Parasitic Worms Transform Spiders into ‘Zombies’ in New Study

A recent study from Lincoln University has revealed a fascinating yet alarming phenomenon in New Zealand’s ecosystems: parasitic worms known as mermithids are turning spiders into mindless creatures referred to as “zombies.” The research, led by PhD student Usha Mendis, aims to uncover the complexities of these nematodes and their impact on local spider populations.

Mermithids target various invertebrates, including caddisflies, mayflies, grasshoppers, and endemic spider species. Mendis highlights the potential ecological implications of this parasitic relationship. “New Zealand has a large number of endemic spiders… over 90% of them are endemic,” she stated. The decline of these spiders could have detrimental effects on biodiversity, as they play crucial roles in the food chain.

When mermithids infect spiders, they alter their behavior and physiology. The process is both gradual and fatal for the host. Spiders affected by the parasite often exhibit abnormal physical traits, including enlarged limbs and swollen abdomens. “They look like zombies,” Mendis noted. However, it is challenging to identify infected spiders until they die and the nematodes emerge, signalling the end of their life cycle.

The exact mechanism through which mermithids enter their spider hosts remains unclear. While researchers understand how these nematodes exit after consuming the spider’s nutrients, the entry point is still a mystery that Mendis is working to solve. She explains that the nematodes require a host to survive, consuming its energy and nutrients as they grow.

Nematodes seek moist environments to progress to their next life stage, which drives infected spiders toward water sources. This behavior often results in spiders being found drowned, as they are compelled to find moisture despite their compromised state. To study the nematodes further, Mendis is employing water traps to collect these parasites from their infected hosts.

The presence of mermithids in New Zealand has only been documented for the past 35 years, indicating that there is still much to learn about their relationship with local spider species. Mendis urges the public to reconsider their perception of spiders, emphasizing their ecological importance despite their unsettling appearance. “Spiders may look disruptive and creepy, but they’re not the enemy. They’ve got their own problems to deal with,” she said.

As research continues, understanding the dynamics between these parasitic worms and spiders could provide crucial insights into maintaining the health of New Zealand’s unique ecosystems.