Was early crocodile a top predator among dinosaurs?


It’s widely-accepted that dinosaur ruled the Earth (unless you believe that the Earth is only 6,000 years old and magically sprang into existence). For around 200 million, roarin’, stompin’, Jeff Goldblum-chasin’ years they were the unquestionable tyrants of the land.


Or were they? Scientists from the US claim to have found an early ancestor of crocodiles which they believe could have been the apex predator in the region in which it lived, certainly bigger than any dinosaurs in the vicinity.

Crocodiles (along with birds) are 2 families of animals, related to dinosaurs, which managed to survive the mass extinction event of 65 million years ago. They (like sharks of the land) have therefore evolved over millions of years to become perfect killing machines.

But interestingly, this was not always the case – once upon a time, the ancestors of modern-day crocs were believed to be small, land-dwelling and primarily vegetarian (which is a bit like finding out Simon Cowell actually had a taste in music at some point in his youth).

The ‘crocodylomorph’ discovered by the team of palaeontologists is described as ‘unusually large-bodied’ for its time period and could be one of the earliest examples of when crocs began to evolve to be bigger and bite-ier (which I promise is a real scientific word…).

So, what’s the point?

It is useful to understand how creatures have evolved in the past so we have a better idea of how and why their adaptations came about (i.e. what happened in their environment to make the change in their traits more helpful to their survival).


Understanding this can be useful in today’s world where we need to understand how changing environments can affect ecosystems and how some organisms might adapt while others might require intervention in order to protect them.

Another reason studying ancient creatures is important is simply for a deeper understanding of our planet’s biological history as this is ultimately part of the jigsaw that answers the grand philosophical questions: ‘Who are we?’ and ‘Where do we come from?’

Plus dinosaurs are friggin’ awesome.

What did they do?

The researchers analysed a skull discovered in the Pekin formation (in modern day North Carolina) and compared it to other ‘crocodylomorph’ fossils to see where it fits in to the evolutionary jigsaw.


Important things to consider were its age and how certain features on the skull were shaped. Features such as the teeth and shape of the jaw can help the researchers to make intelligent guesses as to how this individual creature lived, and by comparing features with other related crocodylomorphs they can guess as to how it evolved over time.

Did they prove anything?

The skull was around 231 million years old and more than 50cm long. The researchers calculated that it would likely have been around 3m long.

Its teeth were ‘elongated, serrated and slightly recurved’, suggesting that it ate meat. Because of its size and carnivorous nature, the team named it ‘carnufex’ – meaning butcher.

The team claims that meat-eating dinosaurs found in the same region and from that same time period were smaller than carnufex, which they say suggests it was a ‘top-order predator’.

So, what does it mean?

The researchers do make a compelling case, generally if something is larger than anything else around and eats meat then it is probably an apex predator (although it might also be a scavenger).

The fact that it was larger than the dinosaurs of its era and location (dinosaurs in other regions at the same time grew bigger) raises an interesting possibility that at one point crocodiles were the predators of dinosaurs.

Given that we are (kind-of) predators of crocodiles (there are plenty of places that sell cutlets of croc), does this mean we are the most successful predators the planet has ever seen? Probably not – in a few million years the ancestors of lions or dolphins or even chipmunks might be lunching on us, so is the precariousness of evolutionary power.


So perhaps we should view our time as the Earth’s dominant species for what it is in the grand passage of time – merely a passing fad – and try not to ruin it for the 7ft tall meat-eating apex-predator chipmunks of the post-apocalyptic future.

Original article in Scientific Reports Mar 2014

All images are open-source/Creative Commons licence.
Credit: AzDude (First); Mike Baird (Second); L Zanno et al.(Third); Fotocitizen (Fourth).

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Zanno LE, Drymala S, Nesbitt SJ, & Schneider VP (2015). Early crocodylomorph increases top tier predator diversity during rise of dinosaurs. Scientific reports, 5 PMID: 25787306


Biochemical ‘memory’ can help bacteria to grow


E_choli_Gram - Copy

When we think of ‘memory’ we typically think of the brain being able to recall facts and events, but ‘memory’ can take other forms: some plastics can ‘remember’ particular shapes, material shapes or magnetic alignment can be used for storing digital data and our immune systems also have a capacity to ‘remember’ past infections.

