Tag Archives: Shark Week

Sensitive Sharks! Everything You Want to Know!

According some experts estimations, sharks have been around planet Earth for somewhere between 425 and 450 million years making them just as old or even older than trees themselves! As such, sharks have had time to evolve numerous methods of sensing their environment, making them expert hunters. In order to understand shark senses, one must first understand where the perception of these different sensations occur in the shark brain.

The shark brain is a Y shaped organ located in the chondrocranium of the shark. The shark brain can be split up between the forebrain, midbrain and hindbrain, each of which will specialize in a different sense. The forebrains specializes in olfactory, midbrain in visual, and the hindbrain specializes in hearing, touch, and electroreception.


Depending on the species sharks can smell up to 1km or more away, hear about 100m away, see about 10m away depending on water clarity. Depending on the sharks environment/habitat there will be corresponding enlargements in the brain. If the shark lives in deeper water where not much light exist or live mostly in the open ocean where food availability tends to be low, they might have enlargements in their forebrains because they have to rely on olfaction to find their food. With over 400 different species of sharks, not all sharks are necessarily the “swimming noses” that we think they are. With such diversity, sharks will specialize in different senses based on the environment of which they live. Even with one sensory specialization, it is the combination of all the shark’s senses that make them such great predator.

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As sharks draw in closer to their prey they use electroreception. Imagine the brain as a biological computer, sending electrical impulses down a highway of motor neurons in order to move the muscles of the body. Sharks are able to detect those electrical impulses from up to 1 meter away. Some sharks, such as the scalloped hammerhead, can sense as low as half a billionth of a volt of electricity. They use special gel filled pores called the Ampullae of Lorenzini in order to sense these weak electrical impulses.

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Sharks will continue to dazzle and amaze us with their sensory capabilities. New research indicates that sharks can even use electroreception to navigate the earth by sensing the magnetic poles. Such extraordinary evolutionary advantages are what will continue to make sharks a dominant predator for a very long time.


Brian Skerry, www.brianskerry.com from https://ocean.si.edu/ocean-life/sharks-rays/hammerhead-shark-sunset









William E. Bemis 2016



Hammerhead video


CIMI Mythbusters: Megalodon

Megalodon, meaning “big tooth”, was a HUGE shark that lived about 16 million years ago. It is thought to be the largest shark to ever exist. Megalodon grew up to 55 feet in length and weighed around 100,000 pounds, compared to a modern great white shark at 22 feet and 4,000 pounds. The teeth found from this shark have been between 5 and 7 inches! The jaw of the megalodon were 7.5 feet tall and 8.5 feet wide, so an adult could stand inside them and have plenty of room left over. Although it would be amazing to see a megalodon in person, unfortunately they have been extinct for about 2.6 million years.

This was a widely accepted fact until the Discovery Channel presented a “mockumentary” in its shark week program titled “Megalodon – The Monster Shark Lives.” Despite a short disclaimer at the end stating that the entire piece was fabricated, it managed to convince 70% of viewers that megalodons exist in waters today. Though it is very difficult to prove that something doesn’t exist, there is absolutely zero evidence pointing to their current existence, and information presented in the mockumentary was completely made up.

Let’s discuss Megalodon alive or extinct. First, the scientists speaking about megalodon are all actors. One of the marine biology experts and shark consultants for “Megalodon – The Monster Shark Lives,” is actually an actor named Darron Meyer, who also played a doctor in the Free Willy sequel movie. The World War II photo, showing a dorsal to caudal fin spanning 64 feet, was doctored. Megalodon fossils only show the sharks at lengths up to 55 feet, and this photo claims a 64-foot span just from dorsal fin to tail!

Though there have been recent discoveries of animals previously thought extinct, such as the coelocanth or megamouth shark, both live in places hard to detect. The coelocanth lives in caves up to 500 meters (1650 ft) deep during the daytime. Though around 15 feet in length, the megamouth shark lives at depths of 120-160 meters (400-525 feet) during the day. Megamouth sharks also feed on plankton, so there would be no bite mark evidence on other animals, which is how scientists discovered the giant squid without ever seeing one. This makes both the coelocanth and megamouth very difficult to detect, leading to their recent discovery.

The megalodon did not live at great depths, and definitely didn’t eat plankton! Fossil evidence indicates that they preferred shallower, warmer waters because of their need for large prey. A megalodon needed about 2,000 pounds of food per day! They were not adapted for life in the deep sea, nor would there be enough food to sustain them. Therefore, they could not currently live deep enough to avoid detection.

If somehow they did avoid detection by living in the deep sea, their prey consisted of mostly large whales. Much like the giant squid attacking sperm whales, scientists would find large sharks and whales with bite marks too big to be attributed to a modern species.

Finally, there are no discovered megalodon teeth that were shed recently. It is possible to find megalodon teeth throughout North America, in places like South Carolina, Maryland, North Carolina and Florida. None of the teeth found have been recently shed. Sharks have rows of teeth and can easily replace a tooth lost in hunting. The megalodon had 46 teeth in the front row. It is estimated that great whites can go through about 50,000 teeth in their lifetime. If each megalodon was currently shedding that many teeth in one lifetime, it is very unlikely that none would be found.

Official Answer from CIMI Mythbusters: Busted


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