Posts Tagged ‘protection’

Female fiddler crabs have sex with the neighbours

// April 20th, 2010 // Comments Off on Female fiddler crabs have sex with the neighbours // Recent Research, Sex and Reproduction

Fiddler Crab

Fiddler crabs may be little, but they have one big appendage, the CLAW! A weapon if ever there was one. Like a lance or an over-sized boxing glove, something about it just screams MAN. So it fits that male fiddlers are the gender so endowed.

Females have two little feeding claws. No giant claw. No weapon of any kind. Unless, of course, you count her good looks and killer form. Turns out that’s all she needs.

This research comes from the ANU (me own university), and there’s apparently a fiddler crab expert here that I have to meet. His name is Richard Milner, and the paper was published in Biology Letters.

ResearchBlogging.orgRichard N. C. Milner*, Michael D. Jennions and Patricia R. Y. Backwell (2009). Safe sex: male−female coalitions and pre-copulatory mate-guarding in a fiddler crab Biology Letters (6), 180-182 : 10.1098/rsbl.2009.0767

Fiddler crabs live in burrows, which are a place to hide when predators come along. Burrows are in high demand, and males will fight for squatting rights. Females can’t fight without a big-ass claw, instead they take over empty burrows.

Burrow-owning females would be sitting ducks for homeless males to come and kick them out, if it weren’t for the male next door.

Male fiddlers will defend the territory of nearby females. The study showed that if the intruder is a male, the neighbour will try to fight him off 95% of the time. That compares to just 15% of the time when the intruder was female. So male fiddlers like to be surrounded by female fiddlers. Go figure.

When picking a sexual partner, female fiddlers chose a neighbour who shares a territory border with her 85% of the time. The remaining 15% was made up of strangers, burrowless males and non-neighbour residents.

Part of that could be convenience, as females are at risk of predation while they search for a mate. Part of it could be gratitude. Part of it could be white knight syndrome, in which the big manly fiddler roughly dispenses of all piddly competition to claim the hand of the fair maiden. Damn I have a problem with personifying animals.

It boils down to one thing: Fiddlers exchange sex for protection. It makes me wonder whether some human relationships amount to much the same thing. Give me your thoughts and complete the following: Humans exchange sex for

Sickle Cell Anemia and Genetic Fence-Sitting

// June 22nd, 2009 // 5 Comments » // How Things Work

Following on from the theme of biological errors and the noise of life, I thought I’d talk about sickle cell anemia, quite a common ailment inherited Mendelian fashion through recessive genes.

If you’re new (very new) to genetics, then check out a picture for what I mean by recessive, and click through to Wikipedia to explain it all (man I love Wikipedia, is it natural to love an online encyclopedia of dubious accuracy? It feels so RIGHT!) Anyways, in the picture white is the recessive gene, and the flower will only have a white phenotype (as in, looks white) if both versions of the genes are the white recessive one.

mendelian_inheritance_3_1

Substitute red with normal haemoglobin (Hb), and white with mutated haemoglobin (HbS – S for Sickle or Screwed) and that’s what’s going on with sickle cell. If both your copies of haemoglobin have the sickle cell mutation, then you get the door prize – haemoglobin that tends to polymerise when it releases oxygen to form long rods (hehe, long rods) in the red blood cells, making them look all deformed and shabby like thus:

Sickle Cell Red Blood Cell
Shaped like a moon, or a sickle – think Grim Reaper!

Okay, I’m being a bit jokey about this, but it’s actually an awful disease – the cells are the wrong shape, and get caught in the blood stream causing blockages, which means progressive organ damage and pain, and they also don’t last as long (10-20 days rather than 120 days) causing anemia. Most people die early.

The weird thing is – this is terrible disease has been around for a long time with a clear genetic link – why hasn’t Darwin fished out out the mutation from the gene pool yet?

Researchers think that the sickle cell mutation was actually selected FOR, because there is evidence that having one copy of HbS and one normal Hb gene protects people against malaria.

Malaria is a highly lethal disease caused by protozoa carried by mosquitos, and even today kills about one million people a year. People who have African heritage often have a higher incidence of sickle cell, because malaria is endemic there. So the picture looks more like this –

scd-malaria

You’re damned if you do and damned if you don’t, but all good if you’re a genetic fence-sitter and take one of each. Indecision for the win!

(Wish I could take credit for the pictures, but still setting up the computer… it arrived yesterday – yay! It’s very sexy)






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