Nematodes with five distinct forms found

January 18, 2016 by Bob Yirka, report
Two morphotypes (morphs I, II) of P. borbonicus, a symbiont of Ficus mauritiana. The beard-like labial morphology is a novelty known only from this species and P. sycomori. Scale bar, 10μm. Credit: Vladislav Susoy & Jürgen Berger

(—An international team of researchers has found that at least one type of nematoad exhibits five distinct forms—each different enough that the microscopic worms were initially thought to be of different species. In their paper published in the journal Science Advances, the team describes their study of the worms that live in South Africa, Vietnam and on La Réunion Island and possible reasons for such diversity among a single species.

As the team notes, it is not uncommon for a single species to have many forms, dogs are one good example—other animals have different coat colors or wing patterns, depending on where they live, etc. But it is unusual for a single species to exist in as many as five different forms where they are so different it is difficult to make them out as from the same species. In this case, the nematoads are of a type that live inside of figs—they are carried to their home when young, by wasps. As they grow, they can take on one of five different forms depending on the conditions they find inside the fig—most of the differences are in the way the mouth is structured. If there are other competing nematoads of another species in a single fig, for example, the grow a lot of teeth and survive by eating the other worms. Those that land in nematoad-free figs, on the other hand, instead grow mouths that are suitable for eating microbes.

As to why the nematoads developed such diversification abilities, the team suggests it has to do with their isolated existence—they equate individual figs to islands, where a young nematoad is wholly at the mercy of its environment, which appears to be of five different major varieties. They note also that few nematoads actually manage to colonize new fruit, thus any species able to do so would naturally need to be able to take advantage of what is found once it arrives. They add that they have also found three related nematoad species that also have five phenotypes, which suggests the characteristic may not be as rare as was initially thought. They suggest there might be some that are able to take on even more than five forms.

Explore further: A worm with five faces

More information: V. Susoy et al. Large-scale diversification without genetic isolation in nematode symbionts of figs, Science Advances (2016). DOI: 10.1126/sciadv.1501031

Diversification is commonly understood to be the divergence of phenotypes accompanying that of lineages. In contrast, alternative phenotypes arising from a single genotype are almost exclusively limited to dimorphism in nature. We report a remarkable case of macroevolutionary-scale diversification without genetic divergence. Upon colonizing the island-like microecosystem of individual figs, symbiotic nematodes of the genus Pristionchus accumulated a polyphenism with up to five discrete adult morphotypes per species. By integrating laboratory and field experiments with extensive genotyping of individuals, including the analysis of 49 genomes from a single species, we show that rapid filling of potential ecological niches is possible without diversifying selection on genotypes. This uncoupling of morphological diversification and speciation in fig-associated nematodes has resulted from a remarkable expansion of discontinuous developmental plasticity.

Related Stories

A worm with five faces

January 4, 2016

For eight years, a research team headed by Ralf Sommer and Matthias Herrmann travel to Réunion Island in the Indian Ocean. The scientists from the Max Planck Institute of Developmental Biology have now discovered a new nematode ...

Every time a fig is born there is a wasp massacre

January 28, 2015

"Don't put all your eggs in one basket" is a common refrain. But usually it is not followed by the words "because your neighbours may kill you". However, this is precisely the scenario faced by some female Brazilian fig wasps ...

Is the humble fig more than just a fruit?

May 2, 2013

Figs and fig trees are familiar to a wide cross-section of human society, both as a common food and for their spiritual importance. What is less well understood is the global nature of this association between figs and humans, ...

Two new species of frogs are discovered in Madagascar

January 12, 2016

The Tsaratanana Massif –the highest mountain on Madagascar and one of the island's most remote regions– is home to several indigenous species. Yet, the majority of these species remain unknown to science due to the fact ...

Recommended for you

A world of parasites

May 25, 2018

Alex Betts, Craig MacLean and Kayla King from the Department of Zoology, shed light on their recent research published in Science, which addressed the impact that parasite communities have on evolutionary change and diversity.

Bumblebees confused by iridescent colors

May 25, 2018

Iridescence is a form of structural colour which uses regular repeating nanostructures to reflect light at slightly different angles, causing a colour-change effect.

A better B1 building block

May 25, 2018

Humans aren't the only earth-bound organisms that need to take their vitamins. Thiamine – commonly known as vitamin B1 – is vital to the survival of most every living thing on earth. But the average bacterium or plant ...

Plant symbioses—fragile partnerships

May 25, 2018

All plants require an adequate supply of inorganic nutrients, such as fixed nitrogen (usually in the form of ammonia or nitrate), for growth. A special group of flowering plants thus depends on close symbiotic relationships ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

5 / 5 (1) Jan 20, 2016
It is a "nematode" and not a "nematoad"!! The title gets the spelling correct but the rest of the article uses a newly invented spelling :) Please correct it.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.