From the editor at New Scientist who brought us such works as How to Fossilize Your Hamster, this is an illustrated compendium of facts that reveal the beauty, complexity, and mystery of the world around us. Drawing on the magazine’s popular “Last Word” column, Why Are Orangutans Orange? covers everything from bubbles to bugs, as well as why tigers have stripes and blue-footed boobies have, well, blue feet.
With over two million copies sold, this series of question-and-answer compendiums is a delight for anyone who loves to learn!
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Why Are Orangutans Orange?
Science questions in pictures â?" with fascinating answers
By Mick O'Hare
Pegasus Books LLCCopyright © 2011 New Scientist
All rights reserved.
All creatures great and peculiar
[?] Happy feet
The blue-footed booby is an extraordinary-looking bird. It has fairly dull plumage but strikingly coloured blue legs and feet. What could be the evolutionary benefit of such a conspicuous feature? Both sexes have blue feet so they don't seem to be for impressing potential mates.
Although not obvious at first sight, during courtship blue-footed boobies (Sula nebouxii) have different-coloured feet depending on their sex: male feet are brighter and more of a greenish-blue, while the females have duller feet that are bluish.
The birds exhibit their feet to prospective partners in a series of courtship displays. These include a kind of ritualised strutting around that allows them to show off their feet, plus stylised or 'salute' landings which serve the same purpose.
I am a member of a research group that studies the sexual behaviour of the blue-footed booby. In one experiment, we altered the colour of the courting males' feet and recorded the females' response. Females paired to males with duller feet were less enthusiastic about courtship and less likely to copulate compared with females paired to males with normal, brightly coloured feet. Similarly, when we altered the females' feet to a duller blue, males became less interested in courting them. Birds in poor health often have dull blue feet.
What's more, females whose mates had dull blue feet produced smaller eggs, and their chicks had a poorer immune response compared with normal females. This may sound surprising, but it is in accordance with theoretical expectations.
All this suggests that males are probably under strong selection pressure to maintain greenish-blue feet during courtship. This will ensure not only that they copulate successfully but also that their mates will lay big, healthy eggs. Overall, our results suggest that foot colour is a trait maintained by mutual male and female preferences.
Institute of Ecology
National Autonomous University of Mexico
Both male and female Sula nebouxii have blue feet, but it is the male that presents his feet prominently in courtship. This, in effect, is a way of saying that he is of the same species as the female.
I cannot offer any specific reason why the blue-footed booby has blue feet, but I would point out that foot colour does seem to be significant in the genus – there is an equally striking red-footed booby, Sula sula. This suggests that as members of the genus evolved, they adapted to different ecological niches which, in turn, meant that there was an advantage in the birds splitting into different 'tribes' that could only mate with their own kind.
This is an example of what is called sympatric evolution, where one species evolves into two within a shared territory. In contrast, allopatric evolution occurs because populations become isolated from each other. For sympatric evolution to succeed, it is essential that some sort of difference between the species arises so that a bird can distinguish between a bird of a related species and one of its own kind.
Australian Centre for Microscopy & Microanalysis
University of Sydney, Australia
Ducking the issue
I have never seen a duck stand as erect as the one shown in the centre of this photo, which I took at Rowsley, Derbyshire. Does anyone know if there is an explanation for this posture or is it just an unexpectedly tall duck?
Most of the birds in the background of the photograph are male and female mallards (Anas platyrhynchos) from which almost all domestic ducks originate and hence commonly and freely interbreed.
But the upright drake is a cross-breed – note the less-clearly defined markings compared with the other drakes. He is half mallard and his other parent was an Indian runner. This is a common breed that is raised for its egg-laying performance and is characterised by its distinctive vertical stance and slender frame, which results in a comical gait. Standard domestic ducks similar to the others in the photograph, which are bred for their meat, retain a more normal horizontal carriage.
Interestingly, the slender upright stance seen in this duck is quite dominant genetically, and interbreeding between Indian runners and other ducks typically results in skinny, upright offspring. Indian runners come in a wide variety of colours, with white and brown being the most common.
Mitcham, Surrey, UK
The erect duck is a hybrid of a mallard duck and a domestic Indian runner duck. Indian runners and the crested version, Bali ducks, came from Indonesia – not India – and were brought to Europe by Dutch traders. They were once known as penguin ducks because of their erect stance.
Coddenham Green, Suffolk, UK
For those who would like to explore the parentage and history of this bird further, check out the Indian Runner Duck Association at www.runnerduck.net. Thanks to Jo Horsley of Llanwrda, Carmarthenshire, UK, and others for pointing this out – Ed.
With the exception of the sperm whale's off-centre blow-hole and some crabs' single large claw, all complex organisms I can think of are effectively symmetrical along one plane of their body. What is the least symmetrical organism?
