Jet lag – the disadvantage of having a clock in the modern world

Air travel challenges our bodies in a way that has never before been encountered in our evolutionary history. It allows us to move rapidly across multiple timezones, quicker than we could have ever moved by foot or animal. Unfortunately, our bodies are unable to adjust quickly enough. We are constrained by our circadian clocks, the things that give our bodies a sense of internal time, which have evolved to coordinate our physiology to the rhythmic and predictable changes in the external environment (as well as other roles) like day and night. The clock keeps its original time when you move timezones like a watch before you’ve reset it. It’s resistant to rapid change, giving us jet lag. However, unlike a watch, the body clock can gradually reset itself over a period of days so that we become tuned to a new local time. Despite this inbuilt mechanism, in an era of global travel it is often too slow.

Is it possible to speed up the resetting process? Can we travel the world without jetlag?


In order to see how we need to have a very good understanding of how the circadian clock links with the external environment. More specifically, we need to know how it responds when the external environment changes.

Let’s go back to the watch setting metaphor. You turn a dial to set a watch. Turning this dial moves the hour and minute hands to the new time, with the amount you turn the dial corresponding to the amount the hands move. If you need to move the hands a lot, you turn the dial a lot. Now, imagine if the hour and minute hands move further when you turn the dial at one time of day and don’t turn at all at another time of day, no matter how hard you try with the dial. This, in effect, is how the circadian clock works – the amount the clock is able to shift is dependent on the time of day. The relationship between the timing of the treatment and the shift it evokes is called a phase response curve (PRC), and it is important in working out how to deal with changes in time zone. Because of this property of the clock, it is possible that treatments that are supposed to help readjustment actually have no effect, or worse, do the opposite of what you need to happen. It is all about the timing.

What does this mean for treating or easing jet lag? Well, simply going outside, exercising, eating or taking medication during your new daytime is not the most efficient way to shift your body’s clock. In some cases could actually slow down your adjustment. The new schedule of light and dark at the destination will affect the circadian clock dramatically but because of the phase response curve, the effect of seeing light at 8am is very different to seeing light at midnight. It also means that, theoretically, it should be possible to design a programme to achieve the quickest adjustment and limit the negative impact of jet lag. Unfortunately, phase response curves can be different in different people (and organisms), which might be one of the reasons why a cure-all hasn’t been found yet. But let’s look at an example to help.

Joanne’s trip

Travelling from GMT +02:00 to GMT +10:00 by plane
Joanne flies from Mozambique, GMT +02:00, to Australia, GMT +10:00. Her internal clock carries on as if it never left Mozambique, staying on Mozambican time. She is not happy because she can’t get to sleep when nighttime arrives in Australia.

Joanne is taking a trip from Mozambique to eastern Australia, a timezone shift of +8 hours from GMT +02:00 to GMT +10:00. When she arrives in Australia, her body thinks it is 08:00 (Joanne’s internal time, JIT) when in fact it is 16:00 (Australian Eastern Standard Time, AEST). By the time it is time to get ready for bed at 22:00 AEST, her body only thinks it is 14:00 JIT. She faces a long struggle to get to sleep as her clock will be keeping her awake. Joanne needs to ‘phase advance’ her body clock, to shift her clock forward, to come into line with Australian day and night.


The strongest signal that affects the timing of the clock is light and so we will look at the PRC for light.

Light has different effects at different clock times
A human phase response curve. The time that light is perceived (according to internal body time) has different effects on the clock, and is able to move it forwards or backwards. When moving west to east, we need to advance the clock and avoid delaying it, which means seeking light in the blue zone between 04:00 and 10:00 (body time) and avoiding it in the red zone between 17:00 and 04:00 (body time)

Advancing the clock requires light exposure during the body’s early morning, from about 05:00 to 10:00 JIT. Joanne’s internal 05:00 – 10:00 period will happen during the day in Australia at 13:00 to 18:00 AEST, perfect for advancing her clock and getting sleepy earlier. The problem is that part of her delay zone (approximately 00:00 to 04:00 JIT) will also occur during the Australian daytime (06:00-10:00 AEST) on the first day in Australia, meaning that if she is exposed to light in this period, which is likely, she will delay her clock, delaying sleepiness and counteracting the effect of “early morning” light. Luckily, she can rely on the fact that her clock will be telling her it’s sleep time, so it is possible that she won’t be up and around for much of the first Australian morning.

