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September 2012 Archives

My significant other is forever telling me that Facebook is a total time-waster. Sometimes I do tend to agree - but also, one can Find Out Stuff! Like the study I've just heard about via Science Alert, on how children get information about genetics and DNA - things we might regard as being in the 'too hard' basket & so best left for senior high school students to grapple with. That grappling begins in year 11, when one of the NCEA Level 1 Science standards asks that students be able to "demonstrate understanding of biological ideas relating to genetic variation".

Is that too late? Jenny Donovan and Grady Venville suggest that it is, arguing that with the rapid growth of knowledge in and applications of molecular biology,

[citizens] of the future will be called upon to make more decisions, from personal to political, regarding the impact of genetics on society. 'Designer babies'; gene therapy; genetic modification; cloning, and the potential access to and use of personal genetic information are all complex and multifactorial issues. All raise ethical and scientific dilemmas.

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Bedbugs. One of the critters that I'd prefer not to encounter on my travels. They come out at night and bite sleeping humans (& other animals), retreating during the day to their dark hideaways, often in cracks in furniture, walls, or floors. This sounds very insanitary but the species that bites humans, Cimex lectularius, isn't generally regarded as a disease vector, and while a review published in 1963 found that bed bugs can carry a range of pathogens, the author also concluded that there was no scientific evidence of actual transmission of disease. At least one recent research study found that Rickettsia could survive in the insects' blood for several days after infection, but again noted no evidence that the pathogen was spread in the bugs' bites.

Now, I know that a bug's gotta do what a bug's gotta do. But even when it comes to their love lives, bed bugs are just not that, well, nice. For mating in the African bat bug (a relative of C.lectularius) sounds more like open warfare than a tender meeting of the sexes.

In this, and in other Cimex species (including lectularius), male bugs don't mess around. Rather than find the female's genitalia & follow a more normal route, the male simply stabs his penis into his mate's abdomen. Ouch! Traumatic insemination, indeed. His sperm are injected into her blood-filled body cavity (insects have an open circulatory system) and make their way thence to her ovaries. Not only is the female physically damaged by this act, but it must also open the door to infection by pathogens. It turns out that males are also susceptible to damage as they are not too fussy about who they mate with, and at times another male 'will do'.

The risk of harm is not trivial, and so individuals with any trait that might minimise the harm is going to be at a selective advantage (& if that trait has a heritable component, the underlying alleles will spread through the population's gene pool). The result is the evolution of 'paragenitals' in both males and females: structures described as 'extra genital funnel[s]' (Dolgin, 2007) that are easy to access and increase the odds that matings will be in that spot rather than randomly all over the abdomen. What's more, the male's penis enters a cavity lined with immune cells (like all animals, insects have an innate immune system), which reduces the odds that the mating partner will pick up an infection. 

There is, of course, a disadvantage to a male bug in looking like a female - more males may start to hit on him. Consequently males' paragenitals differ from females' in that they are more open (their funnel is a different shape). But the story doesn't stop there. It turns out that at least some female bat bugs' paragenitals look more like those of the males - and that this deception works: counting the scars on their abdomens, & comparing the results with the scores for more girly girls, showed that male-like females had suffered fewer of those random mating stabbings.

I shall let the reporter at Evolution (on Facebook, where I first spotted this story) have the last word:

If you're having trouble envisioning this cross-dressing insanity, picture this - the males are dressed like girls, and the girls dressed like guys who are dressed like girls, and everyone's doing this to avoid sex.

(Avoid it as much as possible. But not completely - for that route would lead to the oblivion of extinction.)

E.Dolgin (2007) Bug sexual warfare drives gender bender: African bat bugs have two types of female genitalia Nature (published online 20 September 2007) doi: 10.1038/news070917-7



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 No, it's a megalopygid moth caterpillar (via Science Alert on Facebook). 

Image: Rainforest Expeditions (on Facebook)

Megalopygids are also called 'flannel moths' (you can see images of both adults and larvae here - the larvae are quite diverse in appearance). I do wonder, after looking at this adult, if they aren't related to the poodle moth I shared with you a few posts ago.

