Tuesday, February 16, 2010

Stuck on You

I've just come back from a marine zoology camp, where I've spent a week working on a group project about competition between two species of limpet. This didn't mean we were racing the limpets. We were looking at competition for a common food source - in this case, delicious microscopic algae that grows on rocks.

Below is a picture of a boulder covered in limpets. You can see why I didn't end up taking many photos on camp.

Our project involved lifting limpets off the rocks with a bread knife and relocating them to produce areas of higher than natural population densities. Then we waited to see if they would exhibit a behavioural response to being in a high density area. Having a shell is a bit like wearing a burqa - it makes it difficult for others to read one's non verbal cues - but I'm sure that the limpets' little faces were contorted with effort as some of them practically galloped away from the higher density areas at speeds of more than 4 cm per hour.

You can think of the intertidal rock pools as being like a great savannah full of grazing beasts. The herbivorous limpets are the gazelles and antelope. The predatory whelks, who drill through the limpets' shells and suck their flesh out, are like the big cats. Check out this vicious killer, Dicathais orbita:

And this glorious creature would be the elephant:

Elephant Snails (Scutus antipodes) are the giants of the intertidal rock pools. Their distinctively shaped shell is usually hidden under thin flaps of skin. When they feel threatened, the skin retracts and the shell is revealed. Having so much juicy flesh can be a liability, so these snails are typically found under ledges at the edge of pools. They come out to graze at night, when there are fewer predators around.

This Elephant Snail was part of a group which we were responsible for relocating at the end of the camp. They had been used in another group's project, in which they were tested for their responses to both a native and an invasive predatory starfish. It was a bit like the witness relocation program. Maybe, in time, these Elephant Snails will be able to come to terms with horrors they witnessed in our laboratory tanks.

Monday, February 1, 2010

Viral media

When I told my Grandma I was going on a camp to study bats, she listened politely for a few moments, then said "Yes, but really, what's the point of bats?". This was a new addition to her repertoire, which usually goes along the lines of: "I don't know why they bother having crocodiles. They're ugly, they eat people...why don't they just shoot them?" Grandma grew up in England, where over a millenia or so, people have done exactly that to their larger wild animals. The English have also replaced most of their wilderness with gardens and fields. In Grandma's opinion, this looks 'much prettier,' and is a great improvement on our ugly Australian bush.

I found it difficult to come up with an impromptu justification of the existence of bats. I didn't have the option of claiming that bats are God's creatures. After discussing mortality with her doctor, Grandma has decided that she's an agnostic. I ended up resorting to the slightly feeble argument that a) bats are cute, and b) they eat insects, which is a good thing if you hate insects. I was betting this argument on the fact that Grandma would hate insects, which, after all, are ugly and eat people. But she claimed to liked them. I'll have to remember this fact for possible point scoring the next time we have a sophisticated discussion about ecology.

I suppose I've always assumed that living organisms have an intrinsic value, not to mention their ecological significance. Even bacteria have their virtues. What they lack in personality, they make up for in useful nutrient recycling activities, or helpful gut-flora action.

However, I feel tempted to draw the line at viruses. These are entities - they can't even be called living things - that don't even bother to have their own cells. They lie around as inert capsules of DNA or RNA, only springing into action when they infect a cellular organism and hijack its cellular machinery to produce more virus genes. These genes get packaged in a protein coat and released into the world as more dormant viruses, which wait around to infect the next organism. A virus is the ultimate example of someone who needs to get a life of their own. Even parasites stoop to excreting and reproducing for themselves.

Maybe Richard Dawkins would understand the simple needs of the virus. The title of Dawkins' book The Selfish Gene refers not so much to the genetically determined selfish behaviour of organisms, but to the selfishness of the gene itself. This is because all the gene wants to do (not consciously, of course) is to produce more copies of itself. According to Dawkins, the carrier is merely the vessel of the gene. Evolution, and the variety of differently shaped bodies it has produced, represents increasingly sophisticated attempts by genes to package themselves in order to ensure their reproduction.

