Crowding, an environmental stressor, blocks long-term memory formation in Lymnaea

Area of Science:

• Neuroscience
• Behavioral Biology
• Environmental Science

Background:

• Crowding is a significant environmental stressor impacting animal behavior and physiology.
• Understanding how environmental stressors affect memory formation is crucial for ecological and evolutionary studies.
• The freshwater snail Lymnaea serves as a model organism for studying memory consolidation mechanisms.

Purpose of the Study:

• To investigate the impact of crowding stress on long-term memory (LTM) formation in Lymnaea snails.
• To determine if crowding affects memory recall or intermediate-term memory (ITM) formation.
• To explore the potential mechanisms by which crowding interferes with LTM.

Main Methods:

• Operant conditioning was used to train Lymnaea snails on aerial respiratory behavior.
• Snails were exposed to crowding (20 snails/100 ml) or uncrowded conditions (2 snails/100 ml) at different times relative to training.
• LTM and ITM formation were assessed through behavioral tests, comparing crowded and uncrowded groups.

Main Results:

• Crowding immediately before or after training significantly blocked LTM formation.
• LTM was formed if crowding was delayed by over 1 hour post-training or ceased 1 hour before training.
• Crowding did not affect memory recall or ITM formation, which relies on protein synthesis but not necessarily altered gene activity.

Conclusions:

• Crowding stress disrupts LTM formation in Lymnaea, likely by interfering with the genomic activity in neurons essential for LTM.
• The findings highlight the sensitivity of memory consolidation processes to environmental stressors.
• ITM formation remains intact, suggesting a specific impact of crowding on the molecular pathways underlying LTM.