Australasian Science Magazine

By Stephen Luntz

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Shades of Grey
Urchins Show Some Spine
Parental Protection from Acidic Ocean
Beauty in the Right Eye of the Beholder
Flu Pandemic Model Improved
Autumn Rain Bands Move South
Cannabis Withdrawal Confirmed
Sea Snakes Stay Home
Reeds Rehabilitate Contaminated Land
Male Infertility Insights
Strange Species Alliance
Bird Blood Is Thicker than Water
Fumigation Replaced by Electrified Logs
Dark Strawberries Bring Health Benefits

Two species of wobbegong sharks lack the capacity to distinguish colours, and Prof Shaun Collin of the University of Western Australia says the discovery could help prevent shark–human interactions for the benefit of both.

The carpet sharks studied are not a threat to humans, but Collin says the finding adds to other evidence that all sharks are colour blind.

Multiple photoreceptors are required for colour vision, but Dr Susan Theiss’ PhD thesis has revealed that wobbegong eyes have only one class of photoreceptor. The finding was published in Biology Letters.

“We’re looking at three more predatory species to confirm,” Collin says. “However, electrophysiological evidence from more than a dozen species suggests that all sharks lack colour discrimination. It’s strange because lampreys, the more primitive group sharks evolved from, have quite sophisticated vision, and we know sting rays can see colour.”

Sharks can’t see violet light, but their single receptor covers most of the rest of the spectrum that is visible to humans. Collin admits: “We’re a little baffled. The capacity to distinguish a ripe fruit from an unripe one was enormously valuable to us. It’s surprising sharks did not find a benefit in being able to see colour signalling, but seals, whales and dolphins are also colour blind, so it is clearly not that important for large marine creatures.”

Collin hopes to put the finding to use by designing wetsuits that either camouflage the wearer to sharks, or signal danger. “Edges and high contrast boundaries must be important to their vision,” he says. “We may be able to make wetsuits look noxious, like a sea snake or something else poisonous, or find something that disrupts the boundaries when seen in silhouette against a lighter background – white pointers attack from below.”

Fishing lines may be similarly disguised to avoid by-catch.

The curious properties of sea urchin spines have been explained for the first time though careful examination of their microstructure. The findings may have applications in engineering.

Sea urchins use their spines for an array of purposes, ranging from defence and protection during storms to transportation. However, these uses require the spines to function in very different ways under different conditions.

“The spine can withstand some types of loads, like compression, which allows the sea urchin to manoeuvre and walk around, but snaps easily when the urchin needs to protect itself from predators,” explains Dr Naomi Tsafnat of the University of NSW School of Mechanical and Manufacturing Engineering.

According to Tsafnat, all of the sea urchin’s spines appear to have the same properties, rather than having some specialised for particular uses.

The spines are hollow and made up of a single crystal of calcite. However, in PLOS ONE Tsafnat published 3D images of sections of the spine, showing how bridging structures spiralling around its axis focus forces that make the spine elastic when experiencing compression. However, the spines snap easily during predator attacks, leaving the assailant with a permanent reminder of the urchin’s defences buried in their skin or mouth.

So if a storm throws an urchin against rocks, the force of direct blows are absorbed elastically, while spines will break off under radial forces, providing a different form of protection.

“While we’re not certain that this evolutionary feature is optimised, it certainly works – the longevity of this creature, having survived hundreds of millions of years is a testament to that,” Tsafnat says. “The spine is both strong and lightweight, and has mechanical characteristics that suit the sea urchin’s needs.”

The urchin used for this study was the purple-spined variety (Centrostephanus rodgersii), which is common in tidal waters along the NSW coast, but Tsafnat says there is no reason to think that other urchin spines would reveal a different pattern. She hopes to extend her work to porcupine and echidna quills to see if land mammals have developed similarly complex structures.

Ocean acidification is a major threat to coral reefs and the fish that live on them (AS, May 2008, pp.31–33), but some fish can adapt under unexpected circumstances.

