EPISODE 59: Food or Sex? The Worm Has to Choose

Welcome to the next episode of The Worm Podcast 🧠

Today we are talking about a problem every animal faces:

where should I spend my energy?

For C. elegans, the answer depends partly on sex.

Hermaphrodites need to balance food, reproduction and survival. Males have an extra problem: they also need to find a mate.

This new study identifies SKN-1B, a neuronal version of the conserved Nrf transcription factor, as part of the switch that helps control those competing priorities.

🍽️ Food or mate?

SKN-1B is expressed in sensory neurons involved in food sensing and metabolism.

In hermaphrodites, SKN-1B promotes food-seeking behaviour.

But males behave differently.

Male skn-1b mutants left food faster when no mate was present, suggesting increased mate-searching behaviour.

Give them a hermaphrodite, or even just hermaphrodite pheromones, and they stayed.

So the worms were not simply more active.

They were changing what they prioritised.

🧬 The effect lasts into older age

The difference became even more interesting as the worms aged.

Wild-type male exploration declined with age.

But skn-1b mutant males maintained exploratory behaviour and were more likely to retain mating ability at day 5 of adulthood.

The authors therefore suggest that SKN-1B normally acts to suppress male mate-searching behaviour, including later in life.

🧠 A sex-specific molecular switch

The transcriptomic effects were striking.

Loss of skn-1b changed only hundreds of genes in hermaphrodites, but thousands in males.

The paper also found sex-specific effects on mitochondrial organisation and function.

So the same neuronal transcription factor can produce very different whole-animal outcomes depending on whether the worm is male or hermaphrodite.

🔬 The signalling pathway

The authors traced part of the behavioural effect through a neuroendocrine pathway involving:

• DAF-7 TGF-β signalling
• insulin signalling
• ODR-10, an olfactory receptor involved in food sensing

In skn-1b mutant males, DAF-7 increased while odr-10 expression fell.

Reducing ODR-10 in wild-type males also increased exploration and food-leaving behaviour.

That links SKN-1B directly to the neural machinery balancing feeding and mating.

🧠 The take-home message

This is not simply a story about male worms being more interested in mating than food.

It is about how the nervous system decides where energy should go.

SKN-1B acts as a sex-specific behavioural and metabolic switch, helping balance:

food × energy × reproduction × ageing

And in males, removing that switch seems to keep mate-searching behaviour going for longer.

📄 Paper discussed

Noviann McLean, Minaxi S. Gami, Nathan Dennis, Yasir Malik, Justin De Araujo, James Evans, Lydia Bennett, Marina Ezcurra and Jennifer M. A. Tullet (2026)

Neuronal Nrf/SKN-1B controls a sexually dimorphic neuroendocrine pathway for C. elegans exploratory behaviour

PLOS Genetics, 22(8): e1012239

DOI: https://doi.org/10.1371/journal.pgen.1012239

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