Astacidea

Abstract: The freshwater crayfishes are a group of decapod crustaceans that have played a critical role in a diversity of biological studies, from physiology, to ecology, neurobiology, conservation, and evolution. Central to many of these fields of study is the dependence on a robust taxonomic framework for accurate communication relating to species diversity and associated attributes. Despite a huge body of taxonomic work since Linnaeus, there has never been a single, comprehensive taxonomic summary of all the species of crayfish of the world. There has also been an abundance of recent taxonomic work in terms of new species descriptions and taxonomic insights gained from a variety of phylogenetic studies. Here we gather diverse taxonomic and phylogenetic information into a single resource. We develop an updated classification system that includes all the crayfishes worldwide and taxonomic changes to better reflect the current phylogenetic knowledge of the group. We also include all the fossil crayfish taxa for a complete classification of extant and extinct crayfishes. Our classification results in two superfamilies (Astacoidea and Parastacoidea), five families, 38 genera, and 669 species (692 including distinct subspecies). We provide a checklist of all species and include validated taxonomic authorities, type localities, figure references, and synonyms. We also provide arguments for our revised classification. The updated and complete classification aims to provide a robust framework for future studies of the freshwater crayfishes of the world.

Abstract: Despite their widespread use as model organisms, the phylogenetic status of the around 520 species of freshwater crayfish is still in doubt. One hypothesis suggests two distinct origins of freshwater crayfish as indicated by their geographical distribution, with two centres of origin near the two present centres of diversity; one in south-eastern United States and the other in Victoria, Australia. An alternative theory proposes a single (monophyletic) origin of freshwater crayfish. Here we use over 3000 nucleotides from three different gene regions in estimating phylogenetic relationships among freshwater crayfish and related Crustacea. We show clear evidence for monophyly of freshwater crayfish and for the sister-group relationship between crayfish and clawed lobsters. Monophyly of the superfamilies Astacoidea and Parastacoidea is also supported. However, the monophyly of the family Cambaridae is questioned with the genus Cambaroides being associated with the Astacidae.

Abstract: Possible phylogenetic trends in male sperm transfer and female sperm storage structures are described. Degree of complexity of genitalia is defined as the relative modification or differentiation from a hypothesized primitive condition. It is proposed that the degree of complexity of male gonopods and female sperm storage organs exhibited by a taxon is a measure of phylogenetic distance from the ancestral slate. In a male decapod ancestor, the endopod of pleopod 1 is considered to have been an unmodified natatory ramus with pleopod 2 similar but with an appendix masculina. The female of such a hypothesized ancestor received sperm via an external spermatophoric mass; sperm storage in a thelycum or internal spermatheca had not developed. Primitive dendrobranchiate shrimps are characterized by open thelyca, morphologically elaborate external spermatophores, and open petasmata or semiclosed petasmata without terminal funnels or spouts. In the most advanced groups, females have closed thelyca and true spermathecae in which spermatophoric masses are deposited; males have semiclosed petasmata with terminal spouts. Several variations in genitalia between these primitive and advanced extremes are found in penaeoid species. In the Pleocyemata, a trend of increasing insemination complexity can be constructed from the Stenopodidea-Caridea to Astacidea and culminating in the Brachyura. Sperm transfer and storage in both the Palinura and Anomura stand apart from this major pleocyemaie trend. The proposed phylogenetic trends in insemination morphology are compared to various schemes of decapod evolution. Best agreement is found with Burkenroad's (1963) hypothesis on decapod phylogeny; the Natantia of Boas (1880) is not supported by a review and analysis of decapod sperm transfer and storage morphology.