Even Ostracods can learn and have ‘memory’: international study reveals aquatic microcrustaceans display more complex behaviour than previously thought
A new international study led by the University of Parma, in collaboration with the BioRobotics Institute of the Sant’Anna School of Advanced Studies (Pisa) and the Cavanilles Institute of Biodiversity and Evolutionary Biology at the University of Valencia, shows that ostracods—tiny aquatic crustaceans enclosed within a bivalved carapace—possess behavioural abilities that are more sophisticated than previously recognised. Published in the international journal BMC Biology, the research provides evidence of visual associative learning and wavelength-specific responses to light in three podocopid ostracod species: Vizcainocypria viator, Loxoconcha elliptica, and Xestoleberis nitida.
The study was coordinated by Elena Bellavere and Giampaolo Rossetti of the Department of Chemistry, Life Sciences and Environmental Sustainability at the University of Parma, in collaboration with Francesc Mesquita-Joanes of the Cavanilles Institute of Biodiversity and Evolutionary Biology at the University of Valencia, and Donato Romano of the BioRobotics Institute at the Sant’Anna School of Advanced Studies.
Using miniature lab-on-a-chip arenas specifically designed to accurately observe the behaviour of microscopic organisms, the research team investigated how ostracods respond to green and blue light under both spontaneous conditions and after conditioning with either positive stimuli, such as the presence of food, or negative stimuli, such as chemical stress cues. The results show that light responses are not simple reflexes but can be modulated by experience and differ according to species, treatment, and light wavelength.
The study provides evidence for a simple form of medium- to long-term associative memory. Some individuals altered their behaviour even 16–24 hours after training. The observed differences involved not only preferences for illuminated or dark chambers but also locomotor parameters such as exploratory activity, inactivity, and movement speed.
The contribution of the BioRobotics Institute of the Sant’Anna School of Advanced Studies focused on the technological and methodological components of the research. In particular, the institute contributed to the design of the experimental paradigms and ethological approaches used in the behavioural tests, as well as to the development of the miniaturised platforms and automated tracking systems employed to accurately quantify ostracod behaviour.
"From a neuroethological perspective, these findings show that even organisms with very simple nervous systems can integrate sensory information, modify their behaviour based on experience, and retain forms of associative memory," comments Donato Romano. "Ostracods therefore represent an attractive model for investigating the evolution of learning and sensory systems in aquatic invertebrates."
"These findings are also highly relevant for bio-inspired robotics," Romano adds. "Understanding how microscopic organisms navigate, learn, and adapt to dynamic and unstructured environments may inspire new approaches for designing autonomous robots capable of efficient exploration, navigation, and learning in complex settings."
Article reference: Bellavere E., Mesquita-Joanes F., Romano D., Rossetti G. 2026. Evidence of visual learning and wavelength differential responses in three podocopids (Crustacea: Ostracoda). BMC Biology. https://doi.org/10.1186/s12915-026-02640-5
