The cookie-cutter shark inhabits the deep ocean and compared to other creatures of the deep, he may seem harmless and not in the least bit frightful. However, if you happen to get a peek at his teeth from his underside, lets just say, you wouldn’t want him taking a nip at you. The cookiecutter shark has 30–37 tooth rows in the upper jaw and 25–31 tooth rows in the lower jaw, however his upper and lower teeth are distinctly different. The upper teeth are small narrow and tapered, while the lower teeth are broader and knife-like, with their bases interlocking to form a single saw-like cutting edge. It also has think lips that enable it have suction to latch onto it’s victim in a parasitic manner, before it twists its body, scooping out a chunk of their flesh and leaving a rounded wound that looks as if it were punched out by a cookie cutter.

These bite marks have been spotted on a huge variety of large marine species such as whales, porpoises, dolphins, seals, deep water pelagic fish (tuna, dolphinfish, jacks etc), squid and other shark species like goblin sharks, blue sharks and the mega mouth shark…phew! That is quite the list for a little guy huh?

What helps the cigar shark snag its meals other than the unusual mouth, is the fact that it has some light-emitting organs called photophores that give the shark’s underside a greenish glow. This helps it’s silhouette appear like a small fish to predators swimming below and attracting their attention. When their curiosity draws them close, the little shark makes its move and latches on to take a bite.

The cookie-cutter shark being small, a deep water inhabitant and not very fast in terms of attacking speed, isn’t usually considered a danger to humans. However, this little creature has managed to put his mark on a few people around the world according to reports. Mostly reports were from shipwreck survivors that displayed small, clean but deep bites during night time and one case of an underwater photographer on an open ocean dive. Other reports are of bodies  that were recovered from the water with cookiecutter shark bites, not being the cause of death though.

Fascinating isn’t it, what a mighty bite this tiny little shark has. Makes me re-think doing deep dives at open ocean dive sites.

*Image credits: NOAA Observer Project and George Burgess, Florida Program for Shark Research, Florida Museum of Natural History

Meet A Small Shark With A Mighty Bite- The Cookie-Cutter Shark was written by Noreen for Aquaviews - SCUBA Blog - Bringing You The Other 70% Of Our World

Marine Biologist believe that the Bluntnose shark is the only surviving species of  shark which is genetically similar to prehistoric sharks making them almost living fossils. These sharks are one of the largest predatory sharks in the world and can grow up to 5.4 m (18 ft) in length and have skin coloration ranging from light brown to a darker black.  The easiest way to distinguish this type of shark is by observing their head shape which true to its name, is snubbed or blunt-nosed ending abruptly; also unlike other sharks the six-gill has only one dorsal fin which is located on the back of its body near its tail and isn’t as prominent as an ordinary shark’s. This shark is also unique to all others as it has six gill slits to breathe from on the side of its head as opposed to the usual five.

The reason behind the bluntnose shark’s unique six gills is to help it breathe in its natural habitat which is typically in ocean depths exceeding 90m (300ft) and recorded to inhabit depths of up to 1875m (6,150ft) below sea level.  Like several deep dwelling creatures of the ocean, the Six-gill is known to migrate each night towards the surface to feed and return to the depths before dawn.

Sighting a  six-gill sharks is extremely difficult, despite the fact that they are perhaps the widest distribution of all sharks and are found all over the world in both tropical and temperate waters. Since the only time a diver can spot a six-gill is on a night dive and in certain locations especially where upward currents force the creature to rise to shallower than normal waters. This shark is not considered dangerous to humans and there have been no reported attacks attributed to the six-gill to date.

photos from NOAA Office of Ocean Exploration and flickr.com by Traumador, Dan Hershman,

Meet The Blunt-Nosed Six-Gill Shark was written by Nevin for Aquaviews - SCUBA Blog - Bringing You The Other 70% Of Our World

Black Tip Reef Shark

One of the more common sightings on a reef dive is the Black-Tip Reef Shark which are found in the shallow coral reefs of tropical waters primarily in the indo-pacific. With a brownish skin color, the tips of the shark’s pectoral fin and dorsal fins are black, with a white underside. It has been recorded at up to 2 m (6.5 ft) in length and over 99 lbs (45 kg) in weight. Black tip reef sharks feed mainly on reef fish and are not known to attack divers.

