Abstract The present paper describes a new species of freshwater crayfish of the genus Parastacus Huxley, 1879 from the municipality of Amaral Ferrador in the state of Rio Grande do Sul, southern Brazil, evaluates its conservation status according to the IUCN Red List Criteria (sub-criterion B1), and updates the identification key for the genus. Parastacus longidactylus sp. n. differs from all analyzed species by the large eyes, the prominent and wide rostral carinae, surpassing the rostral basis and extending to the proximal third of the postorbital carinae, postorbital carinae and rostral carinae prominent and with similar lengths, chelipeds carpus dorsomedial surface not divided longitudinally by groove and long dactylus, surpassing the fixed finger. The possible extent of occurrence was estimated to be 6,968 km² and the species was recorded in only one location in the Camaquã River basin. The main threats to the region are the replacement of native vegetation by crops and livestock, water pollution and soil erosion. However, because there is only one known location where Parastacus longidactylus sp. n. occurs we suggest classifying the species as Data Deficient.

Abstract Cymothoa ianuariiSchioedte & Meinert, 1884 is rediscovered almost 136 years after its original description and redescribed from specimens collected in the state of São Paulo. This species is mainly characterized by adult females with cephalon with conspicuous eyes and not deeply immersed in pereonite 1, pereonites 5-6 much wider than 4, pleotelson twice as wide as long and pleopods 1-5 decreasing in size; Cymothoa excisaPerty, 1833 and C. oestrum (Linnaeus, 1758) are recorded from the state of Bahia. Illustrations and an updated distribution map for these species in Brazil are provided.

Abstract Two new species of Parastacus Huxley, 1879 are described from the Atlantic Forest in southern Brazil: Parastacus buckupi sp. nov. from a highland stream in the hydrographic basin Maquiné river, Maquiné, state of Rio Grande do Sul; and Parastacus pilicarpus sp. nov. from a first order stream in the hydrographic basin Araranguá River, Morro Grande, state of Santa Catarina. Parastacus buckupi sp. nov. is distinguishable from all other Parastacus species via its large and globose chelipeds, by the presence of tufts of long and simple setae in the cutting edge of cheliped fingers, which are more abundant proximally and by possessing a telson with an acute distal margin. Parastacus pilicarpus sp. nov. is diagnosed mainly by the distal portion of the carpus which possess tufts of long, simple setae, and by having an epistome whose anteromedian lobe is heptagonal and as long as it is wide. Finally, P. pilicarpus antennal scales lateral margin terminates in a very strong terminal spine and mandibles incisive lobe has nine teeth, with the first tooth from the anterior margin being the largest. The conservation status based on the sub-criterion B1 of IUCN Red List allowed us to classify these species as “ENDANGERED” and “DATA DEFICIENT”, respectively.

Abstract In this contribution we describe a new species of burrowing crayfish of the genus Parastacus Huxley, 1879 from a swamp forest in southern Brazil and determine its conservation status. The distinction of the new species is based on morphology and the mitochondrial DNA marker 16S rRNA. The extinction risk was assessed according to the sub-criterion B1 of IUCN that estimates the Extent of Occurrence (EOO). Parastacus tuerkayi sp. nov. is morphologically distinguishable from all species of Parastacus by having three lines of verrucous tubercles on the dorsomesial margin of the cheliped propodus and a suborbital angle exceeding 90°. The EOO comprises 647,674 km², and the species is classified as “endangered”. Phylogenetic relationships indicate the distinct position of this new species in relation to the already described species.