Why are sharks so awesome? - Tierney Thys

Zašto su ajkule tako strava? - Tirni Tajs (Tierney Thys)

Prevodilac: Goran Stanić Lektor: Tijana Mihajlović

Sharks have been celebrated as powerful gods

Ajkule su slavljene kao moćni bogovi

by some native cultures.

u nekim domorodačkim kulturama.

For example, Fijians believe the shark god Dakuwaqa,

Na primer, Fidžijci veruju da je bog-ajkula, Dakuvanga,

mogao zaštititi ribare od opasnosti na moru.

could protect fisherman from the dangers at sea.

And today, sharks are recognized as apex predators of the world's ocean

A danas se ajkule smatraju za sam predatorski vrh svetskih okeana

and include some of the Earth's longest living vertebrates.

i spadaju u jedne od najdužih živih kičmenjaka na Zemlji.

What is it that makes these fish worthy of our ancient legends

Šta je to što ove ribe čini vrednim naših drevnih legendi,

and so successful in the seas?

a isto tako veoma uspešnim u morima?

Većina njihove lovačke snage potiče iz jedinstvenog niza bioloških osobina

Much of their hunting prowess stems from a unique set of biological traits

honed for more than 400 million years.

usavršavanih više od 400 miliona godina.

Njihovi hrskavičavi skeleti su manje gusti od koštanih

Their cartilaginous skeletons are less dense than bony ones

and require less energy to move.

i zahtevaju manje energije za pokretanje.

Velike uljane jetre pružaju plovnost njihovim hidrodinamičnim telima

Large oily livers lend buoyancy to their streamlined bodies,

i dok se mišići trupa koštanih riba pripajaju direktno na njihov skelet,

and while trunk muscles of bony fishes attach directly to their skeletons,

isti se kod ajkula pripajaju na njihovu kožu.

those of sharks also join to their skin.

This special design transforms them into pressurized tubes

Ovaj specifičan dizajn ih pretvara u cevi pod velikim pritiskom

whose springy skin can efficiently transmit muscular forces to the tail.

čija elastična koža može efikasno preneti snagu mišića na rep.

Shark skin has additional remarkable features.

Koža ajkula ima i dodatne izvanredne karakterisitke.

Despite its smooth external appearance,

Uprkos svom glatkom spoljašnjem izgledu,

at the micro level, it has a coarse texture

na mikroskopskom nivou ima hrapavu teksturu

thanks to thousands of tiny teeth-like scales

zahvaljujući hiljadama sićušnih ljuski nalik na zube

koje se nazivaju dermalni zubići.

called dermal denticles.

Each denticle is coated in a substance called enameloid,

Svaki zubić je obložen supstancom pod imenom enameloid,

koja pretvara kožu u čvrsti oklop.

which turns the skin into a tough shield.

Plus the structure of denticles varies across the body

Dodatno varira i sama struktura zubića duž tela

in such a way as to reduce noise and drag

na takav način da smanjuje šumove i otpor

dok se ajkula kreće kroz vodu.

when the shark moves through water.

Što se tiče zuba u njihovim ustima,

As for the teeth in their mouths,

ajkule ih mogu proizvesti i do 50 000 u svom životu.

sharks can produce up to 50,000 in a lifetime.

On average, they can lose one tooth a week,

U proseku izgube jedan zub nedeljno,

a svaki put kada se to desi,

and each time that happens,

it's rapidly replaced.

ubrzo je zamenjen drugim.

Thanks to a layer of fluoride coating their teeth,

Zahvaljujući sloju fluorida koji im oblaže zube,

sharks also avoid cavities.

ajkule nemaju karijes.

Međutim, zubi nisu isti kod svih ajkula.

But teeth aren't the same in all sharks.

They can vary across species and by diet.

Oni se razlikuju od vrste do vrste i u zavisnosti od ishrane.

Some are dense and flattened,

Neki su zbijeni i spljošteni,

useful for crushing mollusks.

što je korisno za mrvljenje mekušaca.

Drugi su u obliku igala za hvatanje riba.

Others are needle-like for gripping fish.

Usta velikih belih ajkula sadrže špicaste donje zube za držanje plena

The mouths of Great Whites contain pointy lower teeth for holding prey

and triangular serrated upper teeth for slicing.

i trouglaste reckaste gornje zube za sečenje.