The oceans absorb around one-third of the carbon dioxide emitted from fossil fuel combustion. This lowers the pH of the surface layers, making it harder for corals to form reefs. Many fish struggle to adapt to acidic water, particularly in forming the otoliths (ear bones) they use to navigate (AS, April 2009, p.9).

Dr Gabi Miller of the Centre of Excellence for Coral Reef Studies put anemone fish into water with carbon dioxide levels equal to those anticipated in 2050 and 2100 from current emissions trajectories. Fish introduced to these conditions suffered high mortalities upon hatching. Survivors were smaller and lighter than those raised as a control in conditions similar to the modern ocean, and also had a higher metabolic rate requiring more food just to survive.

All this is depressingly familiar, but Miller also found that fish whose parents had been introduced to the acidic waters as adults were healthy, at least in the first month of life. The parents also seemed unaffected by the transfer. “Our work with anemone fish shows that their babies, at least, can adjust to the changes we expect to occur in the oceans by 2100, provided their parents are also raised in more acidic water,” Miller says.

“This was totally unexpected. I thought any parental effects would be negative,” Miller says.

Unfortunately, by the time Miller came to analyse her data she had too few fish to extend the study, so she will need to reconstruct the experiment to see what happens as the fish age.

Miller has yet to examine the otoliths from her study, explaining: “These are really small fish so they’re hard to extract”. She admits to puzzlement as to how parental exposure can help fry, but says: “We think it is an epigenetic effect, with certain genes being turned on or off”.

The work has been published in Nature Climate Change but Miller warns against interpreting the results too widely. “They are definitely not the ‘canary in the coal mine’ as they have quite a large ability to cope with changed conditions anyway,” she says. “We need to extend these studies to other types of fish, especially those humans rely on for food.”

Miller says anemone fish were chosen because “they make a good lab rat”. They adapt more easily to laboratory conditions and are small enough for easy management.

Male Gouldian finches rely on their right eyes to determine if a potential mate is attractive.

Gouldian finches are brightly coloured, and come in three varieties with black, red or yellow head feathers. Mating success between the red- and black-headed birds is poor, and both prefer to mate with others of the same colouring (AS, June 2009, p.11). Dr Simon Griffith of Macquarie University’s Department of Biological Sciences says the black-headed males show the strongest preference for similarly coloured mates, so these were chosen as research subjects.

Sixteen male finches were placed in a cage with four compartments, including a neutral area and sections where they could interact with a black-headed male and one of each sort of female. When both eyes were open or their left eye covered, the males preferred the company of the black-headed female. However, Griffith reveals in Biology Letters that when their right eye was covered the males spent roughly equal amounts of time engaging with each of the other finches.

The study was inspired by evidence that the part of the brain controlling mate selection is strongly lateralised in the related zebra finch.

“This work will help us to understand how a complex process, such as determining the attractiveness of a potential partner, can be limited to just a single eye and side of the brain,” Griffith says. “One of the consequences of this finding is that individuals should approach and display to a potential mate from the right side, and perhaps this is the reason that many animal displays are side-on.”

Although MRI studies have shown that the parts of human brains associated with love and lust are also strongly lateralised, Griffith doubts that people wearing eye patches are similarly undiscerning. “Mammals have a corpus callosum that means signals pass much more efficiently between hemispheres in the brain than for reptiles or birds,” Griffith says. “So while there might be a very slight delay, messages from the other eye will be integrated.”

A newly developed model of the spread of influenza during a pandemic could help public health officials confront future outbreaks.

