Nematode worm NUI MAYNOOTH
Fight Club

Survival of the fittest: Early life experiences can make worms fight to the death

The research by NUI Maynooth represents a significant breakthrough in the study of the fundamental behaviour of animals.

JUST AS EARLY life experiences have been studied and found to impact on peoples’ behaviours later in life, a study into the behaviour of nematode worms has discovered that early life experiences can trigger them to fight to the death in later life.

Fighting to the death is rare amongst most animals, but the new study,  carried out by NUI Maynooth, represents a significant breakthrough in the study of the fundamental behaviour of animals.


The study indicates that the difference in fighting between the generations of nematode worms is due to a developmental switch at a juvenile stage in their development.

The new research has found that this tendency to fight to the death amongst male worms is unique to those that have experienced crowding at a juvenile stage in their development, causing arrested development.

Speaking to, NUI Maynooth Biology Lecturer Dr Christine Griffin said the study into simple animals, like that of the nematode worm, can give a good model for more complex animals and the study of aggression and fighting, stating that “simplicity can make it easier” to study.

“This is an interesting finding in terms of our thinking towards animal behaviour and fighting,” she said, adding, “conditions during early stage development have a profound effect on the expression of fighting in adults.  Nematodes may be simple animals, but many of the biochemical and neural processes that take place in them have parallels in higher animals including humans”.


“Fighting, let alone fatal fighting, has not previously been described in any other nematode and fighting to the death is relatively rare amongst animals. Studying their behaviour helps us develop better pest control strategies – as well as providing us with a fascinating insight into the fundamental behaviour of animals and the external conditions that influence their fighting instincts,” said Griffin.

The study looked at worms that kill insects, using symbiotic bacteria that they carry around with them and reproduce inside the insect cadavers. Several generations can pass through a large insect and eventually, tens or even hundreds of thousands of nematode descendants emerge from the spent cadaver in soil and wriggle away in search of fresh hosts.

These are exactly the kind of conditions where we might expect fatal fighting to evolve, said Griffin.

However, killing is only a feature of the first colonists that enter the insect, not of the worms of subsequent generations that develop later inside the insect. For worms of later generations, there would be too many competitors – and many of them close relatives – to make fighting a profitable course of action.

Griffin said that this breakthrough has opened up wider questions for their research as in does the quality of the females they are fighting over add to the likelihood of them fighting, to whether they will fight the brothers and sisters they are related to. This will be what Griffin and her team of researchers will investigating further.

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