Tildes Talks - The amazing Velvet Worm |Ngākeoke

Is it a worm? Is it a caterpillar? No, it’s a 550-million-year-old living fossil and voracious predator! 

The peripatus or ngākeoke is also sometimes called the velvet worm. There are nine described species of ngākeoke in Aotearoa, but there are likely to be many more species that have yet to be discovered. Ngākeoke are large, up to 8 cm long, and like caterpillars, have pairs of legs along their body. They are a striking colour and can range from dark blue and black to purple and yellow. 

Ngākeoke have an interesting mix of worm and insect characteristics, which once led scientists to call them the missing link between the two groups. They are segmented like worms and don’t have a distinct head, but their circulatory system and mouth parts are very insect-like. In reality, they are their very own ancient group. 

Despite looking like caterpillars, their diet is vastly different. Instead of peacefully munching on leaves, the Ngaokeoke is a voracious predator. The peripatus hunts at night and will shoot other invertebrates with sticky fluid. Once the prey is ensnared, the Ngāokeoke inject their victim with saliva, which dissolves them into a sticky soup that the Ngāokeoke can ingest. As well as shooting prey with their sticky fluid, it can also be used as a defence mechanism.

Ngāokeoke reproduction is no less strange. Males will pass a sperm packet to the female, but she may hold it for up to two years before the eggs or embryos begin development. Furthermore, females have two uteri, so they can have two separate pregnancies of different ages at the same time! That sounds like hard work! Some lay eggs while others give birth to live young. 

Ngākeoke are incredibly ancient. The oldest fossils were discovered in the 550-million-year-old Burgess Shale fossil deposits in British Columbia during the Cambrian Period, making ngākeoke as old as the evolution of the spinal cord! During the Cambrian Period, Ngākeoke lived in shallow marine environments, but apart from moving onto land, they have remained virtually unchanged. 

Present-day ngākeoke are divided into two families and are found in South America, South Africa, Southeast Asia, and Australasia. The evolutionary age of ngāokeoke and the locations of present-day species suggest that it was present on the supercontinent Gondwana before it split, and our endemic ngākeoke species have been isolated ever since. 

Today, ngāokeoke can be found in damp environments, burrowing into rotten logs in the ngahere and gardens. I have found many on the island over the years. They must stay in damp environments as their skin is covered in pores and can easily dry out. The open pores are also what give ngākeoke its velvety appearance. 

Ngaokeoke don’t venture far from home, which leads to the isolation of populations. While nine species have been described, there likely are many more, as a lack of gene flow between populations leads to different species evolving. Populations are also incredibly difficult to study, which makes it difficult to find new species. Could it be that Waiheke has its very own species? 

We can help these fascinating creatures by undertaking predator control to reduce rats, which eat them. 

We can also let our gardens go wild! Ngākeoke like good vegetation cover and rotting logs, so leaving a wild corner can help these critters as well as many other insects, lizards, and birds. 

Finally, we can help stand up for conservation to make sure that proper consultation and surveying are carried out before large modifications are made to the environment, as they could lead to the extinction of an entire Ngāokeoke species.

Story by Tilde Sorensen