Astacidea

Astacidea can be distinguished from most other decapods by the presence of chelae on each of the first three pairs of pereiopods (walking legs), with the first pair substantially larger than the second and third pairs. The last two pairs of pereiopods are simple and lack claws, except in Thaumastocheles where the fifth pereiopod may bear a minute pincer. This claw configuration separates Astacidea from spiny lobsters (Palinuridae) and other decapod groups that lack such prominent chelae on multiple leg pairs.

Members occupy diverse aquatic environments including marine, freshwater, and semi-terrestrial habitats. Marine species include true lobsters inhabiting oceanic waters. Freshwater crayfish species occupy rivers, streams, and lakes. Some species, particularly among Parastacidae, are semi-terrestrial burrowers in semi-marshland zones, constructing relatively complex burrows of varying depths; these include species of Parastacus, Virilastacus, and Samastacus in South America.

Global distribution spanning oceans and fresh waters worldwide, with notable absence from mainland Africa and parts of Asia. In South America, two distinct biogeographic regions are recognized: Uruguay and Brazil (Atlantic coastal sub-tropical), and central-southern Chile (Pacific coastal temperate). Australian and New Zealand regions harbor significant Parastacidae diversity. The invasive marbled crayfish Procambarus virginalis has established populations across Europe (Sweden, Belarus, Germany, Slovakia, North Macedonia) and tropical Africa (Malawi).

Development includes embryonic and post-embryonic stages with temperature-dependent growth rates. In Procambarus virginalis, juvenile growth to 1.4 g body weight requires approximately 4316 degree-days (biological zero 7.6°C), while breeding period growth to 15 g requires 10630 degree-days. Sexual maturity timing varies dramatically with climate: in temperate European waters, individuals hatching in early summer reach maturity in their third summer; in tropical Malawi, maturity occurs in the first summer with maximum lifespan under two years. Throughout the range, sexually mature individuals produce 2–5 clutches per life cycle. Chilean Parastacidae exhibit low fecundity, slow growth, late sexual maturity, and prolonged ovarian and embryonic development.

Many species exhibit burrowing behavior with varying degrees of terrestriality. Semi-terrestrial burrowing species have limited migration potential, smaller population sizes, and reduced gene flow compared to aquatic burrowing species. Aquatic species generally show greater mobility and population connectivity.

Several species are exploited as human food sources, including true lobsters and some crayfish. In Chile, Samastacus spinifrons and Parastacus pugnax face overexploitation pressure without regulatory legislation for extraction, trade, or transport. Samastacus spinifrons is of particular interest for aquaculture due to advantageous biological characteristics. Many species are threatened by habitat degradation from anthropogenic pressure; Chilean Parastacidae species are classified as endangered due to combined pressures of habitat deterioration, low reproductive output, and overharvesting. The marbled crayfish Procambarus virginalis represents a significant invasive species in multiple continents.

• PolychelidaSister clade to Astacidea within Reptantia; distinguished by being restricted to deep waters and lacking the characteristic three pairs of chelae on walking legs that define Astacidea.
• Palinuridae (spiny lobsters)Often called "lobsters" but not true lobsters; distinguished by lacking claws on the first three pairs of walking legs, instead bearing long spiny antennae and a compressed carapace without the prominent chelae characteristic of Astacidea.
• GlypheideaFormerly included within Astacidea but now recognized as a separate infraorder; contains fossil taxa and two extant species (Neoglyphea inopinata, Laurentaeglyphea neocaledonica) with distinct morphological features.

• BugGuide
• Wikipedia
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• A checklist of the Chilean Parastacidae (Decapoda, Astacidea)
• Distributional patterns of the South American species of Parastacidae (Decapoda, Astacidea)
• Prevalence and Potential Evolutionary Significance of Color Mutations in Freshwater Crayfish (Decapoda: Astacidea)
• Characterization of the Cambaroides wladiwostokiensis Birstein & Vinogradov, 1934 (Decapoda: Astacidea) Mitochondrial Genome Using Genome Skimming and the Phylogenetic Implications within the Astacidea Infraorder
• Prevalence and potential evolutionary significance of color variants in freshwater crayfishes (Decapoda: Astacidea)
• Diversity and distribution of Australian freshwater crayfish with a check-list of the world Parastacidae and a key to the genera (Decapoda, Astacidea, Parastacoidea)
• Modeling the growth of the invasive river crayfish species Procambarus virginalis (Decapoda, Astacidea) under different temperature conditions