Behavior of blue mussels (Mytilus edulis L.) under the fluctuating environmental conditions

Abstract

Bottom invertebrates of coastal waters live under the conditions of permanently fluctuating environmental factors. However, the relationship of these permanent (current) fluctuations with the functional activity of bottom animals has not been determined thus far. Most studies on their physiology and behavior of bottom invertebrates have been performed under relatively constant or forcedly varied, controlled laboratory con- ditions. These experiments have shown that artificial (usually considerable with respect to amplitude gradi- ents of water temperature and salinity cause significant changes in some parameters of the activity of bivalves (1-4). turbed) experiment methodology, i.e., without alter- ation of natural processes. The blue mussels were col- lected in the lower level of the intertidal zone of the bays Yarnyshnaya and Dal'nyaya Zelenetskaya and were kept in aquaria with a strong flow of unfiltered seawater that was supplied to the aquaria directly from Dal'nyaya Zelenetskaya Bay. The conditions in flow- through aquaria were essentially identical to the condi- tions of the upper subtidal zone, i.e., the level from which water was pumped in. The results of a special study on the corresponding of the conditions in the tanks to natural ones (6) showed that the difference between the experimental tanks and the natural envi- ronment with respect to the main seawater characteris- tics (temperature, salinity, phytoplankton, and seston) was insignificant in all seasons, and their fluctuations were correlated ( r varied from 0.88 to 0.97). The behavioral responses of adult blue mussels (30- 50 mm) were recorded by means of a mechanical acto- graph permanently during several months. The acto- grams (records of valve movements) were used to determine the following parameters of the mollusk behavior: SGS (percent of the maximum gapping of the shell valves during the period of the study), the fre- quency of contractions (adduction, ADD, number of contractions per day), and the amplitude of valve open- ing (AMP, percent of the maximum). SGS was selected as the main behavioral parameter (7). Ethological studies were performed from 1986 to 2003. Most data used in this study were obtained during the experiments performed in 1986-1991; however, they had not been treated and had remained unpub- lished until recent time.