Aegla lata Bond-Buckup & Buckup, 1994 is considered extinct in the type locality. New populations of this species, however, have been found in northern Paraná state, Brazil. We revised the taxonomy of A. lata based on morphological data obtained from the type material and specimens recently obtained from streams of the Tibagi River sub-basin, Paranapanema River basin, Upper Paraná Ecoregion. Moreover, Aegla jacutingan. sp. is described and illustrated. The new species resembles A. lata in the shapes of the body and chelipeds. Both species are nevertheless separated by particular morphological characters of the carapace, chelipeds, and epimeron as well as by molecular (COI mtDNA) differences. Both species can be distinguished from their congeners based on morphological and molecular evidence.

Freshwater crustaceans of the genus Aegla are endemic to southern South America. In Brazil, the greatest diversity of aeglid species occurs in river basins in the Rio Grande do Sul state. Nevertheless, recent studies have shown that the potential for discovering new species of Aegla in the Paraná state is huge. In recent years, for example, seven new species have been described for the state of Paraná. Furthermore, there is a need to solve problems related to cryptic species and refine taxonomic information about the group. Here we expand our current knowledge of the freshwater biodiversity of Aegla in the region by describing three new species. Aegla nanopedis sp. nov., Aegla abrupta sp. nov., and Aegla santosi sp. nov. were discriminated based on morphological and molecular evidence. Particular morphological characters of the carapace, chelipeds, epimeron and uropods distinguished the new taxa. Molecular results also support the separation of the new species from the closely related species A. jacutinga, A. castro and A. lata. The new species have limited distribution and are categorised as endangered (Aegla nanopedis sp. nov.) and vulnerable (Aegla abrupta sp. nov. and Aegla santosi sp. nov.) according to International Union for Conservation of Nature Red List Categories and Criteria. http://www.zoobank.org/urn:lsid:zoobank.org:pub:7A9A4BB-9B79-429B-B053-34A5D3667CD4

Aegla lata Bond-Buckup & Buckup, 1994 is a critically endangered species, extinct in its type-locality. Its currently known geographical distribution is restricted to small streams of the lower Tibagi River Basin (Paraná state, southern Brazil), where it is vulnerable to the environmental degradation that takes place in these watersheds. Scientific knowledge on the species is limited to the original description and a few occurrence records. No information about its biology is available. Aiming to fill this gap, we investigated the relative growth, sexual maturity, sexual dimorphism, and the reproductive and recruitment periods of A. lata. Monthly sampling occurred from May 2014 through June 2015 in the Bule stream in the southern limit of Mata dos Godoy State Park, Londrina, Paraná state, Brazil (23°27ʹ20.86″S, 51°16ʹ32.44″W). The analysis of allometric growth was used to differentiate juveniles and adults. According to the development stage of the chelae, two sequential groups of adult males were recognized (morphotypes I and II). The estimated average cephalothorax length (CL) at the onset of morphometric maturity of males and females are similar, suggesting puberty molt takes place at nearly the same size in both sexes. Males and females are heterochelous, with a clear predominance of the left chela as the most developed of the pair. Both chelae are larger in adult males than in adult females of similar CL. The reproductive period is markedly seasonal, extending from the austral autumn to winter (May to August), as well as those recorded in other species of Aegla from similar latitudes. A single annual recruitment pulse was detected from October 2014 to February 2015.

Freshwater crustaceans of the genus Aegla are endemic to southern South America, and present greater richness in the river basins of the state of Rio Grande do Sul, Brazil. However, recent studies have shown the enormous potential for discovering new species of Aegla in the state of Paraná. In the last six year the number of species recorded has almost doubled, increasing from 9 to 16. In the present work, we expand the current knowledge about the diversity of Aegla in a set of poorly explored drainage basins in the western region of the state and describe a new species, Aegla urussanga n. sp., based on morphological and molecular evidence. A combination of morphological characters supports the new species: orbital spine absent, non-elevated epigastric prominences, robust protogastric lobes with scales, anterior dorsal margin of epimeron 2 armed and with pronounced concavity, sub-rectangular palmar crest of chelipeds, internal margin of the ventral face of the ischium of the cheliped with a proximal stout spine, a distal stout spine, and up to three tubercles with spiniform scales. The molecular data, based on partial COI sequences, also support the distinction of the new species from others that occur in adjacent river basins. The species with the smallest genetic distance from A. urussanga n. sp. is Aegla castro Schmitt, 1942 which occurs in the Iguaçu River basin. The new species occurs in distinct streams, probably interconnected in the past and currently isolated by the Itaipu reservoir and is the second species of Aegla described from the complex of drainage basins called Paraná 3 basin.

The geographical distribution of marine organisms, as a result of complex natural processes through geological time, has been changed, sometimes drastically, by species introductions. Instances of species introduction have been recorded worldwide, and the Brazilian coast is no exception. The present review provides an update of the geographical distribution of members of the brachyuran subfamily Mithracinae along the Brazilian coast. Of the 30 species of this subfamily recorded from Brazilian waters, the known geographical limits of more than 17 have been extended in recent decades. The records compiled here demonstrate the great importance of the Amazon River outflow on the geographical distribution of members of Mithracinae, acting as a biogeographical barrier for some species.

A new species of freshwater anomuran crab, Aegla buenoi n. sp., is described. The new taxon was collected from two streams within the Cinzas River basin, Paraná state, Brazil. We used morphological and molecular data (COI mtDNA) to distinguish the new species from its congeners. Aegla buenoi n. sp. is differentiated by morphological diagnostic features of the cephalothorax, chelipeds, second abdominal epimeron, and uropods. Molecular results confirm the separation of A. buenoi n. sp. from closely related species (A. castro Schmitt, 1942, A. lata Bond-Buckup & Buckup, 1994, and A. jacutinga Marçal & Teixeira, 2020). Hence, our study increases the known diversity of aeglids and reports the first species of Aegla from the Cinzas River basin.