Apparently the larvae, which are 2-3cm long, are called 'puss caterpillars', presumably because the long hairs that cover their bodies make them look vaguely (very vaguely!) cat-like**. But you wouldn't want to stroke them. Hidden in all that seemingly soft fluffiness are spines tipped with venom that causes a burning pain, & inflammation that can last for several days - with the nastiest species, in a worst-case scenario the victim may go into shock. So you'd want to restrain the urge to touch, if you came across one (in the southern US, Mexico, or Central America).


** I'm afraid I don't think 'cat' when I see that image; it reminds me more of a certain millionaire's hairpiece...

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Today in the Herald I learned that eye colour can reflect personality. Apparently

[r]esearchers from the University of Queensland and the University of NSW analysed the eye colour of 336 Australians - most with a northern European background. They answered a series of questionnaires measuring aspects of their personality like agreeableness, conscientiousness and neuroticism.

The story went on to say that blue eyes were linked to competitiveness, and that this would be useful in acquiring a mate during the extreme conditions in northern Europe during the last Ice Age. Along with its own, slightly different version of the story, Medical Daily helpfully provides a link to the original paper (which is a couple of years old). The abstract (Gardiner & Jackson, 2010) tells us that

The current study investigates whether eye color provides a marker of Agreeableness in North Europeans. Extrapolating from Frost's (2006) research uncovering an unusually diverse range of hair and eye color in northern Europe, we tested the hypothesis that light eyed individuals of North European descent would be less agreeable (a personality marker for competitiveness) when compared to their dark eyed counterparts, whereas there would be no such effect for people of European descent in general. The hypothesis was tested in Australia to provide consistent environmental conditions for both groups of people. Results support the hypothesis. Implications and conclusions are discussed.

My first thought was - in extreme environments, when the whole group has to work together to survive, would a strong competitive streak really be that useful, or would cooperative behaviour be favoured? 

The survey participants were university students, & the way they were classified was interesting: 

Participants of White UK origin were classified as North European in origin (63.1%) and all other white Europeans were classified as being of Non-UK White European descent. Our designation of participants from the UK as being classified as North European and subject to the effects of the Ice Age is in-line with Frost’s (2006) theoretical account... We chose UK participants as being representative of North Europeans because we thought that its relative isolation as an island would be more likely to have led to less migration than other parts of Europe which might be more commonly defined as being part of North Europe such as the Scandinavian countries.

Yet the British Isles have a long history of migrations from Europe (going well back into prehistoric times). 

Respondents self-reported their eye colour, presumably selecting from the categories listed by Gardiner & Jackson (blue, green, hazel, brown, or black). A more objective measure would have seen photographs assessed by a third party. (It would be useful to know whether the participants knew what was being studied, as prior knowledge of the hypothesis, for example, could have biased their choices when completing the surveys.) The researchers found that 

light-eyed Europeans are less agreeable than their dark eyed counterparts

who tended to see themselves as more altruistic and helpful. Medical Daily reported that the researchers "believe the link has evolutionary roots", & the journal article bears this out. Oh goody - evolutionary psychology. I do like a good story. According to the research article, 

sexual selection was stronger in ancestral Northern and Eastern Europeans because the steppe-tundra environment of the last ice age skewed the operational sex ratio towards a male shortage. There were two causes for this shortage of males: firstly, men had to hunt over large distances in search for herds thereby often incurring injuries and dying younger; secondly, women had fewer opportunities to gather food and thus required more male provisioning, resulting in less polygyny.

Evidence, please. Evidence that men 20,000 years ago were dying off at a higher rate than women. Are sex ratios skewed, in the skeletal remains we have available from this time period? (Sex ratios tend to be slightly skewed in favour of males in modern hunter-gatherer populations such as Inuit & Australian Aborigines.) 

Also, what was that Ice Age environment really like? Up close to the kilometre-thick glaciers that pushed down from the north, conditions would have been severe, but further south? OK, there were periods when the average temperature was rather colder than now: these are the 'glacial' periods. And glacial periods were separated by 'interglacials', lasting thousands or tens of thousands of years, when things were more temperate & in fact temperatures approximated those we experience now. The 'Ice Age' wasn't one long spell of unremitting cold. Would there really have been sufficiently strong selection, for sufficiently long periods of time, to generate the eye-colour frequencies observed in modern populations? Or are we looking at the result of a bottleneck event, for example?

The article goes on to say that the supposed skewed sex ratio would have generated strong competition between women for the available men, and goes further: that because blue-eyed women are supposedly more competitive, they'd have won out and achieved more matings, spreading their genes around.

