OUR SERIES, ANIMALS IN RESEARCH, PROFILES THE TOP ORGANISMS USED FOR SCIENCE EXPERIMENTATION. HERE, WE LOOK AT _CAENORHABDITIS ELEGANS_ – A ROUNDWORM. When you think of a worm, what do you

see? For some it’s the squeamish thought of treading on one in bare feet after rain; for others it’s the periodical doses of dewormer for the family pet. Perhaps it’s even the slimy tubes

that happily munch through the compost. Well, now you can add “medical research star” to your list. One species of worm - _Caenorhabditis elegans_ - has contributed more to medical science

in the past few decades than you might think possible. Some 50 years ago, South African biologist Sydney Brenner made the bold claim that solutions to the important problems in molecular

kind of virus that infects bacteria). With this background, Brenner went in search of a model organism that would be suitable for studies of development and the nervous system. A small

animal that could be easily cultivated and that had a short life cycle would be required. Ultimately, Brenner alighted on a nematode (roundworm) called _Caenorhabditis elegans_. Measuring

only 1mm, growing readily on simple agar plates with bacteria for food, and taking only three days to develop from an egg to a fertile hermaphrodite adult, the nematode fitted the bill. More

commonly referred to simply as “the worm”, Brenner’s model organism of choice is now the subject of research in hundreds of laboratories around the globe, including, at my count, at least

ten labs in Australia. In each of these worm labs, researchers study animals derived from a single sample that was taken from mushroom compost in Bristol in the UK in the 1950s. THE ELEGANT

WORM From these humble beginnings, the worm has afforded us notable insights in many areas of biology. In line with Brenner’s aspirations, _C. elegans_ has proved to be an excellent tool for

studying development. Remarkably, every worm grows in essentially the same way – from a single cell, the fertilised egg, to an adult, with precisely 959 somatic cells. The worm is

transparent, so these cells can be observed using light microscopy. Through painstaking work requiring several years at the microscope, British biologist John Sulston meticulously mapped the

process of worm development, documenting the timing and direction of every cell division. This cell lineage is a vital tool that enables researchers to answer questions about how

development is controlled at the level of a single cell. The worm has also lived up to the hope of providing insight into the workings of the nervous system. Unlike our nervous system, which

contains many billions of neurons, the worm has only 302 neurons. Neurons are complex cells, which extend long processes and communicate between themselves, and with other cell types, via

synapses. After sectioning the worm into about 20,000 slices, American biologist John White and colleagues used electron microscopy to build a picture of all worm neurons, their processes

and their 8,000 synapses, providing us with a complete wiring diagram of this relatively simply nervous system. As with the developmental cell lineage, this neuronal wiring diagram is an

important tool in enabling researchers to address many interesting questions relating to neuronal development and function. DIFFERENT STRAINS Despite the worm’s simplicity and the many

obvious differences between worms and humans, if you look at what is going on inside our cells, we in fact have much in common. Take, for example, programmed cell death – the death of some

of an organism’s cells as part of its natural development. This process is vital for normal development but also plays an important role in cancer. Seminal discoveries about programmed cell

death were made using _C. elegans_ as a model system and earned Brenner, Sulston and Robert Horvitz the Nobel Prize in Physiology or Medicine in 2002. Another major discovery made using _C.

elegans_ was that of RNA interference, gene silencing by double-stranded RNA. For this, Americans Craig Mello and Andrew Fire were awarded the Nobel Prize in Physiology or Medicine in 2006.

Then, in 2008, American worm researcher Martin Chalfie shared in the Nobel Prize in Chemistry for his contribution to the development of green fluorescent protein as a tool for visualising

biological structures in living organisms. Aside from these seminal Nobel-winning discoveries, research using _C. elegans_ continues to yield new information in diverse areas of biology such

as behaviour, metabolism and ageing, to name but a few. Many resources are shared among the worm research community, facilitating these endeavours. These include an extensive collection of

worm strains carrying mutations in particular genes and bacterial strains that can be fed to worms to reduce the function of any gene of interest by RNA interference. Since around 40% of the

genes implicated in human disease have equivalents in worms, these tools also make it possible to learn more about the underlying mechanisms of many diseases by examining the function of

the related gene in the worm. It is also straightforward to introduce new genes into _C. elegans_, including those from humans. This approach has, for example, been used to create worm

models for studying Alzheimer’s disease. Such disease models can further be exploited to screen for drugs which may ultimately be used to treat human disease. Through the past 50 years _C.

elegans_ has proved to be a very powerful model organism, revealing to us important lessons about our own biology. The collaborative spirit that characterises the _C. elegans_ research

community, which is epitomised in the publication of The Worm Breeders Gazette, a newsletter for sharing results and techniques, will ensure that the next half century in worm world is

equally productive. TO READ MORE IN THE ANIMALS IN RESEARCH SERIES, FOLLOW THE LINKS BELOW: _DROSOPHILA MELANOGASTER_ (THE FRUIT FLY) _DANIO RERIO_ (ZEBRAFISH)