A diagram explains this better, starting when Joanne arrives in Australia and predicting day-by-day how much her clock will shift (approximately, according to the human PRC) with a perfect schedule of seeking morning light and avoiding evening light.

Flying eastward from Africa to Sydney. Seeking light in her internal morning and avoiding light in her internal night will help her skip the clock forward 2 hours per day. Seeking bright light at the right time should be easy as it always occurs during the Australian daytime. She’ll have to be careful to avoid bright light on the plane (day 0) and on the first morning in Australia (day 1) until 10:00. She could also use melatonin in this schedule, which she would need to take just before bed. This might help her readjust in two or three days instead of the four shown here.

It would take 4 days to shift the 8 hours to Australian time. In reality, Joanne may feel fine sooner than this because of her Mozambican lifestyle shifting her to a more morning type – she normally goes to sleep by 20:00, which would mean she would be sleepy at the right time on day 3.

Coming back is a little more simple, though Joanne will be waking up too early. On the first day, when Joanne’s body clock is saying, “Get up!”, it will be midnight in Mozambique. Joanne needs delay her clock by avoiding light in the advance zone and seeking light in the delay zone.

Flying westward from Sydney to Mozambique. Joanne needs to delay her clock so that she sleeps later and later each day. Seeking light in her internal evening and avoiding light in her internal morning will help her delay the clock two hours per day. It is not possible to fit in melatonin on this schedule because she would need to take it in the middle of her sleep for it to have the right effect.

Both these requirements should be simple: her delay zone lines up with Mozambican afternoon and her advance zone coincides with Mozambican night. The problems could arise if she’s awake in the Mozambican night because her body is telling her it’s daytime. In this case, she should try not to expose herself to bright light e.g. by turning on lights or playing on the computer, because that would slow the shifting of her internal day. It’s not fun being awake when you’re supposed to be sleeping though, so, if she is bored, she should only use very dim light. Very dim red light and no blue light is the most optimum combination, because these correspond to the wavelengths to which the eye is least sensitive and most sensitive respectively for entraining the circadian clock. Programmes such as f.lux, Twilight, and Night Shift could help, as they put a filter on screens to reduce bright blue light.

Another option would be to begin shifting before she departs – this wouldn’t speed up the overall time it takes to shift but would help her reach destination timing sooner after landing. This would need careful planning as she may have to alter her lifestyle quite a lot – for example being really careful to avoid bright light in the evening in Mozambique before her flight to Australia.

Even with this schedule, it takes a few days to adjust. Is there anything else that could be done?

Melatonin 3 mg pills
Melatonin 3 mg pills.
Murrur | CC BY-SA 3.0 via Wikimedia Commons

While not licensed in the UK for the treatment of jet lag, melatonin could help. Melatonin is a hormone produced in the brain and synchronises circadian clocks in cells and tissues throughout the body. Like light, melatonin can shift the clock and has a phase response curve when given as a drug (at doses between 0.5 mg to 5 mg) that is roughly opposite that of light. Melatonin advances the clock between 13:00 and 01:00 with a peak response at 16:00, and delays the clock between 03:00 and 12:00 with a peak response at 10:00. When given alone, melatonin is no more effective than bright light, but combined light and melatonin treatments result in larger shifts than either treatment alone and effects which are roughly additive. For example, if on day 1 Joanne seeks light between 13:00 and 16:00 AEST and takes melatonin at midnight, and continues this combination as she shifts, she might be able to fully reset in 2 or 3 days. Taking it so late into the night (at the peak response) is quite inconvenient, but a compromise can be reached which takes into account the fact that melatonin causes drowsiness (and is a licensed to treat insomnia). Joanne could instead take it at 21:00 AEST, still in the advance zone, but also taking advantage of the drowsiness it causes to get to sleep. Unfortunately, melatonin may have some negative side-effects, especially in people with epilepsy and diabetes and also possibly interacts with the blood thinner warfarin, so requires further testing before it could be licensed as a common-use jet lag remedy.