Bacteria are also believed to display a kind of ‘memory’ too, which helps them to digest nutrients they have encountered recently. A new study by researchers in the US explores this ‘memory’ in E. coli to see how it impacts on their ability to grow in environments where the food source changes.

So, what’s the point?

Bacteria are hardy survivors – the Mad Max of organisms. They are thought to be one of the very first forms of life to have evolved, and will certainly be around long after humans have gone (in fact, they’ll almost certainly have eaten our physical remains).

Central to their incredible capacity to survive is their ability to eat different things. Now while this might not seem particularly impressive to us – a species that invented the bacon ice-cream sundae or the cheeseburger in a can – species of bacteria have evolved to eat substances as unappetising as concrete, petroleum and nuclear waste (although no peer-reviewed tests have been conducted to see if any can eat the cheeseburger in a can).


When a bacterium is exposed to a new food source, it typically takes a while to become adjusted to it (the so-called ‘lag phase’). In this phase, the bacterium is generating the biochemical machinery (enzymes etc.) needed to digest the new nutrients it finds itself surrounded by.

During the ‘lag phase’ the bacteria are not dividing and so growth of the bacterial population is temporarily stunted. The researchers wanted to see if bacteria could, in effect, be trained to grow on more than one food source and reduce or eliminate the ‘lag phase’.

This idea is not completely crazy – the authors claim that ‘memory’ has been previously observed in bacteria, as some of the metabolic machinery for the original food source will still kick around inside the cell even after the bacterium has adjusted to the new food source.

Figuring out whether or not bacterial ‘memory’ helps them to quickly adapt to changing environments could be important in understanding how to control the growth and spread of bacteria. This is not just useful for killing harmful bacteria that we don’t want, but also for culturing or harvesting bacteria that we do want, for instance those used in waste treatment or for producing therapeutic molecules such as human insulin.

What did they do?

The researchers developed a microfluidic device, which fed a culture of bacteria (E. Coli) a stream of either glucose or lactose, with the feed changing every 4 hours for 3 complete glucose/lactose cycles (24 hours in total).


As the feed flows past the culture, individual bacteria are washed away, and are measured at a point downstream. The number of bacteria washed away in the stream is used as an indication of the total size of the population.

In a second experiment, they tested how long this ‘memory’ persists by growing bacteria on lactose for four hours, switching to glucose for a varying time (4, 5.5, 7, 9 and 12 hours) then measuring the ‘lag phase’ (if any) when the feed was switched back to lactose.

Did they prove anything?

The first time lactose was introduced (after 4 hours of glucose), there was a significant ‘lag phase’ as the bacteria adjusted to the new food (see Graph A below). However, the next time glucose was introduced, the ‘lag phase’ was much shorter and in subsequent changes of glucose/lactose there was no ‘lag phase’ at all, with the transitions described as ‘seamless’ (see Graph B below).

bacterial phenotypic memory

However, in the second experiment where the exposure time to glucose was varied, they found that when the bacteria were deprived of lactose for longer than four hours, the ‘lag phase’ reappeared. The ‘lag phase’ generally increased as the time away from lactose increased (see Graph C above).

In further tests, they looked at the lactose-digesting machinery (specifically proteins known as LacY and LacZ). They stated that LacY and LacZ are degraded extremely slowly, so this alone is unlikely to be the cause of the increase in ‘lag phase’.

However, they reckoned that LacY and LacZ are passed on from mother cell to daughter cell as each bacterium divides, causing ‘dilution’ of these proteins in each resulting cell (all of the residual LacY/LacZ of the mother cell would be shared between mother and daughter after division).

This can explain why there is little change in the length of the ‘lag phase’ at lactose-deprivation times below 4 hours (not much cell division occurs), but above this time there is a general increase in the ‘lag-phase’ as the number of cells dividing increases with time (sharing roughly the same amount of LacY and LacZ between a larger number of cells).

So, what does it mean?

There certainly appears to be a link between the length of time since the bacteria were exposed to lactose and the length of the ‘lag phase’, and the reasoning that cell-division is responsible appears to be consistent with the results.

This study could help scientists to better understand the mechanisms behind the growth behaviour of bacteria – important information in trying to control them. This is essential for harnessing their incredible capabilities technologically and curtailling their potential to harm us too.

