She said sharks have no bones and shrimp swam backward.

Swordfish and some sharks have circulatory mechanisms that keep their brains and eyes above ambient temperatures, and thus increase their ability to detect and react to prey.

Tunas and some sharks have similar mechanisms in their muscles, improving their stamina when swimming at high speed.

In New Zealand, rays are killer whales ' most frequent prey, and they have also been observed hunting sharks ( particularly makos, threshers and smooth hammerheads ).

Many of the humans-turned-sharks are described as having skin patterns that no natural sharks have: similar to the cloth patterns of blankets that are wrapped around infants.

As evidence of these movements, bull sharks tagged inside the lake have later been caught in the open ocean ( and vice versa ), with some taking as little as 7 – 11 days to complete the journey.

It does not always have a lethal effect on large predators, such as sharks, but it can kill humans.

As a result of these three defenses, porcupinefish have few predators, although adults are sometimes preyed upon by sharks and orcas.

Despite their appearance of being slow, crocodiles are top predators in their environment, and various species have been observed attacking and killing sharks.

He was so impressed by her and her friend Elizabeth Philpot that he wrote in his journal: " Miss Philpot and Mary Anning have been able to show me with utter certainty which are the icthyodorulites dorsal fins of sharks that correspond to different types.

Sharks and rays typically have five pairs of gill slits that open directly to the outside of the body, though some more primitive sharks have six or seven pairs.

Since that time, sharks have diversified into over 400 species.

Only scales have been recovered from the first sharks and not all paleontologists agree that these are from true sharks.

Because sharks do not have rib cages, they can easily be crushed under their own weight on land.

Generally sharks have only one layer of tesserae, but the jaws of large specimens, such as the bull shark, tiger shark, and the great white shark, have two to three layers or more, depending on body size.

Most sharks have eight fins.

Unlike bony fish, sharks have a complex dermal corset made of flexible collagenous fibers and arranged as a helical network surrounding their body.

Tiger sharks have a large upper lobe, which allows for slow cruising and sudden bursts of speed.

Unlike bony fish, sharks do not have gas-filled swim bladders for buoyancy.

One of the biggest differences between the digestive systems of sharks and mammals is that sharks have much shorter intestines.

Some species, such as nurse sharks, have external barbels that greatly increase their ability to sense prey.

Lampreys and sharks only possess a cartilaginous endocranium, with both the upper and lower jaws being separate elements.

* The Environmental Defense Fund ( EDF ) classifies mahi-mahi caught by line / pole in the US as " Eco-Best " in its three-category system, but classifies all mahi-mahi caught by longline as only " Eco-OK " or " Eco-Worst " due to longline " high levels bycatch, injuring or killing seabirds, sea turtles and sharks.

When Hurricane Hugo destroyed the island's only Olympic-sized swimming pool in 1989, Duncan was forced to swim in the ocean and he quickly lost his enthusiasm for swimming because of his fear of sharks.

Squid comprise some 60 % of the diet of sharks in Suruga Bay ; this includes not only slow-moving, deep-dwelling types such as Chiroteuthis and Histioteuthis, but also relatively large, powerful swimmers of the open ocean such as Onychoteuthis, Sthenoteuthis, and Todarodes.

It was only loans from the Public Service Investment Society, set up by the PSA in 1928, that prevented many of them falling into the clutches of loans sharks.

Since its discovery in 1976, only a few megamouth sharks have been seen, with 54 specimens known to have been caught or sighted as of 2012, including three recordings on film.

Jawless fish and sharks only possess a cartilaginous endocranium, with the upper and lower jaws being separate elements. Bony fishes have additional dermal bone, forming a more or less coherent skull roof in lungfish and holost fish.

The original " Bruce " sharks rotted behind sheds on the lower lot of Universal Studios, the only pieces that were salvageable were the chromoly tube frames.

Authors may regard the two terms as synonymous, or equate ovoviviparity only with aplacental yolk-sac viviparity, in which the embryos are solely sustained by yolk ( as opposed to secondary provisioning by their mother in the form of " uterine milk ", such as in the stingrays, or unfertilized eggs, such as in the mackerel sharks ; the latter is referred to as intrauterine oophagy ).

Orcas and large sharks are the only natural predators of leopard seals.

Nurse sharks typically attack humans only if directly threatened.

Among fish, a true cloaca is present only in elasmobranchs ( sharks and rays ) and lobe-finned fishes.

The aquarium is currently one of only two aquariums in the United States to exhibit Great Hammerhead sharks ; the other is the Adventure Aquarium in Camden, New Jersey.

For this reason, most iridescent sharks kept in home aquaria grow to only 15 to 30 cm ( 6 to 12 inches ) in length and die prematurely from organ failure.

The presence of only one lateral keel on the tail and the lack of lateral cusps on the teeth distinguish the makos from the closely related porbeagle sharks of the genus Lamna.

One of only four known endothermic sharks, it is seldom found in waters colder than.

Drum lines are also viewed, by some people, as an alternative: they consist of baited hooks aimed at catching only large sharks ( though turtles are sometimes hooked ).

Adults are threatened only by the largest and fastest hunters, such as toothed whales, particularly the false killer whale, pelagic sharks such as the mako and great white, large Atlantic blue marlin and Pacific blue marlin, and black marlin.

Whitetip reef sharks generally remain within a highly localized area ; only rarely do they undertake long movements, wandering for a while before settling down somewhere new.

During the party Carter comes up to her and tells her the three test sharks are becoming more " pack-like " and that they'll only eat other sharks, as they had expertly synchronized an attack on the same tiger shark and devoured it.

Normally, North Atlantic sharks only stray as far south as South Carolina and the Gulf of Guinea, but pregnant females from the western North Atlantic population are known to range into the Sargasso Sea, almost as far as Hispaniola, to give birth.

Among sharks, the porbeagle's capacity for elevating body temperature is second only to the salmon shark's.