Judged on these terms, viruses are nature's car poolers, house sitters and refusers of plastic bags. They say no to unnecessary packaging. They don't waste valuable resources growing their own cells when there are plenty of other people's cells to go around.

But, as with a sanctimonious hippy, I just can't warm to them. When it comes to genes, I prefer the ones that have as much ornate gift wrapping as possible. The more colours and accessories the better.

Call me a sucker for a cheap gimmick, but these genes glow in the dark!

It's not just a visual aesthetic that counts against viruses. There's also a lack of narrative drama. Sure, swine flu got a lot of media coverage, but how did this make the virus feel? What does a pathogen really get out of life when it's incapable of conscious thought, unconscious thought, movement, sensory perception, feeding and mating? What is the point of viruses?

The elephant in the room, of course, is that viruses make a mockery of our limbs, brains, emotions, genitalia and rational thoughts. If we're just doing in a more elaborate way exactly the same thing they're doing with a few sticks of non-sentient genetic material and a protein coat, - that is, replicating our DNA ad infinitun - then we have to ask the question: what is the point of us? Which, in my books, is all the more reason to despise them. Essentially, I'm saying that I hate viruses because they are irreconcilably different to us, yet at the same time remind us of ourselves. Because this means I have to identify with something I hate, I only hate them more. Of course, Fascism is not always a good thing, but let's just say there's a time and a place.

Saturday, December 5, 2009

Foure Footed Beastes

This illustration was made in 1230 AD. The tusked animals are elephants. The top panel shows soldiers riding an elephant into battle, while the bottom panel shows an ailing elephant being supported by the rest of its herd. It's obvious from the animals' fur, pig-like heads, and dog-like limbs that the artist has never seen a real elephant. The images are true to a verbal description of an elephant, as a large animal with tusks, large ears and a long trunk. But a lot has been lost, and gained, in the translation from words to image.

I find these sorts of images compelling, although it's difficult to explain exactly why this is so. On a basic level, these illustrations are funny because to modern eyes, they are so obviously wrong. More than words, an image seems to lay an authoritative claim to the truth, and when it is so transparently inaccurate, there's a cheap thrill in catching the artist out in the act of fabrication. There's also the charming naivete of this image, and the mental acrobatics of trying to put myself in the mind of someone in whose world the elephant is still a quasi-fictional beast.

In a similar vein is this image of a hyena, which appeared in Edward Topsell's book Foure Footed Beasts, in 1607. Below is a photograph of a real hyena for comparison.

The text below the illustration reads:

'This beast aboundeth near Caesarea (?) in quantity resembling a Fox, but in wit and disposition a Wolf; the fashion is, being gathered together, for one of them to go before the flock singing, or howling, and all the rest, answering him with correspondent tune: In hair, it resembleth a Fox...'

Below are depictions of a sloth (1573), and a crocodile (c. 1170), which is devouring a water serpent. As with the elephant illustrations, the crocodile's claws, long tail, and spiky backbone are all accurate features of the animal, but their translation from words into an image leaves a lot to be desired.

The crocodile image comes from a type of Medieval book known as a bestiary, which was essentially a compendium of animals. Each animal in a bestiary was the subject of a story, the purpose of which was to illustrate an aspect of Christianity. The story accompanying this image is that the water-serpent allowed itself to be eaten by the crocodile, but would then devour the crocodile's innards and escape. The crocodile symbolised Hell, while the hydra represented God.

The animals in bestiaries often speak, or perform miraculous acts. It's difficult to say whether the people reading these stories interpreted them as allegories or scientific fact, partly because the medieval mind had no concept of science as a way of thinking. Areas of knowledge that today would fall under the auspices of science were mixed up with religion and myth, with no distinctions made between these ways of explaining the world. Scientific knowledge has shaped the modern worldview to the extent that we take the scientific method for granted. So I suppose another part of the appeal of these images is the unsettling thrill of trying to imagine a world in which it wasn't yet possible to think in this way. I think the scientific method is a wonderful thing, but maybe part of me enjoys the iconoclasm of trying to recreate a Medieval concept of nature. There's something comforting about the thought that no one had to study for biology exams in the days before biology was invented.

