Environmental influence on activity levels and behavioural allocation in the polychaete Nereis virens (Sars)

Influence of environmental factors such as temperature, food, and photoperiod on activity levels and behavioural allocation of Nereis virens was examined using laboratory experimental essays. Animals were subjected to 4 temperatures (1, 6, 13, and 18 °C), two food concentrations (low and abundant), and two photoperiod regimes (6 and 12 h of daylight) for 10-day periods. A general linear model was used to evaluate how these three factors and their possible interactions affected relative activity levels. Furthermore, a log-ratio redundancy analysis was used to examine the relationship between behavioural allocation and environmental factors. Activity levels increased with temperature and food abundance. Extreme cold induced quiescence, yet the polychaetes retained their ability to react to food stimuli, especially at higher food abundances. Food abundance explained the greatest amount of variation in behavioural allocation. However, its effect varied with temperature. Feeding predominated under low food conditions, whereas storage (accumulation of organic matter in their burrows) predominated under abundant food conditions, especially at higher temperatures. Animals seemed to anticipate food shortage, which is often synchronised by temperature in a natural environment. The potential for carbon sequestration resulting from food storage is therefore present and may be controlled by these same exogenous factors that usually characterise seasonal variations.