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Comparative physiology of young and old cohorts of bay scallop Argopecten irradians irradians (Lamarck): mortality,growth, and oxygen consumption
Institution:1. Consejo Nacional de Investigaciones Científicas y Técnicas, FCEN, Universidad Nacional de Cuyo, Padre Jorge Contreras 1300, 5500 Mendoza, Argentina;2. Departamento de Física Médica, Centro Atómico Bariloche, Avenida Bustillo 9500, 8400 S. C. de Bariloche, RN, Argentina;3. Fundación Escuela Medicina Nuclear, Garibaldi 405. 5500, Mendoza, Argentina;4. Laboratorio de Procesado de Imagen (LPI), E.T.S. Ingenieros de Telecomunicación, Universidad de Valladolid, Valladolid, Spain;5. Applied Chest Imaging Laboratory (ACIL), Brigham and Women’s Hospital, Harvard Medical School, 1249 Boylston St. 02115, Boston, MA, USA;6. Biomedical Image Technologies Laboratory (BIT), ETSI Telecomunicacion, Universidad Politecnica de Madrid, and CIBER-BBN, Avenida Complutense 30, 28040, Madrid, Spain
Abstract:The bay scallop Argopecten irradians (Lamarck) undergoes rapid population decline in its second year of life. Pre-(1st-yr) and postreproductive (2nd-yr) bay scallops were held in cages at two sites on Long Island, New York, U.S. Survival, growth, and metabolic rates of the two cohorts were compared monthly throughout the autumn and winter. Second-year scallops, the harvestable crop of the year, maintained a positive energy balance until late November–December. Both age classes experienced similar relative tissue weight losses during overwintering (9–11% at the site where milder environmental conditions prevailed, and 24–25% at the more stressful site). Ambient water temperature explained a significant proportion (93%) of the seasonal variation in the rate of oxygen consumption. Thus the northern bay scallop A.i. irradians shows a limited ability to acclimatise oxygen consumption to seasonal temperature changes over the range of 1–23°C. A significant increase in oxygen uptake was associated with increased gametogenic activity of young scallops in May. Metabolic rate at this time was 50% higher than that predicted based on temperature, providing an estimate of the metabolic cost of reproduction in this species. The weight-normalized oxygen uptake rate of senescent scallops was significantly lower than that of young scallops. Mass natural mortality of the older cohort occurred during the winter, before the onset of a second gametogenesis; only 50% of the population survived beyond late January in 1985. Mortality was delayed by 2.5 months during a similar experiment conducted in 1986. Results of this study suggest that senescent mortality of New York bay scallop populations is not directly linked to the energy drain of a second reproductive event following overwintering stress.
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