How Climate Change Shaped This Adorable Skunk’s Evolution

The Field Museum/Robby Heischman
The Field Museum/Robby Heischman

If you’re like many people, you’ve often thought, “Boy, am I sure glad there are lots of types of spotted skunks.” (Us too.) And thanks to science, we now know whom to thank for this wonderful diversity: climate change. A report on the sweet-faced skunks’ strange history was published this week in the journal Ecology and Evolution.


Robert C. Dowler

The western spotted skunk (Spilogale gracilis) is a button-nosed, wee critter, maxing out at around just 2 pounds. To maximize its stench-dispersal powers, the skunk flings itself into a little handstand, waving its back legs and rear in the air as noxious gas sprays from a gland under its tail.


Jerry W. Dragoo

For all its exotic appeal, S. gracilis is surprisingly local, making its home up and down the left side of North America from the temperate rainforests of the Pacific Northwest to the hottest desert in Mexico.

Speciation, or the splitting of one species into two, usually happens when two populations of organisms are divided by some physical boundary, like a mountain or a waterfall. Because the two groups are living in slightly different environments, they face slightly different pressures, and eventually evolve into slightly different creatures.

To find out if that’s what happened with S. gracilis, the authors of the current study collected DNA samples from 97 skunks in a range of habitats and areas of the American Southwest.


Sampling skunks is odiferous work.
The Field Museum

They found that the skunks could be divided into three subtypes. But the subtypes aren’t separated by rivers or mountain ranges, nor have they ever been. Instead, the researchers say, the family was split up by climate change a very, very long time ago.

“Western spotted skunks have been around for a million years, since the Pleistocene Ice Age,” lead author Adam Ferguson, of The Field Museum and Texas Tech University, said in a statement. “During the Ice Age, western North America was mostly covered by glaciers, and there were patches of suitable climates for the skunks separated by patches of unsuitable climates.”

It was largely these shifting patches of hostile terrain that kept the skunk families apart. These findings are important not only for lovers of skunk history, but for scientists, conservationists, and policy-makers who care about where our planet and its inhabitants are going.

“What we know about the past can inform what we expect to see in the future,” says Ferguson. “Understanding these genetic subdivisions that happened as a result of changing climatic conditions can help us conserve skunks and other animals in the future.”

Fossilized Fat Shows 550-Million-Year-Old Sea Creature May Have Been the World's First Animal

Ilya Bobrovskiy, the Australian National University
Ilya Bobrovskiy, the Australian National University

A bizarre sea creature whose fossils look like a cross between a leaf and a fingerprint may be Earth's oldest known animal, dating back 558 million years.

As New Scientist reports, researchers from the Australian National University (ANU) made a fortunate find in a remote region of Russia: a Dickinsonia fossil with fat molecules still attached. These odd, oval-shaped creatures were soft-bodied, had rib structures running down their sides, and grew about 4.5 feet long. They were as “strange as life on another planet,” researchers wrote in the abstract of a new paper published in the journal Science.

Another variety of fossil
Ilya Bobrovskiy, the Australian National University

Although Dickinsonia fossils were first discovered in South Australia in 1946, researchers lacked the organic matter needed to classify this creature. "Scientists have been fighting for more than 75 years over what Dickinsonia and other bizarre fossils of the Edicaran biota were: giant single-celled amoeba, lichen, failed experiments of evolution, or the earliest animals on Earth,” senior author Jochen Brocks, an associate professor at ANU, said in a statement.

With the discovery of cholesterol molecules—which are found in almost all animals, but not in other organisms like bacteria and amoebas—scientists can say that Dickinsonia were animals. The creatures swam the seas during the Ediacaran Period, 635 million to 542 million years ago. More complex organisms like mollusks, worms, and sponges didn’t emerge until 20 million years later.

The fossil with fat molecules was found on cliffs near the White Sea in an area of northwest Russia that was so remote that researchers had to take a helicopter to get there. Collecting the samples was a death-defying feat, too.

“I had to hang over the edge of a cliff on ropes and dig out huge blocks of sandstone, throw them down, wash the sandstone, and repeat this process until I found the fossils I was after,” lead author Ilya Bobrovskiy of ANU said. Considering that this find could change our understanding of Earth’s earliest life forms, it seems the risk was worth it.

[h/t New Scientist]

The Weird, Disturbing World of Snail Sex

iStock
iStock

Romance is rare in the animal kingdom. Instead of wooing their partners before copulating, male ducks force themselves onto females, depositing genetic material with spiky, corkscrew penises. Then, there's tardigrade sex, which is less violent but not exactly heartwarming. Females lay eggs into a husk of dead skin. The male then ejaculates onto the eggs while stroking the female, and the whole process can take up to an hour.

But you can't talk about disturbing mating rituals in nature without mentioning snails. If you're unfamiliar with snail sexuality, you may assume that snail sex falls on the vanilla side: The mollusks, after all, are famous for being slow-moving and they don't even have limbs. But if you have the patience to watch a pair of snails going at it, you'll notice that things get interesting.

The first factor that complicates snail sex is their genitalia. Snails are hermaphrodites, meaning individuals have both a male set and female set of parts, and any two snails can reproduce with each other regardless of sex. But in order for a couple of snails to make little snail babies, one of them needs to take on the role of the female. That's where the love dart comes in.

The love dart, technically called a gypsobelum, isn't exactly the Cupid's arrow the name suggests. It's a nail-clipping-sized spike that snails jab into their partners about 30 minutes before the actual sex act takes place. The sliver is packed with hormones that prepare the receiving snail's body for sperm. Depending on the species, only one snail might release the dart, or they both might in an attempt to avoid becoming the female of the pair. You can watch the action in the video below.

For sex to be successful, both snails must insert their penises into the other's vaginal tracts at the same time. Both snails deposit sperm, and the strength of the love dart ultimately determines whether or not that sperm fertilizes their partner's eggs.

That's assuming the snail survives the little love-stab. In human proportions, the love dart is the equivalent of a 15-inch knife. Fortunately, snails are resilient creatures, and gastropod researcher Joris Koene tells KQED he's only ever seen one snail die from the transfer.

Snails also have a way of making it up to their partners after skewering them with a hormone stick. Their sperm deposit contains a dose of fortifying nutrients, something scientists refer to as a nuptial gift. It may not equal the energy expended during sex, but its enough to give them a small post-coital boost.

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