Parasitic Worms Transform Spiders into “Zombie” Hosts in New Zealand

A recent study led by PhD student Usha Mendis at Lincoln University has unveiled a disturbing phenomenon involving parasitic worms known as mermithids. These nematodes infect various invertebrates, including spiders, effectively transforming them into “zombies.” Mendis aims to investigate the impact these parasites have on local ecosystems, particularly in New Zealand, where over 90% of spider species are endemic.

The mermithids infiltrate the bodies of spiders, leading to significant physical changes. Infected spiders often exhibit larger limbs, distorted body shapes, and swollen abdomens. Mendis describes this transformation, stating, “They look like zombies.” Unfortunately, the process is fatal for the spiders, as the parasites consume their energy and nutrients, ultimately leading to the host’s death.

Mendis has identified three types of spiders currently affected by these nematodes and is working to clarify the species involved. She emphasizes the ecological importance of spiders, noting, “If something were to happen to them, it would not be good for our biodiversity.” Spiders play a crucial role in the food chain, and their decline could disrupt the balance of local ecosystems.

The life cycle of the mermithids is complex and not fully understood. Researchers know that the nematodes emerge from the spider’s body, but the entry mechanism remains a mystery. Mendis is keen to uncover how these parasites infiltrate their hosts. “They can’t live without a host. They consume the energy and nutrients of the host, and grow inside it,” she explains.

Moist environments are essential for the nematodes to thrive and reproduce. Infected spiders instinctively seek out water, often resulting in their drowning. Mendis is employing water traps to collect these nematodes, which she believes will help in understanding their lifecycle and their relationship with spiders.

Despite mermithids being reported in New Zealand for just over 35 years, much remains unknown about their impact. Mendis urges the public to reconsider their perception of spiders, acknowledging their vital role in ecosystems. “Spiders may look disruptive and creepy, but they’re not the enemy,” she says. “They’ve got their own problems to deal with.”

As Mendis continues her research, the implications of her findings could shape our understanding of biodiversity and the interconnectedness of species within ecosystems. The fate of spiders in New Zealand may depend on uncovering the secrets of these parasitic nematodes, and the urgency of this research underscores the delicate balance of nature.