In this section I introduce some interesting information about sharks and their abilities, in the form of questions and answers

Which is the smallest known shark?
The smallest known sharks are two: the dwarf lanternshark, Etmopterus perryi, maximus 21 cm, and the cylindrical lanternshark, Etmopterus carteri, maximus 21 cm. Very small sharks are also the pygmy ribbontail catshark, Eridacnis radcliffei, maximus 24 cm, the african lanternshark, Etmopterus polli, maximus 24 cm and the green lanternshark, Etmopterus virens, maximus 26 cm.
(informations from: "Sharks of the world", Compagno-Dando-Fowler, Princeton University press 2005)

Which is the greatest known shark?
The whale shark (Rhincodon typus) can arrive to a length of 18 m and with these dimensions he also represents the greatest fish actually known.
 

 How many sharks are actually known?
The sharks actually known, are 453, with 8 orders and 34 families, following the classification of the books “Sharks of the world” by Compagno, Dando, Fowler, Princeton University press 2005 and “FAO Species Catalogue Sharks of the World”, Compagno 2001. Complete sharks list


Do the sharks have the swimming bladder? How do they succeed in floating?
No, the sharks don't have the swimming bladder (an inside afloat body that can fill him with gas, present in the bony fishes, whose function is above all of support to the floating).
The floating of the sharks is facilitated by the cartilagineus structure and from the great liver that can reach the 25% of the weight of the animal.


Do the sharks lift the head out of the water?
Some sharks, and also the white shark (Carcharodon carcharias), lift the head out of the water, probably to observe.


Are the sharks animal with cold blood (eteroterm)?
These animals are eteroterm, thay have cold blood (the same temperature of the water where they swin). Some kinds os sharks, as the white shark, have a temperature of the body superior in comparison to that of the water that surrounds them, thanks to the admirable net.
The admirable net is a whole of capillary that have the function of changing heat, it is connected to muscular bands very developed, next to the vertebral column. Through the exchanges of heat of the admirable net the inside musculature and the brain remain to greater temperatures of those of the water in which these animals swim.


Do fossils of sharks exist?
The sharks have a skeleton made of cartilage and only some parts have calcified. The cartilage degrades very easily and quickly in comparison to a bony skeleton. For this motive only teeth and portions of vertebrae succeed in becoming fossilized and to be studied by the man.


Can the sharks swim to the back?
No, the sharks don't succeed in swimming back (contrarily of the bony fishes) in how much their pectoral fins are not so mobile to allow them this movement.


Does the shark close the eyes during the attack?
Yes, during an attack, for protection, some sharks can rotate back the eyes to the back (white shark Carcharodon carcharias and mako shark Isurus oxyrinchus), while others have an eyelid (the nictitant membrane) that is closed above the eye.
For some instant the shark is therefore deprived of sight and he mainly uses the ampullae of Lorenzinii to individualize the prey.


Are there predators of the sharks?
The sharks can be plundered by greater sharks and by the orcas. (Orcinus orca: sea mammal that can overcome the 8 meters of length and the 8000 kg of weight)


Are there sharks that swim in sweet (not sea) water?
Yes, the leuca shark or zambesi (Carcharhinus leucas) swims both in salty waters and in sweet waters, and in fact he succeeds in also going up again rivers for hundreds of km (es: river Zambesi).


Are there sharks that eat plankton?
Thin to they are now known three kinds of sharks that are nourished of plankton filtering the water that enters from their mouth. They are the whale shark (Rhincodon typus, up to 18 m.) the basking shark (Cetorhinus maximus, up to 13 m.) and the megamouth shark (Megachasma pelagios, up to 5 m.).


Do all the actual sharks have the mouth in ventral position?
No, contrarily of the majority of the sharks, the orders Orectolobiformes and Squatiniformes are composed from sharks that possess the mouth in terminal position. To the Orectolobiformeses belong, for example: Stegostoma fasciatum, Ginglymostoma cirratum, Nebrius ferrugineus, Rhincodon typus. this last, with a length that can reach 18 m, is currently the actually known greatest fish.
To the order Squatiniformes belongs, for example, the angel shark (Squatina squatina), that is a shark from the flat body, whose gills opening extend until the ventral surface.


Can the hammer shark reproducein asexual way?
Yes. A female exemplary of Sphyrna tiburo has in fact given birth, in the Henry Doorly Zoo, in Nebraska, not having had contacts with a male shark from its capture, three years before. Considering that the ability to preserve the masculine germinal cells (sperms) in the female of the Sphyrna tiburo doesn't overcome the 5 months, the birth of the small shark would confirm the asexual way. The female egg is developed up to form the small shark without the fertilization with a male sperm.
 

