Entomology, chemical ecology, evidence-based environmentalism and science in general. I like big bugs and I cannot lie.

Monday, 29 December 2008

All change

You know that awkward situation when you say your long goodbyes to someone you won't be seeing for a while, then see them at the bus stop ten minutes later and have to make stilted conversation until you say your long goodbyes again? That's the way I feel at the moment. I've just discovered that the LSHTM's trachoma survey won't be going out to The Gambia until April, so Jeff has had to mothball his plans for a return to batchelor life in January (the pizza menus are back in the drawer, the strippers have been hastily cancelled). Whilst the delay means I will be spending winter in Britain after all, and I had thought I could get away without buying a new pair of winter boots, it does at least give me longer to perfect my fly-rearing techniques (memo to self: animals need water) and to master all the gear.

Of course this does also mean that you'll have to put up with my wittering a little longer. While I still have your attention though, could the person I promised to lend "My name is light" by Elsa Osorio to please step forward? I've found the book now but can't remember who you were. I hope I can get away with blaming this on Aspall, and would like to assure you that your friendship means a lot to me and I greatly appreciate you as an individual. Whoever you are.

Thursday, 25 December 2008

Happy Christmas/Yule/Winterval!

Here's something to put you off your turkey:

Ophthalmomyiasis in Hawaii.
Author(s): Kajioka, Eric H N; Nagao, Cherie F K;
Karas, Stefan; Hardman, John M; Navin, James J Source: Hawaii Med J
Volume: 63 Issue: 3 Pages: 78-9
Published: 2004 Mar

Ophthalmomyiasis is the infestation of the eye by fly larvae. Commonlycaused by Oestrus ovis, a female sheep botfly will accidentally deposit her larvae into a human eye, resulting in disease. Prompt recognition and treatment of this condition will improve patient care and reduce potential complications. We report a case of ophthalmomyiasis in a young man from Molokai who was infested while unloading a Christmas tree.

PubMed ID: 15124740

Happy Christmas everyone!

Sunday, 21 December 2008

Bitter Oranges

This has nothing to do with my PhD, but I'm posting it here because it gets the highest readership of any of my blogs*. On my way home on Monday I noticed a group of people outside the Orange Tree Pub, waving banners and shouting. I do like a bit of shouting so I went to see what was going on. It turned out that the British Nazi National Party were having their Christmas party in there. I grabbed a placard and am proud to have played some small part in forcing some of them to spend their Christmas celebrations standing outside the pub in the freezing drizzle, attempting to intimidate us whilst icy water dripped on their shaven heads.

The BNP is, sadly, a legal political party so there's no reason why they shouldn't be able to hold their Christmas party in a pub. However, I doubt that I'm alone in not wanting to drink in the same pub as a bunch of racist wankers, who think that rape is no worse than force-feeding someone chocolate cake and that mixed race people should...actually, I don't have the strength to go on. I shall be writing to the manager of the Orange Tree to explain that I feel this way, and also to Youngs, the chain that owns the pub, and would encourage as many people as possible to do the same. A word of warning though, the manager of the Orange Tree is clearly a BNP sympathiser as they've met there before, so if you do write to the pub it'd be safer not to put a return address – just because we know their addresses doesn't mean they need to know ours.

If you have a receipt to show that you have drunk in a Youngs pub recently, include it with your letter to add weight to your assertion that you won't be drinking there in future. This shouldn't be too difficult for anyone who, like me, is a habitual drunkard** with a confetti of old receipts in her bag, but probably wouldn't be possible for someone like Imogen who I think alphabetises her handbag contents.

The addresses are as follows. There's also a Facebook group.

The Orange Tree:

Roger & Tracey Stearn
Orange Tree
45 Kew Road


Young's brewery:

Young & Co.’s Brewery, P.L.C.
Riverside House
26 Osiers Road
London SW18 1NH


Normal service will resume next week peeps. I know you're missing those flies.

