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 the food webs ignoring its role in these ecosystems. Trichodactylus borellianus is an omnivorous species that has a diverse natural trophic spectrum. This paper evaluates in laboratory the predation’s ability of T. borellianus on different prey and possible changes during three ontogenetic moments, and also 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 separately and then all together. These prey (cladocerans, oligochaetes and golden mussels) corresponded to a different food offers of different shape and mobility that represents the natural diet of this crab. The crabs were capable to prey on 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 were captured more efficiently and was the only one that the consumption increased with the 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 of 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 lower mobility indicates that the balance of the gain and loss of energy makes it an advantageous prey and susceptible to predation. Otherwise, the mussel, which is an invasive species, although was not positively selected by T. borellianus, may represent a new trophic resource to this crab.