Debido al aporte de materia orgánica, la vegetación ribereña juega un papel importante en la estructura y complejidad de los ríos (Boothroyd et al., 2004). La vegetación rivereña se encuentra más conectada a la vida que sucede dentro del río que fuera de él, cumpliendo un rol fundamental en la cadena trófica de estos ambientes y en la determinación de la composición de las comunidades que lo habitan, como son los macroinvertebrados (Vannote et al., 1980;Corbacho et al, 2003). Los cambios en el uso del suelo se reflejan en los recursos hídricos, que sufren degradación de su calidad a través de la contaminación

South America is considered a world biodiversity hotspot, especially for freshwater ecosystems where there is significant biodiversity and endemism across different taxonomic groups. Native South American crayfishes are characterized by small range distributions, high levels of endemism and specific habitat requirements. Although this group may be considered one of the most threatened among South American freshwater crustaceans, IUCN Red List assessments for most of these species are ‘data deficient’. IUCN assessments are technical evaluations of species risk of extinction based on biological indicators of population features, thereby providing a ‘conservation status’ for each species based on common and international standards. Attempts to assess the conservation status of native South American crayfishes have been limited mainly owing to a lack of fundamental data and also misinterpretations of present information. Thus, a revision of the state of knowledge of native South American crayfishes (taxonomy, phylogeny and distribution, genetics, ecology and threats) was carried out coupled with IUCN assessments of conservation status. Globally, the lack of information on the biology of these species is still the major obstacle to making reliable conservation status assessments. For this reason, the Data Deficient (DD) category is still appropriate for many species. However, based on the Extent of Occurrence (EOO) and severely fragmented populations, number of locations and decline in area, extent or quality of habitat, it is recommended that some species (especially Virilastacus spp.) should be moved to threatened categories (VU, EN or CR). The data suggest that others are appropriately in the Near Threatened (NT) category, because they almost reach the thresholds for threatened categories. The assessment of conservation status is essential to support future conservation actions, especially for species allocated to threatened categories. This study has identified new species under threat and also areas for future study to provide relevant data for conservation assessment for ‘data deficient’ species. Copyright © 2014 John Wiley & Sons, Ltd.

Various authors have reported the occurrence of supernumerary gonopores in many species of Parastacus, which has generated discussion about their sexual system. In this study, we examine the external and internal sexual characters of 102 specimens of the burrowing crayfish, Parastacus pilimanus, captured in the province of Maldonado in southeast Uruguay, with the aim of clarifying its sexual system. In this study, we show that in all the specimens analysed, female and male gonopores co-existed externally, and we verified the presence of only one type of gonad internally: either ovary (intersex females) or testis (intersex males), from which one pair of oviducts and another of sperm ducts originated, connecting the gonad to the respective gonopores. We also verified that all specimens smaller than 27.2 mm cephalothorax length (CL) (N = 73) had the same external morphology. Nevertheless, dissection revealed that their gonads were already differentiated. We established that 54.8% of these specimens were intersex females, while the remaining percentage corresponded to intersex males. Twenty-nine specimens were found with a CL equal to, or above, 27.2 mm. Of these, 34.5% (N = 10) were intersex males with the same external morphological traits that characterize all specimens smaller than 27.2 mm CL. The remaining 19 specimens (65.5%) were intersex females, 15 of which presented secondary sexual characters, probably associated with egg incubation. The evidence gathered suggests that Parastacus pilimanus has permanent intersexuality, similar to Parastacus pugnax and Parastacus varicosus in Uruguay. We conclude by identifying some topics that require further study, in order to understand the adaptive value of this type of intersexuality. RESUMENVarios autores han reportado la ocurrencia de gonoporos supernumerarios en muchas especies de Parastacus, lo que ha generado discusión acerca del sistema sexual de ellas. En este trabajo nosotros examinamos los caracteres sexuales externos e internos de 102 especimenes del camarón excavador Parastacus pilimanus capturados en el Departamento de Maldonado, sureste de Uruguay, 3 )

No abstract

Hyalella is a genus of epigean freshwater amphipods endemic to the Americas. The study of morphological characters alone has traditionally dominated the description of new species. Recently, molecular systematics tools have contributed to identifying many cryptic species and a high level of convergent evolution in species complexes from North America and the South American highlands. In this study, we evaluate for the first time the molecular diversity in Hyalella spp. in Uruguay, a country located in the humid pampa ecoregion, based on four molecular markers. Thus, we investigate the systematic position of H. curvispina in the context of the available phylogenetic hypothesis for the genus. Phylogenetic and morphological analyses confirm that there is a “curvispina complex”. This complex includes H. curvispina and several similar morphological forms but is paraphyletic in relation to some altiplano species. In addition, we found one provisional new species. The results obtained are contrasted with previous studies to help understand the mechanisms of genetic differentiation and speciation of the genus, which seems to have a strong tendency towards morphological convergence.