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

ROMERO, M.C.,; VANELLA, F.,; TAPELLA, F.,; LOVRICH, G.A.

JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY

Elsevier

Año: 2006 vol. 333 p. 40 - 48

0022-0981

Abstract Munida gregaria is the most abundant galatheid crab species in the Beagle Channel (55ºS 68ºW) off Tierra del Fuego, Argentina. This species has two different and simultaneous feeding habits: predator and deposit feeder. The objectives of this work were 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 and oxygen consumption experiments, respectively. Animals were placed in individual chambers at 8 ±1ºC. The assimilation experiment was conducted using four types of diet: isopods (CRU), algae (ALG), pulverized fish food (PFF), and particulate organic matter (POM). The crabs’ routine metabolism and postprandial oxygen consumption -or specific dynamic action SDA- were measured using Clark-type polarographic electrodes. Two kind of food were offered: CRU and PFF, to simulate both feeding habits. Assimilation in M. gregaria for both feeding habits presented values >90% for dry mass and energetic content. Consumption rate varied between 15 and 50 mgingested · gDM-1, and was significantly higher for CRU and PFF diets. Females showed significantly higher consumption rates than males for all diets. On average, the routine metabolism of M. gregaria was 15 ±5 µl∙h-1·g-1. Deposit feeding may confer energetic advantages to female Munida gregaria, especially because this diet has a low energetic cost of assimilation. Deposits of high-energy content showed the highest consumption rates among four the experimental diets. In terms of mass and energy, the deposit diet also showed the highest assimilation efficiency. The postprandial oxygen consumption was lower in females and in the deposit feeding experiment. We suggest that females may prefer the deposit feeding habit to maximize their ingested energy, allowing them to devote more energy to reproduction. This is attained by a high consumption rate and by minimizing the energy used in assimilation.