Habitat stability, predation risk and 'memory syndromes'

ArticleThis is the author's accepted version. The article has been published Open Access and is available at http://www.nature.com/srep/2015/150527/srep10538/full/srep10538.htmlCopyright © 2015 Macmillan Publishers Limited. All Rights Reserved.Habitat stability and predation pressure are thought to be major drivers in the evolutionary maintenance of behavioural syndromes, with trait covariance only occurring within specific habitats. However, animals also exhibit behavioural plasticity, often through memory formation. Memory formation across traits may be linked, with covariance in memory traits (memory syndromes) selected under particular environmental conditions. This study tests whether the pond snail, Lymnaea stagnalis, demonstrates consistency among memory traits (‘memory syndrome’) related to threat avoidance and foraging. We used eight populations originating from three different habitat types: i) laboratory populations (stable habitat, predator-free); ii) river populations (fairly stable habitat, fish predation); and iii) ditch populations (unstable habitat, invertebrate predation). At a population level, there was a negative relationship between memories related to threat avoidance and food selectivity, but no consistency within habitat type. At an individual level, covariance between memory traits was dependent on habitat. Laboratory populations showed no covariance among memory traits, whereas river populations showed a positive correlation between food memories, and ditch populations demonstrated a negative relationship between threat memory and food memories. Therefore, selection pressures among habitats appear to act independently on memory trait covariation at an individual level and the average response within a population.Leverhulme Trus

Susceptibility to Predation Affects Trait-Mediated Indirect Interactions by Reversing Interspecific Competition

Numerous studies indicate that the behavioral responses of prey to the presence of predators can have an important role in structuring assemblages through trait-mediated indirect interactions. Few studies, however, have addressed how relative susceptibility to predation influences such interactions. Here we examine the effect of chemical cues from the common shore crab Carcinus maenas on the foraging behavior of two common intertidal gastropod molluscs. Of the two model consumers studied, Littorina littorea is morphologically more vulnerable to crab predation than Gibbula umbilicalis, and it exhibited greater competitive ability in the absence of predation threat. However, Littorina demonstrated a greater anti-predator response when experimentally exposed to predation cues, resulting in a lower level of foraging. This reversed the competitive interaction, allowing Gibbula substantially increased access to shared resources. Our results demonstrate that the susceptibility of consumers to predation can influence species interactions, and suggest that inter-specific differences in trait-mediated indirect interactions are another mechanism through which non-consumptive predator effects may influence trophic interactions

The repeatability of cognitive performance:A meta-analysis

This is the author accepted manuscript. The final version is available from The Royal Society via the DOI in this record.Behavioural and cognitive processes play important roles in mediating an individual's interactions with its environment. Yet, while there is a vast literature on repeatable individual differences in behaviour, relatively little is known about the repeatability of cognitive performance. To further our understanding of the evolution of cognition, we gathered 44 studies on individual performance of 25 species across six animal classes and used meta-analysis to assess whether cognitive performance is repeatable. We compared repeatability (R) in performance (1) on the same task presented at different times (temporal repeatability), and (2) on different tasks that measured the same putative cognitive ability (contextual repeatability). We also addressed whether R estimates were influenced by seven extrinsic factors (moderators): type of cognitive performance measurement, type of cognitive task, delay between tests, origin of the subjects, experimental context, taxonomic class and publication status. We found support for both temporal and contextual repeatability of cognitive performance, with mean R estimates ranging between 0.15 and 0.28. Repeatability estimates were mostly influenced by the type of cognitive performance measures and publication status. Our findings highlight the widespread occurrence of consistent inter-individual variation in cognition across a range of taxa which, like behaviour, may be associated with fitness outcomes.PKYC is supported by Japan Society for the Promotion of Science (PE1801); JOvH was funded by an ERC consolidator grant (616474). MC and this research was supported by a grant from the Human Frontier Science Program to ASC and JM-F (RGP0006/2015)

Combining Stressors That Individually Impede Long-Term Memory Blocks All Memory Processes

The effects of stress on memory are typically assessed individually; however, in reality different stressors are often experienced simultaneously. Here we determined the effect that two environmentally relevant stressors, crowding and low calcium availability, have on memory and neural activity following operant conditioning of aerial respiration in the pond snail, Lymnaea stagnalis. We measured aerial breathing behaviour and activity of a neuron necessary for memory formation, right pedal dorsal 1 (RPeD1), in the central pattern generator (CPG) that drives aerial respiration in untrained animals, and assessed how these traits changed following training. In naïve animals both crowding and combined stressors significantly depressed burst activity in RPeD1 which correlated with a depression in aerial breathing behaviour, whereas low calcium availability had no effect on RPeD1 activity. Following training, changes in burst activity in RPeD1 correlated with behavioural changes, decreasing relative to their naïve state at 3 h and 24 h in control conditions when both intermediate-term memory (ITM: 3 h) and long-term memory (LTM: 24 h) are formed, at 3 h but not 24 h when exposed to individual stressors when only ITM is formed, and did not change in combined stressors (i.e. when no memory is formed). Additionally, we also found that Lymnaea formed short-term memory (STM: 10 min) in the presence of individual stressors or under control conditions, but failed to do so in the presence of combined stressors. Our data demonstrate that by combining stressors that individually block LTM only we can block all memory processes. Therefore the effects of two stressors with similar individual affects on memory phenotype may be additive when experienced in combination

What's hot: The enhancing effects of thermal stress on long-term memory formation in Lymnaea stagnalis

Summary The pond snail, Lymnaea stagnalis, naturally inhabits slow flowing, shallow and stagnant environments in the northern temperate zone. Consequently, it will experience wide temperature fluctuations dependent on prevailing weather conditions. We hypothesize that periods of warming act as a thermal stressor to alter memory formation. Snails were exposed to an acute 1h period of 30°C pond water and we determined how memory formation following operant conditioning of aerial respiration was affected. In snails used here (the Dutch strain), a single 0.5h training session (TS) results in intermediate-term (3h) but not long-term memory (LTM). Applying the thermal stressor during training caused memory enhancement (i.e. LTM lasting 24 h). However, the breathing rate also increased in warm water, which might explain the enhanced memory. Therefore, we applied the thermal stressor (1h at 30°C) up to 4h before or 1h after training. This did not alter baseline breathing rate during the period when snails would experience training. However, the thermal stressor weather experienced prior to or following the single TS, resulted in an enhanced memory that persisted up to 48h (i.e. LTM). We conclude that memory enhancement is due to the stress associated with the thermal stimulus.</jats:p