Energetic Physiology of the Caribbean Estuarine Clam Polymesoda arctata (Deshayes, 1854) Exposed to Different Environmental Conditions under Laboratory

The estuarine clam Polymesoda arctata is one of the commercially important bivalves of the Caribbean, which is currently considered endangered by overexploitation and habitat loss. With the purpose of gain knowledge about its environmental requirements for aquaculture and restocking purposes, its energetic physiology performance was evaluated under laboratory conditions in response to the variation of food concentration and water quality registered in their natural habitat. Different physiological variables, including the rates of filtration (FR), pseudofeces production (RR), ingestion (IR), absorption (AR), oxygen consumption (OCR), and ammonium excretion (UR), as well as absorption efficiency (AE) and scope for growth (SFG), were estimated in five successive experiments, where different concentration levels of food or particulate organic matter (1.8, 4.0, 7.3, and 13.0 mg L−1 equivalent to 2.3, 5.0, 9.3, and 16.6 mg of the microalgae Isochrysis galbana L−1), salinity (5, 15, and 25‰), temperature (27, 29, and 32°C), ammonia concentration (7, 48 and 77 µg NH3-N L−1), and dissolved oxygen saturation (24, 48, and 93%) were tested. Intermediate conditions of food concentration, salinity, and temperature resulted in higher values for most of the physiological variables measured, except for the higher values of OCR and UR obtained at low salinity, as well as the higher values of AE, AR, and SFG measured at low temperatures. Most of the physiological variables increased under conditions of lower ammonia concentrations and higher dissolved oxygen saturation in the water. Although this species exhibited physiological plasticity, tolerance, and enough energy for growth and reproduction under the environmental variations of its habitat, it also showed a high sensitivity to its environment, having the highest SFG values under intermediate conditions of particulate organic matter (7.2 mg L−1 or 9.3 mg of I. galbana L−1), salinity (15‰), and temperature (27–29°C), as well as at low ammonia concentration (7 μg NH3-N L−1) and high dissolved oxygen saturation (93%). Based on our results, we recommended the use of this values for reproductive conditioning of broodstock and juvenile culture in laboratory, and also as an input for selecting areas for aquaculture farming and restocking experiments.