LABORATORY EXPERIMENTS ON BEHAVIOUR AND MOVEMENT OF A FRESHWATER MUSSEL, LIMNOPERNA FORTUNEI (DUNKER)

Experiments on the movement and behaviour of a freshwater musselLimnoperna fortunei (Dunker) were conducted m the laboratory.Small mussels of 5–12 mm shell lengths moved over 100cm during a day within plastic containers, with a maximum distanceof 300 cm. However, their movement was concentrated during thefirst five hours of the experiments. The distance moved decreasedwith increasing shell length, and mussels larger than 27 mmmoved less than 20 cm. Both small (< 15 mm) and large (>15mm) mussels showed negative photo-taxis and positive geotaxisunder the light, but positive geotaxis of small mussels tendedto be weak in darkness or under the shade Small mussels hadstrong thigmotaxis with a preference for settling in the angledcrevices between the vertical walls and the flat bottoms ofthe containers Small mussels tended to aggregate, after movement,and the presence of large mussels facilitated secretion of byssalthreads by the small mussels. The possible adaptive significanceof these behaviours and movement are discussed in relation toresponse to predation and dislodgement by waves or water current (Received 11 September 1995; accepted 18 December 1995)