By email; no postal address supplied
Flatfish received the largest vote, but there are plenty of other strange candidates out there – Ed.
The least symmetrical organism is the halibut, which has both eyes on the same side of its head.
Norwich, New York, US
There are different symmetries in nature. We tend to assume bilateral symmetry is normal because that is what we and most of the organisms we notice (vertebrates and arthropods) display. But bilateral symmetry is the exception rather than the rule; many creatures exhibit radial or even spherical symmetry. Some alter their symmetry over time – for example, a starfish will start out as a bilaterally symmetrical larva and become radially symmetrical as it matures. Humans, a few days after conception, are basically a spherically symmetrical organism called a morula.
Many organisms do not have any clear geometrical symmetry but demonstrate some kind of fractal symmetry, where their structures look similar at a variety of scales. Many plants and fungi are a bit of both: think of the leaves and the apples on an apple tree.
Humans are not quite bilaterally symmetrical: our liver is on the right side, our spleen on the left, while our right lung has three lobes and the left two. We even slip into fractal symmetry when it suits the purpose: take a close look at the capillaries which transport blood to the tissues. We are not even superficially symmetrical. Next time you get out of the bath ask yourself, 'Do they both hang the same?' This works for either sex.
We are all changed and shaped by both our genes and our environment. To put it another way, we all conform to a pattern while being eccentric. Heck, that's life.
Smethwick, West Midlands, UK
Members of the genus Histioteuthis, squid that live down to depths of 1000 metres, are unique in the animal kingdom as their left eye is two to three times the size of the right. The reasons for this trait, which gives rise to its common name of the cock-eyed squid, are unclear. There is also a corresponding asymmetry in the optic lobes of the squid's brain. The specimen pictured below was filmed on board ship after being caught off the coast of California.
Department of Optometry & Visual Science
City University, London, UK
One suggestion is that the depth at which cock-eyed squid live is about as far down as sunlight can penetrate. The squid trains one eye on the illuminated water above while the other looks down into blackness – Ed.
Asymmetry is commonest among organisms that have little need of well-defined structures in their bodies. Some algae, fungi and sponges never developed much symmetry, while parasites can abandon symmetry when they grow opportunistically to secure food. An example of the latter is Sacculina, a barnacle that injects its soft body through a crab's shell and then grows a lump of reproductive tissue plus a tangle of feeding filaments throughout the crab's body. And some members of the group of tiny crustaceans known as copepods form shapeless reproductive sacs within cysts in the flesh of fishes. Such creatures need no symmetry.
Somerset West, South Africa
There is a wonderfully quirky group of asymmetric barnacles called verrucomorphs, shown in the photograph opposite. They are either 'right-handed' or 'left-handed' – apparently a random choice – their form being determined by the loss of calcareous plates from either the right or left side of the shell wall, plus a reduction in the number of plates in the shell's lid to two from the usual four. Why they have adopted this asymmetric form is uncertain, particularly as both forms occur together. Their soft tissue, as it happens, retains bilateral symmetry. These and other asymmetric barnacles were first comprehensively described by Charles Darwin in a monograph published in 1854.
One of my young chickens has just produced an unusually coloured egg (at the right of the photo). The egg on the left is more typical of the breed. I know egg shell colour is variable, even in eggs laid by the same hen on different days, but how did one egg undergo such a sudden and distinct colour change?
The answer probably lies in the fact that, until shortly before they are laid, hens' eggs are white. The brown pigmentation associated with breeds such as the Rhode Island red and the maran is a last-minute addition during egg formation and, like a fresh coat of paint, can come off surprisingly easily.
More than 90 per cent of the shell of a hen's egg consists of calcium carbonate crystals bound in a protein matrix. The shell starts to form after the egg has reached the uterus, where it stays for around 20 hours prior to being laid.
During this time, glands secrete the shell around the membranes that hold the yolk and albumen. In brown-egg-laying breeds, the cells lining the shell glands release pigment during the last 3 to 4 hours of shell formation. Most of the pigment is transferred to the cuticle, a waterproof membrane that surrounds the porous eggshell.
Several factors can disturb the cuticle formation process and thus pigmentation, such as ageing, viral infections – including that perennial chicken farmer's nemesis, bronchitis – and drugs such as nicarbazin, which has been widely fed to poultry to combat a disease caused by a type of protozoan. Possibly the most significant factor affecting egg pigmentation is exposure to stress during the formation of the egg.
If a flock of hens is disturbed by a fox during the night, for example, they might well lay paler eggs in the morning. The adrenaline the hens release puts egg-laying on hold and shuts down shell formation. The egg's pigmentation will be affected if the cuticle doesn't form properly.
