News - 19 November 2021

Assassin spider found!

The assassin spider (Zephyrarchaea austini). Image: South Australia Museum, Dr Jess Marsh.
It was feared extinct in the aftermath of the 2020 summer bushfires that devastated Kangaroo Island, but the fascinating assassin spider (Zephyrarchaea austini) has been found alive and well. We caught up with honorary research associate at the South Australian Museum, Dr Jess Marsh, about her life working with invertebrates and her rediscovery in some leaf litter of this ancient and unusual arachnid.

Honorary research associate at the South Australian Museum, Dr Jess Marsh.

What made you want to study spiders?

When I was a kid, I was always creating homes for creatures in jars and collecting all sorts of insects and spiders, so I think I’ve always been interested in them. I spent my younger years in Kenya, which had some pretty amazing invertebrates. Whilst at university though, I actually wanted to be a primatologist. That all changed when I got a part-time job working in a museum to support my studies. My job was to document the biology collections—to go through all the specimens and label and database the information—and I loved it! The collections I loved working with most were the spiders. They just fascinated me. The more I got to know the spider fauna, the more this fascination grew.

What are your two favourite facts about the assassin spider?

Definitely a stand out for me are their highly specialised body forms—their raised ‘neck’ and elongate jaws, which give them such a charismatic and unique appearance. The fact that these bizarre-looking features also make them such effective predators of other spiders adds to the intrigue. Another favourite fact is just how ancient the group is. Fossilised assassin spiders, looking very similar to modern species, have been found dating back to the Mesozoic period, 252-66 million of years ago. The fact that they would have been alive then, doing their thing and looking and acting very similar to modern species, but with dinosaurs roaming around the place is just mind-blowing.

Dr Marsh in the field.

What makes this species so important for biodiversity and its ecosystem? And in general, how is the arachnid world faring with climate change and habitat loss?

This species is a specialised predator of other spiders, which is pretty unusual for spiders. Invertebrates are crucial for ecosystem function, and most people are familiar with the roles for example that pollinators play. But, of equal importance are the regulators of the system, the predators, parasitoids and herbivores that keep the balance of species in check. In order to have a functioning ecosystem, all of these components play their part.

The species is only known from Kangaroo Island. It has a very small range, and is a short-range endemic species. Short-range endemic species, such as the assassin spider, represent an important part of biodiversity, yet are highly vulnerable to extinction events, where, for example their entire range can feasibly be impacted in a single fire event.

Many spiders and other arachnids are really vulnerable to drying out— most lack a hardened exoskeleton, which means they lose moisture quickly and need to stay in high humidity or shaded areas. In addition to that, many are habitat specialists, which means they can only live in a certain type of habitat. This means that they are less able to move to other areas if habitat is cleared and many are reliant on small areas. All of these features make them increasingly vulnerable to climate change, and threats such as fires, habitat loss and fragmentation.

What's the prognosis for the species and what will be key for its recovery?

The key for recovery for Zephyrarchaea austini will really hinge on the protection of its habitat—in preventing fires, reducing pig activity and protecting the area from fragmentation and clearance. If we can locate other populations of the species and can adequately protect their habitat, then the species does have a chance. However, given the extent of the fires, which removed much of the suitable habitat and the low dispersal ability of the species, recovery even then, will likely be slow.

This species is reliant on damp areas—living near creeklines in areas of high rainfall; habitats that are likely to be impacted by climate change. There is hope, but for species like these that are already living on the edge, it is going to be a difficult climb.