Another possibility is through scheduling meal times. Food is a strong timing cue within the body, especially for peripheral tissues like the liver, and ties into the close relationship between cellular metabolism and the circadian clock. It’s a natural timing cue as humans tend to eat during the day and not at nighttime. Food restriction diets are able to rapidly reset the circadian clock, and in one study in mice, a time-restricted diet was able to shift the clock in the liver by 10 hours in 2 days. It seems like a miracle cure, a kryptonite as one site calls it, and “Food eases jetlag” is an appealing headline e.g. New Scientist, Live Science because it seems so simple (unfortunately these headlines often take an interesting result, in this case that there is evidence for a separate brain region that controls food-entrained circadian rhythms, and spin it to the most general conclusion).

Diet plans have been developed which tie in to this evidence in an attempt to speed up the resetting of the clock. One method involves alternating feeding-fasting cycles in the week before travel before a long fast on the travel day, only eating again at destination breakfast time. A simpler method involves fasting for 12-16 hours on the day of travel and having breakfast on arrival. You can even use a calculator to work out your own schedule – for Joanne, she would need to stop eating at 10:30 SAST on the day of her flight from Johannesburg, and eat again at breakfast time in Australia, 08:30 AEST (12:30 am SAST), when she’ll still be on the plane. Westward, she should fast from 02:30 AEST to 08:30 SAST (16:30 AEST), a few hours after she has landed. Unfortunately, whilst there are plenty of nice anecdotes, there is very little strong scientific evidence. Only one controlled study on the feasting-fasting diet has shown any effect.

It’s a little cliche but more research is needed on all of these treatments. Controlled studies on humans in real conditions are required to tease apart how the clock responds to air travel across timezones and what effect treatments have in real life. Can a perfect light schedule really shift you in 4 days? Could a light schedule be designed that would actively disrupt this shifting, by seeking light at all the wrong times? Does melatonin really help, at what dose and time, and is it possible to avoid the side effects? And is feeding-fasting a kryptonite that can eliminate jet lag or is it just one aspect in an overall programme to help with circadian readjustment?

My feeling is that these treatments will form part of an overall programme. I don’t believe there will be a single kryptonite method. The mechanism of the circadian clock is just far too robust to be reset instantly. After all, it is a mechanism that has evolved in plants and animals for millions of years, is tied into almost every physiological process, and works at the same rate despite temperature changes (a property called temperature compensation) unlike most other biological processes. It is resistant. My advice to Joanne is to follow the light schedule, which has the strongest evidence behind it, perhaps try the fasting diet, and above all be patient. It may take a few days but the body will adjust eventually. Oh, and don’t wake me up when you’re sitting there at 2am wide awake. My circadian rhythm is just fine thanks.

Featured Research:

Minors et al., A human phase-response curve to light, Neurosci Lett (free at ResearchGate)

Burke et al., 2013, Combination of light and melatonin time cues for phase advancing the human circadian clock, Sleep (free)

Crowley et al., 2015, Phase advancing human circadian rhythms with morning bright light, afternoon melatonin, and gradually shifted sleep: can we reduce morning bright-light duration?, Sleep Medicine (free at ResearchGate)

Burgess et al., 2008, A three pulse phase response curve to three milligrams of melatonin in humans, J Physiol (free)

Vollmers et al., 2009, Time of feeding and the intrinsic circadian clock drive rhythms in hepatic gene expression, PNAS (free)

Yoon et al., 2012, Meal Time Shift Disturbs Circadian Rhythmicity along with Metabolic and Behavioral Alterations in Mice, PLoS ONE (free)

Reynolds and Montgomery, 2002, Using the Argonne diet in jet lag prevention: deployment of troops across nine time zones, Mil Med (abstract only)

Eastman and Burgess, 2009, How To Travel the World Without Jet lag, Sleep Med Clin (free)

If you’re interested in calculating your own light schedule (with and without melatonin) for any long haul flight, try the jet lag calculator at Jet Lag Rooster. There is evidence that the schedules that calculator generates work – one report of a significant negative correlation between following of schedule and severity of symptoms in twenty participants. A small sample, but it’s something!

p.s. Animals also get jet lag. This is easy to investigate – you just change the light cycle in the house they are living in. Sadly there was once a researcher who didn’t realise this and flew his animals from Germany to US. I imagine his grant agency would’ve been less than impressed when they realised this mistake!

