DISCO INFERNO GREEN-BANDED BROODSAC

The parasitic flatworm that turns a snail’s eyestalks into colourful, pulsating glowsticks

- Nick Baker

The green-banded broodsac – what kind of a name is that? Normally we name an animal after the appearance or behaviours of the adult, but in the case of the fluke Leucochloridium paradoxum, unless you want to go poking around the guts of snails or the bums of birds, its broodsac – a membranous sac containing larvae – really is the most visible part of this parasitic flatworm’s life. And when I say visible, it’s no exaggeration.

If you’re lucky, you might come across the unassuming amber snail (Succinea putris) putting on an uncharacteristic and extrovert performance. With its eyestalks pulsating in high-contrast patterns of green, black and red, you are witnessing the phenomenon that gives this fluke its name. These are the fluke’s broodsacs and they are part of a complicated life-cycle that involves a bird, a snail and a fluke.