*Six, and my Mum who my Dad prints it out for.

**You can delete this bit before printing Dad.

Friday, 19 December 2008

Just before Predator struck...

Steve suggested that in addition to the volatiles, the flies may be using heat to home in on the eyes and having done a quick Google search for thermal images of faces (most of them nicked from here) it looks like he's on to something:

And while I have no evidence that flies are attracted to coffee cups, I thought this one was rather nice too:

Thursday, 18 December 2008

Schoolgirl error

Until today I have been taking care of an experimental colony of houseflies, Musca domestica. I say until today because I took a couple of days off this week to see my supervisor in Durham, catch up with a few people and fail to get injected with a few more nasties. I made sure that the flies were at a life cycle stage that could be safely left, made sure they had enough food, and forgot to give them water.

Dead flies don't come back to life no matter how hard you shake the cage.


At least this means I don't have to come in over Christmas to feed them, but this isn't much consolation for me and even less for the flies.

On a more positive note Imogen has written an interesting blog post which I will respond to when I have a second. I'm flattered but a bit surprised to be described as articulate, as by the time that conversation took place I'd consumed half an orchard's worth of cider and started calling Richard Richmond again.

Saturday, 13 December 2008

Why is The Gambia such a funny shape?

As with most oddly shaped countries in Africa, it's because of the way the Europeans went about nicking it- in this case, how the British nicked it from the French, who had in turn already nicked it from the people living there in the first place. Apparently the length of the country is the distance a British navy warship could get up the river Gambia, and the width is the distance the ship could fire a cannon. I was initially sceptical when I heard this, but Wikipedia confirms it so it must be true.

Tuesday, 9 December 2008

Oh shit!

I've just has my first delivery of cowshit to test for attractiveness (to flies, not to me). Problem is I was expecting a kilo at most and I've got half a steaming binbag full. I've had to put it in the insectary fridge as it won't fit anywhere else, and putting it in this shared fridge is fractionally less antisocial than putting it in the kitchen fridge. Emma suggested putting it on the windowsill as it's cold outside, like we did with milk as undergraduates in halls. The only drawback is that the milk had a tendency to fall off onto peoples' heads....

Suggestions welcome!

Monday, 8 December 2008

Sticky Christmas!

This email's just gone round the lab:

"Hello everybody.
Once again, due to our unrivalled ability to breed healthy insects, we have a surplus of Giant Spiny Stick Insects (Eurycantha calcarata). These are currently at the "teenager" stage, so are a perfect size to sneak into the house without frightening your partner/children/parents.
If you are lacking ideas for a Christmas present, how about a nice new pet?! :-)"
If anyone wants one let me know and I'll get it for you. Just remember folks, a stick insect is for life, not just for Christmas.

Thursday, 4 December 2008

Lost in your eyes

Having seen what it’s done to Lou’s sanity I wouldn’t want to be a medic, but it’s always fun to be a tourist and I’m enjoying reading up on the eye to get some idea of what sort of volatiles I’ll be finding in tears. Until now I’d never given tears much thought, beyond them being the soggy stuff that leaks out at weddings or when someone uses a track you really like to advertise cheese strings, but the lachrymal film (to use its posh name) actually turns out to be pretty amazing.

Closest to the eye is the mucin layer, composed of jelly-like glycoproteins (protein molecules with sugar molecules stuck on, for those not in the know). This provides a nice smooth friction-free surface for the eyelids to slide over, and holds the water layer above it in place. This liquid layer is the part I’d always thought of as tears, and is what washes away any grit that gets in your eye, as well as doing something complicated to the optical properties that I’m too dense to understand. It’s apparently a mistake to think of these as two distinct layers, they shade into one another as the glycoproteins get less dense the further you go from the eyeball. So don’t.

