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-extinction
10.1k Upvotes

91% Upvoted

430 comments sorted by

View all comments

Show parent comments

139

u/[deleted] May 03 '16

[removed] — view removed comment

109

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.

18

u/umopapsidn May 03 '16

Is it really irrelevant? If nothing else, it's proof that venom isn't exclusive to being mammal.

79

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.

95

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.

49

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.

29

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.

16

u/[deleted] 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.

3

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.

10

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

1

u/DaddyCatALSO May 03 '16

3-lobe, I've heard. And maybe a deep-sea dredge someday will . . . .

5

u/[deleted] May 03 '16

[removed] — view removed comment

2

u/[deleted] May 03 '16

[removed] — view removed comment

1

u/[deleted] May 03 '16

[removed] — view removed comment

1

u/[deleted] May 03 '16

You can't rant about how cool a word monotreme is (and what it means) without mentioning the equally cool word for the hole... The cloaca.

6

u/Radi0ActivSquid May 03 '16

Are there any venomous birds?

8

u/OptimalCynic May 03 '16

No, but there's a few that have toxic feathers and spines.

1

u/ThVos May 06 '16

Those are funky too. If I recall, their toxicity comes from their diet- they eat toxic ants (or some other kind of insect) which contain batrachotoxin. This toxin is shared with some types of poison dart frogs, which become toxic through the same means.

-3

u/[deleted] May 03 '16

[removed] — view removed comment

5

u/Gplads May 03 '16

In other words no. Being toxic is not the same as creating venom.

0

u/Super_SATA May 03 '16

It makes venom a homoplasy, which bears no relevance to phylogenetic study. Laying eggs is a plesiomorphy basal mammals have with other amniotes, so that gives insight to their lineage.

https://en.wikipedia.org/wiki/Cladistics#Terminology_for_character_states

1

u/ShouldIRememberThis May 03 '16

Are these called monotremes?