Scientists replicate weird development of tiny, jumping worm in the lab

25 Jun 2018

A different nematode relative of Steinernema carpocapsae. Image: D Kucharski K Kucharska/Shutterstock

A tiny, jumping worm has a rather unusual sexual development when compared with other nematodes, and it could help give answers to evolution and genetics.

Because of their abundance and simplicity, nematodes are an essential part of many biological studies.

In fact, C. elegans – the ‘lab rat’ of nematodes – has been used extensively, having had its entire genome mapped and nearly every aspect of its biology characterised, particularly its neurons.

For years, it was assumed that other nematodes’ neurons were similar to those of C. elegans, until researchers at the University of Illinois demonstrated the vast diversity in neuronal anatomy present across species.

Now, a new study undertaken by the previous research team has shown that gonad development also varies in other nematodes relative to C. elegans, specifically Steinernema carpocapsae, a nematode used in insect biocontrol applications in lawns and gardens.

Typically, the gonads within nematodes develop within a structure called the gonad arm, a tube through which multiple reproductive organs migrate into place throughout the animal’s postembryonic development.

But Steinernema is a totally different kettle of fish, according to the team, and its findings can help scientists understand how diversity arises, an open question with relevance to evolution and genetic processes.

Juvenile nematode

A newly hatched Steinernema carpocapsae juvenile. Image: Nathan Schroeder/University of Illinois

Incredible jumping power

These tiny creatures, less than 1mm long, stand upright on their tails and are capable of jumping at enormous heights, 10 times higher than their body length.

This ability lets the worm jump on to a passing insect and, once infected, the worm expels symbiotic bacteria from its gut, killing the insect. The worm then starts feeding off the insect and bacteria, which by this point has spread throughout the insect’s body.

Exposure to this bacterial stew is what triggers the nematode to begin its postembryonic sexual development and then reproduce with other nematodes nestled inside the same insect.

This, of course, is pretty difficult to replicate in the lab for analysis, but the team was able to trick the worms into thinking they were in an insect by putting them in a high density of this bacteria.

“One of the issues in terms of commercialisation of Steinernema biocontrol products is being able to produce a lot of them,” said researcher Hung Xuan Bui.

“Can we somehow increase the overall reproductive output of these animals? Understanding more about the gonad development, where babies are actually being made, might move us in that direction.”

Colm Gorey was a senior journalist with Silicon Republic