The image below is a woodblock print of a rhinoceros, which was made by the artist Albrecht Durer in 1515. A chapter in Science, Medicine and History (ed. B.A. Underwood) charts the history of this image, which became the European world's defining image of a rhinoceros for the next 250 years.

Compared to a real rhinoceros, the print is strikingly accurate in some respects. But the plicae, or skin folds, of the real rhino have been depicted as elaborate plates that resemble Medieval armor, and the animal has a completely fanciful horn between its shoulder blades.

Durer never saw a rhinoceros. He made the print from descriptions of the animal and from a sketch made by another artist of an Indian rhino that was a gift to the Pope. It's believed that Durer may have heard about the two-horned species of African Rhino (pictured below), which had been described in classical texts. Even though the species he was drawing has only one horn, he may have tried to make his image more believable by adding a second horn, not on the nose as in the real-life African species, but on the animal's back.

Over the next few centuries, Durer's image became the defining image of the rhinoceros, and was reproduced and plagiarised, complete with its embellishments, in numerous scientific texts. Later images became even more fanciful, exaggerating the morphology of the armor plates and size of the second horn. The drawing below was claimed to show several newly discovered species of rhino, but the mark of Durer's image is obvious.

Durer's rhino and its fictitious dorsal horn even found it way into this early C17th coat of arms, of the Society of Apothecaries.

In the eighteenth century, a traveler to Africa quoted local (presumably European) hunters as saying they often saw three horned rhinos, with the third horn being positioned in the location of Durer's fictitious horn. Apparently, only male animals carried the third, dorsal horn. Continual reproductions had made Durer's image so persuasive that it had influenced people's observations of the real animal.

The saga of Durer's rhinoceros can be read as a cautionary tale about the hazards of observer bias, not to mention the pitfalls of plagiarism. The modern scientific method stipulates that results must be able to be replicated by another party. This means modern science largely avoids the problems of falsification and bias that seemed so rampant in the middle of the last millennium. But these images are a reminder of the enduring possibility of human fallibility, and of truth being in the eye of the beholder.

My favourite historical scientific image is this drawing, made by Nicolas Hartsoeker in 1694.

This is a human sperm cell, or spermatazoon. Spermatozoa were discovered by the Dutch microscopist Anton van Leeuwenhoek in 1677. At the time this drawing was made, one school of thought on the origins of human life held that an entire miniature person was carried in the head of the sperm. The only contribution of the mother was to nourish and protect the baby. This theory was known as 'spermism'. As you can see, this drawing shows a tiny person curled up inside the cell. Since male babies would, in turn, carry their own offspring in miniature, the generations of humanity could be imagined to be like a set of Babushka dolls, which had originally all been contained in the testicles of Adam. And since a whole person was contained inside the cell, some people concluded that sperm cells had souls. This idea was used to support the argument that masturbation was a sin.

I had trouble researching this image because many sources gave conflicting information. Some sources claim that Hartsoeker, and sometimes also van Leeuwenhoek, claimed to have actually seen the little person, or 'homunculus', sitting in the head of the sperm. According to other sources, no such claims were made. Although the artist had seen sperm cells under the microscope, and believed in spermism, he would not have been able to see through the cell membrane to determine whether the homunculus was present. It's possible that in creating the image, he was merely representing a concept, as opposed to drawing from life what he thought, with his biased vision, he was seeing.

Somehow, the second scenario is much less appealing than that of a seventeenth century scientist gazing through a lens and thinking he could make out a little person in his own sperm, in the same way that children think they can see a face in the moon. Perhaps the first scenario has gained traction because it has much more comic potential, and seems to fit better with our ideas about the ignorant dark ages of science. If this is the case, maybe our modern minds are not so far above biased interpretation as we like to believe.

Thursday, November 19, 2009

Batting average

Here are some photos from a field biology camp I went on in September. It was held in the Strathbogie Ranges, in northern Victoria. I was in the bat group. Our project was to work out whether higher temperatures resulted in more insect activity and therefore more bat activity. We trapped the bats using a harp trap, which looks like this. The frame is strung with fishing line, which the bat flies into. It bounces off the trap and into the canvas bag below.

