The Best Australian Science Writing 2013 (11 page)

   A Kuiper belt will not keep your pants up.

   Kelvin is not the first name of a former prime minister.

   Rectinol will not cure asteroids.

   Shoemaker-Levy is not a Jewish cobbler.

   Niels Bohr was actually quite engaging.

   And a Van Der Graaf generator is not a machine for producing Swedish backpacker clones.

Circuses

Quantum cats

Animals on drugs

Rhianna Boyle

From the 1940s until the 1960s, a pregnancy-test kit did not consist of a sterile white stick bought from the chemist, but of a fat, spotted amphibian called the South African clawed frog. As with the modern test kits that superseded them, the frogs were used to test women's urine. Thankfully, this did not involve holding a frog midstream in the toilet bowl.

Instead, these ‘pharmaceutical frogs' were kept in hospital laboratories and pharmacies. The test involved injecting the urine into the frog's lymph sacs. If the frog laid eggs within 12–18 hours, this meant that the woman was pregnant. Frogs' eggs are externally fertilised, so without a male around to do the honours, the female frog would never see her eggs hatch. Presumably, the whole experience left her feeling quite pissed-off, as well as pissed on.

This procedure was called the Hogben test, after Lancelot Hogben, the biologist who invented it. Testing facilities were required to either breed their own frogs, or have them crated in from Africa, where they were readily harvested from the wild. Most chose the latter, which led to a substantial pregnancy-testfrog export industry in southern Africa. In 2004, the global frog trade was identified as the probable transmitter of the chytrid
fungus, a skin-eating organism that had been mysteriously killing off native frog species all over the world. But that's another story.

The tale of the Hogben test is interesting because it shows how, despite the vastly different ways that animals' bodies have evolved from those of their common ancestors, when it comes to our hormones, evolution has taken the ‘if it ain't broke, don't fix it' approach. Hormones work like a lock and key, where the hormone molecule physically fits into its receptor in the body, triggering a reaction. In the Hobgen test, our human hormone ‘key' fits into the frogs' receptor ‘lock', triggering ovulation.

Therapeutic hormone treatments work on the same principle. The similarity of hormones produced across the animal kingdom is the reason diabetics could at one time inject themselves with insulin extracted from the pancreases of cattle and pigs, and also why the contraceptive pill once contained hormones harvested from horse urine.

Not all hormones are the same across species. This is why growth hormones, before they could be produced artificially, were not sourced from animals but from human cadavers. In general, though, the hormones that affect our bodies are close cousins to those that affect the bodies of other animals, right down to creatures as different from us as shellfish and crustaceans.

The shared chemistry of animal bodies means that we are affected not only by the same hormones, but also by the same drugs. And there is growing evidence to suggest that this may be a source of grief for many aquatic creatures.

Excess molecules of the drugs we take ultimately end up in our urine, or are excreted through our skins and washed down the plughole. Unfortunately, sewage treatment plants are not effective at removing all contaminants from raw sewage, and many waterways have detectable quantities of pharmaceuticals flowing down them.

In fact, considering the range of pharmaceuticals present in some of the world's rivers and oceans, the healing waters at Lourdes pale in comparison. Tests of waterways in developed parts of the world have detected (amongst other things): analgesics, antibiotics, anti-epileptic drugs, anti-inflammatories, antihistamines, beta-blockers, cholesterol-regulating drugs, codeine, diuretics and paracetamol.

If you're an allergy-prone, epileptic crustacean with high cholesterol, you're set. Otherwise, you could be spending your life soaking in drugs that have a decidedly less-than-therapeutic effect. Of course, just because these drugs are present, doesn't mean that they are necessarily harmful. The impact of a drug depends on the dose. But while research into pharmaceutical pollution is a relatively new field, the potential effects are enough to make scientists anxious.

For aquatic animals, it's a depressing thought. So perhaps it's just as well that the most commonly detected pharmaceuticals in our waterways are antidepressants. One kind of antidepressant is a compound called fluoxetine, which is the main ingredient in Prozac. And one animal that might be exposed to fluoxetine is a miniature saltwater crustacean called an amphipod.

To find out what might happen to wild amphipods that find themselves swimming in Prozac soup, some scientists at the University of Portsmouth raised amphipods in water containing various concentrations of fluoxetine. What happened was that the dosed-up amphipods stopped lurking in the dark corners of their tanks, as amphipods habitually do. Instead, as the researchers deftly put it, the animals ‘saw the light', and swarmed towards it.

It's tempting to imagine, anthropomorphically, that after a few weeks on the medication, the amphipods began to experience an improved mood, and realised that what had been holding them back in life was fear – their fear of being eaten by predators. Maybe, with their new-found self-confidence and a few
affirmations, they realised it was self-defeating to spend their lives hiding at the dark bottom of the water column. Instead, perhaps, they decided to live in the moment and swim on the surface of the water.

Unfortunately, in the wild, a stray, self-actualised amphipod on the water's surface would immediately be eaten by a fish. And while it wouldn't be at all anthropomorphic to say that this would make the fish very happy indeed, it could cause some serious problems for amphipod populations.

Prozac works in humans because it affects the way the body processes a neurotransmitter, or chemical messenger, called serotonin. Crustaceans also have serotonin, but our different evolutionary paths have used the same neurotransmitter for different ends.

In crustaceans, it is used to control both movement in escape responses, and breeding behavior. It seems that by interfering with amphipod serotonin levels, fluoxetine is either making them ‘escape' towards the surface without provocation, or sending them upwards looking for sex.

In other animals, serotonin controls reproduction, and it has been found to increase the fertility of both zebra mussels and a group of miniature crustaceans called Daphnia. However, just as humans are advised not to mix medications, other experiments on Daphnia have shown that mixing Prozac and pesticides can be risky. When exposed to both fluoxetine and the herbicide clofibric acid, which is also found in polluted water, these crustaceans developed serious malformations of the shell, antennae and tail spines.

It's not just Prozac causing problems. In 1994, intersex trout began to turn up in trout populations downstream of sewage outfalls in English rivers. These populations also contained a much higher than average proportion of females. Scientists eventually identified oestrogen hormone pollution as the cause. Since then,
oestrogens in the environment have also been shown, amongst other things, to have similar effects on some frogs; to skew the sex ratio of amphipod populations in favour of females; and to affect the larval development of barnacles.