At the end of every month, Janaki Lenin will quickly review interesting recent research on living things.
Ants forage far from their nests. How do they find their way around? Until now, scientists thought as the insects walked from their nests, they memorised the scenery on their path and used the orientation of their bodies as navigational aids. If they had to return to their nests with a heavy load, they walked backwards. Would backward-walking ants know to recalibrate the scenery despite the change in direction?
Scientists studied an Andalusian desert ant that forages alone unlike other ants that fan out in processions. They trained the ants to run a route with several right angle turns. When they gave them a heavy crumb that the insects couldn’t carry, they dragged their prize backwards. Every now and then, they dropped their loads, looked around, picked up the crumb and corrected their course.
Scientists found that the ants use the Sun and their memories of the outbound path to navigate. Different regions of their pinhead-sized brain memorise the path. Their understanding of the terrain is independent of their body orientation.
Hummingbirds see the world differently
A hummingbird beats its wings 80 times a second. It can hover in front of a flower, snatch flying insects, and fly backwards. It shoots through the air at nearly 50 kilometres per hour and can rev up to almost 100 kilometres per hour during courtship. Do these high speeds lead to a life on the fast lane? How does it see the world and react appropriately?
The part of the hummingbird’s brain that deals with movement is much larger than other birds. Typically, the neurons of other animals are tuned to detect motion coming from behind so they aren’t surprised by predators. Neurons in the hummingbird brain, however, appear to focus on movement in all directions. While it’s alert to the big picture, it suffers from a drawback unlike other animals – it can’t see predators approaching from behind.
Baboons produce vowel-like sounds
Scientists thought humans can talk because their larynx descended to its current location. Babies younger than a year, other primates, and Neanderthal man cannot articulate vowels because their voice box is located too high. Researchers studying babies and Neanderthals showed that a high larynx is not a handicap to making vowel sounds. But they didn’t know whether monkeys, especially baboons, could produce these sounds.
Now they have discovered that baboons can make at least five sounds that have the properties of vowels. Despite their larynx being situated high, they made sounds comparable to ɨ æ ɑ o u. They also produced a sequence of two vowel-like sounds that sounded like wahoo.
These sounds indicate that non-human primates could have a form of speech.
Predatory instinct at the flick of a switch
Scientists have identified how the brains of predators are wired. A bunch of neurons in the amygdala, the seat of emotion, motivates predators to pursue prey. Another group of neurons that control the muscles of the jaw and neck cause the animals bite and kill. These two groups are not connected and the drive to hunt is not related to eating.
By using laser stimulation, the researchers selectively activated these neurons in mice. When the laser was off, the mice behaved normally. But when it was turned on, the rodents acted like predators, chasing and biting bottle caps and wooden sticks. The hungrier they were, the worse the biting frenzy.
When the researchers activated the ‘hunting’ neurons but deactivated the ‘killing’ neurons, the mice pursued their inanimate prey but didn’t ‘kill’ them.
The team is now exploring how the neurons controlling pursuit and killing are coordinated.
An invading virus replicates rapidly or lies dormant. How does it choose its strategy?
While researchers were investigating communication between bacteria that were under attack, they found small molecules released by viruses. Other viruses could ‘read’ these molecules and thus coordinate their attacks.
The team infected bacteria with virus and then filtered them out of the culture, leaving only the growing medium. They grew more bacteria on the filtered medium and infected them with the same virus. Instead of going into attack mode, the new bacteriophages, or virus that infects bacteria, went dormant.
The researchers discovered a protein called peptide in the culture and identified the gene encoding it. When the new phages detected lots of peptide in the medium, they went dormant.
At the beginning of infection, viruses replicate fast and kill their hosts. Destroying hosts is a short-term strategy and they’d soon run out of fresh hosts to infect. At some stage, viruses switch from attack to bide-your-time mode. To communicate this change in strategy to the next generation, each successive generation uses peptides. The researchers called it the arbitrium system of communication, after the Latin word for decision.
The researchers identified each virus uses a different peptide so only others of its species can decode the message.
Seals may use their whiskers to find fish
Harbour seals can detect the turbulence created by fish as they make a getaway and follow their trail. The seals also prey on flatfish that hide in the sand. The fish remain still and blend with their surroundings. How do seals find these fish? These fish breathe by pumping water through their gills. Scientists think seals detect these faint water currents generated by the fish’s gills to find them. They conducted an experiment with three captive harbour seals. Even when the animals were blindfolded, they were able to detect water current that resembled breathing fish.
But flatfish may have a way of outwitting their predators. They may stop breathing when seals are around. With no water turbulence to give them away, they may escape attention and heave a sigh of relief.
A parasitic wasp manipulates the behaviour of another parasite
Science has just discovered the crypt-keeper wasp Euderus set from southeastern United States. The two-millimetre-long iridescent insect is a parasite of the crypt gall wasp Bassettia pallida, which makes galls in the developing stems of sand live oak trees.
The gall wasp develops within the woody growth it creates. In spring, it transforms into an adult and bores its way out of its crypt. The crypt-keeper wasp lays its egg in the developing gall wasp. When the infected gall wasp becomes an adult, its parasite begins to manipulate it. It bids the gall wasp drill a tiny exit hole, far too small for its body size. Eventually, the gall wasp dies while attempting to escape, with its head lodged against the hole.
When the crypt-keeper reaches adulthood, it eats its way through the gall wasp’s body before gobbling up the head and making good its escape. Euderus can’t drill a hole through the wood by itself. If its host doesn’t make the hole, it is more likely to die within the crypt-like gall. Neither can it let its host escape since a gaping hole would allow the elements in and kill the developing wasp.
Janaki Lenin is the author of My Husband and Other Animals. She lives in a forest with snake-man Rom Whitaker and tweets at @janakilenin.
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