Again, evidence, please. If this proposed mechanism shaped our behaviour so strongly, well, we're only 12,000 years or so out of the last glacial period, so there would presumably still be evidence of similar sexual selection in today's populations. In fact, Gardiner & Jackson comment that 

blue eyes are still much rarer than brown and thus selection based on rare color advantage, even in the present time, may still exist in North Europe.

Somehow I doubt it: 99% of Estonians, 75% of Germans, and 90% of Danes have blue eyes. Rare colour selection, if it exists, should be in favour of brown-eyed people, in those Northern European populations.

E.Gardiner & C.J.Jackson (2010) Eye color predicts disagreeableness in North Europeans: support in favor of Frost (2006) Current Psychology 29: 1-9 doi: 10.1007/s12144-009-9070-1

Quick Personality Survey!
This cat's markings look like:


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The dream is over! Dr Poonpipope Kasemsap, the IBO Chairperson, contacted NZIBO chair Dr Angela Sharples last night. The Indonesian government has stepped in to support the organisers and the 25th IBO will be hosted in Bali in either the 1st or 2nd week of July 2014.

As Angela has said to me, on a positive note it will be wonderful to visit Indonesia. They will organise a wonderful event and the Balinese version of manaakitanga is world reknowned. Poon and the IBO steering committee have been incredibly supportive of NZIBO and despite us letting the organisation down it's great to know we are still able to compete in future IBOs. This really was a major concern for NZIBO, so we were very relieved to hear this. 

But we do wish the NZ government understood the importance of consistently supporting excellence in Science education, at all levels. At some point, New Zealand - as a competing nation - will be expected to host the Olympiad. Hopefully the support will be there in the future.

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Sir Paul Callaghan was a great scientist, a superb science communicator, and a visionary with a very clear idea of the importance of science and science education to New Zealand's future: a future where our population is 'science-savvy' and where students are attracted to study for careers in science, technology and engineering. If that's to happen, we need to catch students early, nuture their natural curiosity, & maintain their enthusiasm for the sciences throughout their educational trajectories.

And for that to happen, our teachers need to be supported in developing and enhancing their own skills. This is particularly the case for teachers in primary schools, where recent reports have identified quite significant issues with delivery of science programs - due at least in part to a lack of professional development and support for primary science teaching.

Which is where the Sir Paul Callaghan Science Academy comes in to it. It reflects Sir Paul's belief that 

You don't need to teach a child curiosity. Curiosity is innate. You just have to be careful not to squash it. This is the challenge for the teacher - to foster and guide that curiosity.

Launched today, the Academy aims to

inspire primary teachers to foster and guide the natural curiosity of children; and promote excellence in science teaching through intensive, best practice, inservice training courses.

The intention is that the 24 teachers who attend each Academy session will then be able to become champions of science** in their own school communities. The program's goals and intended outcomes are praiseworthy, and its success would be a living memorial to a great New Zealander.


** great to see that they will receive ongoing mentoring; I must hope that their schools will receive the resourcing to allow their champions to fulfill this demanding role


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From Nature (& via a commenter at Silly Beliefs): science wins over creationism.

In South Korea, the Society for Textbook Revise, STR [sic] - associated with the Korea Association for Creation Research - has apparently been pushing textbook publishers to remove two examples of evolution from school textbooks. You may be surprised to hear that we're not in Texas any more, Dorothy, given how similar this sounds to calls in the US for students to learn about the 'theories' around the development of life on earth. The STR argued that because scientists were 'debating' the two textbook examples (Archaeopteryx, and the evolutionary history of horses), the examples were 'flawed' & so shouldn't be taught. (Which, at the very least, shows a misunderstanding of how science operates.)

Soo Bin Park reports in Nature that, initially, the textbook publishers were going to do as STR wanted; however, following an outcry from scientists, the South Korean government set up an expert panel to look into the issue. The outcome? 

A reaffirmation that 

the theory of evolution is an essential part of modern science that all students must learn in school

and that Archaeopteryx should be retained in the texts.  Regarding the horse example, the panel commented that the textbooks presented it in 'too simplistic' a manner and that it should be revised or replaced, perhaps with an explanation of cetaceans' evolutionary history. This did make me wonder if perhaps the books' authors had gone down the route of what the late, great Stephen Jay Gould described as the 'fox terrier problem' and the 'creeping fox terrier clone'.