The first two nights of the camp were very cold (down to zero degrees), so we spent a lot of time walking around in the bush late at night but catching nothing. This was great preparation for a major part of real field work: dealing with frustration and disappointment. Then it warmed up, and we woke up one morning to this miraculous sight.

We caught two species of microbat: the Southern Forest Bat and the Little Forest Bat. It's difficult to tell which is which from the photos, because the two species look very similar, and are distinguished by (among other features) subtle differences in their fur and the morphology of the tips of their penises.

Here's an echidna I ran into one day. I took a video (pasted at the end of this entry) because echidnas' rolling gait always makes me laugh. Echidnas are mammals, because they produce milk, but unlike most mammals, they lay eggs. This is not their only reptilian feature. They also have a reptilian-style pelvis, which explains why they walk with their legs splaying out to the side, like a lizard. However, their archaic physiology shouldn't be taken as a sign of low intelligence. According to our lecturer, Kath, laboratory tests have shown that echidnas have the intellect of a domestic cat. I probably wouldn't want to stroke one on my knee, though.

However, I suspect that Kath might. Here she is demonstrating how to capture an echidna bare-handed. Understandably, the echidna was not happy. Being an intelligent creature, it communicated its disgust in a way it was sure humans could understand: by pooing all over Kath's pants. This was fortunate because one of the groups was collecting mammalian faecal samples, and was able to scrape the poo into a zip lock bag.

Here's a Mountain Brushtail possum, or bobuck, who is being measured and having his details recorded. The possum looks a bit dopey because he has just been sedated. This possum would later wake up to find that while he was out of it, he had gotten a tattoo. Fortunately, it wasn't a dolphin, or text from Kabbalah. Possums aren't that stupid. The tattoo was an identification number so he can be included in a long term population study of bobucks in the Strathbogies.

Here's a male Superb Fairy Wren in breeding plumage. Another group was capturing these birds with a fine net strung between trees, and fitting them with leg bands. This was so individual birds could be identified, in order to give an idea of their social structure. I've seen groups of fairy wrens around and always assumed that they consisted of one colourful male and his harem of brown females. But in fact each group consists of just one breeding pair. The other brown individuals are subordinate males, often offspring from previous years, who stick around to help the breeding pair raise their young. Other females are chased out the territory.

Continuing the theme of previous blogs about promiscuous birds, fairy wrens have one of the highest proportions of illegitimate young of any birds - about 70 per cent of offspring come from extra pair matings. Male fairy wrens have been observed picking up yellow flowers in their beaks and offering them to females in other territories in the hope of gaining matings. This kind of behaviour is known as the 'sneaky fucker' strategy, which is the official biological term. So many words in biology have complicated Greek or Latin roots. I'm all for this kind of simplification.

Here's a small-eyed snake, the bite of which will cause kidney failure. Luckily, this was only a baby.

I saw my first wombat on camp. It had a bad case of mange and was caught in the headlights for a few seconds as we drove between bat study sites. However, wombats were active around our camp, as this great photo shows. This picture, along with a lot of the better shots in this blog, were taken by my fellow bat-person, Stan.

I'll leave you with this message (the first video), spoken in bat by one of our subjects. The clicking sound is a sonar hunting call made by the bat. Bats use echolocation to 'see' insects in the dark. The call would not usually be audible to humans, but we can hear it through the Anabat sonar detector sitting on the table. It translates the sound into an audible pitch. Unfortunately, the detector does not, as my Mum suggested, translate into English. I'll let you decide what this bat is saying.

Thursday, August 13, 2009

It's just not natural

I find it funny when conservative politicians and religious leaders attempt to categorise human sexual preferences, gender roles, relationships or parenting arrangements as 'natural' or 'unnatural'. Anyone who appeals to the natural world to justify their own position on human morality clearly doesn't know much about nature. It's likely that when such people think of nature, they form a mental image that looks something like this picture:

Look at this wholesome, monogamous, nuclear swan family. Mum and dad swan form a lifelong pair bond, stake out a territory, and raise a brood of cygnets every breeding season. Admittedly, these are black swans, which might be off-putting for some conservative politicians, but you have to admit that all in all, it's a lovely sight.

