Similar feeding habits of two morphs of Munida gregaria (Decapoda) evidence the lack of trophic polymorphism.

PEREZ BARROS, PATRICIA; ROMERO, MC; CALCAGNO, J A; LOVRICH, GA

REVISTA DE BIOLOGIA MARINA Y OCEANOGRAFIA

INST OCEANOLOGIA

Año: 2010 vol. 45 p. 461 - 470

0717-3326

Munida gregaria and M. subrugosa were originally described as two different species on the basis ofseveral morphological characters, but recently studies evidenced that both former species constitute the same biologicalspecies, so that hereafter they are referred to as two morphs of M. gregaria: ‘gregaria’ and ‘subrugosa’. Notwithstandingtheir synonimization, the occurrence of two sympatric morphs represents an interesting case for the study of theprocesses involved in the maintenance of these two morphotypes in nature. We hypothesized that the distinct shapesof mouthparts of both morphs may be related to different feeding habits. Adults of M. gregaria, morphs ‘gregaria’and ‘subrugosa’, were collected in the Beagle Channel by epibenthic trawling during November 2004. The trophicniche of both morphs highly overlapped. Both occupied the same trophic position in the food web of the BeagleChannel, showing the same feeding habits. As predators they fed mainly on crustaceans and algae, and as depositfeeders they ingested particulate organic matter and organisms associated with the superficial layer of the sediment.However, the relative abundance of crustaceans was higher in stomachs of ‘subrugosa’ than in those of ‘gregaria’, ahigher proportion of stomachs of ‘gregaria’ contained more algae than in ‘subrugosa’, and a greater frequency ofoccurrence of unicellular preys was found in the diet of ‘gregaria’. Despite these differences, this study provided noevidences to support the existence of a trophic polymorphism between morphs of M. gregaria, at least based on thefeeding habit of adults.