In other words, had they used the 'traditional' iconography where the evolutionary history of modern horses is presented in a fairly linear fashion, from the little Hyracotherium (I still prefer the lovely name Eohippus!) to modern Equus, with only 2-3 intermediaries? We now know that the horse phylogeny is more complex than that. And, had they described Hyracotherium as 'about the size of a fox terrier', something that Gould found to be repeated in just about every book he (well, his research assistant) looked at? It turns out that the fox terrier would have been a rather large one: Eohippus/Hyracotherium was about 60cm long & 20cm at the shoulder, and weighed around 22kg - more like a small labrador! 

Incidentally, those two names reflect the way this species was named. Hyracotherium was first described - on the basis of an incomplete specimen - by the English anatomist and palaeontologist, Richard Owen. Subsequently the American palaeontologist Othniel Marsh found a complete skeleton and named it Eohippus. Subsequent comparison found the two specimens belonged to the same species, and Owen's name was applied to both under the rule of priority used in scientific taxonomy. (Brontosaurus went the same way, replaced by the older - but, to me anyway, less euphonious Apatosaurus.)

S.B.Park (2012) Science wins over creationism in South Korea. Nature published on-line): doi: 10.1038/nature.2012.11377


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A nice piece in Nature, by Tony Ballantyne (& hat-tip to PZ Myers, who somehow finds these things first), speculates on how things could be for those who selectively reject the bits of science they don't like: in this instance, vaccination, but creationism could easily be substituted in this storyline.

T.Ballantyne (2012) If only... Nature 489: 170 doi:10.1038/489170a



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This is not biology at all :-)

I've previously seen (& linked to) videos of people walking on the surface of a mix of cornflour and water. (Marcus will be able to explain the physics behind it.) But now - via PZ Myers - we have:

Walking on Custard

 If my embedding skills fail, follow the link in Custard :-)

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A couple of days ago I posted a stunning photo of a peacock, and talked a bit about the possible genetic underpinnings of its colour patterns. My friend & blog-buddy Grant then pointed me at the story of a cat that has a similarly amazing colouration. Venus even has her own Facebook page! (I will definitely be using both these images & their stories with my first-year class next week.)

As you can see,  one half of Venus's face is black, with a yellow eye, while the other half is orange - with a blue eye. What a stunning cat!

The underlying reason for her striking colouration isn't clear. She could be a chimera, formed from the fusion of two fertilised eggs, so that some of her cell lines would have different DNA from the rest. She could equally well be a particularly impressive example of the results of X-chromosome inactivation in female mammals. In that case, of the two X chromosomes in the cells of the right-hand-side of Venus's face, the one with the 'orange' allele would have been inactivated. That side of her face is black because all cells have functioning X chromosomes that are expressing the 'black' allele. The reverse would be true for the orange side of her face.

Which leaves the question: why does she have a blue eye on the orange side?

In the comments thread to my original post, herr doktor bimler noted that

[the] X-chromosome mosaicism of female mammals turned up a lot in colour-vision research, because women carrying a colour-deficiency gene on one X chromosome end up with their retinas being more-or-less coarse patchworks of colour blindness. In the extreme case people can be red-green deficient in one eye and normal in the other**.

This can also be true for haemophilia, where the gene locus involved in the most common form of this disease is found on the X chromosome. (Haemophilia C is not sex-linked.) Heterozygous women, with one normal and one recessive, deleterious allele, are regarded as carriers, unaffected but with the potential to pass the 'haemophilia' allele on to some of their children, with damaging effect in those sons who receive it. But - and I must get my class to consider this one next week - such women are mosaics for X chromosome genes. If the 'haemophilia' X chromosome is 'on' in all the cells of their bone marrow, those women would also be haemophiliac.


**Being a person with a dry sense of humour, herr doktor concluded that such women "must spend their lives hiding from the colour vision researchers who wish to experiment upon them."

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Last year one of the books on my reading list was The Immortal Life of Henrietta Lacks, by Rebecca Skloot. I found it a fascinating and moving story. Henrietta Lacks died of cervical cancer, but even before her death doctors had begun to culture cells removed from her cervix (something that was done without her knowledge). Amazingly, these cells didn't divide a few times and then become senescent; instead, they continued - and continue - to divide without end. HeLa cells are probably one of the most widely used cell lines (they've even been up in space) and in that sense, something of Henrietta lives on today.

