effectively isolating the population of botos now known as the new species Inia araguaiaensis. The paper announcing the discovery was aptly titled A New Species of River Dolphin or: How Little Do We Know Our Biodiversity. Three of the four previously known species are endangered, and while I. araguaiaensis likely is as well, researchers are excited to study how it became a distinct species.
Another rare animal has been officially described and named, a newly discovered species of beaked whale. Only a few specimens have been recorded, mainly when they wash up on beaches, but for good reason. This new species belongs to a family of whales that dive quite deeply, with regular dives to 1,000 meters. They can also hold their breath for an hour, making them quite hard to study. Like the hammerhead shark, these specimens were originally lumped in with another species back in 1963, by researchers who could only rely on morphology to distinguish new species. More recently, the toolbox has expanded, and a team lead by Merel Dalebout dug bone fragments from all the preserved specimens they could find for DNA analysis. These, combined with DNA from tissue samples from more recent specimens, distinguish the new species’ unique linage several ways: through unique mitochondrial DNA, Y-chromosome, and autosomal chromosome patterns. This species was named based on DNA from seven specimens- besides suffering from a case of mistaken identity, it’s a rare creature. But now it has a name, Mesoplodon hotaula.
All of these creatures have been around for millions of years- it’s only humans who have recently recognized their existence. While it’s not uncommon to discover several dozen new species of insects in one go- in this case, cockroaches (yuck), larger species are much more rare. But especially in marine environments, they are still being catalogued- all the more exciting in light of current species extinctions. While difficult to quantify exact rates of extinction, both background rates (historical rates) and rates today, there is little argument that human activity has accelerated species death. Whether new species names are bestowed as a result of genetic sleuthing or being in the right place at the right time to meet rarer species, getting to know these species is a boon to conservation efforts, scientists, and any humans interested in learning about their amazingly varied global neighbors before they disappear.