Assimilation and oxygen uptake associated with two different feeding habits of Munida gregaria (=M. subrugosa

CAROLINA ROMERO,; FABIAN VANELLA,; FEDERICO TAPELLA,; GUSTAVO ALEJANDRO LOVRICH

JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY

ELSEVIER SCIENCE BV

Año: 2006 vol. 333 p. 40 - 48

0022-0981

Munida gregaria is the most abundant galatheid crab species in the Beagle Channel (55 8S 68 8W) off Tierra del Fuego,Argentina. This species has two different and simultaneous feeding habits: predator and deposit feeder. The objectives of this workwere to determine whether either of the two different feeding habits imply differences in assimilation and oxygen consumption.Subsamples of 40 and 20 crabs of each sex were randomly selected, transported to the laboratory, and used in assimilation andoxygen consumption experiments, respectively. Animals were placed in individual chambers at 8F1 8C. The assimilationexperiment was conducted using four types of diet: isopods (CRU), algae (ALG), pulverized fish food (PFF), and particulateorganic matter (POM). The crabs’ routine metabolism and postprandial oxygen consumption – or specific dynamic action SDA –were measured using Clark-type polarographic electrodes. Two kinds of food were offered: CRU and PFF to simulate both feedinghabits. Assimilation in M. gregaria for both feeding habits presented values N90% for dry mass and energetic content.Consumption rate varied between 15 and 50 mgingested gDM1, and was significantly higher for CRU and PFF diets. Femalesshowed significantly higher consumption rates than males for all diets. On average, the routine metabolism of M. gregaria was15F5 AlO2 h1 g1. Deposit feeding may confer energetic advantages to female M. gregaria, especially because this diet has alow energetic cost of assimilation. Deposits of high-energy content showed the highest consumption rates among four theexperimental diets. In terms of mass and energy, the deposit diet also showed the highest assimilation efficiency. The postprandialoxygen consumption was lower in females and in the deposit feeding experiment. We suggest that females may prefer the depositfeeding habit to maximize their ingested energy, allowing them to devote more energy to reproduction. This is attained by a highconsumption rate and by minimizing the energy used in assimilation.