A bat eating from a banana flower

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Fast food for bats

Just like cheeseburgers, too many fast bananas makes for an unhappy meal for bats.

Banana flowers are fully of tasty sugars that nectar-feeding bats love to indulge in, but this might not be great for their gut – especially if they are mass-produced bananas.

“Organic and conventional monoculture banana plantations both provide a very reliable food source for some nectar-feeding bat species,” explains Priscilla Alpízar, first author of the study published in Frontiers.

“However, bats foraging in the intensively managed plantations had a reduced diversity of gut microbes, which could be a sign of gut dysbiosis, an unhealthy imbalance of its microbial symbionts.

“In contrast, bats foraging in the organic banana plantations had diverse and individualized gut microbiotas that were more akin to their natural forest-foraging counterparts.”

The study suggests that large banana farms –  AKA BatDonalds – can be detrimental to native wildlife because their gut biome is essential to keeping them healthy.

Blood sisters

Moving on from bananas to blood…

It’s not exactly Sex and the City, but female vampire bats (Desmodus rotundus) like to hunt with their girlfriends.

Researchers tagged 50 female vampire bats in Tolé, Panama, and found that they preferentially “met up with” their roost-mates when foraging. The bats also used three distinct calls to communicatee: “downward sweeping” social calls, antagonistic “buzz” calls, and “n-shaped” feeding calls.

The study, published in BLOS Biology, suggests that the bats choose “trusted” bats to forage with to keep themselves safe. This collaboration may help them save time when looking for prey or choosing where to bite. Using the different calls, they may also be able to quickly judge friend from foe when flying.

Earless worms still listen

Earless worms need not worry, because they can just listen through their skin instead.

Researchers, led by Shawn Xu from the University of Michigan, US, found that some earless worms (Caenorhabditis elegans) can still response to sound because their skin picks up the soundwaves instead.

These are the same worms that see without eyes.

“There was just one more primary sense missing – auditory sensation, or hearing,” says Xu.

“But hearing is unlike other senses, which are found widely across other animal phyla. It’s really only been discovered in vertebrates and some arthropods. And the vast majority of invertebrate species are thus believed to be sound insensitive.”

The researchers played soundwaves to the worms, which quickly moved away from the source of the sound. Instead, the researchers described the wobbly body as a “whole-body cochlear” as the skin and fluid inside the worm vibrated like the cochlea in a human ear.

“Our study shows that we cannot just assume that organisms that lack ears cannot sense sound,” says Xu.

“We believe the sense of hearing has probably evolved independently, multiple times across different animal phyla. We knew that hearing looks very different between vertebrates and arthropods.

“Now, with C. elegans, we have found yet another different pathway for this sensory function, indicating convergent evolution. This stands in sharp contrast to the evolution of vision, which, as proposed by Charles Darwin, occurred quite early and probably only once with a common ancestor.”

The study was published in Neuron.

Robots inspired by… sperm?

Cornell University scientists have created cell-sized swimming robots that can be steered by ultrasound waves. Credit: Cornell University

These little swimmers are a bit different to what you might imagine.

Researchers at Cornell University, US, had created tiny cell-sized robots that are powered by ultrasound waves. They can be remotely controlled to swim around the human body to deliver drugs.

Their inspiration: The swimming motion of sperm and some bacteria.

But how to power it? By using bubbles and soundwaves, of course.

“Bacteria and sperm basically consume organic material in the surrounding fluid, and that is sufficient to power them,” says Mingming Wu, who leads the lab. “But for engineered robots it’s tough, because if they carry a battery, it’s too heavy for them to move.”

The robot has tiny hydrophobic cavities that cause little air bubbles to cling to its surface. These air bubbles oscillate when an ultrasound transducer is aimed at the robot, propelling it forward. The robot can be turned to the left or right depending on which bubble is oscillated.

“For drug delivery, you could have a group of micro-robotic swimmers, and if one failed during the journey, that’s not a problem; that’s how nature survives,” Wu says.

“In a way, it’s a more robust system. Smaller does not mean weaker. A group of them is undefeatable. I feel like these nature-inspired tools typically are more sustainable, because nature has proved it works.”

The paper was published in Lab on a Chip.

Schematic of the swimmer and electron microscope image of a swimmer (top left). Credit: Cornell University

Galaxies running low on gas

Gas – the stuff stars run on – is an essential star-making ingredient for galaxies.

Now, a team of astronomers led by Kate Whitaker from University of Massachusetts, US, have found six galaxies that are running very low on gas and have stopped making stars.

These galaxies have become inactive, or “quietescent”, because they literally don’t have the fuel. This is a hypothesis astronomers have had for a long time, but didn’t enough data to back it up.

The galaxy cluster MACSJ0138.0-2155 magnifies and distorts the image of a galaxy at a distance of 17 billion lightyears, enabling astronomers to study it in great detail. Credit: ESA/Hubble & NASA, A. Newman, M. Akhshik, K. Whitaker.

“For a long time, we have suspected that running out of gas is one of the main reasons that some galaxies cease to form star – but now we have the evidence,” explains Georgios Magdis of the University of Copenhagen, Denmark, who was part of the team that discovered the six galaxies.

But the reason why these galaxies ran out of gas is still a mystery.

“Did a supermassive black hole in the galaxy’s centre turn on and heat up all the gas?” ponders Whitaker. “If so, the gas could still be there, but now it’s [too] hot.

“Was the gas blown out of the galaxy? Or did the galaxy simply use it all up? These are some of the open questions that we’ll continue to explore with new observations down the road.”