Dr Joshua Ross of Adelaide University’s School of Mathematical Sciences used data collected by the UK Health Authority during the 2009 swine flu pandemic for a paper published in BMC Medicine. Such was the concern about the close relationship between the cataclysmic Spanish Flu of 1918 that the Birmingham health authority responded to 424 households reporting flu symptoms by taking swabs and blood samples for laboratory testing to see if swine flu really was the culprit and monitor transmission to fellow occupants

“Traditionally, information on individual clinical outcomes is simplified to binary data – an individual is infected or not,” Ross said. “This new approach uses all these different levels of recorded data to develop a model that fits the whole process. Combining this with modern statistical methods we are able to make much more accurate estimates about transmissibility and clinical outcomes.”

Ross says that most existing models assume a constant level of transmissibility between members of the same household. “We added extra layers to our model that attempt to account for whether people might have some other disease with similar symptoms and the accuracy of the test,” Ross says. “We also included a parameter that estimated the heterogeneity of the infection.”

Ross says it is not known exactly how the severity of symptoms relate to rates of transmission, but he and his UK colleagues were still able to incorporate the possibility that transmissibility varies between cases.

The 2009 outbreak was unusual for the variation in both severity and transmission rates, which led to confusion as to whether people had flu or some other respiratory disease.

Declining autumn rains were a contributing factor to south-eastern Australia’s long drought, and the last three April–May periods have been dry even after summer rainfall rebounded.

Dr Wenju Cai of CSIRO Marine and Atmospheric Research has linked this trend to the southward expansion of the Hadley cell in research published in Scientific Reports.

The Hadley cell moves warm air from the Equator towards the poles, and is a major factor in the location of tropical rain belts and subtropical deserts. The Hadley cell has expanded to higher latitudes in both hemispheres over the past 50 years.

While this expansion is believed to be associated with anthropogenic global warming, Cai says it is not well understood why the expansion seems to be greatest in autumn. “In the Southern Hemisphere we are getting a bigger shift in summer and autumn, and in the Northern Hemisphere in their autumn. The climate models don’t predict this,” he says.

“The Hadley cell is comprised of a number of individual branches, so the impact of a southward shift of the subtropical dry zone on rainfall is not the same across the different semi-arid regions of the Southern Hemisphere,” Cai says.

The consequence is that towns in south-eastern Australia are getting the autumn rain that would once have been associated with locations 200–400 km north of them. Since late autumn is a time when southern Australia gets more rain than the north, this has led to a significant drying out.

This southward shift explains 85% of the rainfall reduction over south-eastern Australia, but fits less well with the drying observed in southern Africa and Chile.

Cai says it is not understood why the cell has moved so much faster over south-eastern Australia. “The next step is to follow up our hunch that it has to do with the proximity to the western Pacific, the cell’s main engine.”

Cannabis withdrawal symptoms – including sleep problems, depression, anxiety and loss of appetite – are real despite the denials of many users and even clinicians, a study of 49 cannabis users has found.

Dr David Allsop of the University of NSW sought regular cannabis users who were not seeking treatment to participate in a trial of the effects of abstinence for 2 weeks. Postcards and advertisements at universities and theaters produced a surprisingly strong response. “People responded to the noble principle of expanding knowledge and helping fellow users,” Allsop says.

Respondents were screened to identify anyone showing a number of the factors used to identify drug dependence, of which experiencing withdrawal symptoms is one of seven.

Symptoms peaked within 3–5 days of quitting smoking, although more dependent users were still experiencing the effects at the end of the 2-week trial.

“A considerable number of people don’t experience withdrawal symptoms,” Allsop says. “Only about 10% of users develop dependence, and people say that if it hasn’t happened to them it doesn’t exist.” It is less clear why some clinicians have resisted evidence for the existence of cannabis withdrawal.

Allsop hopes the findings can be used in education campaigns about the effects of cannabis, and in assisting those attempting to give up. “There is no equivalent of nicotine patches for cannabis users,” he says.

“At the moment the best course of treatment is cognitive behavioural therapy and motivational support. If you educate people about the symptoms and what they can expect you can work with them to develop strategies to cope.”

Turtle-headed sea snakes are far less likely to travel between coral reefs than previously thought, putting populations at risk of extinction. The findings add to an alarming picture of species extinction and decline in the Timor Sea.

