The three different ways mammals give birth - Kate Slabosky

Sesalci rojevajo mladiče na tri različne načine - Kate Slabosky

Translator: Anja Praprotnik Reviewer: Matej Divjak

What do these animals have in common?

Kaj imajo te živali skupnega?

More than you might think.

Več, kot bi si mislili.

Along with over 5,000 other species, they're mammals,

Z več kot 5000 drugimi vrstami, se uvrščajo med sesalce

or members of class mammalia.

oziroma v razred Mammalia.

All mammals are vertebrates, meaning they have backbones.

Vsi sesalci so vretenčarji, kar pomeni, da imajo hrbtenice.

But mammals are distinguished from other vertebrates

A sesalci se od ostalih vretenčarjev razlikujejo

by a number of shared features.

po številnih skupnih lastnostih.

That includes warm blood,

Mednje sodijo topla kri,

body hair or fur,

dlakavost,

the ability to breathe using lungs,

sposobnost dihanja s pljuči

and nourishing their young with milk.

in hranjenje mladičev z mlekom.

But despite these similarities,

Kljub podobnostim pa obstajajo

these creatures also have many biological differences,

med temi bitji tudi številne biološke razlike

and one of the most remarkable is how they give birth.

in ena najzanimivejših je način rojevanja.

Let's start with the most familiar, placental mammals.

Začnimo z najbolje poznanimi, placentalnimi sesalci.

This group includes humans,

Ta skupina zajema ljudi,

cats,

dogs,

mačke,

pse,

giraffes,

žirafe

and even the blue whale, the biggest animal on Earth.

in celo sinjega kita, največjo žival na Zemlji.

Its placenta, a solid disk of blood-rich tissue,

Posteljica, trdna plošča dobro prekrvavljenega tkiva,

attaches to the wall of the uterus to support the developing embryo.

se pritrdi na steno maternice in vzdržuje razvijajoči zarodek.

The placenta is what keeps the calf alive during pregnancy.

Posteljica ohranja mladiča pri življenju med nosečnostjo.

Directly connected to the mother's blood supply,

Ker je direktno povezana z materinim ožiljem,

it funnels nutrients and oxygen straight into the calf's body

pošilja hranila in kisik naravnost v telo mladiča

via the umbilical cord,

prek popkovine

and also exports its waste.

ter odstranjuje njegove izločke.

Placental mammals can spend far longer inside the womb than other mammals.

Placentalni sesalci lahko ostanejo v maternici veliko dlje od ostalih sesalcev.

Baby blue whales, for instance, spend almost a full year inside their mother.

Mladi sinji kiti, na primer, preživijo v materi skoraj celo leto.

The placenta keeps the calf alive right up until its birth,

Posteljica ohranja mladiča pri življenju vse do rojstva,

when the umbilical cord breaks

ko se popkovina pretrga

and the newborn's own respiratory,

in mladičev lastni dihalni,

circulatory,

krvožilni

and waste disposal systems take over.

in izločalni sistemi prevzamejo njeno funkcijo.

Measuring about 23 feet, a newborn calf is already able to swim.

Novorojeni sinji kit, ki meri okrog 7 metrov, že lahko plava.

It will spend the next six months

Naslednjih 6 mesecev bo popil

drinking 225 liters of its mothers thick, fatty milk per day.

225 litrov gostega, mastnega materinega mleka dnevno.

Meanwhile, in Australia, you can find a second type of mammal -

Medtem lahko v Avstraliji najdemo drugo vrsto sesalcev -

marsupials.

vrečarje.

Marsupial babies are so tiny and delicate when they're born

Mladiči vrečarjev so tako majhni in krhki, ko se rodijo,

that they must continue developing in the mother's pouch.

da morajo z razvojem nadaljevati v materini vreči.

Take the quoll, one of the world's smallest marsupials,

Vzemimo rod Dasyurus, ene najmanjših vrečarjev na svetu.

which weighs only 18 milligrams at birth,

Ob rojstvu tehtajo le 18 miligramov,

the equivalent of about 30 sugar grains.

kar ustreza 30 kristalom sladkorja.