The Mount Mulanje Pygmy Chameleon

DSCF7127 - pygmy chameleon small
Rescuing the Mulanje Pygmy Chameleon from the path.
Christine Cambrook | CC BY-NC-SA 4.0

By far the rarest animal that I have encountered during my time in Mozambique has been the Mount Mulanje Pygmy Chameleon, Rhampholeon platyceps. A stunning little creature, it is endemic to the Mulanje massif, only being found in the southern and eastern-facing mid and high altitude evergreen forest of the massif. This includes the Ruo Gorge, where we came across the little guy (or possibly girl) above. Unfortunately its forest habitat remains only in fragmented patches and, due to its restricted range and the high threat of deforestation, it is declared Endangered by the IUCN Red List. We were lucky that this individual was crossing the path in front of us.

The Mulanje Pygmy Chameleon was first described in 1892 in a paper by A. Günther to the Zoological Society of London. The paper is titled Report on a Collection of Reptiles and Batrachians transmitted by Mr. H. H. Johnston, C.B., from Nyassaland and is available for free here. Like many papers of the day, Dr Günther was communicating the findings of others and it opens with a description of the people involved in what today might be considered equivalent to an author list:

Acting under instructions from Mr. H.H. Johnston, C.B., F.Z.S., Mr. Sclater has sent to the British museum a series of specimens of Reptiles and Batrachians collected by Mr. Alexander Whyte, F.Z.S., the naturalist attached to Mr. Johnston’s staff, in the Shire Highlands of south of Lake Nyassa, principally upon Mount Zomba and Mount Milanji.

This scientific description in a zoological journal misses out the context of this discovery. In 1982 the British Central Africa Protectorate, what is now Malawi, was only a year old. Mr. Harry H. Johnston was sent to the region by the British just three years earlier, in order to negotiate with the Portuguese to protect British interests and prevent Portuguese occupation of the area. (Later, Sir) Harry Johnston was an explorer and a politician, a fixture in the seven major European powers’ Scramble for Africa, negotiating treaties with local chiefs to establish Malawi as British territory. He later became the British Central Africa Protectorate’s first Commissioner. However, Johnston was also a naturalist and this paper demonstrates some of the work that his team did to categorise the fauna of the area.

Unfortunately, Johnston’s labelling of the location of collected species was sometimes imprecise – the specimens described in this paper are labelled as being collected in the Shire Highlands, a 7,300 km2 plateau in southern Malawi which includes Mulanje, Blantyre, some 75 km to the west, and Zomba, some 50 km to the north. The confusion caused by this poor location label probably caused later biologists to describe a sub-species for the same animal. These biologists collected specimens from the Lichenya Plateau and Ruo Gorge and seemingly saw enough differences to define two sub-species, Rhampholeon platyceps platyceps and Rhampholeon platyceps carri. Later analysis resolved this separation.

The original paper is full of descriptions of animals “new to our knowledge of the Reptilian Fauna of the Nyassa district”. The beautifully detailed sketch on plate 34 of the pygmy chameleon (labelled #1. A different species, #2, is also sketched) demonstrates the chameleons in their assumed habitat. Notice the absence of the tail, honestly described in the text as being “lost by accident”.

sketch of rhampholeon platyceps
Oops. The tail’s missing. 
Günther (1892)

“pairs of very small tubercles are placed at regular distances along the vertebral line”

The distinguishing tubercles are clear in the following photo, a thin line of green-grey along its back of its greyish brown body. Head-on you can see that Dr Günther’s simple sketch of the head was just right, with the characteristic triangle shape on the head clear in the photo. The bulging black eyes are reminiscent of the compound eyes of flies.

