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]

A Same-Sex Penguin Couple Has Adopted an Egg at a Berlin Zoo

LisaStratchan/iStock via Getty Images
LisaStratchan/iStock via Getty Images

At first glance, king penguins Skip and Ping don’t appear to be too remarkable a sight when viewed by spectators at their enclosure at Germany's Zoo Berlin. But look closer and you may see one of them nurturing an egg under one of their skin folds. Skip and Ping, a same-sex penguin couple, have effectively adopted an egg and hope to raise it as their own baby.

A story by writer Liam Stack in The New York Times details their pursuit of parenthood. According to Stack, the penguins arrived at Zoo Berlin in April and were observed to have a degree of baby fever, trying to coddle everything from a rock to a fish. Taking note of their coupling, zookeepers passed on an unhatched egg laid by a female at the zoo. They immediately took to it, taking protective measures and growing ornery when employees got too close. Ping has taken to sitting on the egg in the hopes it will hatch.

That’s not guaranteed. Zookeepers aren't certain whether the egg was fertilized. If it is, it’s likely to crack open in early September, giving Skip and Ping an opportunity to expand their family.

Earlier this year, a same-sex penguin pair named Sphen and Magic began rearing a chick in Australia’s Sea Life Sydney Aquarium. The doting parents sang to and fed their adoptive offspring.

[h/t The New York Times]

Airlines Are No Longer Allowed to Ban Service Dogs Based on Breed

chaivit/iStock via Getty Images
chaivit/iStock via Getty Images

As the species of service and emotional support animals have become more diverse, airlines have had to make some tough decisions. Birds, monkeys, and snakes have been barred from boarding airplanes with passengers, but even more conventional pets like dogs have been rejected based on their breed. A new rule from the U.S. Department of Transportation (DOT) aims to change that. As Travel + Leisure reports, the agency now forbids airlines from discriminating against service dogs of particular breeds, including pit bulls.

Last year, Delta banned all pit bulls from flying, regardless of whether or not they were certified therapy animals. United Airlines also banned pit bulls last year, along with 20 other dog breeds, including pugs, bulldogs, mastiffs, and shih tzus.

Under the new DOT guidelines, these policies are no longer legal. The statement reads: "The Department’s Enforcement Office views a limitation based exclusively on breed of the service animal to not be allowed under its service animal regulation. The Enforcement Office intends to use available resources to ensure that dogs as a species are accepted for transport."

The new rule applies specifically to service animals, or animals that have been trained to perform a job that's essential to their owner's wellbeing. Emotional support animals, which don't require special training and aren't covered by the Americans With Disabilities Act, don't qualify.

Even if a pet is a certified service animal, airlines still have the right to reject them in certain cases. Air travel companies can request documents related to an animal's vaccination, training, or behavior history. If they find anything in the papers that indicates they're not safe to fly, airlines can turn them away on that basis.

In the same statement, the Department of Transportation clarifies which species of service animals should be allowed on flights. Miniature horses are now included on the list of service animals airlines must allow to fly, while ferrets, rodents, snakes, reptiles, and spiders are the only species airlines can ban outright.

[h/t Travel + Leisure]

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