Effects of elevated temperatures on the scope for growth and resistance to air exposure of the clam Ruditapes decussatus (L.), from southern Portugal
P. Sobral and J. Widdows

The infaunal bivalve Ruditapes decussatus (L.) was collected from Ria Formosa, Faro, southern Portugal, and subjected to a range of selected temperatures (20-35 °C). Physiological measurements (clearance rate, respiration rate, excretion rate and absorption efficiency) for the calculation of scope-for-growth were under taken at 20, 27 and 32 °C after 48 hours acclimation. Experiments on tolerance to air exposure were performed at 20, 28 and 35 °C. Increasing temperature resulted in lower clearance rates, leading to a marked reduction of scope for growth. At 32 °C scope for growth was negative indicating that clams were having to utilize their energy reserves. Respiration rate and excretion rate were temperature independent in the range 20 - 32 °C, due to seasonal thermal acclimation to environmental fluctuating temperatures. When exposed to air, shell valve gaping was observed at all experimental temperatures, resulting in the utilisation of aerobic metabolic pathways and the utilisation of energy reserves, desiccation and consequently death. Median lethal times were ca. 72 h, 48 h and 10 h at 20, 28 and 35 °C, respectively. Temperatures above 28 °C can therefore significantly weaken clams resistance to air exposure and affect their performance in water. Even if effects of exposure to high water and air temperatures, on the tidal flats in the summer, are unknown, raising temperatures constitute a significant physiological stress for the clams.

Contents of this volume Sci. Mar. 61(2) : 163-171 Back PDF
Please, send comments to
ICM (CSIC) - Passeig Marítim de la Barceloneta, 37-49. E-08003 Barcelona (Spain)