IMG_1220 - pygmy chameleon adjusted
Getting a close up.
Andrew Beale | CC BY-NC-SA 4.0

Back on the forest floor you can appreciate the famous camouflage ability of chameleons. The Mulanje Pygmy Chameleon might not be as vibrant as some species (see the Panther Chameleon for an impressive display) but it certainly can blend in with its surroundings. Marching up the Big Ruo path on our way to Minunu Hut, I’m sure we would have never had seen it had it been in the leaf litter to the side.

IMG_1212 - pygmy chameleon on ground
Back down on the forest floor.
Andrew Beale | CC BY-NC-SA 4.0

Since this animal was first described in the scientific literature, the world around them has changed, and not to their benefit. The population of Malawi has risen from approximately 700,000 to 16,500,000, and is projected to rise to 45,000,000 by 2050, putting huge pressure on the land and consequently on the chameleon’s habitat. World Bank data shows that between 1990 and 2010 the population increased by 50 % (9,408,998 to 14,769,824) and, in the same time, forested area decreased by 17 %. The Mulanje massif is experiencing the full extent of the deforestation and the Ruo Gorge, where we found this particular chameleon, is one of the few remaining patches of rainforest (which also makes it a beautifully cool route up to the plateau). Another species unique to Mulanje, the Mulanje cedar tree Widdringtonia whytei, is critically endangered – a toxic combination of demand for its timber and the poor growth of infant trees when surrounded by other plants. Both these species are losing the competition for space with the surrounding human population, an imbalance that groups such as the Mount Mulanje Conservation Trust are working to address.

Recently, pygmy chameleons closely related to the Mulanje Pygmy have been described from Mozambican “sky islands” just over the border from Mulanje. These “sky islands” are, like Mulanje, isolated inselbergs of erosion-resistant rock and rise out from the planes beneath them like islands in the sky. Mt. Chiperone, Mt. Mabu, Mt. Namuli and Mt. Inago range from 50 to 200 km from Mt. Mulanje and harbour similar evergreen rainforest habitats as can be found on Mulanje. In 2014, Branch and colleagues described four newly discovered pygmy chameleon species, isolated from one another by their restriction to evergreen mountain rainforest. All within the same genus as the Mulanje Pygmy Chameleon, Rhampholeon maspictus (Mt. Mabu), Rh. nebulauctor (Mt. Chiperone), Rh. tilburyi (Mt. Namuli) and Rh. bruessoworum (Mt. Inago) are examples of allopatric speciation – speciation that occurs as populations become isolated from one another.

The speciation hypothesis could be this. These mountains were once connected as part of a large plane. They became mountain islands due to their geological composition, resisting the erosion of the surrounding planes. As the montane rainforest habitat became restricted to the remaining high lands, so too did the ancestral pygmy chameleon that once inhabited the whole area. Over time the multiple populations of this single species diverged, enough to become reproductively isolated from one another, becoming new and separate species. If this was the case, we might expect that the evolutionary relationships between chameleons inhabiting current day mountains to related to the geographical distance between them. This is indeed what was found by Branch and colleagues – chameleons on Mt. Inago appear to have diverged first (ca. 11-20 Mya), followed by those on Mt. Mulanje and Mt. Namuli (ca. 6-16 Mya), followed by chameleons from Mt. Mabu, Mt. Chiperone and Malawi Hills (Rh. chapmanorum) which appear to have diverged from each other more recently (4-9 Mya). This reflects the geographical distance between the mountains and the present of geographical boundaries (such as rivers).

Mountains of Zambezia3
The mountains surveyed and Mt. Tumbine, another 1500m+ peak.

The four surveyed mountains were chosen based on a Google Earth search of the area to find large (greater than 5000 ft or 1500 m) isolated mountains in Mozambique similar to Mulanje. Mount Tumbine, which rises above the town where I live, Milange, was not included. While not as big as Mts Namuli, Inago or Chiperone, it still rises over 1500 m and has patches of rainforest similar to those in the Ruo Gorge. Tumbine is close to Mulanje, just 3.5 km separates the 900 m+ parts of the mountain, but it is isolated from Mulanje by a river, the Malosa. Could Mt. Tumbine also have a resident population of pygmy chameleons and, if so, do they form a different species to the others? Only an expedition will tell…

Featured research:

Günther, (1892), Report on a Collection of Reptiles and Batrachians transmitted by Mr. H. H. Johnston, C.B., from Nyassaland, Proceedings of the Zoological Society of London

Branch et al., (2014), Pygmy chameleons of the Rhampholeon platyceps compex (Squamata: Chamaeleonidae): description of four new species from isolated ‘sky islands’ of northern Mozambique, Zootaxa

Do we have the right to eradicate species?

