Tiny worms make complex decisions, too

Amazing stuff! Eat or be eaten!

"They were surprised to find that worms can take multiple factors into account and choose between two different actions, despite having only 302 neurons compared to approximately 86 billion in humans.

The findings ... have important implications for the way researchers assess motivation and cognitive abilities in animals. ...
Even simple systems like worms have different strategies, and they can choose between those strategies, deciding which one works well for them in a given situation. ...
The researchers found that P. pacificus chooses between two foraging strategies for biting its prey and competitor, another worm called Caenorhabditis elegans: 1) predatory strategy, in which its goal for biting is to kill prey, or 2) territorial strategy, in which biting is instead used to force C. elegans away from a food source. P. pacificus chooses the predatory strategy against larval C. elegans, which is easy to kill. In contrast, P. pacificus selects the territorial strategy against adult C. elegans, which is difficult to kill and outcompetes P. pacificus for food."

From the highlights and abstract:

"Highlights

• Non-fatal biting by the predator P. pacificus deters competing prey from food

• Non-fatal biting of adult prey is territorial aggression, not failed predation

• Territorial and predatory biting are associated with different prey search tactics

• P. pacificus switches between predatory and territorial foraging strategies

Summary

Animals with diverse diets must adapt their food priorities to a wide variety of environmental conditions. This diet optimization problem is especially complex for predators that compete with prey for food. Although predator-prey competition is widespread and ecologically critical, it remains difficult to disentangle predatory and competitive motivations for attacking competing prey. Here, we dissect the foraging decisions of the omnivorous nematode Pristionchus pacificus to reveal that its seemingly failed predatory attempts against Caenorhabditis elegans are actually motivated acts of efficacious territorial aggression. While P. pacificus easily kills and eats larval C. elegans with a single bite, adult C. elegans typically survives and escapes bites. However, non-fatal biting can provide competitive benefits by reducing access of adult C. elegans and its progeny to bacterial food that P. pacificus also eats. We show that the costs and benefits of both predatory and territorial outcomes influence how P. pacificus decides which food goal, prey or bacteria, should guide its motivation for biting. These predatory and territorial motivations impose different sets of rules for adjusting willingness to bite in response to changes in bacterial abundance. In addition to biting, predatory and territorial motivations also influence which search tactic P. pacificus uses to increase encounters with C. elegans. When treated with an octopamine receptor antagonist, P. pacificus switches from territorial to predatory motivation for both biting and search. Overall, we demonstrate that P. pacificus assesses alternate outcomes of attacking C. elegans and flexibly reprograms its foraging strategy to prioritize either prey or bacterial food."

Tiny worms make complex decisions, too - Salk Institute for Biological Studies Salk scientists surprised to discover flexible decision-making capabilities in a worm with just 302 neurons

Flexible reprogramming of Pristionchus pacificus motivation for attacking Caenorhabditis elegans in predator-prey competition

C. elegans worm (right) escaping the predatory P. pacificus worm (left).

Graphical abstract