Physiological rates in different classes of sizes of Perna perna (Linnaeus, 1758) submmited to experimental loboratory conditions

Abstract

Physiological studies of the mussel Perna perna in Brazil are almost 30 years behind those of other, more exhaustively investigated species, such as Mytilus edulis. Little is known about the variations in physiological rates due to size and the consequences of maintaining P. perna in laboratory conditions. This work investigated the variations in respiration, clearance, excretion and absorption efficiency rates of P. perna, classified by size and acclimatized in a laboratory, monitoring the mussels' respiration rates and biometry over a period of 30 days, in laboratory conditions. The respiration, clearance and excretion rates presented an allometric relation with the dry weight of the organisms, with b values of 0.66, 0.48 and 0.91 respectively. On the other hand, these same rates, when considered by weight (specific rates) showed a relationship that was inverse to the size of the organisms. Only the absorption efficiency was independent of the weight of the mussel. In terms of acclimatization, it was observed that it takes 10 days for the respiration rate of the mussel P. perna to stabilize in laboratory conditions, after which it follows a routine metabolism.Keywords: Perna perna, physiology, acclimatization, respiration, clearance, excretion, absorption efficiency. RESUMOTaxas fisiológicas do mexilhão Perna perna (Linnaeus, 1758) em diferentes classes de tamanho e condições de manutenção em laboratório O estudo da fisiologia dos mexilhões Perna perna no Brasil apresenta uma defasagem de aproximadamente 30 anos em relação a outras espécies mais exaustivamente investigadas como Mytilus edulis. O conhecimento acerca das variações das taxas fisiológicas em função do tamanho e as conseqüências da manutenção de P. perna em laboratório foram pouco estudadas. Neste trabalho, investigaram-se as variações das taxas de respiração, clareamento, excreção e a eficiência de absorção de P. perna aclimatados em laboratório em diferentes classes de tamanho, assim como foi realizado um acompanhamento de suas taxas respiratórias e de sua biometria ao longo de 30 dias de manutenção em condições laboratoriais. As taxas de respiração, clareamento e excreção apresentaram uma relação alométrica com o peso seco dos organismos, obtendo-se como valores de b de 0,66, 0,48 e 0,91 respectivamente. Por outro lado, estas mesmas taxas quando ponderadas pelo peso (taxas específicas) mostraram uma relação inversa com o tamanho dos organismos. A eficiência de absorção foi à única taxa que mostrou independência com o peso do mexilhão. Em termos de aclimatação, observou-se que o mexilhão P. perna leva 10 dias para estabilizar a sua taxa de respiração em laboratório, entrando em metabolismo de rotina.Palavras-chave: Perna perna, fisiologia, aclimatação, respiração, clareamento, excreção, eficiência de absorção. 326RESGALLA JR., C., BRASIL, E. S. and SALOMÃO, L. C.

The effect of temperature and salinity on the physiological rates of the mussel Perna perna (Linnaeus 1758)

“…Initially, the acclimation capacity was evaluated after 15 days, the time required to enter a state of routine metabolism (Resgalla Jr. et al, 2006) and demonstrate physiological compensations to the variations in temperature and salinity, i.e. to present the same routine metabolism, irrespective of the treatment administered.…”

“…Groups of 20 organisms were maintained in four-liter flasks with aeration and constant photoperiod (12 h light-dark cycle). Two liters of the maintenance water were renewed daily and food was inoculated (phytoplankton Chaetocerus gracilis) at a concentration of 500 Cells.mL -1 (Resgalla Jr., 2004 andResgalla Jr. et al, 2006) in order to establish a standard metabolism in the test organisms, eliminating seasonal variations in their metabolism. All the groups of mussels were kept in filtered seawater (0.5 µm) for 24 h prior to the physiological tests, in order to clean the digestive tract and stimulate their metabolic rates.…”

“…For each flask, concentrations of 140 Cells.mL -1 of phytoplankton and filtered seawater were inoculated for one hour. This concentration was initially established because it lower than 5 mg.L -1 , the lowest concentration at which the rejection or formation of pseudo-feces occurs (Resgalla Jr. et al, 2006, andWiddows et al, 1979). At the start and the end of the test, with an interval of 1 h, 50 mL of the seawater with phytoplankton was removed from each flask in order to determine the turbidity for absorbance in 750 and 230 nm through a spectrophotometer (Greenberg et al, 1992;Resgalla Jr. 2004 andResgalla Jr. et al, 2006).…”

“…At the initial and final times and at intervals of 3 h, 15 mL samples of the incubation water were collected in the test flasks to determine the total amonical nitrogen, according to the colorimetric method of Strickland and Parsons (1972), modified by Baptista et al (1987). The excretion rate was estimated according to the equation: After the tests, biomass data was obtained by dissecting the organisms and their shells and drying the tissue in an oven at 60 °C for 48 h. The specific rates for respiration, clearance and excretion were corrected for the standard weight of 1 g (Bayne et al, 1985) according the allometric correlation coefficients between weight and rate, whose respective b values were 0.66; 0.48 and 0.91, according to the results obtained by Resgalla Jr. (2004) and Resgalla et al (2006). The results of the physiological rate tests for temperature and salinity were compared in variance analysis (ANOVA) and by the analysis of the Tukey test after their standardization in Log 10 (Zar, 1996).…”

Faecal bacteria in Perna perna (Linnaeus, 1758) (Mollusca: Bivalvia) for biomonitoring coastal waters and seafood quality

“…These clearance rates may also be related to a biometric variable such as size or weight (RESGALLA JR. et al, 2006). Knowledge of this relation could be important for preventive actions in public health, particularly in respect to the consumption of mussels as seafood.…”