The kangaroo, another marsupial,

Kenguru, še en vrečar,

gives birth to a single jelly bean-sized baby at a time.

povrže naenkrat enega samega mladiča v velikosti bombona.

The baby crawls down the middle of the mother's three vaginas,

Mladič zleze navzdol po srednji izmed materinih treh vagin,

then must climb up to the pouch,

nato pa mora splezati navzgor do vreče,

where she spends the next 6-11 months suckling.

kjer ob sesanju mleka preživi naslednjih 6-11 mesecev.

Even after the baby kangaroo leaves this warm haven,

Še ko mladi kenguru zapusti to varno zavetje,

she'll return to suckle milk.

se bo vračal v vrečo sesati mleko.

Sometimes, she's just one of three babies her mother is caring for.

Včasih je le eden izmed treh mladičev, za katere mati skrbi.

A female kangaroo can often simultaneously support one inside her uterus

Kengurujka lahko pogosto vzdržuje enega v maternici,

and another in her pouch.

drugega pa v vreči.

In unfavorable conditions,

V neugodnih razmerah lahko kengurujke

female kangaroos can pause their pregnancies.

nosečnost začasno ustavijo.

When that happens, she's able to produce two different kinds of milk,

Ko pride do tega, lahko proizvajajo dve različni vrsti mleka,

one for her newborn,

eno za novorojenca,

and one for her older joey.

drugo za starejšega mladiča.

The word mammalia means of the breast,

Beseda mammalia pomeni "od prsi,"

which is a bit of a misnomer

nekoliko neustrezno ime,

because while kangaroos do produce milk from nipples in their pouches,

saj kenguruji res proizvajajo mleko iz bradavic v svojih vrečah,

they don't actually have breasts.

vendar nimajo dojk.

Nor do monotremes, the third and arguably strangest example of mammalian birth.

Isto velja za stokovce, tretjo in najnenavadnejšo vrsto sesalcev.

There were once hundreds of monotreme species,

Nekoč je obstajalo na stotine vrst stokovcev,

but there are only five left:

danes pa jih je le še pet:

four species of echidnas and the duck-billed platypus.

štiri vrste kljunatih ježkov ter kljunaš.

The name monotreme means one hole

Ime so dobili po stoku ali kloaki,

referring to the single orifice they use for reproduction,

odprtini, ki jo uporabljajo tako za razmnoževanje,

excretion,

kot za izločanje in

and egg-laying.

nošenje jajc.

Like birds,

reptiles,

Tako kot ptice,

plazilci,

fish,

ribe,

dinosaurs,

dinozavri

and others,

in drugi,

these species lay eggs instead of giving birth to live young.

te vrste ležejo jajca, namesto da bi rodile žive mladiče.

Their eggs are soft-shelled,

Njihova jajca imajo mehko lupino

and when their babies hatch, they suckle milk from pores on their mother's body

in ko se mladiči izležejo, sesajo mleko iz por na materinem telesu,

dokler niso dovolj veliki, da se prehranjujejo sami.

until they're large enough to feed themselves.

Despite laying eggs and other adaptations that we associate more with non-mammals,

Čeprav nosijo jajca in imajo značilnosti, ki jih povezujemo z nesesalci,

like the duck-bill platypus's webbed feet,

kot na primer kljunaševa plavalna kožica,

bill,

kljun

and the venomous spur males have on their feet,

in strupena ost, ki jo imajo samci na nogah,

they are, in fact, mammals.

so vseeno sesalci.

To pa zato, ker imajo značilnosti, ki definirajo sesalce

That's because they share the defining characteristics of mammalia

and are evolutionarily linked to the rest of the class.

in so evolucijsko povezani z ostalimi člani razreda sesalcev.

Whether placental,

Placentalni sesalci,

marsupial,

vrečarji

or monotreme,

in stokovci,

each of these creatures and its unique birthing methods, however bizarre,

vse te živali in njihove edinstvene metode rojevanja, še tako bizarne,

have succeeded for many millennia in bringing new life and diversity

so mnogo tisočletij uspešno prinašale novo življenje in raznolikost

into the mammal kingdom.

v kraljestvo sesalcev.