Original article in PLoS Genetics Sep 2014

All images are open-source/Creative Commons licence.Credit: Bobjgalindo (First); A Gatilao (Second); NIH/NIAID (Third); G Lambert and E Kussel (Fourth)

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Lambert, G., & Kussell, E. (2014). Memory and Fitness Optimization of Bacteria under Fluctuating Environments PLoS Genetics, 10 (9) DOI: 10.1371/journal.pgen.1004556

Guiding light to boost algae biofuel production



Algae are aquatic organisms which make ponds murky and biofoul the hulls of boats and ships and slow them down. But these these tiny green creatures could also be the future of fuel production – they produce natural oils (lipids) which can be extracted and turned into a wide range of hydrocarbon fuels including diesel and kerosene.

Finding ways of growing the algae as efficiently as possible is essential for this technology to become commercially viable, and developing photobioreactors (basically glorified jars of algae) which can maximise the amount of sunlight that the algae receive is an important part of improving this efficiency.

A team of researchers from the US has investigated using a quirk of light exploited in fibre-optics to improve the distribution of light in an algae tank and boost growth.

So, what’s the point?


This study uses Slab waveguides, which exploit a phenomenon known as ‘total internal reflection‘, where light waves are trapped inside an object, continually bouncing off the inside edges (see images above).

Total internal reflection allows a light wave to be guided in a similar way to how a pipe or hose guides a flow of water, and is used in applications such as fibre-optics. Here, the researchers wanted to use the phenomenon to guide some of the incoming sunlight into the darker parts of the algae tank, where it doesn’t usually penetrate.

While the researchers say that using waveguides to scatter light in photobioreactors has been done before, this study tests different scattering schemes in order to distribute light as evenly as possible throughout the tank.

By making the distribution of light as even as possible, it will hopefully improve the growth rate of algae and therefore produce biofuel more efficiently.

What did they do?

In order to make the light leave the slab waveguide, the researchers attached tiny pillars designed to scatter some of the light from the waveguide, distributing it into the tanks (see image below).

pillars on waveguide

The waveguide/pillar system effectively turns incoming sunlight (which would normally only light up the outer surface of the algae tanks) into a series of small lights which can be spread evenly throughout the inside of the tank.

However, because light is being removed from the waveguide by each pillar, the intensity of the light is much lower at the end of the waveguide than it is at the start. So the researchers wanted to see if they could vary the distances between the pillars in order to compensate for this by having pillars more spread out at the beginning and more concentrated at the end (‘gradient’ system, see image below).

pillar spacings on waveguide
Did they prove anything?

In an experiment using dye-stained water (to imitate a thick biofilm), the researchers found that their ‘gradient’ pillar system successfully distributed light of roughly the same intensity across the length of the waveguide.

They then tested their system in a thin bioreactor against a similar system with evenly-distributed pillars. Crucially, they found that by changing the spacings between the pillars (more spread out at the start of the waveguide) boosted algae growth by ‘at least 40%’.

So, what does it mean?

It seems as if their idea has worked – the ‘gradient’ pillar scheme appears to distribute light evenly across the tank and led to an increase in algae growth compared to the evenly-distributed pillar scheme.

This is a simple, but quite clever, engineering solution to the problem of enabling sunlight to penetrate into a tank of algae and could help large-scale algae biofuel-production to become a reality one day.

There is also potential to use waveguides to collect light that would normally fall outside the tank, boosting the overall amount of light available for the algae.

It may be a while before algae are helping us to drive around, but research like this adds another piece to the jigsaw that could help the dream of green fuels become realised.

Original article in Optics Express Sep 2014

All images are open-source/Creative Commons licence.Credit: IGV Biotech (First and title); Josell7 and Sai 2020 (Second); Ahsan et al. (modified by TSIC) (Third and Fourth); NEON_ja (Fifth)

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Ahsan, S., Pereyra, B., Jung, E., & Erickson, D. (2014). Engineered surface scatterers in edge-lit slab waveguides to improve light delivery in algae cultivation Optics Express, 22 (S6) DOI: 10.1364/OE.22.0A1526

Centrifuging people to see if gravity affects perception



Which way is up? It’s a question that’s needs to be answered for seeds to grow in the right direction, homing pigeons to navigate and for Stoke City defenders to know where to hoof the ball.