Unfortunately, there are some animals in our community who don't share these good, solid swan values. I hope this isn't too shocking, but I'm about to show you a picture of some filthy, dirty sex.

Of course, if you're an earthworm, life in the humus layer means everything you do is filthy and dirty. But, as you can see, the two mating worms are joined at two points. This is because earthworms are hermaphrodites. They mate by matching their male and female organs in a complementary fashion. It's thought that the evolutionary reason for this is that producing both sperm and eggs allows the worms to maximise their reproductive output in an environment in which it might be difficult to meet other worms. After mating, the worms move on and will probably never see each other again. Put simply, worms are promiscuous lady-boys who like it both ways because this gets them twice the amount of sex. And, being hermaphrodites, they become both single mothers and absent fathers at the same time.

You might think it's ridiculous to expect invertebrates to stick to good old fashioned values like monogamy. But some invertebrates manage it. Bonellia viridis is a marine invertebrate from a relatively obscure phylum known as Echiura. Members of this species are either male or female, and form lasting, monogamous pairings. If simple marine creatures can manage this, why is it so difficult for a complex primate like a human being? If only we could become more like Bonellia, the world would be a better place.

Yes, if we were more like Bonellia, a woman of marriagable age would lie in wait until a baby boy drifted her way. Then she would swallow him and imprison him in her reproductive tract, feeding him off her bodily fluids until he matured and began to pump out sperm on tap. This what happens in the Bonellia world. The female lies on the ocean floor until she meets with a tiny free-swimming larva. The larva is then sucked inside the female's feeding tube and remains as a parasite in her genital sac, with the sole purpose of sperm production, for the rest of his life. Yes, folks, there's no such thing as divorce in the Bonellia world. Those guys really know how to make a relationship last. What a great example to set for their larvae!

Some young animals are not so lucky. This lizard has two mummies. The desert-dwelling whiptail lizard (Cnemidophorus uniparens) is a species in which, as in a prison or boarding school, the entire population is female. This may seem like a sure way to go extinct. But, along with a few species of reptiles, fish and insects, these lizards have a special feature that allows them to survive. Whiptail lizards can reproduce by parthenogenesis, which means that they can lay eggs that hatch into young without being fertilised. While these lizards can become single parents, the chances of a female ovulating increase if she engages in ritual courtship behaviour with another female. This behaviour resembles that of related, non-parthenogenic lizards, and may include mounting. Then, after a female has laid her eggs, changes in her hormone levels cause her to behave like a male, and court another lizard who is pre-ovulatory.

With creatures like this in the world, it's nice to see that there are still animals like the Sand Tiger Shark (also known as the Grey Nurse Shark), who do it the old-fashioned way. No funny business there. Boy shark meets girl shark, then here come the little nippers! Just a normal family - Mum, Dad and a couple of extremely sharp-toothed embryos who devour each other in the womb. Ultimately, just one of the offspring is born, having grown big and strong on the flesh of his siblings.

via videosift.com

One reason the natural world is a useless place to look for moral guidance is that animal behaviour is a result of evolution. The evolutionary process has no moral dimension, and represents only the triumph of superior function. And, on a more obvious level, virtually every human behaviour, from cooperation and maternal love to rape, infanticide, and cannibalism, are all technically natural to the extent that they have parallels in nature. American sex researcher James Weinreich has said that 'If animals do something we like, we call it natural. If they do what we don't like, we call it animalistic'.

But enough talk, because here comes our young swan family again. The cygnets will soon be growing adult plumage, finding mates, and raising young of their own. But what's this? Maybe only a mother would know, but one of the cygnets doesn't look at all like papa swan. Junior does, however, bear a striking resemblance to that handsome male swan from the couple in the next nest...