Recent research indicates that the same is true of the clonal cell line implicated in the Devil Facial Tumour Disease that is killing Tasmanian devils (with population declines of up to 90% in some parts of Tasmania), spread via bites inflicted during social interactions. From the paper just published in PLoS One (Ujvari et al, 2012): 

Devil Facial Tumour Disease (DFTD) is a unique clonal cancer that threatens the world's largest carnivorous marsupial, the Tasmanian devil (Sarcophilus harrisii) with extinction. This transmissible cancer is passed between individual devils by cell implantation during social interactions. The tumour arose in a Schwann cell of a single devil over 15 years ago and since then has expanded clonally, without showing signs of replicative senescence; in stark contrast to a somatic cell that displays a finite capacity for replication, known as the "Hayflick limit".

DFT cells are apparently stable chromosomally, and the tumour cells of different individuals are genetically identical - rather surprising since the tumours have proliferated and their cells passed on to thousands of Tasmanian devils in the short time since DFTD was first identified. This capacity for seemingly endless division is due to the action of the enzyme 'telomerase' on structures called telomeres, found on the ends of eukaryote chromosomes.

Normal somatic (body) cells replicate only a few times and then enter 'replicative senescence' (Uvjari et al. 2012). This is because the telomeres - tandem DNA repeats bound up with a particular protein complex called 'shelterin' - shorten each time the cells divide. The only 'normal' cells where this doesn't happen ** are the cells that give rise to eggs and sperm, due to the action of telomerase, which maintains the length of the telomeres. The same is true for cancer cells.

DFT cells have quite short telomeres, and the research team found that their length is maintained through up-regulation of telomerase gene expression; the shelterin protein complex protects them from continuous elongation. What's more, it seems that this control is done at the level of individual cells, with up-regulation in cells where telomeres have become shorter over several cycles of cell division, and shelterin blocking further elongation of 'normal-length' telomeres. Ujvari & colleagues suggest that

The short telomeres and up-regulation of telomerase likely counteract each other. The short telomeres lead to increased genetic instability but the telomerase activation facilitates tumour growth by either inhibiting further chromosomal instabilities or by circumventing checkpoints that recognise dysfunctional telomeres. Longer telomere lengths may ensure the success and survival of DFT cells by stabilising chromosomal rearrangements and preventing further genomic instabilities.

These features of DFT cells promote survival of the tumours and are the result of natural selection. Coming to a better understanding of the evolution of these features in DFTD could offer useful insights for those seeking to understand tumour development in our own species.

Ujvari B, Pearse A-M, Taylor R, Pyecroft S, Flanagan C, et al. (2012) Telomere Dynamics and Homeostasis in a Transmissible Cancer. PLoS ONE 7(8): e44085. doi:10.1371/journal.pone.0044085


In other intriguing research, it appears that mice engineered to have no functioning telomerase age more quickly than normal, but that this decline may be reversed by switching the enzyme back on through adding a particular chemical to their diet. I suppose I should not be surprised to see that the woo-meisters have seized on this: you can purchase a dietary supplement that claims to achieve the same effect in humans (if the glowing testimonials can be believed...) 


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I used to enjoy watching CSI (the original series), back when Gil Grissom (actor William Petersen) headed that fictional forensics lab. It was never the same after he left.

Anyway, one episode that I still remember involved a crime being committed by someone who was a genetic chimera: someone who had developed from an embryo formed when two fertilised eggs fused together. (There's a fascinating blog post about chimeras over at upshot was that some cell lines in that indivdual's body had one set of DNA, with other cells having a different genetic makeup. In such individuals it's possible for different tissues to express genes from one or the other lot of DNA, something that's called mosaicism (it's also possible in all female mammals, where one or the other X chromosome is randomly inactivated when the embryo is at around the 1000-cell stage of development). 

I was reminded of that episode when I saw this photo on Science Alert's Facebook page (ah, the wonders of modern social networking!):

You'd need to look at the DNA from the white & 'normal' sides of this bird to be sure whether what we're seeing here is definitely the result of a chimera displaying mosaicism. But isn't it a stunning image?

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