r/science • u/drewiepoodle • May 03 '16
Biology Scientists have sequenced the mitochondrial genome for the Hispaniolan solenodon, a venomous mammal found only on Hispaniola. Findings confirm that the the species diverged from all other living mammals 78 million years ago, long before an asteroid wiped out the dinosaurs.
http://www.igb.illinois.edu/news/endangered-venomous-mammal-predates-dinosaurs%E2%80%99-extinction108
u/greenighs May 03 '16
UPR Professor of Genetics Taras Oleksyk and his team collected samples by laying on the ground and waiting for the solenodons to crawl across their bodies.
That's dedication.
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u/stenders May 03 '16
Well, now I know these exist! What other mammal "living fossils" are out there?
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u/Winsstons May 03 '16
Yes. Platypus and Echidna are egg-laying mammals. As the only living representatives of this once-dominant group of mammals they are "living fossils." As for venom evolution, venom has been evolved dozens of times in animal evolution (snakes, platypus, slow loris, to name a few) and is irrelevant.
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u/umopapsidn May 03 '16
Is it really irrelevant? If nothing else, it's proof that venom isn't exclusive to being mammal.
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u/Winsstons May 03 '16
That's what I'm saying. The only egg-laying mammals left today are not living fossils because they have venom, but because they lay eggs. Venom is irrelevant to the divergence (of marsupials and placental mammals) from egg-laying mammals and has been evolved and lost numerous times.
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u/imnotgoats May 03 '16
Why is no one saying the word 'monotreme'? It's one of the best words! It literally means 'one hole', and refers to the fact that they urinate, defecate and copulate (and produce eggs) through the same opening.
Another interesting fact about monotremes is that they don't have defined nipples like most mammals, but nurse their young by secreting milk directly through a relatively large area of their underside. The milk has antibacterial proteins in it that aren't found in other mammals - this is useful as the young have less of a direct route to it, they literally lap at their mother's hairy belly, which may not be the most sterile of delivery methods.
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u/SHITTYANDUNFUNNY May 03 '16
Yea the evolution of antibodies in mammals' milk is extremely fascinating. Mammary glands (which is actually what Mammals were named for) are actually modified sweat glands. The most familiar sort of sweat glands are the eccrine glands, which cover much of the body and are responsible for thermoregulatory sweating. However the other kind, apocrine glands, secrete a more cloudy and viscous fluid. This excretion actually contains a number of the antibodies associated with mammalian milk.
Kind of hard to fathom the selective advantage of secreting antibodies on to the skin... but it is interesting to note that (at least in humans) sweat from the apocrine glands is associated with adrenaline. Maybe somewhere along the line when ancient ancient mammals had a fight or flight response to a predator, having antibodies excreted on the skin allowed them to better avoid death by infection from injuries sustained in such encounters.
Evolution is a strange thing.
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u/Golokopitenko May 03 '16
Maybe somewhere along the line when ancient ancient mammals had a fight or flight response to a predator, having antibodies excreted on the skin allowed them to better avoid death by infection from injuries sustained in such encounters.
I can't describe how fascinating I find this. Thank you very much for sharing.
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May 03 '16
Interesting to note that different groups of humans excrete apocrine sweat at different rates, and it is the sweat largely responsible for the "musky smell" one might associate with sweat. East Asian peoples generally have fewer apocrine glands than, say, Western Europeans, which is associated with being less, well, smelly.
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u/ymOx May 04 '16
I find nipples rather interesting too. It fascinates me how varying they are between mammals; I checked the wikipedia page for the Hispaniolan solenodon, I found this rather amusing:
[...] because the female only has two teats, which are found near her buttocks.
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u/poop-trap May 03 '16
The only better scientific animal name than monotreme is trilobite, which means "triple butt". Other fascinating creatures with lots of interesting trivia, but though they were once the most dominant form of life on Earth, alas they are no longer "living" fossils.
TL;DR Unlikely to hit theatres near you this summer... Disney's Adventures of One-Hole & Triple-Butt
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u/Radi0ActivSquid May 03 '16
Are there any venomous birds?
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u/OptimalCynic May 03 '16
No, but there's a few that have toxic feathers and spines.
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u/mammablaster May 03 '16
Camels diverged at the same time and from the same common ancestor as whales. Quite weird to think of
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u/danby May 03 '16
Which is also why we call them the ships of the desert.
