The Super Slow Greenland Shark Hunts Sleeping Prey
by Victoria Gill
Researchers have measured the swimming speed of the ocean’s slowest shark. Data-logging tags revealed that Greenland sharks “cruise” at 0.34m per second - less than 1mph.
The study showed that, even when the languid fish embarks on a burst of speed in order to hunt, it is far too slow to catch a swimming seal. Since the species is known to eat seals, the scientists think it probably “sneaks up on them” as they sleep under the water.
The Greenland shark was already known to be the world’s slowest swimming shark, but its sluggishness surprised the scientists. Yuuki Watanabe from the National Institute of Polar Research in Tokyo, who took part in the study, said that, when you account for the size of its body, it is the slowest fish in the ocean. Previous research had revealed seal remains in the stomachs of the sharks…
What: Helicoprion is a fossil shark. Though it has been known to science for over 100 years, it is still poorly understood. Teeth are the part of it that has ever been found. This not that strange for a fossil shark, as sharks do not ossify their skeletons - they are cartilaginous all of their lives. Thus it is extremely rare to find a fossilized shark skull or skeleton. What makes Helicoprion such a scientific puzzle is the arrangement of these teeth. They are in a spiral, with the smallest teeth in the center. Modern sharks go though dozens upon dozens of teeth in their lifetimes, and fossil sharks were no different. What was very different however, is these extinct sharks retained their older teeth, instead of shedding them as we see in all modern forms. There are well preserved fossil sharks from the Devonian which incorporated their older teeth into bumps and ridges on their heads, but they did not develop an elaborate spiral as seen in Helicoprion.
The biggest problem with reconstructing Helicoprion is determining the location of the spiral. Some of the first studies of this shark located the spiral on the upper jaw (the first small image above), but closely related fossil finds have shown unarguably this structure was located on the lower jaw. However, even with the position on the lower jaw certain, there are other debates and various reconstructions, two more of which are shown above. A recent study conducted by researchers at the Smithsonian concluded that these placements outside of the body were not realistic, as this would create too much drag when the shark swam, not only slowing it down but alerting it’s prey as it approached. They have interpreted the spiral to be located in the throat region of Helicoprion - their reconstruction is the large one shown above.
Every once in a while an issue comes along that unites everyone around a common goal. This year, that issue was the protection of sharks, and the goal was to end the shark fin trade here in California.
We accomplished that goal October 7, 2011 when California Governor Jerry Brown signed AB 376 into law, prohibiting the sale, trade, distribution and possession of shark fins within the state.
By the time of the Governor’s signature, tens of thousands of Californians had gotten involved in the effort. Dozens of environmental non-profits, Asian-American organizations, animal welfare groups, and aquariums campaigned for the bill, joined by community groups, chefs, celebrities, and policymakers. Leonardo DiCaprio sent letters of support; scientists from all over the world helped with research papers and offers to field questions from the Governor’s office…