Effect of food quality and concentration on physiological rates of the mussel Perna perna (Linnaeus, 1758)

Abstract

Physiological rates of clearance, absorption, respiration and excretion were studied in the mussel Perna perna, as function of the changes in organic substrate (phytoplankton) and in the concentration of the seston (phytoplankton and silt), in experimental laboratory conditions. The respiratory and excretion rates did not change with both concentration and quality of food. Clearance rate showed an initial increase followed by an inhibition, as the organic matter concentration increased. However, as the seston increased this rate increased but without inhibition. Absorption efficiency rate was directly proportional to the food quality but showed an inverse relationship with the organic matter content. Considering both filtration and absorption efficiency rates, the incipient concentration to produce pseudofaeces (or rejection) was estimated as 4-8 mg.L-1. Minimal organic matter content in the seston that resulted in fecal metabolic loses and, consequently, in negative absorption efficiency rate, was less than 20%. These data clearly show that the feeding physiology of Perna perna is similar to the others suspension-feed bivalves so far studied.