For years, it was assumed 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 Nathan Schroeder, assistant professor in the Department of Crop Sciences at U of I and leader of the previous study, has shown that gonad development also varies in other nematodes relative to C. elegans. Specifically, he and graduate student Hung Xuan Bui focused on Steinernema carpocapsae, a nematode used in insect biocontrol applications in lawns and gardens.
The gonads in all 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. This happens in a highly predictable manner in C. elegans, with very low variability among individuals. Not so with Steinernema.
Schroeder says finding and understanding examples of variability within and among species can help scientists understand how diversity arises, an open question with relevance to evolution and genetic processes.
The story stays eccentric:
Aside from showing that Steinernema development differs from C. elegans, the study also represents an advancement in terms of studying organisms whose development occurs almost entirely inside another organism.
These tiny roundworms, less than a millimeter long, stand upright on their tails and jump up to 10 times their body length with the goal of landing on and infecting an insect. Once they find a bug, Steinernema expels symbiotic bacteria from its gut, which is what kills the insect.
That’s when the nematode starts feeding on the insect and the bacteria that, by this point, has spread throughout the insect’s body. Being exposed to this external bacterial stew is what triggers the nematode to begin its postembryonic sexual development and then to reproduce with other nematodes nestled inside the same insect. As one can imagine, it could be rather difficult to replicate that environment in the lab.
“Bui was able to trick them. He put them in a high density of this bacteria, and essentially tricked them into coming out of this juvenile stage to undergo normal reproductive development without being inside the insect,” Schroeder says.Paper. (public access) – Hung Xuan Bui et al. Postembryonic ventral nerve cord development and gonad migration in Stinernema carpocapsae. Journal of Nematology, 2018 DOI: 10.21307/jofnem-2018-005 More.
Bui tricked the nematode worms? He tricked them? That would make a good episode in a sane light comedy set in a U bio lab.
But seriously, readers, sit back and imagine if, confronted with the development scenario of the nematode worm, one would be tempted to invent Darwinism (natural selection acting on random mutations) as an explanation for how diversity arises? Didn’t such an explanation depend on not really knowing all this?
See also: Epigenetics: Worms passed on environment memories 14 generations (nematodes)