Even if the pigment is laid down, there is no guarantee that it will last, as Morris Steggerda and Willard F. Hollander found in 1944 while they were studying eggs from a flock of Rhode Island reds in the US. When they cleaned the eggs, the brown pigment occasionally came away; the harder the eggs were rubbed, the more pigment was removed. Only those shells with a glossy sheen retained their colour, suggesting their cuticles had been fully formed, with a protective layer that acted rather like the varnish on an oil painting.
As for the egg photographed by your questioner, the bird was probably disturbed while the cuticle was being formed and so the pigment, inadequately protected, was rubbed off the larger, rounder end of the egg as it was forced out.
The issue may have some significance for public health. The waterproof cuticle is the egg's defence against bacteria. As shell colour is affected by how well the cuticle forms, it also provides a visual test of how free from harmful bacteria an egg may be.
Norwich, Norfolk, UK
Before an egg is laid, the hen's shell gland secretes pigment into the fluid bathing the egg's surface. The fluid smears readily, and any disturbance while the egg dries can create marks. Farmers are therefore fussy about the kind of bedding they use in nesting boxes.
Eggs are usually laid big end first. The hen that laid the egg in question may have resorted to using friction to release the partly laid egg from its cloaca, possibly by rubbing the egg against the bedding it was sitting on.
Alternatively, the hen may have paused halfway through laying, perhaps disturbed or exhausted, with the egg half-protruding from its cloaca. The part of the egg still within the cloaca had time to achieve a deep colour before the hen relaxed again, and this accounts for the sharp boundary in coloration seen in the photo. Such a scenario is unusual but it does happen.
Somerset West, South Africa
Life on Uluru
Some decades ago I was lucky enough to climb Uluru in Australia's Northern Territory. Recent rain had left pools on top of the rock and, curiously, in many of them there were strange aquatic invertebrates as seen in the photo. They look like ancient trilobites. Why and how are they on top of the famous, massive rock, and what are they? What happens to the creatures when the puddles dry up?
Dwellingup, Western Australia
The animals pictured are shield shrimps, Triops australiensis. They are crustaceans in the class Branchiopoda – meaning 'gill-legged' – and this term reflects the fact that they use their legs for breathing as well as for movement.
Their external morphology appears to have remained unchanged for 220 million years or more, and one shield shrimp, Triops cancriformis, has been claimed by some to be the oldest extant animal species. They occur in bodies of fresh or slightly salty water that periodically dry out, such as ephemeral lakes, farm dams, ditches and even puddles left after rain.
The eggs of these animals have a very strong shell and are resistant to drying out. In some species, a period of desiccation is necessary for the creature's development. The eggs can tolerate freezing and temperatures up to 80 °C, and may remain viable for 25 years. In some species, hatching may take up to a year following exposure to suitable conditions, but in T. australiensis it usually takes several weeks at most. Once hatched, development from egg to adult may take only a further few weeks in summer temperatures. The animals have a lifespan of up to three months, and adults reach a length of about 35 millimetres.
The shrimps feed on microscopic organisms, aquatic worms, other shrimp species, frogs' eggs and tadpoles, decomposing vegetation and other detritus, and sometimes even moulting individuals of their own species. The small size and the robustness of the eggs allow them to be carried on the wind for hundreds of kilometres from their pools of origin, and it is probably this mode of transport that would have delivered the eggs to the top of Uluru.
It is also possible that the eggs might have been carried up in mud caked on a visitor's boots. Although in this instance such a method of transport is essentially innocuous, it is nevertheless a salient reminder of the need to ensure that all clothing and equipment is cleaned before moving from one ecosystem to another.
Woodbridge, Tasmania, Australia
I bought a packet of desiccated shield shrimp eggs (Triops australiensis) on the internet for my boyfriend's 30th birthday. As the name Triops suggests, shield shrimps have three eyes: two compound eyes and one 'naupliar eye' – a simple median eye, first appearing in the larval stage. They closely resemble their Triassic ancestors, which existed around 220 million years ago.
Blown around with the dust, eggs eventually settle in crevices and grooves – even on the top of the great rock – where they may remain viable for up to 10 years. I guess that means my boyfriend has an excuse for not hatching them yet.
School of Earth and Environmental Sciences
University of Adelaide, Australia
Excerpted from Why Are Orangutans Orange? by Mick O'Hare. Copyright © 2011 New Scientist. Excerpted by permission of Pegasus Books LLC.
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Table of Contents
1 All creatures great and peculiar,
2 Ice, bubbles and liquid,
3 Clouds and stuff in the sky,
4 In your kitchen,
5 Goo and gardening,
6 Bugs and blobs from the deep,
7 Sand, saws and the Klingons,