Freshwater Crabs

The Aeglidae are the most abundant and widely distributed freshwater decapod “crabs” in southern South America. Aegla alacalufiUnlike true brachyuran crabs, however, in aeglids the fifth pair of pereiopods is reduced in size, lacking walking capacity (Martin & Abele, 1988); they also possess tiny chelae with which they groom branchiae and eggs attached to female's pleopods and the abdomen's underbelly (Martin & Felgenahuer, 1986). All aeglids are primarily aquatic and occur in lakes, streams, and caves, at depths of down to 320m in Chilean lakes (Jara, 1977), and at altitudes of up to ~3,500 m of altitude in northeastern Argentinean cordilleras (Bond-Buckup & Buckup, 1994).

Aeglids are the only anomuran family restricted to the Neotropical region of South America. Taxonomically, aeglids are included within the anomuran superfamily Galatheoidea, but there is some morphological evidence (e.g., gill structure and caparace sutures) and molecular data that suggest the Aeglidae should be in their own superfamily (Martin & Abele, 1986; Pérez-Losada et al., 2002b; Tudge & Scheltinga, 2002). From a conservation perspective, several of the known species are very restricted in distribution, and they and their habitats are considered threatened (Pérez-Losada et al., 2002a). From an ecological perspective, aeglids are unique because they are the only anomuran family entirely restricted to freshwater habitats.

The ecological role of Aegla species has not been assessed but their omnivorous diet includes periphyton, decaying allochtonous vegetable matter, aquatic invertebrates (Bahamonde & L, 1961; Burns, 1972; Lara & Moreno, 1995, Castro-Souza & Bond-Buckup, 2004), and fine particulate organic matter (Isler, 1988). Additionally, they constitute a relevant dietary item for the non-native rainbow trout (Oncorhynchus mykiss) in Chile and South Brazil and brown trout (Salmo trutta fario) in Chile (Burns, 1972; Arenas, 1978; Buckup, personal observation), and for the Chilean and Brazilian species of river otter Dr. Jara and Dr. Pérez-Losada collecting ''crabs'' in Patagonia(Medina, 1998).

The present Aeglidae belong to a single genus, Aegla Leach, 1820, consisting of 63 described species (Bond-Buckup & Buckup, 1994; Bond-Buckup, 2003); including, newly described species based on recent molecular phylogenetic analyses (Jara et al., 2003). By our count, there are at least six additional species waiting to be described. Of these species, 57 are found mainly in rivers, only two in lakes, and four in cave habitats.

Our Patagonia study focuses on the phylogeographic patterns of a few selected species for comparisons against one another and to compare to the other organisms in the study. These species include Aegla abtao, Aegla alacalufi, Aegla neuquensis, and Aegla riolimayana.

Further Information

Copies of related articles can be found at the Crandall Lab Publications page.