Does the shark attack the man?
Only some sharks kinds that reach great dimensions can represent a danger for the man, as all the great raiders that live on the earth. The 50% of the sharks don't overcome the meter of length, him 82% don't overcome the 2 meters, and only 4% reach superior dimensions to the 4 meters. The man doesn't reenter among the usual sharks preys.


How many shark attacks happen every year in the world?
Every year, in all the seas of the globe, there are about 60 unprovocked attacks to the man, about 0-6 deadly.


How many sharks are killed by the man every year?
The man every year captures and kills around 100 million sharks..
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Which are the sharks present in italian waters?
Read the answer
 

What about the last sharks attacks in italian waters?
July 1926, Varazze (Ligurian Sea), deadly attack to a swimmer to around 200 m from shore. (white shark of around six meters) 

September 1956, Circeo (Tyrrhenian Sea), attack to a scuba diver to around 2.5 km of distance from the beach. (white shark of around four meters) 

August 1962, Circeo (Tyrrhenian Sea), attack to a scuba diver.
(white shark) 

September 1962, Circeo (Tyrrhenian Sea), deadly attack to a scuba diver with numerous fishes chased suspended on the belt. (white shark) 

July 1963, Riccione (Adriatic Sea), attack to a scuba diver during activity of fishing. (white shark of around four meters) 

September 1978, Capo d'Anzio (Tyrrhenian Sea), attack to a scuba diver.
(white shark of around five meters) 

June 1983, Riomaggiore (Ligurian Sea), attempt of attack to a scuba diver.
(white shark of around three meters) 

July 1986, Punta Secca (Sicily), attack to a swimmer to around 300 m from the shore. (white shark of around three meters) 

February 1989, Baratti Gulf (Tyrrhenian Sea), deadly attack to a scuba diver.
(white shark of around six meters) 

June 1989, Marina di Carrara (Tyrrhenian Sea), attack to a surfer extended on the table. (shark of around three meters) 

July 1991, Portofino (Ligurian Sea), attack to the kayak of a swimmer to around 20 m from the shore. (white shark of around three meters)
More informations.
 

Which are the most dangerous sharks?
The most dangerous sharks for the man are:
1) GREAT WHITE SHARK (Carcharodon carcharias)
2) TIGER SHARK (Geleocerdo cuvier)
3) ZAMBESI SHARK (Carcharhinus leucas)
4) MAKO SHARK (Isurus oxyrinchus)
5) OCEANIC WHITE TIP SHARK (Carcharhinus longimanus)
Is it possible to see their photos and biological informations HERE.

Is it possible to see white shark in nature and in captivity?
White shark in captivity: the man has never succeeded in maintaining and therefore to study better a white shark in captivity, at least up to the year 2003..
It is important to understand that the study in captivity of an animal, whose presence in the waters of the world is drastically decreased, can serve to acquire greater awareness on the necessity of protection that it requires from the man. Examining its behaviors in captivity in fact the man try to fill those biological and ecological gaps that concern this shark and at the same time also the exposure to the public can contribute to cancel so many common places on the so-called one "men's eater".. 

In the June 2003 for the first time the Monterey Bay Aquarium in Monterey, California, has succeeded in maintaining in captivity a white shark for 10 days. 
In September 2004 a female, captured for mistake by professional fishermen, is given to the aquarium and for 198 days this white shark perfectly suits her for the life in captivity and she is exposed to the public with great success. 
In March 2005 this white shark, not to excessively prolong her permanence in captivity and to protect her from excessive stress, is released in open sea and studied for 30 days, aquiring in this way an important massive structure of data and biological information.
From August 31 st 2006 the Monterey Bay Aquarium holds in captivity another sample, which shows to have suited well for the new situation, normally feeding himself and increasing of weight and length.
On January 16 th 2007, after 137 days inside the aquarium, this shark is released, and thanks to the application of a satellitar tag (electronic signaller) that April 16 th 2007 is detached, all of its movements have been reconstructed in open sea within these three months. The shark has swum up to the south point in the Baja California, crossing more than 1000 km and reaching depth superior to the 300 m.
In the month of August 2007 a white shark is accidentally captured by the net of fishermen, in California, and he is brought to the Monterey Bay Aquarium, where the animal grows of weight and length for 162 days to be released in liberty in February 2008.  The last white shark that the Monterey Bay Aquarium has taken care has been in the summer 2009: the animal as his predecessors, is regularly fed growing of dimensions and he have returned in liberty November 4 th 2009.

Currently are two the principal destinations in the world that can be reached to observe the great white shark in nature: the region of Gansbaai and particularly the island of Dyer in South Africa and the area of Dangerous Reef, offshore the peninsula Eyre in southern Australia. 