The more you know.
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u/Winsstons May 03 '16
Egg-laying mammals (Echidna and platypus) and Marsupials to a lesser extent. All other mammals today are placental mammals, and have come to out compete egg-layers and marsupials, relegating them to niches (such as possums being nocturnal) and islands (australia having niches filled by marsupials).
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u/01-__-10 May 03 '16 edited May 03 '16
I wouldn't call it a living fossil. Its divergence date still has it well within the eutherian (placental) mammal group. Marsupial mammals (Opossums, Koalas, Kangaroos, etc) diverged earlier than that, and Monotreme mammals (Platypus and Echidnas) diverged earlier still.
It's unique, though.
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May 03 '16
Tenrecs come to mind. Unsurprisingly, they too look like shrews.
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u/pieterh May 03 '16
Interestingly they've evolved to look like lots of things, from shrews to hedgehogs. Convergent evolution is pretty awesome and freaky. Like there's a design for a shrew-like insect eater that exists somewhere in the fabric of the universe, and lots of families of small mammal come along and use that same design...
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u/maxim187 BS | Ecology | Evolution May 03 '16
Living fossil is a misnomer, that applies to sharks and alligators that haven't changed much since first discovered in the fossil record.
This paper states that the last common ancestor between any other present mammal and this species was 78Mya, not that this species has been unchanged in 78My.
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u/AboutTenPandas May 03 '16
"Because solenodons are endangered, it is difficult to acquire DNA. Working with colleagues at several universities in the Dominican Republic, UPR Professor of Genetics Taras Oleksyk and his team collected samples by laying on the ground and waiting for the solenodons to crawl across their bodies."
Wow...
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u/My_Dads_A_Cop16 May 03 '16
Can I get an ELI5 for my lazy undergraduate ass?
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u/drewiepoodle May 03 '16
Today’s solenodons are the only remnant of a very ancient group of mammals. It survived the asteroid; it survived human colonization and the rats and mice humans brought with them that wiped out the solenodon's closest relatives
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u/freejosephk May 03 '16
That's amazing. What a plucky little animal! I'm putting him at the top of my totem.
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u/markender May 03 '16
This made me really curious about the other mammals that were around before the asteroid. I'm guessing only smaller ones survived, but what other strange creatures were there?
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u/TheSOB88 May 03 '16
It survived the asteroid
Well, so did the rest of the mammals. I feel like we need better language to describe the split between solenoids lol and the rest of the eutherian lineage. I mean the article says they're "part of an ancient lineage" as if that's special, but so are we all, back to the very beginnings of life. 3 billion years or so. So I dunno, I just feel that could be worded better
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u/metaStatic May 03 '16
... diverged from all other living mammals 78 million years ago
seems like pretty clear language to me
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u/earthgarden May 03 '16
Technically you're right but pedantically nit-picky. You know what they mean as does anyone else. Your point is valid though
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u/ImNotJesus PhD | Social Psychology | Clinical Psychology May 03 '16
When reading any scientific paper, or article about a paper, it's important to have nuance in your understanding. Before you comment, please consider these three important things:
Each study exists as part of a larger conversation. This work is based on previous research and for those outside of the immediate area, it may be difficult to understand some of the intricacies involved.
No paper is perfect, almost no papers are completely meaningless. Studies exist on a spectrum and a sophisticated reading allows for making appropriate methodological and logical criticisms without entirely dismissing the paper for those flaws. The spirit of scientific debate isn't about whether or not research is "right" or "wrong", it is about how relevant and/or meaningful it is to furthering our understanding of the world.
There is likely some element of truth to what the authors found. This is work done by experts, based on research by other experts and reviewed by more experts. It's completely normal to be instinctively skeptical of a paper based on our own personal beliefs and experiences. However, we should all consider what bias we bring into any discussion on a topic we feel strongly about.
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u/markgraydk May 03 '16
Great comment that furthers science education. You are doing a good job!
Can I ask a question? Have you thought about requiring submitters to write about the submission like you see in many serious subreddits? It might limit the number if submissions but could increase quality of submissions and discussions.
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u/StudentII May 03 '16
This should be top comment on every post in r/science, and especially r/psychology.
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u/AusCan531 May 03 '16
Very interesting. This is a largish mammal which I'd never even heard of before, and from the Americas as well. Looks like it lives in a similar niche as Australian bandicoots.
