Space jellies, zombie guppies and urination physics: A weird week for science

1. Jellyfish dizzy on their return to planet Earth

Back in 1991, the shuttle Columbia carried 2,478 jellyfish polyps to the International Space Station, the Atlantic Magazine‘s Megan Garber reported yesterday. By the missions end, there were about 60,000 jellyfish orbiting the Earth.

Why send jellyfish to space? Well, to find out what would happen if a human baby were born in space and then returned home, of course.

Jellyfish and humans don’t share much in terms of body parts, but one thing they do share is those tiny crystals that help us determine motion and gravity. In humans, these crystals are made of calcium carbonate and are located in the ear, where they stimulate nerve cells and communicate to the brain movement and orientation. In jellyfish, these crystals are made of calcium sulfate line the edges of the animal’s bell.

After being raised in space, the jellies were returned to Earth and observed. Unfortunately for those hypothetical space babies, the jellies did not enjoy an uneventful homecoming. As biologist RR Helms at Deep Sea News reports, the jellies were essentially suffering from a permanent case of vertigo: their motor abilities were hindered and their movements were not similar to those of Earth-born jellies.

Read the full stories here: I Don’t Think You’re Ready for This, Jelly” and “Jellyfish go to space, say it was “meh, kinda sucky”

2. Zombie baby guppies born from dead fathers

In a recent issue of the Journal of Experimental Biology, Andy Turko reports that researchers have discovered that 25% of all guppies in a Trinidad river population were conceived posthumously…after the biological father died.

Female Trinidadian guppies can store sperm up to a full year, the last male to fertilize the female’s eggs generally wins in the genetic race. In their investigation of stored sperm in female guppies, Andres Lopez-Sepulcre and his team of international scientists painstakingly tracked a changing population of guppies at a site in the Guanapo River in Trinidad. They tracked who died when and who parented whom by taking scale samples from baby guppies and determining their genetic parentage:

The research team found that almost 50% of reproductively active males sired young after they had died and, amazingly, over 30% of reproductive males were successful only after they were dead. Some offspring were even fathered by males that had been dead for 8 months.

Female guppies live almost five times as long as male guppies, so the researchers think this tactic may have evolved to protect genetic material of the short lived males. From the female prospective, Turko reports:

[T]he researchers proposed that using sperm from many males, both dead and alive, would produce offspring with higher genetic diversity. In a fluctuating habitat like a Trinidadian stream, this should increase the odds of producing some offspring that are genetically well suited to whatever environmental conditions the future has in store.


3. Law of urination discovered

Have you ever wondered how to calculate the rate of urine flow for any mammal? Well, wonder no more! New Scientist‘s Jacob Aron reported yesterday about a team of scientists from the Georgia Institute of Technology, who were filming animals at a local zoo when they noticed that animals of “various sizes, both male and female, took a similar time to empty their bladders.” Like any curious scientist would do, Patricia Yang and her team decided to investigate the phenomenon.

Turns out mammals like dogs, cows, goats and elephants all take about 21 seconds to urinate. It has to do with bladder size, urethra length and that mysterious force of the universe: gravity.

In this case size matters, as it means urine feels the pull of gravity stronger at the bottom of the elephant’s urethra. This means that as it travels down the pipe, the urine accelerates and its flow rate rises, resulting in an elephant’s large bladder being emptied in a similar time to those of smaller animals.

Medium-sized animals like dogs and goats have shorter urethras, so get less of a gravitational boost: their flow is slower. In addition, they have smaller bladders. The result of both effects is that they empty their bladders in roughly the same time as elephants.

The law of urination, as Aron reports, says that “the time a mammal takes to empty a full bladder is proportional to the animal’s mass raised to the power of sixth.”

Read the full story here: “Universal law of urination found in mammals” (there’s even a video!)