While living in Mozambique I have seen first-hand the tremendous suffering caused by mosquitoes and the diseases that they transmit, especially in children. Friends have lost children to malaria and, in this rainy season especially, neighbours are frequently coming down with the disease. According to the Gates Foundation, malaria, transmitted by the mosquito Anopheles gambiae, caused 627,000 deaths in 2012. It’s a scourge to the human race. When you add in dengue and chikungunya, two other mosquito-borne diseases, and the strong (but not yet conclusive) association between the zika virus and microcephaly, mosquitoes become the animal incarnation of the Grim Reaper.

A happy sight? A dead mosquito

Nevertheless, I was shocked to read an article in the Guardian in which so many ecologists, entomologists, parasitologists would have no problems with “wiping them off the face of the earth”.

A few quotes:

  • Professor Steve Lindsay, a public-health entomologist at the University of Durham agrees: “I have no problem with taking out the mosquito.”
  • Professor Hilary Ranson, head of vector biology at the Liverpool School of Tropical Medicine. “I spend most of my time trying to keep them alive and study them, but that’s in order to try to kill them. Ultimately I wouldn’t be too sentimental.”
  • Jules Pretty, professor of environment and society at the University of Essex: “Here you can ask the question: if there was a loss of a whole species, would there be a human benefit? And in this case, the human benefit is so great that I think you have to say: ‘OK, I can hold these two thoughts at once.’”

These are really quite strong statements. And for the most part I see where they are coming from. The human argument against mosquitos (or the diseases that they carry) is very strong – you only have to look at the number of deaths they cause, the suffering from the diseases, the long term effects of the disease. The economic argument is strong, at least in terms of man-hours and productivity loss because of illness – estimated at billions of dollars every year.

An estimated 207 million people suffered from the disease in 2012, and about 627,000 died. About 90 percent of the deaths were in Sub-Saharan Africa, and 77 percent were among children under age 5.

Gates Foundation

If we did eradicate them, wouldn’t ecology suffer? A pitcher plant in the north east of America, benefits from the micro-community including mosquito larvae that lives in its leaves, as they make nutrients such as nitrogen available for the plant. The mosquitofish Gambusia affinis, a specialised predator of mosquitoes, could go extinct without mosquitos to feed on. This loss could have major effects up and down the food chain. A primary food source of insects, spiders, salamanders, lizards and frogs would be lost and the migratory birds that fly through the Arctic tundra would no longer benefit from the vast summer swarms of mosquitoes. Also, mosquitoes do pollinate plants. But, in most cases, the ecological role played by mosquitoes is actually small, and according to a report in 2010, other species could fill in – birds would switch to other swarming flies that would fill that niche, and other organisms could step in to process detritus in water systems. The evidence suggests that ecology wouldn’t suffer that much, unlike if, for example, bees go extinct. So the ecological argument for keeping mosquitoes is not strong. As one article is titled, “What Purpose Do Mosquitoes Serve? It’s hard to justify the existence of these annoying critters.”

It seems very clear: eradicating mosquitoes isn’t just a good thing to do for humanity, it also isn’t too bad for the world either.

One animal that might have to find a new dinner menu if mosquitoes were no more – a female jumping spider. CC BY-SA 3.0 | JonRichfield

A couple of thoughts:

One. It isn’t the mosquitoes that kill people, it is the diseases they carry. Malaria kills people, not Anopheles gambiae. The Gates Foundation defines malaria eradication as “removing the parasites that cause human malaria from the human population. Simply interrupting transmission is not sufficient to achieve eradication”. Sure, it might be easiest to eliminate malaria by eliminating A. gambiae but we should bear in mind that it’s not A. gambiae that kills. I can testify to how annoying they and how much their bites itch (and Aedes aegypti‘s bites are even more painful) but that isn’t a reason to eradicate them.