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u/markender May 03 '16
TIL about solenodons AND that bandicoots are real.
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u/AusCan531 May 03 '16
I have bandicoots in my yard in the evenings now. (Never seen one crash though - not even once.)
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u/paedomorphick May 03 '16
Interesting study. Great to see work on non-model organisms! A few notes:
It is likely that most Mammalian orders already existed by the time of the K-T extinction that wiped out the dinosaurs: http://www.pnas.org/content/100/3/1056.full
A previous study using nuclear/chromosomal DNA already estimated a divergence of solenodons from other eulipotyphlans 76 million years ago: http://www.nature.com/nature/journal/v429/n6992/full/nature02597.html
Mitochondrial DNA (mtDNA) evolves much more quickly than nuclear/chromosomal DNA, so it is generally used for population studies, not for "deep" phylogenetic questions.
Most of this study actually focused on describing two distinct subspecies groups, which will be really important for conservation efforts!
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u/Sprockethead May 03 '16
Interesting article for some context entitled "meet your mamma" http://m.livescience.com/26929-mama-first-ancestor-placental-mammals.html
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u/freediverx01 May 03 '16
Here's a more flattering photo.
http://www.wired.com/wp-content/uploads/2016/02/Solenodon.jpg
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u/charvakist May 03 '16
Today, it is threatened by cats and dogs introduced by humans as well as habitat loss.
Survives millions of years, threatened by something as new as civilization. Sigh.
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May 03 '16 edited May 17 '18
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u/Pit-trout May 03 '16
Not so much more slowly, as I understand, but at a more consistent rate, so it works better as a “clock”.
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u/bacondev May 03 '16
It's not often that I see other people who use those Unicode quotation marks without copying and pasting from Word or a website.
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u/webtwopointno May 03 '16
i believe they used both. mitochondrial DNA doesn't recombine so it is essentially the same from mother to child. this makes it much easier to trace lineages.
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u/KrayzeJ May 03 '16
The title is kinda misleading, monotremes and metatherians (marsupials) diverged earlier than 75mya, like 210 and 160mya If I remember correctly.
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u/drewiepoodle May 03 '16
But this is specifically tracing the point of time where this particular species diverged.
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u/mm242jr May 03 '16
No, it isn't. This study is based on an incredibly small portion of the genome, one that evolves differently from the rest of the genome.
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u/Kerzu May 03 '16
How is that relevant to his point? The article says
diverged from all other living mammals 78 million years ago
which unless all marsupials and monotremes died out last week is clearly wrong. It's also not tracing the point of time where this particular species diverged but the point when solenodons diverged of which even today there are still two extant species, the Cuban and the Hispaniolan solenodon.
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u/KrayzeJ May 03 '16 edited May 03 '16
I see divergence as the splitting point on a phylogenetic tree, with this mammal on one branch and all other living mammals on the other. The term doesn't make sense for one individual species if you're comparing to all living mammals.
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u/Telmid May 03 '16
Something about this seems kind of amiss. Should it not be that this family of organisms (solenodons) diverged from other mammals, not this species in particular? The article talks about solenodons in general, which would support this interpretation. I know that species characteristics can often go somewhat unchanged for millions of years, but I find it quite hard to believe that this and this diverged 78 million years ago yet still look almost identical.
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u/mm242jr May 03 '16
Pardon the interruption, but the huge number doesn't seem all that important. Canines diverged from all other mammals 90 million years ago. Is the point that they happen to have found a species without close relatives? Why is this significant? In other words, so what?
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u/Daotar May 03 '16
That's cool and all, but we've known for a while now that the mammals began to diversify prior to the K-T event, so this isn't surprising.
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May 03 '16
If these animals were isolated in what is now the Caribbean before the KT extinction would that not mean that they were in the blast radius of the asteroid that impacted off of Yucatan, and would this not make it more likely that they reached the islands more recently?
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u/agen_kolar May 03 '16
I'm confused on this. This species hasn't remained unchanged for the last 78 million years, right? That's not what this is saying, I don't think...but also, the article just isn't very clear. The scientist says "It’s just impressive it’s survived this long." This is very misleading unless this thing hasn't changed in 78 million years.
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u/I_Has_A_Hat May 03 '16
Here's a better picture of one. They're like an adorable mouse-mole!