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In praise of the spineless


Velvet worms

Velvet worms are considered to be ancestors of the arthropods, the most successful group of animals on Earth today. (Source: Robyn Stutchbury)

How often have you heard the terms 'creepy crawlies', 'bugs' or 'little critters'? What about your arachnophobic friends? Why are they so fearful of small, furry animals with eight hairy legs and eight sparkling eyes? It seems there are deeply ingrained prejudices in our society that keep so many from recognising the beauty and wonder of our invertebrate companions.

Yet this fear and repulsion is often absent in younger children. Very rarely do they say 'yuck' when confronted with an invertebrate; instead there is the frequent 'awesome' from these eager beavers as they peer through a microscope at some small spineless animal.

From early childhood I have been captivated by the beauty and unfathomable diversity of invertebrates. I was fortunate that this passion led me into my career as an academic invertebrate zoologist. I am, unashamedly a spineless biologist. Work, hobby and pleasure have become but one.

I still have vivid childhood memories of almost suffocating excitement when finding something new as I fossicked in rock pools near my seaside home in Sydney. The vast majority of rock pool animals are invertebrates, and a lifetime of academic research into this remarkable group has only added to their magnetism.

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Velvet beauties

Over 95 per cent of the animal world is spineless. The spineless animals — invertebrates — lack a vertebral column or backbone.

Invertebrates are animals and yet to many, animals are those cuddly, furry creatures we keep as pets or see in zoos: the mammals. Quite often, even the broader concept of 'animals' doesn't extend beyond mammals to the rest of the vertebrate world, such as fish, amphibians, reptiles and birds.Yet invertebrates make up a massive 31 one out of the 32 major groups of animals on Earth. All the vertebrates fit into just one group.

Although my research has covered various aspects of invertebrate biology, my main interest has been a group called the Onychophora, known commonly as peripatus or velvet worms. These land animals live in forests, in rotting vegetation and soil.

There is something remarkably elegant about peripatus as they move unhurriedly on their 13 to 34 pairs of hydraulic, stumpy legs. This and their velvet texture, which gives the appearance of a tiny rolled Persian carpet, make them appealing to even the most creepy-crawly phobic person. Instead of the scuttling of the jointed legged arthropods or the slime of worms, slugs and others, peripatus glides majestically over your hand.

But they are not just pretty faces. Importantly, onychophorans are considered to be ancestors of the arthropods, the most successful group of animals on Earth today. Onychophorans are all highly carnivorous, feeding on termites, beetles and other creatures of the forest floor. They enmesh their prey in threads of sticky slime ejected from turrets on either side of their head. They in turn would provide larger animals with a tasty meal and in some forests they form a major component of lyrebirds' diet.

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So what?

Although this small group of invertebrates is pursued by only the most fanatical of spineless biologists, there are good reasons for such a pursuit. Through genetic studies it has been shown that onychophorans provide an insight into our understanding of evolutionary processes such as those that result in the formation of new species. This in turn is critical to the maintenance of biodiversity.

It was recently announced that scientists have estimated there are 8.7 million species of living things on Earth. Of these, only about 2 million have been formally identified, named and described. Even using estimates from onychophoran research, which in 1985 suggested that there were only seven species of peripatus in Australia, the discovery of over 70 new species since then is an increase by an order of magnitude. Extrapolating this order of magnitude in onychophoran biodiversity suggests that a huge number of species remain to be discovered.

With increase in human population and its increasing dependence on the Earth's diminishing resources, we are already aware of an alarming increase in extinction of species as habitats are disturbed. It is so very possible that many species will become extinct before they are identified. 'So what?' you ask. Not only our quality of life, but also our very survival could depend on our knowledge of and hence the maintenance of biodiversity.

About the author Dr Noel Tait is an honorary research scientist at Macquarie University in Sydney. Although retired, he and his wife Robyn Stutchbury, a science communicator by profession, regularly share their enthusiasm for invertebrates with young children through visits to primary schools and writing natural history books.


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Published 05 September 2011