A Remarkable Anomuran: The Taxon Aegla Leach, 1820. Taxonomic Remarks, Distribution, Biology, Diversity and Conservation

Abstract

The family Aeglidae comprises three genera, one extant (Aegla) and two extinct genera (Protaegla and Haumuriaegla), the latter two genera are known only from fossils from marine sediments (indicating a marine origin for the group). Aegla contains all extant species and constitutes a monophyletic group within the Anomura. All 78 species and subspecies described so far are entirely adapted to freshwater habitats and are endemic to temperate and subtropical regions of continental South America. While most species are found in epigean habitats, there are a few cave-dwelling species in southeastern Brazil. The reproductive period varies from 8 to 12 months (in species from colder higher latitudes), to 4–7 months (in species from lower latitudes where warm-rainy and cold-dry seasons alternate). The adult males of seasonally breeding species include two morphotypes, one non-reproductive and the other reproductive. Eggs are large and few in number, and post-embryonic development is epimorphic. Juveniles have limited dispersal capacity and recruits tend to remain with the parental population. Aegla is the most severely threatened group among South American freshwater decapods because of habitat degradation, high endemism, a restricted area of occupancy, and a severely fragmented spatial distribution with reproductively isolated subpopulations.