CONICET | Buscador de Institutos y Recursos Humanos

AbstractGrowth is determined by an organism´s physiology, physical environment, and biologicalconditions, including food availability and any intra‐ and inter‐specific interactionsthat can affect feeding activity. To analyse how all these factors interact to producefinal growth in the herbivorous/detritivorous crab Neohelice granulata, we performedfield and laboratory experiments with juveniles and adults from three populationswhich differed genetically as well as in their physical environment and the organicmatter (OM) content in the soil that serves as food. We evaluated (a) growth in thefield: Juveniles of the three populations were cross‐transplanted in exclusion cages;(b) effect of the presence of adults on juvenile feeding: We measured the feeding activityof small juveniles in presence/absence of an adult male as potential predator inthe field; and (c) effect of diet on cannibalism: We analysed the cannibalistic behaviorof adult males from two of the populations in the laboratory after they had receivedprotein‐rich (24%) and protein‐poor (3%) diets. In experiment (a), final size was similarfor the crabs from all three origins but growth differed between sites. Experiment (b)showed that the presence of adults interfered with feeding activity at the two siteswith lower weight indicators. In experiment (c), we observed that low protein dietincreased the cannibalistic behavior of adult males, and this effect was more intensein crabs from the poorest food site. Our results contribute to understanding the setof factors and interactions involved in the response of individuals to the prevailingconditions in natural environments in order to maintain a growth rate, perhaps at theexpense of different reserve accumulation. They also enable discussion of the limitationsof approaches used in laboratory experiments.