Ova raznovrsnost omogućuje ajkulama da pikiraju plen u različitim okruženjima.

This variety enables sharks to target prey in a diversity of ocean environments.

Many species also have another peculiar trait -

Mnoge vrste poseduju još jednu specifičnu osobinu,

the ability to launch their jaws out of their mouths,

mogućnost da izbace vilicu iz svojih usta,

dodatno ih otvore

open them extra wide,

and grab prey by surprise.

i iznenada ugrabe plen.

Tokom evolucije,

Over the course of evolution,

shark brains have expanded,

mozgovi ajkula su se proširili

coupled with the growth of their sensory organs.

zajedno sa rastom njihovih čulnih organa.

Današnje ajkule mogu da namirišu nekoliko kapi krvi

Modern-day sharks can smell a few drops of blood

and hear sounds underwater from 800 meters away.

i čuju zvukove pod vodom sa udaljenosti od 800 metara.

Posebno dobro čuju na niskim frekvencijama,

They're particularly well-tuned to low frequencies,

including those emitted by dying fish.

uključujući i one koje ispuštaju ribe na samrti.

And like cats, they have reflective membranes called tapeta lucida

Poput mačaka, imaju reflektivne membrane koje se zovu tapeta lucida

at the backs of their eyes

sa zadnje strane očiju

that dramatically improve their vision in low light.

koje im drastično poboljšavaju vid pri slabom svetlu.

As if these heightened abilities weren't enough,

Kao da ove ojačane sposobnosti nisu dovoljne,

sharks have even honed a sixth sense.

ajkule su obogaćene šestim čulom.

They're able to hunt using a network of electrosensory cells

One mogu da love pomoću mreže elektrosenzornih ćelija

pod nazivom Lorencinijeve ampule.

called ampullae of Lorenzini.

Ove ćelije su ispunjene hipersenzitivnim gelom

These cells are filled with hypersensitive jelly

which allows them to detect electrical signals from prey,

koji im omogućuje da detektuju električni signal plena,

including the slightest twitch of a muscle.

uključujući i najmanje trzanje mišića.

Najreprezentativnije vrste ajkula

Some of the most iconic shark species,

like Great Whites, Makos, Porbeagles, and Salmon Sharks

poput velike bele ajkule, kučka, kučine i losos ajkule,

owe their success to another surprising trait:

toliko su uspešne zbog još jedne iznenađujuće osobine.

warm blood inside a cold-blooded creature.

Imaju toplu krv, iako su hladnokrvna bića.

Unutar njihovih tela

Inside their bodies,

they have bundles of arteries and veins

nalaze se snopovi arterija i vena

called rete mirabile.

koji se zovu „rete mirabile“.

Here, venous blood warmed up by the shark's working muscles

U njima se venska krv ugrejana od strane pokretnih mišića

passes right next to arteries carrying cold, oxygen-rich blood from the gills.

kreće tik uz arterije koje prenose hladnu, oksigenizovanu krv iz škrga.

Ovakav raspored prenosi toplotu u krv

This arrangement transfers heat to the blood

that gets cycled back to the body's vital organs.

koja se vraća nazad u vitalne organe.

Topli mišići omogućuju brže, mnogo snažnije plivanje,

Warmer muscles enable faster, more powerful swimming,

dok topliji trbusi potpomažu varenju

while warmer bellies aid digestion,

i bržem razvijanju mladunaca u utrobi.

and the more rapid development of young in utero.

And warmer eyes and brains keep the sharks alert in cold waters.

Takođe, toplije oči i mozgovi drže ajkule u pripravnosti u hladnijim vodama.

With these amazing adaptations, there's more to revere than fear

Gledajući ove neverovatne adaptacije, više se treba diviti ovim 500 vrstama

from the 500 shark species roaming our oceans.

koje lutaju našim okeanima, nego ih se plašiti.

Unfortunately, one-third of these species are threatened

Nažalost, čak jedna trećina ovih vrsta je ugroženo

due to overfishing.

zbog preteranog ribolova.

After millions of years in the making,

Nakon miliona godina razvitka

these apex predators may be meeting their greatest challenge yet.

ovi vrhunski predatori se možda susreću sa najvećim izazovom do sad.