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View count:380,880
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Duration:04:47
Uploaded:2015-06-05
Last sync:2018-11-21 14:20
Hank shares news about two unusual animals in crisis: the saiga, which have lost about half of their total population in the past month, and the smalltooth sawfish which has been found to reproduce in the wild, without sex.

Hosted by: Hank Green
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Sources:
saiga
http://www.newscientist.com/article/dn27598-mystery-disease-claims-half-world-population-of-saiga-antelopes.html?utm_source=NSNS&utm_medium=SOC&utm_campaign=hoot&cmpid=SOC%257CNSNS%257C2015-GLOBAL-hoot#.VWdm1FxVikp


http://dotearth.blogs.nytimes.com/2015/05/29/previous-mass-die-offs-of-the-endangered-saiga-antelope-hint-at-a-warm-wet-weedy-culprit-in-kazakhstan/

http://www.cms.int/saiga/en/news/more-10000-saigas-found-dead-central-kazakhstan

http://www.nytimes.com/2015/06/02/science/saiga-antelope-mystery-disease-die-off.html

http://www.cms.int/saiga/en/news/more-10000-saigas-found-dead-central-kazakhstan

http://www.merckvetmanual.com/mvm/generalized_conditions/hemorrhagic_septicemia/overview_of_hemorrhagic_septicemia.html

http://www.cms.int/en/news/update-more-27000-saigas-confirmed-dead-cms-sends-out-emergency-expert-mission

http://www.edgeofexistence.org/mammals/species_info.php?id=62

http://www.nature.com/news/mysterious-die-off-sparks-race-to-save-saiga-antelope-1.17675


sawfish

http://dx.doi.org/10.1016/j.cub.2015.04.018

http://www.ansci.wisc.edu/jjp1/ansci_repro/misc/project_websites_08/tues/Komodo%20Dragons/what.htm

http://sb.cc.stonybrook.edu/news/general/2015_06_01_parthenogenesis.php?=marquee3

http://www.eurekalert.org/pub_releases/2015-06/cp-ses052715.php
Imagine if 120,000 of any kind of animal just died within a couple of weeks. If a 120,000 crows just fell from their perches or out of the sky in your part of the world, that would be sad. It's strange and totally terrifying. If 120,000 dolphins washed up on the shore, it would be an ecological calamity. Now imagine if those 120,000 dead animals accounted for half of that species's entire population on Earth.

Well that's exactly what's happening with the saiga, a weird and unique kind of antelope found in the cold steppes of Central Asia. They're downright prehistoric looking animals with giant eyes and floppy trunk-like snouts. They're basically like living fossils, having grazed around Asia for about 5 million years. So last year there were about 260,000 saiga in Asia, mostly in Kazakhstan. But suddenly beginning around May 10th, they started dying in huge numbers. Within about 10 days the toll was at 27,000, then a few days later 80,000.

Then the Kazakh government contacted the UN for help figuring out what was going on. The UN Convention on Migratory Species sent a team of British biologists to investigate, and so far they still don't know what's killing the saiga, even as the death toll has exceeded 120,000. The outbreak seems to have started after the females gathered into herds in early May as they usually do to give birth. Suddenly, hundreds of females and their young started dying, after showing symptoms like foaming at the mouth, diarrhea, and difficulty breathing. At first, some people thought that the disease had to do with unusually heavy Spring rains. Others suggested that the saiga had started grazing on toxic weeds that were being spurred on by warm, wet weather. Other experts even considered the effects of recent rocket launches, like leaking fuel since Kazakhstan is the home of the Russian Federation's launch and landing sites.

But the UN researchers told new scientists that they think part of the cause may be an infection of the blood known as hemorrhagic septicemia. This disease has been known to devastate herds of animals like camel, buffalo, and bison often in as little as 8 hours after symptoms start to appear, and with a mortality rate of 100 percent. This seems like a likely culprit since blood-borne infection could easily sweep through a large group of animals giving birth around the same time. But the biologists said that the bacteria that usually causes this kind of infection, called pasturella, aren't necessarily dangerous on their own. Around 5 percent of most cattle and buffalo for instance are walking around with pasturella at any given time, so there must be something else that's weakening the saiga's immune system and allowing the bacteria to take over. But what that is, whether it's another bacterium, or a virus, or sudden changes in weather just isn't clear, and neither is how scientists could stop it.

But on the other side of the world, another equally endangered and ancient looking animals seems to have found a strategy for survival, and it's never been documented until now. Smalltooth sawfish in Florida have been found to give birth to young without ever having mated---the first time that so called "virgin births" have been recorded in the wild among animals that could reproduce sexually if they wanted to. Biologists were studying the DNA of sawfish in Southwestern Florida when they discovered that about 3 percent of the population were... not quite clones, but strange kind of copies of their mothers. It turns out that some of the females had been undergoing parthenogenesis, reproducing by using unfertilized eggs.

We've talked before about how some animals can have babies without having sex. It's pretty common in invertebrates like insects. But in invertebrates, it's only been observed in some reptiles, and birds, and sharks in captivity or in some other kind of isolation where no males were available for a female to mate with. In the case of the sawfish, there were some guys for the ladies to choose from, but the population was really small. In fact, the scientists were studying that particular group because they wanted to know if members of the same family were mating with each other. But apparently, the females found an alternative.

Parthenogenesis is thought to begin when a progenitor cell in a female, kind of like a proto-egg, divides to create a single egg with three left-over sister cells. But instead of taking a sperm cell, the egg just absorbs one of the sister cells. They can combine their genetic material and divide to create an embryo. The end result is what biologists call a half-clone. While the mother has two sets of chromosomes that it inherited from its parents, its offspring winds up with two identical copies of just one of those sets. The researchers say that while biologically ageneious, the fact that sawfish are reproducing this way may be a sign of how depleted their numbers have become, because of overfishing and habitat loss. I mean if it's a choice between asexual reproduction and total extinction, what would you choose?

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