Parasites – as I’ve discussed before – are a fascinating case study in the lengths that nature will go to create creatures capable of extreme lifestyles.  The way that some parasites hijack their hosts and alter their form and function is equal parts amazing and repulsive.  Ants, like snails, are common victims:

The spores of the [Cordyceps] fungus attach themselves to the external surface of the ant, where they germinate. They then enter the ant’s body through the tracheae (the tubes through which insects breathe), via holes in the exoskeleton called spiracles. Fine fungal filaments called mycelia then start to grow inside the ant’s body cavity, absorbing the host’s soft tissues but avoiding its vital organs.

When the fungus is ready to sporulate, the mycelia grow into the ant’s brain. The fungus then produces chemicals which act on the host’s brain and alter its perception of pheromones. This causes the ant to climb a plant and, upon reaching the top, to clamp its mandibles around a leaf or leaf stem, thus securing it firmly to what will be its final resting place.

The fungus then devours the ant’s brain, killing the host. The fruiting bodies of the fungus sprout from the ant’s head, through gaps in the joints of the exoskeleton. Once mature, the fruiting bodies burst, releasing clusters of capsules into the air. These in turn explode on their descent, spreading airborne spores over the surrounding area. These spores then infect other ants, completing the life cycle of the fungus.

Which brings me to a science fiction short story that I listened to earlier this week on the Escape Pod podcast:  Tim Pratt’s ‘On a blade of grass’.

The best sci fi authors take a concept ground in truth and extrapolate it out.  In this story (text / audio) Pratt uses some earthly parasites as inspiration for a much more galactic tale.  I don’t want to spoil anything, but ‘On a blade of grass’ certainly got me thinking… and I wonder… might Tim Pratt be on to something?

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6 Responses to “On a blade of grass”

  1. Derrick says:

    Freaky stuff. Parasites altering your thought patterns is disturbing, but what makes it exponentially worse is that it is a deliberate act, altering your thoughts and emotions in a specific way to affront a particular goal. With bonus points – and this is the REALLY scary part, if you consider the implications – for developing this behavior via biological evolution.

    Simple organisms like fungus and bacteria evolve dramatic changes extremely rapidly, and who knows just how many such parasites (symbiotes?) live in us right now, already affecting how we think?


    • Andrew says:

      What I really love about that story is how it made me think. Follow along with me here:

      One of the leading theories about how life arose on this planet is that it arrived via interstellar dust/debris.

      If life is not – strictly speaking – native to Earth, then it arose somewhere else.

      Even freakier, what if this “somewhere else” has a lifeform that propagates itself by seeding the universe with evolution-based life infected with wanderlust that will inevitably take to the stars…

      If that’s the case, then we’re just interstellar fodder….. yikes!

  2. Derrick says:

    Also – that’s a great site, there, definitely going to follow it. More bite-sized interesting reading material is always welcome!

  3. Longasc says:

    Now I wonder how long it takes till they discover parasites that influence human behaviour… scary stuff!

    Creepier than most horror movies.

  4. Derrick says:


    They already have. The cat litter parasite discussed in the story? That’s not fiction.

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