Thermal biology of the interstitial polychaete species Ophryotrocha labronica (Polychaeta, Dorvilleidae)

The gonochoric polychaete Ophryotrocha labronica is a widespread interstitial species commonly found in the fouling communities of harbour and lagoon environments. A number of manipulative experiments have revealed a strong influence of temperature on the life history and demography of this species. Furthermore, significantly different patterns in life-history and demographic traits have been demonstrated among populations inhabiting regions of the Mediterranean Sea with different climatic profiles. However, limited investigations have been carried out so far on the thermal biology of this species. We have conducted an experimental characterisation of the thermal biology of O. labronica, and described mortality curves of individual male–female pairs kept at one of seven different temperatures, ranging between 5 and 35 °C. For each pair, life-history traits (size at first reproduction, growth and total egg production) were also characterised. In a separate experiment, the upper and lower thermal limits and relative acclimatory ability of individual polychaetes were determined using several sublethal end-points, as well as lethal limits. A series of trials were conducted to test the effect of acclimation temperature, duration of acclimation and temperature change rate during warming/cooling experiments. Results are discussed in the light of O. labronica's ecology and life history.