Yfke van Bergen

EATING ON THE MOVE

With their puny legs and graceful wings, it’s clear that bats evolved to fly, not walk. Yet some bats are surprisingly good at scurrying along the ground in pursuit of their prey. Vampire bats are particularly agile crawlers and have chunkier legs than other bats. This has led to the suggestion that other bats are poor walkers because their hind limbs are too weak to cope with the forces associated with pounding the ground; their fragile legs would simply snap if they tried to support their body weight. Armed with a specially designed walkway for bats, Daniel Riskin at Cornell University set out to test this hindlimbstrength hypothesis (p. 1309).

ANGELFISH TAKE SPONGE REEFS BY STORM

When Nicolai Konow flew to Australia to begin his PhD with David Bellwood at James Cook University, he was planning to work on butterflyfish. But once he saw his first angelfish, there was no turning back. Swimming with these colourful reef fish, he realised that ‘they do things with their jaws that no other fish do!’ Puzzled by their peculiar mouths, Konow set out to unravel angelfish’s biomechanical secrets (p. 1421).

VIRTUAL REALITY LAB RATS ARE ON THE BALL

We may spend inordinate amounts of time removing unwanted body hair, but hairy body parts are a matter of life or death if you’re a cricket. Perched on the end of a cricket’s abdomen is a small pair of hairy appendages called cerci. The cerci’s mechanosensory hairs are sensitive to the slight air currents generated by wasps’ wings or toads’ tongues, alerting the cricket so it can make a timely escape from a predator sneaking up from behind. But nobody has looked to see how structural variability in the cerci’s sensory hairs influences crickets’ predator detection performance. To find out how morphological variability affects sensitivity to predators, Olivier Dangles and colleagues in Jérôme Casas’ team at the University of Tours decided to measure the hairy appendages of crickets living in a range of environments (p. 461).

MUTABLE FEET GET A GRIP

To see how stick insects initiate changes in direction during walking, Dürr and Ebeling examined the sequence of stick insects’ leg movements during straight and curved walking. They tethered stick insects onto an air-cushioned Styrofoam ball and videotaped them as they sauntered across the top of the ball. At the same time, they recorded in which direction the insects walked by tracking the rotation and backward and sideward translations of the ball using motion sensors. They filmed the insects walking in a straight line and then rotated a black and white pattern around the insects – a visual motion stimulus that they knew would provoke the insects to start turning.

MANTIS SHRIMP DELIVER DOUBLE WHAMMY

Small insects like fruit flies don’t bother with ventilation mechanisms to breathe, they simply rely on diffusion to supply their tissues with oxygen – at least, that’s what many researchers thought. Now, a study by Fritz Lehmann and Nicole Heymann suggests that this conclusion was a bit premature. Studying CO2 release in flying fruit flies, the pair discovered that these tiny insects do indeed ventilate, but in a rather unconventional way: they use their “tongue” as a pump (p.·3645)!

FOLLOW THE WAGGLE DANCE FOR A SHORTCUT

Nobel laureate Karl von Frisch was one of the first to describe the remarkable waggle dance that honeybees perform to direct other colony members to a tasty food source. Since his pioneering work, numerous researchers have taken up the challenge to decipher the components of this intriguing ‘dance communication’. Now, Rodrigo De Marco and Randolf Menzel at the Free University of Berlin reveal how a bee incorporates information about the whereabouts of a sugary treat into her waggle dance (p.·3885).

BLUE BLOODS: HOW A CRAB MAKES ITS SHELL

Messerli and his Woods Hole colleagues decided to see if the microalgae maintain a neutral pH inside their cells. When they loaded a fluorescent pH-sensitive dye into the algal cells and monitored the cells’ fluorescent intensity, they found that the pH inside the algal cells is indeed close to neutral. And when they moved the algal cells to different pH levels, their internal pH didn’t change; the cells clearly control their neutral internal pH. ‘So there is a huge proton gradient between the neutral algal cell and the acidic river,’ Messerli says.

HYDRA FINDS A PLANT GENE IN THE FAMILY TREE

Habetha and Bosch are intrigued by the genetic basis of the relationship between Hydra viridis and Chlorella, the algal symbiont that lives in Hydra’s epithelial cells and gives the creature its familiar green colour. Since all eukaryotic cells are products of symbiosis between once freeliving bacteria, ‘studying this ancient interkingdom communication process can provide us with interesting evolutionary insights,’ Bosch says. Habetha and Bosch want to know which genes are activated when Hydra harbours its symbiont, to find out what regulates this intimate coexistence.

CLICKING PORPOISES GET THEIR BEARINGS

During steamy summers, itchy bites remind us that female mosquitoes are remarkably adept at tracking us down. To add insult to injury, mosquitoes urinate on us while they greedily gorge on our blood. As Geoff Coast explains, feeding mosquitoes swell up to twice their size, and to make sure that they can still take off after their feast, the insects urgently need to pump out all the unwanted water and salts from their blood meal. In the 1980s, Klaus Beyenbach and his colleagues reported that mosquitoes solve this problem by flushing out copious amounts of sodium-rich urine. They found that the insects release a peptide that triggers sodium-rich urine production, and they dubbed this hormone mosquito natriuretic peptide, or MNP. For years, MNP’s chemical identity remained elusive. Now, Coast and his colleagues reveal that MNP is a calcitonin-like diuretic hormone (p.·3281).

ARCTIC CORMORANTS ARE TRUE SURVIVORS

Arctic great cormorants are poorly equipped to cope with harsh polar winters; they have very meagre fat reserves and their partly wettable plumage offers little insulation. Yet a small population of these diving birds stubbornly overwinters north of the polar circle, along the coast of Greenland. Suspecting that the birds have physiological or behavioural adaptations to survive in their hostile home, David Grémillet and his colleagues painstakingly collected physiological data from great cormorants for an entire year. Incredibly, they found that cormorants don’t appear to have any such adaptations, yet still make it through the Arctic winter (p.·4231).