Dr Vimoksalehi Lukoschek of the ARC Centre of Excellence for Coral Reef Studies found that populations of the sea snake on adjacent reefs showed substantial genetic differences, indicating that mating is rare between neighbouring populations.

“The genetic divergence we found confirms that snakes rarely travel to other locations to mate, regardless of the distance, and means that if one population were to decline or disappear it is unlikely to be ‘replenished’ by neighbouring snakes because snakes rarely move between reefs,” Lukoschek says.

The findings were confirmed by Prof Rick Shine at the University of Sydney: “For 8 years, sea snakes on two reefs that are adjacent to each other in New Caledonia have been captured, tagged with a microchip device and released. In almost all instances, the snakes were repeatedly recaptured on the same reef during summers and winters.”

Lukoschek says that other research she has conducted, some of it not yet published, leads her to believe that the pattern will be the same for other reef-associated sea snake species, although she emphasises that there are many sea snake species with very different lifestyles. “All the reef-associated species in the region are closely related and from a recently evolved group,” she says.

“This is of great concern given that some Australian populations of turtle-headed and other reef-associated sea snakes have undergone massive declines or local extinctions in recent years, particularly at Ashmore Reef in the Timor Sea and also on some reefs in the southern Great Barrier Reef,” Lukoschek says.

Sea snake populations have undergone catastrophic collapse at Ashmore Reef in the past 20 years, with some species also disappearing from other reefs in the Timor Sea. Lukoschek says she does not know why this occurred or the implications for the wider ecology.

“Ashmore Reef suffered a major loss of coral some time ago, with partial recovery since. However, I don’t think this is the reason because Scott Reef lost even more coral cover and it still has sea snakes.”

A trial of plants as a way to control contamination of mine sites and urban landfill has been hailed as a success, with the potential to provide clean energy spin-offs.

Contaminated sites are frequently capped with clay to prevent toxins leaking into the surrounding environment. However, under extreme Australian conditions the clay often cracks, allowing water to enter. If the water is acidic it can mobilise heavy metals, which then leach into groundwater. The water can also contribute to methane formation.

Prof Nanthi Bolan of the CRC for Contamination Assessment and Remediation of the Environment explains that plants could provide a solution, absorbing much of the water before it can reach the cracks. Trials were conducted with giant reeds, sunflowers and mustard but success required more than planting a few seeds.

“Clay is very low in carbon, very low in nutrients,” Bolan says. “The test site is very close to a sewage treatment plant so we realised we could apply both waste water and biosolids to get the plants established.”

Bolan admits the irony of adding extra water when the goal is to reduce the amount getting through the clay, but says that irrigation was essential in the Adelaide summer, and careful monitoring was conducted to see that none got through.

“Sunflower and mustard are both edible, and we don’t want to be growing those on contaminated soil so we’re only planning to pursue the giant reeds,” Bolan says.

However, he sees promise as the reeds are fast-growing and abundant. With 70 t/ha produced each year, the giant reeds could be harvested for ethanol or biochar production, or for burning as fuel.

Moreover, as they are relatives of bamboo and sugarcane, the reeds do not need to be replanted every year. “Some people get seven crops before they need to replant,” Bolan says.

The reeds are not native, and can be highly invasive in waterways. However, they spread through parts of their rhizome, or stem, rather than through seeds, so they are unlikely to become a weed around dryland sites.

Investigations are underway on appropriate native species to fulfil the same role.

Scientists have identified a protein with a key role in sperm health, with possible implications for treating male infertility, contraception and wider health questions.

Prof Moria O’Bryan of Monash University’s Faculty of Medicine, Nursing and Health Sciences leads a team that has published a paper in PLOS Genetics showing that sperm are crippled and unable to swim when the protein RABL2 is not produced properly. There is also a 50% reduction in sperm production and a 17% shortening of the tails.