Our bodies can sense the direction of gravity – and it helps us to figure out how our bodies are orientated relative to the ground, which is essential for maintaining balance. This is rarely an issue for most of us here on Earth but for astronauts on the moon, where the gravity is only around 1/6th of what it is here, keeping upright is more problematic.

This can result in some of the most dangerous pratfalls known to humankind, although thankfully no-one has yet damaged their space-gear as a result of lunar stumbles (or had a video of their embarrassing topples sent in to You’ve Been Framed).

But precisely how much gravity do we need to feel to maintain balance as well as we do on Earth? A new study by researchers from Canada and Germany tries to find out – by placing intrepid volunteers in astronaut-style centrifuges.

So, what’s the point?

The researchers say that our idea of ‘up’ is determined by a combination of three things: our body position (i.e. standing up vs. lying down), visual cues and direction of gravity sensed by our bodies.


They wanted to test how important a role gravity plays in this complex mix and just how much pull is required to help us to understand how we are orientated. This could have implications in future manned space missions as well as helping us to better understand the way our bodies sense our surroundings.

What did they do?

It might sound like an experiment designed to find how much vomit a human can produce, but willing participants were spun in a centrifuge while either sitting or lying on their back or sides.

As they were spun round, the letter ‘p’ would appear on a screen in front of the participants’ faces in a range of orientations. The participants had to indicate whether they thought each letter was a ‘p’ or a ‘d’, while a special computer algorithm varied the orientations of the letter to find the angles at which each person chose ‘p’ and ‘d’ in a 50:50 ratio.

The researchers wanted to see whether this angle changed depending on how fast the centrifuge spun. They could then compared these to control experiments, where participants completed the same task, but either sitting up (experiencing gravity along their bodies) or lying on their sides and back (experiencing gravity across their bodies) without being spun around.

Did they prove anything?

The researchers found that as centrifugation speed (simulated gravity) increased, the angle at which the participants selected ‘p’ and ‘d’ in a 50:50 ratio got closer to zero. In other words, feeling the pull of simulated gravity allowed participants to establish the ‘perceptual upright’ closer to what it was in reality.

The scientists compared the results obtained for different body positions as well, trying to calculate how important gravity, visual cues and body position are at each centrifugation speed. Their graph suggests that as simulated gravity increases, the contribution of gravity towards the ‘perceptual upright’ increases, while the contributions of visual cues and body position decrease (see graph below).

contribution of gravity

So, what does it mean?

While a pattern appears to emerge from this study linking increased gravity to the ‘perceptual upright’ only 10 participants were tested. As a result of small sample size the errors are pretty large, and the errors of the extreme values of g vs. ‘perceptual upright’ overlap (Figure 3A in the paper) so it’s difficult to say conclusively whether or not the effect of gravity is genuine.

This still seems like an interesting idea and certainly using centrifuges to test how we sense gravity does appear to be promising. While more tests need to be done there can be no doubt that sticking people in centrifuges is pretty cool (I’d definitely volunteer for the next set of tests!).

Original article in PLOS One Sep 2014
All images are open-source/Creative Commons licence.Credit: NASA GSFC (First); M Berch (Second); L R Harris et al. (Third)
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Harris, L., Herpers, R., Hofhammer, T., & Jenkin, M. (2014). How Much Gravity Is Needed to Establish the Perceptual Upright? PLoS ONE, 9 (9) DOI: 10.1371/journal.pone.0106207

Can our brains process words while we sleep?



Learning by listening to things while you sleep might be a desperate last resort for budding linguists and university students cramming for their finals, but how much can the human brain actually take on board while in a state of unconsciousness?

It is fairly well-established that the brain processes information while we sleep (such as dealing with memories and ‘information of the day’) and can even respond to certain external stimuli (for instance the hypnic jerk is believed by some to be an ancient response evolved by humans to prevent us from falling from trees as we slept).

Now a team of scientists from France and the UK have tried to see whether or not our sleeping brains can process words to the point where they can understand simple meanings of those words.


So, what’s the point?

The human brain is capable of incredible things – the source of music, logic, poorly-written science blogs and language.

In order for language to work our brains need to be able to interpret the meanings of words. While this might seem like an obvious and simple task, you have to remember that individual words come loaded with various connotations and nuances (the word ‘set’ for instance is described on dictionary.com as having 100 separate meanings involving subjects as diverse as surgery, tennis and chickens).

