Trophic ecology of the lobster krill Munida gregaria in San Jorge Gulf, Argentina

Abstract

The "langostilla", Munida gregaria, also called lobster krill or squat lobster, is a very common galatheid crustacean in San Jorge Gulf and around the southern tip of South America. Previous studies have shown that this species plays an important role in the trophic webs wherever it has been studied. In order to determine its natural food sources, we analyzed 10 samples (30-36 individuals each) taken from different sites in San Jorge Gulf. Moreover, stomach analyses were performed on 32 fish species, 4 mollusk species, and 7 crustacean species from the gulf. The lobster krill is primarily a detritivore or surface deposit-feeder and secondarily a predator and/or scavenger. Its main energy sources are particulate organic matter and their associated bacteria, small live organisms on the surface of the sediment layer (ostracods, copepods, foraminifers, other protists), and animal debris. Polychaetes are the main prey of lobster krill in the study area. This dual complementary feeding behavior is common in the studied galatheids, making them a fundamental link between detritus and benthic and demersal top predators. Some species of these predators constitute important fisheries. Different life-cycle stages of the squat lobster were preyed on by 32 of the examined species. However, the spectrum of predators is still incomplete, with other species feeding on larvae and juveniles of the species.