Science

Flowers With Halos, Asexual Worms, Vicious Tadpoles and Other Amazing Animals

A quick review of interesting research on living things from the last month.

Ursinia speciosa. The region at the base of the petals contains a dark pigment but appear blue due to the presence of a floral disordered grating on the cell surface. Credit: Edwige Moyroud

Ursinia speciosa. The region at the base of the petals contains a dark pigment but appear blue due to the presence of a floral disordered grating on the cell surface. Credit: Edwige Moyroud

Flowers with halos

Plants have a blue pigment problem. Bee vision favours the blue end of the spectrum – blue, green, and ultraviolet, but only 10% of flowering plants bear blue flowers. Many of the others have evolved a clever workaround. Their colourful petals have microscopic ridges that scatter light creating a blue halo.

Scanning electron microscope image of an imprint from a tulip petal. Credit: Tobias Wenzel and Silvia VIgnolini

Scanning electron microscope image of an imprint from a tulip petal. Credit: Tobias Wenzel and Silvia VIgnolini

Although these nanostructures vary in different plant species, suggesting they evolved independently multiple times in the past 100 million years, they produce the same blue halo effect.

How do parrots produce blue colour?

Parrots have a similar problem.

Many colourful birds get pigments to colour their feathers from their diets. But parrots aren’t one of them. Amino acids in their genes control the production of yellow, red, and orange pigments in their feathers. Called psittacofulvins, they are unique to the vertebrate world. But some budgerigars that belong to the parrot family can also paint their feathers blue. How do they produce this colour?

Scientists mapped the birds’ genome and found one amino acid that produces yellow had been substituted to produce blue. Wherever this alternative protein is expressed, blue replaces yellow.

How do bees make a beeline for home?

The flight path of bees in search of nectar can be convoluted as they meander all over the countryside. But once they are fully loaded, they don’t retrace their steps. Instead, they fly home in a straight path. How do these insects remember all the twists and turns on their outbound journeys and compensate for them on the inbound ones?

By studying sweat bee (Megalopta genalis)  in Austria, scientists cracked the mystery. They fitted bees with tiny electrodes and put them in flight simulators. They also examined their nerve cells under a microscope. They say a neuron network in the central complex of bee brains that are smaller than a grain of rice assesses the speed and direction of the flight path. This insect navigation unit memorises all the details of the outbound journey even though it flies at night, building a complex map of the countryside. They get their compass bearings from polarised light. When the time comes to head home, bees know their location in relation to their hives and are thus able to fly straight back without using landmarks. These tiny insects accomplish this even though they have 100,000 times fewer neurons than humans.

Worms that survive without sex

Sex maintains the genetic health of a species. Without it, mutations accumulate which doom the survival of progeny. Yet some species, like the roundworms Diploscapter pachys and Diploscapter coronatus, have opted for asexual propagation and survive without any ill-effects. The roundworms haven’t had sex for at least 18 million years but show no sign of suffering from a disadvantage.

Researchers discovered the worms have aced the art of cloning. The nematodes fused the six pairs of chromosomes of their sexual ancestors into one humongous pair. They skipped meiosis, a key step in cell division in the reproduction of sexually producing creatures, removing the scope of any errors creeping in.

A nematode and an ant are the only two creatures that scientists know that have one pair of chromosomes. But these organisms mate to produce offspring.

Even ants have self-control

Given a choice between small immediate reward and large delayed reward, crows, primates, and humans display self-control by holding out for the larger reward even if they have to wait for it.

In an experiment, researchers gave ants a choice of a dilute sugar drop close to their nest and a rich sugar drop farther away. More than half (69%) the ants opted to walk double the distance showing they can resist temptation. When the researchers offered the same reward at both locations, the ants preferred the one close to their nests.

Guppy mothers give birth to almost mature young

Life for guppies in the mountain streams of Trinidad is hard. Waterfalls separate their populations. The ones living below waterfalls have to run a gauntlet of predators. Further up the mountains, they have little to fear from predators, and they proliferate. High numbers mean more competition, and they have to scrabble for food.

Guppy mothers have different strategies to give their young a better head start in life. When predators abound, they produce many small young at frequent intervals. When algal food is scarce, guppy mothers give birth to few large babies.

Do the young living upstream of waterfalls mature faster? Or do one down below mature earlier? Or do the mothers of large offspring delay going into labour, giving birth when their young are almost adults?

By measuring the fry’s development, researchers ruled out the first two options. The young at both elevations grow at the same pace and mature at the same phase of development. High-elevation mothers delay giving birth until their young are almost mature. The fry, born with an extra dollop of yolk, are vigorous with sturdier bones and stronger muscles and therefore stand a better chance at competing for scarce resources.

Ant queens turn undertakers

A queen that died of a fungal infection. Credit: Christopher Pull

A queen that died of a fungal infection. Credit: Christopher Pull

Ant queens typically do one thing only – lay eggs – while scores of worker ants keep the nest functioning. If any ant dies, worker ants disposes the corpse. What do queens do when there are no worker ants to take care of business? Nests of black garden ant (Lasius niger) are often founded by two queens. If one of them dies before worker ants hatch, the surviving queen has to bury the dead partner if she is to avoid contracting infections. The future of the colony could suffer a setback or doom if the surviving queen also falls sick or dies. Queens that dismember and bury the dead had better chances of survival than ones that didn’t take this effort.

Why do cetaceans need large brains?

One theory says marine mammals need large brains to range far and wide to exploit more resources. The ones with bigger brains have a varied diet and live in a wide range of latitudes. Another contends they produce heat so the animals can live in cold oceans.

By analysing cetacean social groups, brain size, and social behaviours, researchers say cetaceans evolved their large brains to support their complex social lives. For instance, they hunt in packs, use tools, form alliances, speak in regional dialects, learn to hunt by watching others, and each individual has a unique vocal signature. Some hunt cooperatively with humans and other species, and even adopt and raise unrelated young. This repertoire of behaviour suggests the demands of such complex social behaviour drives the development of large brains. According to the ‘social brain hypothesis’, humans evolved big brains to cope with community living. Cetaceans, it appears, are no different.

Bird feeders change the beaks of birds

Many in Britain feed birds by setting feeders in their gardens. However, this isn’t as popular an activity with Europeans. Researchers compared the beaks of great tits in Britain and Holland and discovered the English ones had longer beaks. This change occurred within the past 50 years since the beaks of museum specimens weren’t as long. The birds that exploited British largess had longer beaks and were more fecund in the UK than European ones.

Tadpoles turn toxins on each other

Tadpoles of many species use toxins to keep predators at bay. At least one species, the common toad (Bufo bufo), turns them on others of its kind. These toad tadpoles become more toxic in crowded situations probably to avoid being cannibalised. But the researchers suggest the toxins might protect the tadpoles from infectious diseases arising from living in dense groups.

Animals do the most amazing things. Read about them in this series by Janaki Lenin.

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.