Another level of complexity in meaning is the categorisation of a word:a simple noun such as ‘ball’ could be considered as a ‘toy’, ‘sporting equipment’ or a synonym of ‘sphere’ and can itself be sub-categorised into different types of ball.

In this study, the researchers wanted to see whether the sleeping brain can distinguish between words which are the names of animals and those which aren’t: a simple interpretation of the meaning of those words.

This kind of study could help to shed light on how our brains work and how we process information, as well as helping us to gain a better understanding of sleep – a state in which we spend around one-third of our lives (although it’s probably closer to half for teenagers and blog-writers).

What did they do?

Volunteers were placed in a dark room, each sitting back in reclining chair with their eyes closed and encouraged to drift off to sleep. Each wore an EEG (electroencephalography) cap to monitor brain activity.

While they were drifting off, the participants were played the names of objects, some of which were animals, and instructed to press a button by their left hand if they heard the name of an animal or to press on by their right hand if it was a non-animal.


Movements of the right-hand side of the body are controlled by the left hemisphere of the brain, and vice-versa, meaning that while conscious, the participants’ brains would associate animal-words with activity in the right hemisphere of their brains with non-animals with the left hemisphere.

Words were played at 6 to 9 second intervals and the participants continued to press the buttons as they descended into sweet slumber, and the words continued to be played while they slept. The EEG caps could monitor brain activity to figure out precisely when they fell asleep, but also to see if the right or left hemispheres continued to light up in response to animal or non-animal words, respectively, even though the participants were no longer pressing the buttons.

Did they prove anything?

Weirdly enough, the volunteers’ brains continued to show stimulation in their right hemispheres in response to animal words and the left hemispheres for non-animals. The scientists reckoned that this shows that their brains could still process the words and interpret the meaning of ‘animal’ and ‘non-animal’ even though the participants were asleep.


In a second experiment, volunteers were presented with a list of words, some of which they had been played while awake and unconscious, and some of which had not been played at all. They had to indicate whether or not they thought each word had been played to them.

Generally speaking, ‘participants could distinguish new words presented during wake period… but crucially not from words presented during sleep’. In other words, while the brain is able to linguistically process words during sleep to some extent, the volunteers did not remember them.

So, what does it mean?

This appears to be pretty strong evidence to suggest that the brain can process the meanings of word that we hear during sleep, at least at a fairly simplistic level of understanding, and begs the question: ‘what else can the brain do during sleep?’

It would be incredibly interesting to find out precisely how sophisticated the brain’s functions are, not only during light sleep, but at deeper stages and the highly-active REM stage too.

While the student dream of being able to learn important exam facts while sleeping off an evening of tequila and aftershocks might not have been realised, this study does provide an exciting insight into what our unconscious mind is capable of.

Original article in Current Biology Sep 2014
All images are open-source/Creative Commons licence.Credit: A Ajifo (First); USNARA (Second); S Kouider et al. (Third); C Hope (Fourth)

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Kouider, S., Andrillon, T., Barbosa, L., Goupil, L., & Bekinschtein, T. (2014). Inducing Task-Relevant Responses to Speech in the Sleeping Brain Current Biology, 24 (18), 2208-2214 DOI: 10.1016/j.cub.2014.08.016

‘Eskimo1’ gene helps plants survive drought conditions



Genetic modification (GM) has been a hot topic for the past couple of decades, and with scaremongering over ‘Frankenstein foods’ you’d be forgiven for thinking that GM is only being used to produce horrifying steroid-addled mutant plants, which will one day develop a taste for human flesh and take over the Earth (like in Day of the Triffids or those annoying carnivorous flowers in Super Mario).

But imagine for a second that scientists are not trying to hasten the end of humanity, but instead to prolong it. What sort of modifications might actually prove useful in trying to provide food for malnourished populations?

A new study by scientists from China and Germany has looked at several ways of improving the drought-resistance of a species of cress plant (Arabidopsis thaliana), by tweaking a number of common plant genes, including some first associated with surviving extreme cold.

So, what’s the point?

Plants are not just static, passive items of scenery – they are living organisms which compete and battle to survive in the same way as animals. So they can respond to external stresses, such as lack of water, and adjust their own biochemical processes to help them survive.