1) Gansbaai is a small village of fishermen that is found to about two hours with car by the more note Cape Town (180 km of distance). 
The area is enough calm and what can offer is the beauty of its nature, and also the not scuba tourist can appreciate with long walks along the coasts. 
The white sharks can be seen in particular way near the island of Dyer, primarily sandy and distant few km from Gansbaai. 
In these zones there are, in fact, numerous seal colonies, together with their pups, appetizing preys for this great raider of the seas. 
As it regards the immersions, there are different centers that organize exits in sea with the metallic cage to see the white sharks, also recommend to the beginners, with the desire however to live strong emotions. 

2) Dangerous Reef owes first of all the name not to the presence of the white sharks, but to the dangerousness of the zone for the navigations, near the Gulf of Spencer. This bluff is found offshore the peninsula Eyre, in southern Australia, also this zone populated from numerous seals, sea lions and therefore also white sharks. In this zone and in the near islets can be observed more than 12000 sea lions, the greatest colony in Australia. Also here the not scuba tourist can appreciate the beauty of the nature, the tones of the ocean and the beaches, both rocky and sandy, also participating in the exits of the organizations that transport the scuba divers in the various zones of immersion. 
Also the emerged earth in fact proposes his beauties, without forgetting, as already mentioned, the numerous seals and sea lions present in every islet of the zone. As it finally regards the immersions, also here they are realized with the aid of the metallic cages of protection, in surface for the beginners and on the fund for more experts.
 

What about sharks reproduction?
In the male sharks the terminal part of the pelvic fins, (equal fins that have the function to stabilize the rout of the animal) become longer and it calcifies more and more to form the claspers (two), the sexual organs through which the shark reproduces himself. The reproduction is internal and appen with the introduction of a clasper (the other one is a backup) in the cloaca of the female shark. This is a very bloody moment, in fact the male repeatedly bites the female on the fins and on the back to stimulate her/ and to hold her firm.
Around the 30% of the sharks has a oviparous reproduction, that is when the female deposes outside the eggs; around 50% has a aplacental viviparous reproduction, that is when the female produces the eggs that develope inside her body and the small sharks go outside completely formed; the remained 20% has a placental viviparous reproduction, that is when the embryo is in contact with her mother through a primitive placenta.
 

Which are the sharks and rays present in the Adriatic Sea?
Read the answer



Do the sharks have to continually swim to breathe?
Some kinds of sharks (above all the great raiders) have the necessity to continually swim to make the water pass through their gills and therefore to breathe. The bentonic sharks, that swin near the fund and generally of average-small dimensions, can be firm and to breathe inhaling the water to make it passin their gills. (read article about SHARKS SPIRACLE)


How many teeth do the sharks have?
The teeth of the sharks are prepared in file, generally six, in the superior and inferior jaws, and they progressively stir in before, so that to replace in continuation the teeth of the most external line, more usury subjects and breakup. In average in the mouth of a shark there are around 300 teeth and during the life they are replaced from there around 20000 a really impressive number!


Why have the hammer sharks the form of the face so strange and particular?
With this morphology the hammer sharks probably get a best floating during the swimming and their organs of sense, through a greater surface, become even more efficient. (see the article"Hammer shark")


Can the sharks perceive the electric fields?
The sharks, through the Ampullae Lorenzinii (to see "The sharks senses") can perceive variations of electric field of as soon as 5 miliardesimis of volt for cm. square.


Witch is the pressure of the bite of a shark?
The pressure of the bite of a shark Carcharinus obscurus of around 2 meters would seem to be of three tons for square centimeter!



What are the dimensions of the greatest white shark captured by man?
The greatest white shark (Carcharodon carcharias) has been captured to Malta, and it was a female of 7,14 meters length. The white shark is the greatest present predatory shark in the seas of the globe, in fact the Whole shark (Rhincodon typus, up to 18 ms.) the Great mouth shark (Megachasma pelagios, up to 5 ms.) and the Elephant shark (Cetorhinus maximus, up to 13 ms.) eat plankton, and therefore aren't not active raiders.


Which kinds of sharks are present in the Mediterranean sea?
In the Mediterranean sea about fifty different kind of sharks are present, among which the white shark (Carcharodon carcharias) thebull shark (Carcharias taurus) the fox shark (Alopias vulpinus) the mako (Isurus oxyrinchus) the grey shark (Carcharinus plumbeus) the verdesca (Prionace glauca) the common hammer shark (Sphyrna zygaena) the elephant shark (Cetorhinus maximus).


 

Marco Angelozzi - www.prionace.it