Posts Tagged ‘reproduction’

The red queen, sex and nematode worms

// July 28th, 2011 // 1 Comment » // Recent Research, Sex and Reproduction

Alice_and_Red_Queen

Alice and the Red Queen by John Tenniel

In Lewis Carroll’s Through the looking-glass– a whacky book if I ever read one – the laws of physics don’t really apply. Hills can become valleys, straight can become curvy, and forward is really backward.

In one scene, Alice chases after the Red Queen, both running as fast as they can, but when they stop Alice realises they are still right where they started. “Now, here, you see, it takes all the running you can do to keep in the same place” says the Red Queen.

And it might be the same with the evolution of predator and prey, host and parasite. Running doesn’t get you anywhere. So says the Red Queen Hypothesis.

c elegans embryo

C elegans embryo. Image by Monica Gotta

As the host adapts to fight the parasite, the parasite evolves to infect the host. It’s an endless race, and extinction faces the first organism to stop running.

So what’s this got to do with sex? Sex is evolution on turbo. Mixing and matching genes increases genetic diversity, giving a species more opportunities to outlast in the ultimate game of survivor.

Field data supports the Red Queen Hypothesis as describing an adaptive advantage of sex. Models and maths support the idea that coevolving species could select for rare genes and unusual combination randomly created by sex. Direct experimentation of coevolution and nookie is tricky business.

New research, published in Science, grew several populations of nematode worms (C. elegans, roundworms) which are usually asexually, but reproduce sexually 20% of the time.

The populations were differently exposed to bacterial parasites (Serratia marcescens) as shown.

C Elegans Sex Research

C Elegans image by Bob Goldstein, University of Carolina, Chapel Hill, remixed by Science Journal. Creative Commons License

One population was given the parasites and left to their own devices. They and their bacteria could evolve together. These nematode worms increased their rate of sexual reproduction to 80-90% over time, and maintained a high level of sexy-times.

The other nematodes were given frozen stocks of bacteria every generation, so the parasites weren’t evolving as the worms did. At first, sexual reproduction increased in the worms, but then it dropped back down to 20% – the same level as nematodes which hadn’t been exposed to the bacteria at all.Alice meets dodo

Parasites on their own don’t increase sex – coevolution does.

A second experiment supported their conclusion. Nematodes mutated to be unable to reproduce sexually (asexual obligates) became extinct after 20 generations when exposed to the parasites. But mutants that always required sex to reproduce (sexual obligates) never became extinct.

When it comes to coevolution, it’s fall behind and be left behind.

Never stop running.

ResearchBlogging.org

Morran, L. et al (2011). Running with the Red Queen: Host-Parasite Coevolution Selects for Biparental Sex Science, 333 (6039), 216-218 DOI: 10.1126/science.1206360
Brockhurst, M. (2011). Sex, Death, and the Red Queen Science, 333 (6039), 166-167 DOI: 10.1126/science.1209420

So many baby octopuses

// March 8th, 2011 // Comments Off on So many baby octopuses // How Things Work, Just for Fun

One of my guilty pleasures is my RSS subscription to Zooborns, a blog all about baby animals. When I check Google Reader, I read sensible, serious blog posts about science until I finally cave and look at the cuteness.

Amongst the treasure trove of nursing giraffes and clinging baby apes was a clutch of baby octopuses! Perhaps clutch isn’t the right word… a handful? An armful! An armful of baby octopuses. Check it out.

Baby octopus at California Academy of Sciences

Baby octopus at California Academy of Sciences

Conception occurs when a male octopus inserts a modified sperm-containing arm into the female’s oviduct, though sometimes he removes his arm and she stores it in her mantel for later. Each egg, as it is laid, contains a long thread which the octopus uses to hold them all together like a bunch of grapes. A thoughtful mother, she protects them from predators and blows water currents across them for cleaning.

Biologist Richard Ross caught the hatching of the eggs on video, and described it as a waterfall flowing upwards towards the surface.

It’s an exciting event, but unfortunately a mother octopus stops eating to care for the eggs and dies which is a total bummer. With millions of tiny planktonic octopus young born, some should survive, though they are hard to feed and raise.

On a lighter note, Zooborns recently posted pictures of a Snow Leopard cub born in Chattanooga Zoo. Snow Leopards happen to be my favourite animal and the cub is so exceedingly cute I might die. A less attractive addition in Australia is the first palm cockatoo zoo bred in 40 years which has passed through the awkward teenage stage and is starting to fly.

Damn I want to work at a zoo.






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