Mastodawn

Huh? Ciliated protozoan Stentor may be capable of associative learning with habituation. #Protozoan #ciliate #wastewater #Pavlov https://www.biorxiv.org/content/10.64898/2026.02.25.708045v1

Associative learning in the protozoan Stentor coeruleus

The capacity for associative learning in protozoa has been a matter of longstanding controversy. In a series of Pavlovian conditioning experiments with the ciliate Stentor coeruleus , we show that temporally pairing weak and strong mechanical stimuli results in a transiently enhanced contraction response to the weak stimulus. Control experiments rule out several alternative explanations, such as non-associative sensitization or arousal. Parametric manipulation of the conditioning protocol’s temporal structure revealed a systematic dependence of learning on the inter-trial and inter-stimulus intervals, though not in the form classically observed in animals. A simple mathematical model, combining associative learning with habituation, can explain why enhancement is transient, and accurately fits the learning curve at the aggregate level. We conclude that Stentor coeruleus appears capable of associative learning, suggesting an ancient evolutionary origin that preceded the emergence of multicellular nervous systems. ### Competing Interest Statement The authors have declared no competing interest. Schmidt Sciences, https://ror.org/044fk6795, Polymath Award United States Air Force Office of Scientific Research, FA9550-22-1-0345

bioRxiv

Victor Mar 14

Huh? Ciliated protozoan Stentor may be capable of associative learning with habituation. #Protozoan #ciliate #wastewater #Pavlov https://www.biorxiv.org/content/10.64898/2026.02.25.708045v1

Associative learning in the protozoan Stentor coeruleus

The capacity for associative learning in protozoa has been a matter of longstanding controversy. In a series of Pavlovian conditioning experiments with the ciliate Stentor coeruleus , we show that temporally pairing weak and strong mechanical stimuli results in a transiently enhanced contraction response to the weak stimulus. Control experiments rule out several alternative explanations, such as non-associative sensitization or arousal. Parametric manipulation of the conditioning protocol’s temporal structure revealed a systematic dependence of learning on the inter-trial and inter-stimulus intervals, though not in the form classically observed in animals. A simple mathematical model, combining associative learning with habituation, can explain why enhancement is transient, and accurately fits the learning curve at the aggregate level. We conclude that Stentor coeruleus appears capable of associative learning, suggesting an ancient evolutionary origin that preceded the emergence of multicellular nervous systems. ### Competing Interest Statement The authors have declared no competing interest. Schmidt Sciences, https://ror.org/044fk6795, Polymath Award United States Air Force Office of Scientific Research, FA9550-22-1-0345

bioRxiv

CellBioNews Apr 20, 2023

Massive #Caribbean sea #urchin die-off caused by a #protozoan #parasite: Study.

#conservation

https://phys.org/news/2023-04-massive-caribbean-sea-urchin-die-off.html

Massive Caribbean sea urchin die-off caused by a protozoan parasite: Study

Scientists have discovered a parasite is behind a severe die-off of long-spined sea urchins across the Caribbean Sea, which has had devastating consequences for coral reefs and surrounding marine ecosystems.

Phys.org