Saturday, 27 June 2009

Tropical Diary: Tick Magnet

You can't blame them. Blood is a highly nutritious food. After all, it sustains thousands of vampires of both the black-cloaked and sparkling varieties.

But there's a dilemma with blood as a resource — it's the perennial problem of supply and demand. If novels and movies are to be believed — and we know that they are impeccable sources of information — one flamboyantly coiffured member of the Undead requires multiple similar-sized food sources to keep it going. That would be sustainable if the population of hosts far exceeded the population of haemovores. But vampirism is contagious. If one vampire feeds on only two victims, which then become blood-suckers as a consequence, and they each feed on two ... Well, you can do the maths. It wouldn't be long before the wealthier Undead were paying for a private army of Van Helsings to keep the situation under control. Really, if you're going to spend your entire life drinking blood — the complete meal in a capillary — then it's a good idea to be smaller than your host or consume modest portions.

Ticks are small. Especially larval ticks. They don't each much at a sitting, either, even though a meal may last several days. And they make the most of their repast, retaining only the nutrient-rich component and regurgitating the bits they don't like. It's the tick equivalent of pushing the sprouts to the side of the plate.

Such a concentrated dinner keeps a tick going for a long while. Most feed only three times: once as a newly hatched larva, a second time as a nymph and a final time as an adult. A blood meal is a tick's rite of passage.

After gorging herself, an adult female tick finds a quiet spot for a nap and starts to digest her last meal. During the following days, she lays between 1,000 and 12,000 eggs. (Some species may produce even more.) Because she will not tend the clutch, she coats the eggs in a waxy material that prevents desiccation. The eggs don't pop out pre-coated — mum picks up each one as she lays it and transfers it to the clasper-like Géne's organs on her back, which secrete the protective wax. Fair enough then, that she loads up on the calories in preparation. That's a big job on an empty stomach.

On hatching, the larvae cluster together, waiting for some hapless vertebrate to blunder into their nest. And as that hapless vertebrate, I can verify they are so small that they can attach to the host without drawing attention to themselves.

Even at this young stage, they exhibit bad table manners. When … er … returning unwanted and waste material during feeding, they also inject a mixture of substances that temporarily stymie the host's immune reaction. Tick bites are painless at first and only start to become swollen, red and damnably itchy a day or two after feeding commences. Often ticks can complete their meal over the course of a few days and drop off before the host notices. And with close to two dozen bites from one brood — count 'em — I speak from experience.

On completing this first meal — the breakfast of their lives — the six-legged larvae turn into eight-legged nymphs. From now on they no longer hang around together but enter a Byronesque phase where they favour shady places, waiting for inspiration. Or, indeed, expiration because they can detect CO2 exhaled from potential hosts. (Another reason to minimise greenhouse gas emissions. Won't someone think of the ticks?)

Despite becoming a buffet for a generation of blood-feeding arachnids, I've developed both a grudge and a grudging admiration for them. I have also developed a mild sensitivity to their bites, so I'm glad that young tick season is almost over. In a few months it will be adult tick season. And then the leeches take over.

If only nailing garlic to the door worked with all blood-suckers.


Denis Wilson said...

Well Snail I salute your originality in suggesting that we limit CO2 emissions for the sake of the juvenile Ticks.
Hope you develop an immunity or resistance to poison.
No self-portraits such as "Armed with ticks", or "6 Legs on one leg".
And as for the Leeches, I can just imagine them.
Best wishes

Kirk said...

I feel my skin is crawling...

Dave Coulter said...

Spiders? Enh. Ticks? Ugh! It's supposed to have been a bad year for them around here, but so far I haven't had the pleasure.

mick said...

Find out what to do for the little "biters" and you'll earn the undying gratitude of all sufferers with tick allergies!

Snail said...

Next time --- and I'm sure there will be a next time --- I'll try to take a pic. Maybe we could have a captioning comp!

Kirk, I'm now scratching bits of me that are tick-free. It's contagious!

Dave, one of the neighbours informed me that they're pretty bad in this area. Now they tell me! Must be all the bandicoots or something acting as hosts.

Mick, the same neighbour said that the local pharmacy sold new tick-removing devices. Must check them out. I tried Claratyne to try to reduce the local response but I'm not sure if it's effective. Haven't got a baseline to compare it against. Must check with a couple of immunologist friends.

Denis Wilson said...

Captions - yes please.
That's what I was trying to suggest. "Armed with ticks" is my first suggestion - but of course, that depends on where you find them.
Discretion might prevent photos!
Leeches are more reliable - they usually settle on the first available patch of skin, so ankle shots are easy.

Anonymous said...

Interesting and entertaining description of the tick's life cycle. I didn't know that the larvae were only 6 legged.

We liberally apply ti-tree oil on ticks before removing them which kills them and provides some relief to the itching. If they have attached in an awkward place we leave them to drop off.
Lavender oil dabbed on neat can also help the itches.
Good luck, I'm sure you'll get used to them

Tyto Tony said...

Leeches are OK, but ticks make me cross ;-)

Gouldiae said...

G'day Bronwen,
A delightful entry, from heading to final sentence, despite the subject. Didn't think I'd enjoy reading about the tick's life cycle so much.
Looking forward to some pics too. And, good luck with the repellent, salve, or whatever.

NanaJude said...

Snail ... so you are there at last.

I cannot imagine how it must feel to have made the move real.

My heartfelt Congratulations and Best Wishes for your new (if tick-infested) life there.

I know that you will take every "interesting" moment and turn it into grist for your writing mill and that we, your friends and followers, will reap the benefits without the itches, though we might very well experience some "itchings" to see the many things you introduce us to, for ourselves.


Snail said...

Gouldiae, I'm hoping that I don't get another chance to photograph ticks! I did encounter a leech the other day but removed it before it got settled in. Ah, well, you have to accept the whole package.

JJ, it is a strange feeling. I'm still unpacking and settling in, so I am yet to realise what I've done! I am enjoying the wildlife --- apart from the bloodsuckers!

Dave Coulter said...

Those quandong fruit look a little like our black walnuts :)