C-repeat/dehydration–responsive element binding factors (mercifully abbreviated to CBFs) are proteins which control how often particular genes are expressed and are commonly found across the plant kingdom.

CBFs are produced by plants in response to external stresses such as dehydration and cold and alter the plant’s internal mechanisms by either activating or suppressing particular genes.


Another way that plants can be modified is through a particular gene called ESKIMO1 (or ESK1). While the name might be unfortunate (‘eskimo’ is considered a pejorative term in some places), a mutated form of the gene can actually prove quite useful in plants trying to conserve water.

The mutation is believed to be a defect in the plant’s water transport system (lower transpiration rate), but while this would mean growth would be hindered under normal conditions, it means water is used more efficiently and can therefore be advantageous if liquid water is scarce (such as in cold or drought conditions).

The scientists wanted to see if controlling both CBFs and ESK1 could improve the survival of Arabidopsis plants in simulated drought conditions.

What did they do?

The researchers used genetic techniques to boost production of CBFs and to suppress ESK1.

To boost the CBFs they spliced in a ‘promoter’ sequence ahead of the CBF code in the plant genome. This means that the proteins coded by the CBF genes will be produced more often and CBF levels will increase.

ESK1 was suppressed by using small-interfering RNAs (siRNAs). These molecules interrupt the process of turning genetic information in the DNA into functioning proteins (specifically binds to mRNA to reduce translation of gene into protein).


The researchers compared how normal (wild-type) plants and their transgenics grew in both normal medium and simulated drought conditions (water contained 30% poly(ethylene glycol) which modifies the osmotic potential).

They then took the most successful transgenic plants and compared them to the wild-type in a greenhouse for five weeks. All of the plants were fully watered for 2 weeks after germination form seeds, not watered for the following two weeks then fully watered again for the final week.

Did they prove anything?

After 14 days of growth, there were no noticeable external differences between wild-type and any of the transgenics and ESK1 suppressed under normal conditions, but under simulated drought several transgenics had ‘better root systems’ and more leaves than the wild type.

root growth

Of the transgenics tested in the greenhouse, all of them outperformed the wild-type. ESK1 suppression was found to be more effective than CBF promotion, but a mutant which both suppressed ESK1 and overexpressed a CBF inducer protein had the highest survival rate of all.

But drought tolerance comes at a price – under normal conditions, the most successful transgenics had lower seed production around half of that of the wild type.

So, what does it mean?

The researchers showed that their transgenic plants were much better at surviving in drought conditions than the wild-type. But under normal conditions, these plants produce far fewer seeds – a major problem because for many staple crops such as wheat and rice, this is the part of the plant that we actually eat.

So unless this issue can be addressed, this method of introducing drought-resistance will not be viable in regions where drought happens infrequently. There seems little point in using a plant that can produce more than the wild-type in a one-off drought year, but much less in the majority of years where rainfall is normal.

However, it might be useful in regions where drought is more common, particularly at the fringes of deserts, or to dispense to farmers if a drought is considered highly likely.

GM crops may have a bad reputation – arguably due to negative media coverage, but the more we can understand about the genetics of plants and their effects on how the plants grow, the easier it will be for us to tune them into useful tools to fight against malnutrition and starvation.

Original article in PLOS One Sep 2014

All images are open-source/Creative Commons licence.
Credit: Peripitus (First); PublicDomainPictures (Second); A Salguero Quiles (Third); Xu et al. (Fourth); USDOA (Fifth)

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Xu F, Liu Z, Xie H, Zhu J, Zhang J, Kraus J, Blaschnig T, Nehls R, & Wang H (2014). Increased Drought Tolerance through the Suppression of ESKMO1 Gene and Overexpression of CBF-Related Genes in Arabidopsis. PloS one, 9 (9) PMID: 25184213

How sex-engineered prawns can fight deadly parasites



Worms. Having them can be as embarrassing as it is irritating, but for most, the worst they can do is force us to take a frantic and furtive scratch when we’re sure nobody’s looking.

But sadly, some parasitic worms can cause far more problems: Schistosoma (blood flukes) can infect the urinary tract and intestines, with unpleasant effects including abdominal pain and diarrhoea and in the long run, kidney failure and liver damage, with the WHO estimating that they kill around 200,000 people per year in sub-Saharan Africa alone.

However, a multinational team of scientists are working on a solution, and they reckon that a humble river prawn – engineered as a male-only population – might just be the answer.