In the last few decades, advances in DNA sequencing have blown apart previous assumptions about bird mating systems. Now that the paternity of the offspring can be analysed, it has been shown that extra-pair matings are common in many species. One of my lecturers, who has a particular interest in adulterous birds, conducted a study and found that on average, 15% of cygnets in a black swan population were fathered by a male other than their mother's mate. An average of 38% of broods contained at least one illegitimate cygnet. It appears that the swans are putting up a veneer of respectability, while secretly acting just as they please. Which, if you're a conservative politician or religious leader, is probably something that comes very naturally indeed.

Friday, July 24, 2009

Foot fetish

I could stay on the internet all day looking at pictures of geckos. Geckos are the fluffy kittens of the reptile world.

The house I grew up in was inhabited by these native robust velvet geckos (below). The term 'robust' is appropriate. From time to time, two geckos fighting on our ceiling would lose their footholds and fall onto the floorboards with a loud smack. Fortunately, it takes a lot of force to burst a gecko. Usually they would merely sit looking stunned for a few seconds, then run up the nearest wall.

At the time I never thought about what might allow them to walk on our ceiling in the first place. It's easy to see how an animal might stick to a smooth surface like glass using vacuum suction, or to many surfaces using a sticky substance like mucus. But it's more difficult to understand how it would walk on a dry, comparatively rough surface like a ceiling.

The answer is that geckos' feet are able to 'share' electrons with the surface they are walking on. Chemistry is not my strong point, so please bear with me as I try to explain this.

Here are some pictures of the undersides of geckos' feet. Note the distinctive ridged patterns.

Traditionally, having hairy palms is meant to be a sign of madness. In the case of geckos, it's a sign of awesomeness. At a higher magnification, it's possible to see that the ridges are composed of extremely fine hairs. Each hair is split at the end into hundreds or thousands of smaller branches.

Like all matter, the hairs on the underside of a gecko's foot are made up of atoms. Here's a diagram of an atom. It probably looks familiar from high school. As you can see, the atom is made up of three kinds of smaller particles. In the centre are the positively charged protons, and the neutrons, which do not carry a charge. The electrons, which are negatively charged, orbit the other particles, like the planets orbiting the sun. The number of electrons (which, in a typical atom, is the same as the number of protons) determines what kind of element the atom is. For example, a hydrogen atom has one electron, while an atom of gold has seventy-nine. The foot of a gecko is made up of many different kinds of atoms, including carbon, nitrogen, hydrogen and oxygen.

If you think of one of these atoms, it's possible to imagine the electrons moving around in orbit. At certain times in the orbit, there are likely to be more electrons in certain areas of the atom than in others. This gives one end of the atom a slight negative charge, and the other end a slight positive charge. One end of a gecko's foot hair atom might be negatively charged, and be adjacent to the end of a ceiling atom that has a positive charge. This results in an attractive force, like that between magnets.

Obviously, because the electrons are in constant orbit, the attraction between the two atoms will be fleeting. However, as the electrons circle around, the charges on the two electrons swap. The previously negative end of the foot atom now has a positive charge, and vice versa in the ceiling atom. The attraction is therefore maintained.

As far as I can tell (again, this is not really my subject area), these kinds of attractive forces must exist between all kinds of matter. Perhaps, at this very moment, there are attractive forces occurring between you and your chair. I spend most mornings trying to overcome the attractive forces between myself and my bed. But if you can imagine the entire surface area of a gecko's foot hairs spread flat, it's possible to appreciate the large number of potential attractions that are compressed in the relatively small area of the foot. It's thought that the geometry of the foot, rather than any properties of the substances in it, is responsible for its remarkable adhesive power.

Geckos now have their imitators. Some scientists from the University of California have invented what they describe as a 'hard plastic gecko-inspired synthetic adhesive'. They believe this product may be useful for medical products, sporting goods and 'climbing robots where a controllable and reusable adhesive is needed'. Imagine! In the future, we could all be living in houses inhabited by hard plastic, gecko-inspired robotic geckos. I'm looking forward to the time when my evenings are interrupted by two pimped up gecko-bots blasting each other off the ceiling in a tiny ball of flames.