Maximum tension developed by the posterior adductor muscle of the giant clam, Tridacna gigas (Linné)

Abstract

1. 1. The isometric closing tension of the posterior adductor muscle of giant clams, Tridacna gigas (L.), was measured under natural conditions on reefs and under more controlled conditions aboard the R/V Alpha Helix. 2. 2. Active tension increased with muscle length up to the maximum in vivo length. 3. 3. Tensions per unit cross section of the adductor averaged 8·0 ± 1·1 kg/cm 2 at 120% minimal length (minimal length = length at full valve closure) when the cross section area is the area at this length. If the tension is calculated with respect to the cross section area at minimal length the value becomes 6·7 ± 0·9 kg/cm 2. The values were relatively constant for clams ranging in size from 6 to 212 kg total weight. 4. 4. The total tension developed by the posterior adductor in large clams was well over 500 kg.