Of greatest interest to me though is what lies above the mucino-aqueous phase (we scientists love giving things complicated names – it makes us sound intelligent and gives us an advantage at Scrabble). This is the tear lipid layer, a thin film of oils, fats and waxes that covers the mucino-aqueous layer in the same way that oil floats on vinegar when you make fancy salad dressing. Generally smelly things tend to be soluble in fats (just think of essential oils, allowing me to get in a gratuitous plug for Jeff’s sister’s company which makes very nice bath things*) so I’m guessing that whatever the flies are smelling is coming from this layer.

The tear lipid layer is itself divided into two layers (layers are so this season, darling). The inner layer is just one molecule thick but these are rather clever molecules that have one end that dissolves in water and one end that dissolves in fats. This anchors all the fats above making up the tear lipid layer (TLL to its friends) to the vertical eyeball, stopping all the oils from sliding down to the bottom of your eye and leaking out. Which would be strange.

So what’s the point of all this? The TLL reduces the rate of evaporation from the water layer, making it last ten to twenty times as long as it would otherwise. It also reduces surface tension, helping spent tears to drain better, and catches fine dust. It contains antibacterial fatty acids and its high viscosity prevents oils from your skin from getting into your eye. And as if that wasn’t enough to make you appreciate an anatomical structure you didn’t know you had ten minutes ago, it also forms a watertight seal between your eyelids when you close them, compensating for microscopic imperfections where they don’t meet perfectly and so stopping your eyes from drying out when you sleep.

The TLL is secreted by the glands of Meibomius (why is it that only people with daft names get medical discoveries named after them? Is there a duct of Smith?). These are tiny little pin-prick glands on the lip of the eyelid, invisible to the naked eye. There are more of them on the upper eyelid than on the lower, so rather more is secreted on the upper lid margin than on the lower. This is because thanks to gravity the TLL is a little thicker at the bottom than the top, so replenishing it at the top is more of a priority. The ducts of the glands run up the inside of the eyelid, so those on the upper eyelid are longer than those on the lower, helping them secrete more. This probably explains why we blink down, why our upper eyelids are longer than our lower eyelids. I always wondered about this when I was younger, but to be fair I was a bit of a weird kid.

Glands of Meibomius, from: Lozato, P. A., P. J. Pisella, et al. (2001). "Phase lipidique du film lacrymal: physiologie et pathologie." Journal Francais D Ophtalmologie 24(6): 643-658.

Blinking squeezes more of the tear lipid secretions out of the glands, and the physical action of the eyelids smoothes it evenly across the eye, so your TLL is refreshed every time you blink. Like so much else your glands of Meibomius become less efficient as you get older, so the average adult needs to blink approximately every 20 seconds to refresh their TLL but babies can go more than a minute without blinking. This probably explains why they always have such a look of bug-eyed astonishment. If you go too long without blinking the TLL will eventually break up, allowing the water layer to evaporate and so bringing the TLL down into contact with the mucins which, in scientific terminology, buggers everything up. This leads to dry, uncomfortable eyes. So blink more people.

Did I mention incidentally that oxygen can get through the whole tear film to the cells on your cornea? Oxygen can get through the whole thing to the cells on your cornea. Isn’t that cool?

Having discovered how amazing your eyes are I am now horrified that anyone wears eye makeup. Eyeliner and mascara are full of foreign fats and oils that can get incorporated into the TLL, disrupting it. Absolutely the worst thing you can do though is use eyeliner inside the lip of your eyelid, as this can block the glands of Meibomius. If this happens there’s a good chance you’d be able to clear them with massage, but if that fails there’s a procedure I read about. Actually I read the first sentence of the paragraph then squealed, jumped back and quickly turned the paper over so I couldn’t read any more. As I was on the tube at the time this resulted in a bit of extra leg room as people shuffled away from me, but I think you get the message. Down with the patriarchy ladies. Ditch the eyeliner, your tear lipid layer will thank you.

Her glands of Meibomius probably aren't very healthy.

*OK the store part of her website doesn't seem to be up yet. Link to follow