“As motility is absolutely essential for fertility, insights into tail function may reveal options for urgently needed male-based contraception,” O’Bryan says.

RABL2 is an intraflagellar transport protein that lead author Ms Jennifer Lo compares to a train. “Our data suggests that the reloading of the train is defective if RABL2 dysfunctions,” Lo says. “The train is still running in sperm tails with dysfunctional RABL2, but it contains fewer passengers. The end result is that sperm formation and motility are abnormal.”

O’Bryan says that sperm with defective RABL2 do not swim like tadpoles, but simply twitch a little. The shortening alone cannot account for this, but raises tantalising questions. “It would be interesting to see if tail length is important. We know there is a lot of difference between length in different species; species with high fertility tend to have long-tailed sperm,” she says.

While drugs to control RABL2 might one day provide an effective male contraceptive, O’Bryan notes it is found in lower concentrations in the brain, kidney, liver and lung, suggesting that any inhibitor created would need to be specific to the testes. RABL2’s role in other organs is not established, although O’Bryan says in the lungs it may form the cilia that move mucus.

The factors that affect RABL2 may be signs of deeper issues that need addressing. “Studies show that when men are exposed to environmental pollutants, sperm are one of the first things to drop off,” O’Bryan says. “For example, toll booth operators have low fertility, and after the flu fertility can be down for months.

“There has been one good study that showed an association between sperm count and general health, so the presentation of a man for infertility treatment offers the opportunity to not only give him the children he desires but also to mitigate future disease.”

Fossilised dung has revealed that New Zealand’s kakapo fed on the pollen of the parasitic plant Dactylanthus. The finding brings together two of the stranger species to occupy New Zealand, and offers hope for the survival of both now they are endangered.

The flightless night parrot has gained international fame after more than four million people watched a YouTube clip of one trying to mate with zoologist Mark Cardawine’s head. It is now extinct on the New Zealand mainland, but some have been transferred to the island sanctuary Hauturu, which remains free of rats and possums.

The absence of introduced species on Hauturu has also allowed Dactylanthus, also known as the wood rose or Hades flower, to survive on the island. The two may turn out to be very good for each other.

In Conservation Biology, Prof Alan Cooper of the Australian Centre for Ancient DNA at Adelaide University reported the discovery of kakapo coprolites from a South Island cave with high concentrations of Dactylanthus pollen.

Dactylanthus has neither roots nor leaves, but survives by attaching a kind of umbilical cord to the trunk of a tree, from which it sucks out nutrients. The name ‘wood rose’ comes from the highly prized rose patterning that forms on the infected tree.

The flower was never common enough to provide a major source of food for the parrot, but Cooper says: “It is a coordinated flowering, so for a few nights a year there would be enough to provide a lot of food, and the smell and quantity of nectar would have made it very attractive. We’re really lucky to have found coprolites from the right time of year.”

Cooper suspects the kakapo fed in a similar manner to the only other known pollinator, the lesser short-tailed bat, by “sticking its nose in but not eating the flowers”. Introduced rats and possums eat the whole flower and consequently not only fail to fertilise the plant but kill it after a few years.

Night cameras have been put in place to see if the kakapo on Hauturu are resuming their ancient role, but as yet no evidence has emerged.

Chestnut-crowned babblers display altruistic behaviour, feeding young that are not their own offspring. However, they are far more likely to do this for their brothers and sisters than for more distant relations.

“Cooperation is a major evolutionary puzzle,” says Dr Lucy Browning from the University of NSW School of Biology, Earth and Environmental Sciences. “One idea is that by helping relatives with whom they share DNA they can pass on their genes indirectly, but testing this idea in birds and mammals has proved surprisingly difficult.

“An alternative theory is that such cooperation is actually selfish because in group-living species like babblers, individuals can increase their own welfare by helping to make their group larger, irrespective of how closely related they are.”

