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Infraorder Astacidea Latreille, 1802
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Freshwater crayfishes are taxonomically distributed among three families; two Northern Hemisphere families, Astacidae and Cambaridae and one Southern Hemisphere family, Parastacidae. There are two centers of species diversity for freshwater crayfishes. The first is located in the Southeastern United States where some 80% of the cambarid species can be found. The second center of diversity is in Victoria, Australia; housing a large proportion of the parastacid species. Freshwater crayfishes naturally occur on all of the continents except Africa (Figure 1). The Astacidae are distributed West of the Rocky Mountains in the Northwest United States into British Columbia, Canada and in Europe. The Cambaridae are found in the Eastern United States and south through Mexico. The Parastacidae are distributed in Australia, New Zealand, South America, and Madagascar.
Geographic Distribution of Crayfish Families
Discussion of Phylogenetic Relationships:
The phylogenetic relationships among the freshwater crayfish families and their relationships to lobster-like ancestors has been of considerable debate for at least 100 years. Two alternative hypotheses have been proposed for the origins of crayfishes. The first supposes a diphyletic origin of astacoids and parastacoids suggesting independent invasion of the freshwater habitat (Huxley, 1880). This idea is supported by the two centers of diversity in the northern and southern hemispheres and by a number of morphological features (Hobbs, 1974). However, Ortmann (1902) argued for a monophyletic origin of the crayfishes. This position has recently been supported by sperm ultrastructure characteristics (Jamieson, 1991) and by embryonic characters (Scholtz, 1993). Because of this ongoing debate, the positioning of Parastacidae is shown as unresolved.
Hobbs (1988) gives a good discussion on the fossil taxa associated with this group as well as their presumed evolutionary history. There are several fossil representatives included within the Astacidea, and a few are closely related to extant crayfish species (based on morphological evidence). However, several recent discoveries may suggest an alternative evolutionary history involving crayfish. Recently, crayfish fossils and burrows have been found in the Triassic formations of Utah (Hasiotis, 1999), Arizona (Miller & Ash, 1988) and North Carolina (Olsen, 1977), dating to 225 million years (during the presence of the Pangean supercontinent). These trace and body fossils confirm that crayfish were established across a variety of ecological settings ranging from fully terrestrial to fully aquatic. The Erymidae were marine representatives. This group was most likely the progenitor to the clawed lobster and freshwater crayfish lines. Members of this group first appear in the fossil record some 245 million years ago and disappear around 75 million years ago.
Hasiotis, S.T. 1999. Crayfish fossils and burrows from the upper Triassic Chinle Formation, Canyonlands National Park, Utah.
Procambarus simulans Photo Copyright ©1998 by Keith A. Crandall
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