Freshwater crabs’ predation: ontogenetic variation in Trichodactylus borellianus (Caridea: Trichodactylidae)

CARVALHO D.; COLLINS P.; DE BONIS C.

INVERTEBRATE BIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2012

1077-8306

Freshwater crabs are rarely represented in food webs, ignoring their role in these ecosystems. Trichodactylus borellianus is an omnivorous species that has a diverse natural trophic spectrum. This paper evaluates, in a laboratory enviroment, the predation ability of T. borellianus on different prey and possible changes during three ontogenetic moments. It also evaluates the selectivity and relative importance of each prey item. Crabs were sorted according to size (juvenile, sub-adult and adult) and three types of prey were given to the crabs separately and then all together. These prey (cladocerans, oligochaetes and golden mussels) corresponded to food offers of different shape and mobility that represent the natural diet of this crab. The crabs were able to prey upon all organisms in the three category sizes. Cladocerans and oligochaetes were the most consumed compared to the golden mussel when offered separately, but this last species was captured more efficiently and was the only one with increased consumption with increasing size of the crab. When given together, the oligochaete was the most selected and important prey both as a percentage of volume and occurrence. Ontogenetic changes in the consumption could be related to differences in the stomach capacity of the crab, the digestion time of each prey and the predator-prey encounter probability. The selection of the most elongated prey and lesser mobility indicates that the balance of the gain and loss of energy makes it an advantageous species to prey upon and is susceptible to predation. Otherwise, the mussel, which is an invasive species, although not positively selected by T. borellianus, may represent a new trophic resource to this crab.