Browning says there is evidence that babblers living in larger groups are less likely to be taken by raptors. “They also all roost together, and in the desert it can get cold at night so there is an energetic benefit from staying warm, so a larger group may help. We also know that there is a much lower chance of succeeding in raising young in a small group.” Consequently, birds that may one day become the colony’s breeding pair have an incentive to see the population grow.

Browning set out to test these two theories at the UNSW Arid Zone Research Station. Birds seeking to increase the colony should help raise young irrespective of genetic relationships. However, behaviour driven by gene promotion should be affected by family ties.

Using radio transponders, Browning tracked which birds visited the nest to feed the young. In the Proceedings of the Royal Society B she revealed: “When helpers are caring for their brothers and sisters they feed them three times more often than when they are unrelated”.

All birds that were not at least half-brothers or half-sisters were classified as unrelated, so Browning could not test if cousins showed intermediary behaviour.

While Browning did not examine what non-feeders did with their spare time, she did find that birds that did less helping weighed more, suggesting there is a price to pay for helping out the family.

Fathers with lots of helpers still seemed to work as hard to give their young the ideal chance in life, but Browning found that mothers used extra assistance to cut down their own contributions. “It may be that the benefit is in allowing mothers to lighten their load and invest more in future egg production.”

Browning is wary of drawing conclusions for humans, saying: “We need to look at lots of species before painting with a bigger brush”.

However, her colleague Dr Andy Russell of the University of Exeter says: “Our results suggest that the evolution of cooperation might have started with offspring helping parents to rear younger siblings, and only latterly, as societies evolved, did cooperation among members of different families become common.”

Electrification could replace methyl bromide fumigation in the export of timber. Methyl bromide is one of the last ozone-depleting chemicals still in use, and signatories to the Montreal Protocol (see p.34, this issue) commit to avoiding it wherever possible. It is also toxic.

Despite these problems, methyl bromide continues to be used for fumigating solid wood packaging and whole logs because chemical substitutes are even more toxic. Without sterilisation there is the danger of introducing pest species to areas where they may do considerable damage.

Heating of logs is an alternative to fumigation, but Dr Allan Miller of the University of Canterbury’s Electric Power Engineering Centre says that putting the logs in a kiln involves greater losses of energy than using electricity.

Miller has demonstrated that by applying 11,000 V across the length of a log it is possible to heat logs to the 50–60°C range required to kill the relevant pests. “The current is quite substantial but the time is quite short, so the energy consumed is not that high,” Miller says.

Wood becomes damaged if local temperatures rise above 100°C and boiling occurs, so Miller has produced specially designed electrodes and a constant monitoring system to ensure that electricity is sent where it is needed without overheating any part.

A new variety of strawberries has twice the concentration of health-preserving nutrients that the fruit normally contains, and its development occurred entirely by accident.

“The breeding program was focused on other things,” says Dr Kent Fanning of the Queensland Department of Agriculture. “They were looking for flavour, size, disease resistance and capacity to survive transport. However, one of the breeders told me he had produced a line that had a particularly dark red colour. I said it might be high in anthocyanin and suggested we test it.”

Anthocyanins exist in many fruits and are thought to provide protection against cancer and heart disease, along with more speculative benefits against dementia and obesity. Fanning acknowledges that even the new breed is not as high in anthocyanins as blueberries, let alone blackcurrants and more exotic fruits such as açaí berries. However, with strawberries likely to be eaten in larger quantities than many other fruits, the new variety could play a part in boosting anthocyanin consumption.

Fanning says that little is known about how much anthocyanin in the diet is enough, but says there is evidence of health benefits at 300 mg/day. Australian figures are unknown, but most Americans get less than 10% that much, and one would need to eat 300 grams of even the new strawberry variety to get such a dose each day.

Different fruits contain slightly different forms of anthocyanins, but Fanning says no feeding studies have been done to establish if there are differences in benefits between the varieties.

Strawberries Australia is conducting research on consumer responses to darker coloured strawberries, but Fanning is hopeful they can be marketed as a premium product.