White Tip Reef Shark

Also a frequent sighted shark, Whitetip reef shark are also found along the indo-pacific coral reefs and sometimes as far east as south Africa and Central America.  The Whitetip shark grows up to 1.6m (5.2ft) in length and is easily recognizable by its white-tipped dorsal and caudal fins. Living off a diet of fish, crustaceans and octopus, this species hunts mainly at night and are seldom aggressive towards humans.

Nurse Sharks

Are found in the shallow tropical and sub tropical waters of the western Atlantic and eastern Pacific regions. Nurse Sharks can grow to a length of 4.3 meters (14ft) and is recognizable by its distinctive mouth which is far ahead of its eyes and made for bottom-feeding. Nocturnal by nature these sharks feed on crustaceans, mollusks stingrays and other fish.  Nurse sharks typically attack humans only if directly threatened.

Whale shark

These colossal creatures grow to a length of 20m and weigh up to 12,000 Kg feeding off zooplankton, squid and small fish. Found in all temperate and tropical regions, whale sharks  are instantly recognizable by its distinct spotted and striped body and wide mouth. Whale sharks are gentle giants and are very popular with divers that enjoy observing and swimming alongside these creatures while feeding. This species, despite its size, does not pose any significant danger to humans.

Blue Shark

All sharks swim very fast, but the blue shark is the fastest. These slender looking blue-skinned sharks can grow up to 12 feet long (4 meters). Inhabiting mainly the tropical and temperate waters of the ocean, the Blue shark is highly migratory. Its diet is mainly composed of squid and small bony fishes. The blue shark is considered to be one of the more dangerous sharks. It has been known to attack humans, which makes it one of species of shark that people most fear, however according to Wikipedia only 4 recorded Blue Shark fatalities have been recorded as of 2008.

Hammerhead Sharks

The most unique species of shark and also one of the more recognizable ones is the Hammerhead shark. Growing to a length of up to 6 m (20ft),it is known for its flat hammer shaped snout. Hammerheads inhabit temperate waters across the world ranging from southern Canada to New Zealand. Known to possess especially well developed electro-receptors  for hunting, hammerheads feed on a variety of fish and bottom dwelling creatures. There have been reported cases where Hammerhead sharks have attacked humans which are why they are feared.

Bull Sharks

Often confused with the great white shark, the bull shark is amongst the top three most dangerous sharks roaming in our oceans. The bull shark has a short, wide, rounded snout and plumper bodies.  Bull sharks are known for their aggressive behavior and the fact that they can live in both freshwater and saltwater. They can live in rivers, estuaries and some lakes in Central America. In fact, some have been found as far as 3000 km up the Amazon and Mississippi rivers. Bull Sharks feed on a wide variety of creatures including turtles, dolphins, seabirds and even other sharks.

Sand Tiger Sharks

Sand Tiger Sharks are also known as Grey nurse sharks are rather slow moving sharks and not aggressive to humans unless provoked. It grows to a length of 3.2 m (about 10.5 ft) and is identifiable by  its grey back and white underside. Found in the coastal waters of tropical and temperate regions, Sand Tiger sharks feed primarily on bony fishes including mackerels, other sharks and rays, squids, crabs and lobsters.

Tiger Sharks

Tiger sharks are perhaps most well known for their aggressive natures and bad reputation as a threat to humans. Second to the Great White, the Tiger Shark is responsible for the second highest number of fatalities related to shark attacks. Growing to a length of 5 meters and reaching a weight of almost 700kg tiger sharks will eat almost anything. They have been known to feed on whales, squid, fish, and turtles and even seabirds.

Great White Sharks

The big daddy of all sharks and also the most feared predator of the seas, the Great White like the Tiger Shark will feed on anything. Averaging about 4 to 6 m (13 to 20 ft) Great Whites diet mainly comprises of seals, dolphins, whale carcasses, seabirds, turtles, squids and other sharks. The Great White Shark is found near the coasts of California, Australia and South Africa. Known to be responsible for almost 10 human fatalities a year, diving with Great Whites must be performed only with highly experienced divers and from the safety of a shark cage. (Also Read: Overcoming The ‘Jaws’ Factor When You Dive)

Photos by:WIlly Volk, StormyDog, richard ling, bryan scott photography, jon hanson, pterantula, Nemo’s great uncle, Thespis377, g-na

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10 Common Shark Sightings was written by Nevin for Aquaviews - SCUBA Blog - Bringing You The Other 70% Of Our World