Some Fish Eggs Can Hatch After Being Pooped Out by Swans

iStock/olaser
iStock/olaser

A question that’s often baffled scientists is how certain species of fish can sometimes appear—and even proliferate—in isolated bodies of water not previously known to harbor them. A new study has demonstrated that the most unlikely explanation might actually be correct: It’s possible they fell from the sky.

Specifically, from the rear end of a swan.

A study in the journal Ecology by researchers at the Unisinos University in Brazil found that killifish eggs can, in rare cases, survive being swallowed by swans, enduring a journey through their digestive tracts before being excreted out. This kind of fecal public transportation system explains how killifish can pop up in ponds, flood waters, and other water bodies that would seem an unlikely place for species to suddenly appear.

After discovering that some plants could survive being ingested and then flourish in swan poop, researchers took notice of a killifish egg present in a frozen fecal sample. They set about mixing two species of killifish eggs into the food supply of coscoroba swans living in a zoo. After waiting a day, they collected the poop and dug in looking for the eggs.

Of the 650 eggs they estimated to have been ingested by the swans, about five were left intact. Of those, three continued to develop. Two died of a fungal infection, but one survived, enduring 30 hours in the gut and hatching 49 days after being excreted.

Because killifish eggs have a thick outer membrane, or chorion, they stand a chance of coming through the digestive tract of an animal intact. Not all of what a swan ingests will be absorbed; their stomachs are built to extract nutrients quickly and get rid of the whatever's left so the birds can eat again. In rare cases, that can mean an egg that can go on to prosper.

Not all fish eggs are so durable, and not all fish are quite like the killifish. Dubbed the "most extreme" fish on Earth by the BBC, killifish have adapted to popping up in strange environments where water may eventually dry up. They typically live for a year and deposit eggs that can survive in soil, delaying their development until conditions—say, not being inside a swan—are optimal. One species, the mangrove killifish, can even breathe through its skin. When water recedes, they can survive on land for over two months, waddling on their bellies or using their tails to "jump" and eat insects. A fish that can survive on dry land probably doesn't sweat having to live in poop.

The researchers plan to study carp eggs next to see if they, too, can go through a lot of crap to get to where they’re going.

[h/t The New York Times]

100 Dachshunds Competed in Cincinnati’s Annual ‘Running of the Wieners’

NORRIE3699/iStock via Getty Images
NORRIE3699/iStock via Getty Images

Every year, to kick off Cincinnati’s Oktoberfest Zinzinnati, 100 dachshunds compete in heats to decide who the fastest dachshund in the Midwest is. This year marks the 43rd annual Oktoberfest—one of the biggest Oktoberfest celebrations outside of Germany (more than 500,000 people attend the three-day event).

On the afternoon of Thursday, September 19, 100 wiener dogs (and their owners and handlers) gathered in downtown Cincinnati for the 2019 "Running of the Wieners." The dogs, dressed in hot dog costumes, ran 10 heats, which lasted 75 feet or five seconds each. The winner of each heat advanced to the final round, where the top three finishers were decided.

Maple, a long-haired, one-year-old dachshund, ran his way into first place—and into our hearts.

Maple’s owner, Jake Sander, told WCPO that Maple is one of five dachshunds in the family, and that he learned to run fast by chasing his brother around. Leo and Bucky, two other doxies, placed second and third, respectively.

Besides the Running of the Wieners, Zinzinnati also hosts the World’s Largest Chicken Dance. However, the wiener dogs are more fun to watch.

Photographer Captures Polka-Dotted Zebra Foal in Kenya

Frank Liu
Frank Liu

Zebras are known for their eye-catching patterns, but this polka-dotted foal recently photographed in Kenya's Masai Mara National Reserve really stands out from the herd. As National Geographic reports, the zebra baby likely has pseudomelanism, a rare pigment condition that's been observed in the wild just a handful of times.

Nature photographer Frank Liu saw the zebra foal while looking for rhinos in the savannah wilderness preserve. After initially confusing the specimen for a different type of animal, he realized upon closer inspection that it was actually a plains zebra born with spots instead of stripes. The newborn foal was named Tira after the Maasai guide Antony Tira who first pointed him out.

Zebra foal with spots walking with mother.
Frank Liu

Zebra foal with spots.
Frank Liu

A typical zebra pattern is the result of pigment cells called melanocytes, which are responsible for the black base coat, and melanin, which gives the animal its white stripes. (So if you've ever wondered if zebras are white with black stripes or black with white stripes, the answer is the latter). In Tira and other zebras with pseudomelanism, the melanocytes are fully expressed, but a genetic mutation causes the melanin to appear as dots rather than unbroken stripes.


View this post on Instagram

A post shared by Frank Liu (@frankliuphotography) on

Though rare, this isn't the only time a zebra with pseudomelanism has been documented in nature. Pseudomelanistic zebras have also been spotted in Botswana’s Okavango Delta, but Liu believes this could be the first time one was found in the Masai Mara preserve.

Zebra stripes aren't just for decoration. The distinct pattern may act as camouflage, bug repellant, and a built-in temperature regulation system. Without these evolutionary benefits, Tira has a lower chance of making it to adulthood: Pseudomelanistic zebra adults are rarely observed for this reason. But as Liu's photographs show, the foal has the protection and acceptance of his herd on his side.

[h/t National Geographic]

SECTIONS

arrow
LIVE SMARTER