Two. A comment on the Guardian article: “If we eradicate the mosquito what vehicle will death find to replace it?”. If other species will fill in mosquitoes ecological role with ease, then other species will surely become the vectors of deadly diseases. A Conversation piece on the eradication of mosquitoes concludes with the same thought.

Three, and perhaps my strongest objection to the sentiment in the Guardian article. Even if mosquitoes were, as far as we could work out, ecologically ‘useless’ and even if it was guaranteed that eradicating them would also eradicate malaria, Dengue and zika, would it still be right to purposefully ensure entire species go extinct? Do we have the right to wipe that species off the face of the earth? I’m not sure. What would that mean for other ‘undesirable’ species? It’s a very dangerous place to go if we start rating which species we can eradicate. Who gets to make that decision? What checks and balances would there be? What do you think? Please make comments at the bottom of the page – I’m interested in your thoughts.

After all, “The ecological effect of eliminating harmful mosquitoes is that you have more people. That’s the consequence,” says entomologist Daniel Strickman, programme leader for medical and urban entomology at the US Department of Agriculture in Beltsville, Maryland. If you’re talking about species that are a menace to other species, serve little ecological ‘purpose’, and have done great damage to the ecosystems around them, then Homo sapiens should be worried.


What can a blind cavefish tell us about circadian clocks?

Circadian clocks and a revolving planet go hand-in-hand. But why so many plants and animals have a circadian clock from an evolutionary perspective is relatively unknown. One way to find out is to study animals that live in non-rhythmic environments. And at the end of 2013, my team published a study on exactly that: the circadian clock of the Mexican blind cavefish, Astyanax mexicanus, from data collected in the laboratory and in the fishes’ natural habitat. We showed that these cavefish fish shows wonderful daily patterns of behaviour and gene expression, confirming that it has a functional circadian clock.

Continue reading “What can a blind cavefish tell us about circadian clocks?”

Presentiment – circadian clocks giving plants and animals a sense of time

Presentiment is that long shadow on the lawn
Indicative that suns go down;
The notice to the startled grass
That darkness is about to pass.

Emily Dickinson

Sometimes you find in literature beautiful expressions of technical terms that are otherwise dry and stuffy. Presentiment, by Emily Dickinson, is one of those beautiful expressions. Why did she decide to write a few words about twilight, and at the same time so succinctly summarise one of the key features of the circadian clock? Apparently Dickinson spent much of her adult life withdrawn from the world and, in doing so, she was probably in a position to watch and notice the hidden-in-plain-sight details of the world, such as how the length of shadows allow you to approximate the time of day and how grass may tell time without watches.

Continue reading “Presentiment – circadian clocks giving plants and animals a sense of time”


In the northern hemisphere, today is the Winter Solstice, the shortest day of the year.

The Solstice normally falls on either the 21st or the 22nd, the date changing based on the exact position of the north pole in relation to the sun. This is the same reason why we have leap years – our calendar year doesn’t match up with the solar year, and so we have to add a day on every four years in order to recalibrate our calendars with our position in space. This year, 2015, the point at which the north pole is furthest from the sun falls on the 22nd December. Continue reading “Solstice”

Parasitoid wasps and GM butterflies

A parasitoid wasp parasitising a caterpillar
A parasitoid wasp parasitising a caterpillar. USDA photo by Scott Bauer

Foreign pieces of DNA are found in the genomes of many animals – these ‘Genomic parasites‘ are pure, genome hopping pieces of DNA code which embed their lifecycle within the DNA in our own cells. You could call this genomic parasitisation a form of genetic modification, just as scientists in labs the world over use simple molecular biology techniques to insert useful genes into genomes to better understand biological processes. However, most of the time, genomic parasites like transposons have no function in their hosts and simply hitch along for the ride, reproducing as the host reproduces. This doesn’t fit our usual understanding of the meaning of genetic modification, which involves humans and active manipulation of the genome, in most cases to improve it.

However, a recent piece of research shows another form of natural genetic modification which also doesn’t involve humans – and this form does affect the life of the host and can confer some advantage. Continue reading “Parasitoid wasps and GM butterflies”