موضوع بالانجليزي عن سمك القرش
تعبير انجليزي عن whale shark
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information about
fish
paragraph about
fishing
موضوع انجليزي عن سمك القرش
موضوع عن السمك
تعبير عن صيد السمك بالانجليزي
انواع السمك بالانجليزي
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معلومات
عن سمك القرش بالانجليزي
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موضوع انجليزي عن سمك القرش قصير
موضوع عن الاسماك بالانجليزي
موضوع تعبير عن سمك القرش
تعبير انجليزي 100 كلمة
تعبير انجليزي 150 كلمة
تعبير انجليزي 102
تعبير انجليزي للصف 11
تعبير انجليزي للصف 12
تعبير انجليزي صف 11
تعبير انجليزي متوقع 2014
تعبير انجليزي متوقع 2015
مواضيع تعبير انجليزي توجيهي 2014
مواضيع تعبير انجليزي للتوجيهي 2012
مواضيع تعبير انجليزي توجيهي 2015
مواضيع تعبير انجليزي للتوجيهي 2014
مواضيع تعبير انجليزي توجيهي 2016
مواضيع تعبير انجليزي توجيهي 2013
مواضيع تعبير انجليزي للتوجيهي 2015
معنى كلمة سمك القرش بالانجليزي
معلومات عن سمك القرش الابيض
موضوع عن الاخطبوط بالانجليزي
معلومات عن الحوت الازرق بالانجليزي
search about The
Great White Shark بحث عن اسماك القرش ...
سمك القرش في الإنجليزية, ترجمة, العربية-الإنجليزية
قاموس - ...
تم
The whale
shark (Rhincodon typus) is a cartilaginous fish, the only member of the genus
Rhincodon and the only present species of the Rhincodontidae family.
Exceptionally reaching 20 meters in length, for a mass of 34 tons, this shark
is considered the largest fish currently living on Earth. However, its
observable size is in practice generally between 4 and 14 meters.
Massive,
moving quite slowly and without aggressiveness, this shark is perfectly
harmless to man. Like the blue whale, its equivalent in mammals of the maritime
megafauna, this sea giant feeds mainly on plankton, algae and microscopic
animals, which it absorbs by its broad mouth.
Easily
recognizable with its checkered livery, the whale shark is found in open seas
and tropical and warm oceans. Its lifetime is estimated to be between 100 and
150 years1 even though the oldest specimen collected was about 70 years old2.
Although there are no precise data on its total population, the species is
considered to be at risk.
Cut
The size of
whale sharks has been the subject of a number of more or less justified
assertions. According to observations made in the Indian Ocean, the size of the
whale shark is almost always between 4 and 14 m (95% of the observations), with
a maximum of observations between 5.50 and 10 m (71% of the cases ) 5. It can
therefore reach a maximum practical length of about 14 m, although the maximum
size of 20 m, for a weight of about 34 t was reported once in 19992. The whale
shark is the largest fish existing today, and only Leedsichthys and Megalo
gifts, now missing, would have passed it. In the rest of the animal kingdom,
however, it is smaller than the blue whale, a mammal that can reach 30 meters
for 170 tons.
Skin
The whale
shark's skin is completely white, while the back of the shark is gray, darker
than most sharks, with many light spots and horizontal and vertical white or
yellow lines forming a checkerboard . These tasks allow the identification of
individuals by photo-identification: fact sheets, sorts of identity cards, are
associated with animals, and are then used by researchers to identify and count
whale sharks6. Galapagos and Australia7 have already been observed and even
filmed an albino whale shark8. As in the rest of the animal kingdom, these
individuals are extremely rare.
The skin of
the whale shark is thicker and harder than that of any other species in the
world, reaching up to 15 cm in thickness, and is covered with dermal denticles.
It is his principal defense.
fins
The first
dorsal fin has a generally triangular shape. The tip is rounded in juveniles
and becomes more upright and angular with age. Its faces have the same livery
in checkerboard as the body. The second dorsal fin is smaller.
The powerful
pectoral fins have a false shape. The upper surface is dark and dotted with
spots while the underside is white.
The caudal
fin is heterocercal, the upper lobe being much larger than the lower lobe (the
asymmetry becomes less pronounced in adults). It provides the driving force.
However, the whale shark is not an effective swimmer, it uses all its body to
swim and moves at an average speed of 5 km / h, a relatively slow speed for a
fish.
Food
This giant of
the seas does not share that name with the whales. It also follows the same
diet. Indeed, the whale shark feeds only on small prey such as plankton and
krill, but also algae, small crustaceans, small squid or fish of less than 10
cm (mackerel, ... ). An analysis of the stomach contents of a specimen caught
off the coast of India in 1961 revealed a wide variety of ingested, including
large quantities of zooplankton, partially digested fish remains, crustaceans,
molluscs and small amounts of algae, suggesting undoubtedly an omnivorous diet.
However, it is necessary to be less categorical because, because of its
filtering behavior, the absorption of algae may be involuntary. It is one of
only four known species of sharks that, like whales, filter their food by swimming
slowly in waters rich in plankton ... mouth gaping. The water rushes into it,
loaded with foods of all sizes and comes out of nutrients.
To compensate
for the small size of its prey, it must swallow large amounts of food (nearly
one tonne of plankton per day). To do this, it filters, thanks to its large
gaps, the water which engulfs in its immense mouth. Its numerous rows of teeth,
a few millimeters long, play no part in the diet. Instead, the shark draws
water, closes the mouth and expels the water through its gills. During the
slight delay between the closing of the mouth and the opening of the gill
slits, the food is trapped against the dermal denticles lining the gill blades
and the pharynx. This unique modification of the gills prevents the passage of
solids larger than 2 mm in size, but leaves the liquid to flow. The particles
isolated by this "sieve" are then swallowed. Whale sharks were caught
"coughing." This is assumed to be a means of removing the
accumulation of particles in the gills11.
Only four
members of the elasmobranch family are reputed to be filterers6:
• the whale shark;
• the big-mouth shark;
• the basking shark;
• the manta ray.
In its
feeding behavior, the whale shark uses two techniques: it can
"filter", in the manner of the blue whale or "gober", in a
similar way to tarpon. Thus, the animal is not content to filter the water
during its movements when the concentration of planktonic food is low.
Immobile, it can also rapidly aspirate large quantities of liquid, which is
more suitable for catching larger prey or compact planktonic clouds12.
Solitary
individuals have been observed feeding passively, swimming gaping mouths, or
sometimes vertically encamped in the sea and opening their mouths to suck prey,
when they are numerous. The latter method is used on banks of small crustaceans
(krill), squid, anchovies or sardines13.
In group
hunting, whale sharks feed, at dusk or at night, by filtering surface water
with open mouth and distended jaw, or by "gobbling" the prey
dynamically.
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