Phew! Attenborough stands correct the textbooks don’t have to be rewritten.īut wait! There’s more work to do. All of these traits would make them easier to spot and to attack. They sat higher above the ground, kept to better-lit areas, stayed in more open spaces, moved around more, and oozed along more erratic paths. By carefully recording their behaviour, they confirmed that the infected animals behave very differently to the uninfected ones. Weslowska and Weslowski were chagrined, and they set out to Białowieza National Park in Poland to observe some of the snails. That author simply suggested that infected snails seek the well-lit upper surfaces of leaves, where they are visible to birds, and never presented any data to back up the claim. In the intervening 178 years, the only evidence that it manipulates the snails came from a German paper published in 1922. Leucochloridium’s hijacking behaviour was first described in 1835. But Wanda Wesolowska and Tomasz Weslowski from Wroclaw University in Poland discovered that this “fact” was based on the shakiest of foundations. Leucochloridium has become a textbook example of a parasite that manipulates the behaviour of its host for its own ends. Instead, it remains exposed out in the open, dangerously so.”Īttenborough isn’t the only person to make such claims. “As the day wears on, it does not like uninfected snails crawl back into the undergrowth out of harm’s way. “For some reason, the presence of the parasite changes the snail’s behaviour,” he said. That works for the fluke, which can only complete its life cycle in the guts of a bird.īut Attenborough claimed that the flukes did more than change the snail into a billboard. In the Trials of Life, a flycatcher swoops in and devours the snail. But it’s also compelling to birds, because the sacs look very much like juicy caterpillars or grubs. The effect was revolting and unforgettable to my young eyes. For some reason, the flukes usually go for the left one, but they’ll corrupt both if two of them share the same snail.
#Zombie snail full#
As they matured, they sent large broodsacs, full of larvae, into the snail’s eyestalks. The eggs hatched, and the young flukes started taking over the snail’s body. Something inside them is pulsating.ĭuring an inauspicious meal, this particular snail had accidentally swallowed the eggs of a fluke-a parasitic flatworm called Leucochloridium paradoxum. Its slender eyestalks have transformed into swollen sacs, with green and yellow stripes, black spots, and red tips. They appear in episode 7, grazing on leaves in a Danish meadow. Its twelve glorious episodes left an indelible mark in my mind, with unforgettable scenes of killer whales beaching themselves to eat sea-lions and elephant shrews bounding along carefully memorised paths.īut if you asked me to list the most memorable scenes from the series, I would tell you about the snails.
#Zombie snail series#
I was ten years old when I first saw Trials of Life, David Attenborough’s landmark series on animal behaviour.
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