So, what’s the point?

The study is based on the Senegal river basin, where rates of schistosomiasis have increased ever since a dam was built on it in 1986.


The authors believe that the dam altered the ecosystem, allowing the spread of several freshwater species, including aquatic snails which carry the parasite in their bodies.

The dam is also believed to have affected the native population of river prawns, which feed on the snails, by limiting access to sites in both the river and estuary which they migrate to at different stages in their life cycle.

The researchers have therefore floated the idea of introducing large numbers of prawns to the river to keep the snail population down, but obviously they want to avoid upsetting the wider ecological balance too much.


Ideally, they want the prawns to just hang around and enjoy the French-style cuisine but don’t want them to reproduce – they want a way to control the prawn population so that the wider environment is not affected by a sudden explosion in prawn numbers.

This is where sex-control comes in: If they can introduce prawns that are only one sex, the population should remain controllable. They reckon male prawns would be more effective than females at chowing-down on the meddlesome molluscs because they ‘grow faster… and reach a larger size.’

What did they do?

To make a large population of prawns, you need to farm them. But if you grow males and females together, you’ll face the tricky task of having to separate them as well as essentially wasting money on breeding all the females too (although you could potentially use them to provide the loyal lab staff with free tempura…).

So it makes sense to engineer a single-sex population in the lab – but how do you go about this?

The scientists looked at a previous successful study on a related species of prawn: M. Rosenbergii, where sex is determined by a ‘masculinity-determining’ hormone made in the ‘androgenic gland’.


In that study, the researchers identified a single DNA sequence that codes for an important protein in the androgenic gland, and were able to suppress this gene (using RNA interference), creating a group of ‘neo-female’ prawns.

Although these prawns could reproduce as females, they are still genetically male and when they breed with regular males, all of their offspring will boys.

So the researchers wanted to see if M. vollenhovenii had an androgenic gland protein that could be manipulated in a similar way. First, they compared the DNA sequences that code the equivalent protein in both M. vollenhovenii, M. rosenbergii and three other decapod species to see how similar they are genetically.

They then tried to see if they could isolate the protein coded for by the gene in M. vollenhovenii using antibodies designed for the equivalent protein in M. rosenbergii (immunohistochemistry). They reckoned that if they could, it would show that the proteins are extremely similar in both species.

Did they prove anything?

The genetic sequence of the protein in M. vollenhovenii was found to be ‘more related’ to M. rosenbergii than any of the other species tested. In addition, the M. rosenbergii antibodies were able to bind to the M. vollenhovenii protein.

This suggests that the M. vollenhovenii androgenic gland protein is very similar to that in M. rosenbergii, so the scientists hope they can manipulate the prawns in the same way to produce all-male populations.

So, what does it mean?

The researchers have proven that the male-determining DNA and proteins are similar between the two species of prawn, but the next step is to see if they can actually generate an all-male population, then get it approved for field tests – obstacles which are likely to take a while.


But the idea of using what are relatively simple methods to manipulate the sex of an animal is extremely interesting and could have wider consequences.

Controlling populations of disease-carrying organisms (or disease vectors) by introducing large single-sex populations is not a new idea, but is one that could be used to solve other problems – a paper published a couple of months ago floated the idea for controlling mosquito numbers (it also involved making them glow fluorescent! Read TSiC article about it HERE).

So will male prawns eventually be the answer to controlling parasites? Who knows, but since they’re bigger than the female prawns, they’re certainly the answer to curing hunger.

Original article in PLOS Neglected Tropical Diseases Aug 2014

All images are open-source/Creative Commons licence.
Credit: D Williams (First and Title); Manu25 (Second); J Van Dyke, Snail Busters, LLC, Bugwood.org (Third); Citron (Fourth); J Tuszynski (Fifth)

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Savaya Alkalay, A., Rosen, O., Sokolow, S., Faye, Y., Faye, D., Aflalo, E., Jouanard, N., Zilberg, D., Huttinger, E., & Sagi, A. (2014). The Prawn Macrobrachium vollenhovenii in the Senegal River Basin: Towards Sustainable Restocking of All-Male Populations for Biological Control of Schistosomiasis PLoS Neglected Tropical Diseases, 8 (8) DOI: 10.1371/journal.pntd.0003060