Diversity and conservation status of Aegla spp . ( Anomura , Aeglidae ) : an update

ABstRAct Th e speciose genus Aegla Leach, 1820 is the only valid extant genus of the anomuran family Aeglidae, bearing 83 known species. Th is diversity may be even greater since there is some evidence for cryptic speciation. Th e genus is endemic to southern South America, occurring in freshwater habitats. We assessed the conservation status of 82 species of Aegla and found almost 70% of them under some level of threat, which represents a concerning proportion. Major threats to the group include freshwater pollution with urban, agricultural and industrial effluents, habitat modification and fragmentation, riparian forest removal, among others. Conservation measures are required to mitigate the major threats to freshwater ecosystems along rivers where the group occurs.

Aegla Leach, 1820 is the only extant genus of the family Aeglidae and can be found in rivers, streams, and lakes of southern South America, occurring from the Rio Grande basin, on the border of São Paulo and Minas Gerais states, Brazil (Bueno et al., 2007), to Duque de York Island, South River basin, Chile (Oyanedel et al., 2011).Th is genus includes 83 described species (Bond-Buckup et al., 2008;2010a;2010b;Santos et al., 2012;2013;2015;Moraes et al., 2016) and probably new species will be uncovered in the next years (Fig. 1).
Th e use of molecular techniques together with traditional systematics has helped to confi rm several new species, as the number of morphological characters for taxonomic use is limited by the conservative morphotype of the group (Bond-Buckup and Buckup, 1994;Pérez-Losada et al., 2004;Santos et al., 2009;2010;2012;2013).Moreover, the existence of cryptic species cannot be ruled out since molecular markers and geometric morphometrics have already pointed to this possibility (Bartholomei- Santos et al., 2011;Marchiori et al., 2014;2015).Th is level of diversity is greater than that observed for crayfi shes of the family Parastacidae (Almerão et al., 2015) and brachyuran crabs of the genus Trichodactylus Latreille, 1828 (Yeo et al., 2006), other crustacean groups inhabiting southern South American continental waters.Bond-Buckup et al. (2008) estimated that 36.5% of the 63 species described at that time were under threat of extinction.Pérez-Losada et al. (2009) assessed the conservation status of 66 aeglid species and found that 32% of them were threatened, that is, species falling within the International Union for Nature Conservation (IUCN) categories Vulnerable (VU), Endangered (EN), and Critically Endangered (CR).Many factors contribute to threat the group along its distribution in southern South America, such as decline in habitat quality, water contamination by extensive use of pesticides in agriculture or by urban sewage, silvicultural practices, construction of hydroelectric plants, among others (Pérez-Losada et al., 2002b;Bond-Buckup et al., 2008;Baumart and Santos, 2010;Santos et al., 2012).Th e presence of some species in restrict areas, as in headwaters, several of them with a few records of occurrence, highlights even more the level of threat to the group's conservation (Magris et al., 2010).
In this study, we present data on the diversity of species of the genus Aegla, as well as updated information on the distribution of these species in diff erent South American hydrographic basins.Moreover, based on data from several scientifi c collections and from years of work and experience of the authors, we evaluated the conservation status of the aeglid species and discussed the main threats to the genus diversity.

mAteRiAl AnD metHoDs
We assessed and updated the distribution of 82 species of Aegla.Based on the updated distribution data, we revised the conservation status for each species previously assessed until 2016, according to the rules established by the International Union for Conservation of Nature (IUCN, 2012).Th ere are fi ve quantitative criteria (A -E) to be applied in order to evaluate if a taxon is under threat, and in which category the taxon should be included (EX -extinct; EW -extinct in wild; CR -critically endangered; EN -endangered; VU -vulnerable; NT -near threatened; LC -least concern; DD -defi cient data; and NE -not evaluated; CR, EN and VU represent threat categories).Th e assessment employs sub-criteria to justify the assignment of a taxon to a certain category.Each species was evaluated in relation to its Extent Of Occurrence (EOO; sub-criterion B1) and Area Of Occupancy

Results
The list of species, with author(s) and year of description, as well as their distributions, are presented in Tab. 1. Records indicate the presence of aeglids in rivers, lakes and streams in catchments in Argentina (14 species), Bolivia (1 species), Brazil (52 species), Chile (22 species, considering Aegla intermedia Girard, 1855), Paraguay (1 species) and Uruguay (4 species), some species occurring in more than one country (Figs. 2, 3).
Based on our assessment, 17 species were classified as critically endangered (CR), 21 as endangered (EN), 19 as vulnerable (VU), one as near threatened (NT), 21 as least concern (LC), three had deficient data (DD), and one was not evaluated (NE).Current and previous conservation status and the criteria used to assign each species to an IUCN category are also shown in Tab. 1.

Discussion
There are currently 83 known species of the genus Aegla, although the existence of A. intermedia is questioned.This species was described based upon specimens collected by the "U.S. N. Astronomical Expedition", in tributaries of Maipu River, near to Santiago, Chile.Despite the effort of various researchers, the species has never been found again in nature and its type-series has disappeared (Bond-Buckup and Buckup, 1994).Hence, the conservation status of this species was not evaluated.
Using updated data from the species distribution, we found 57 species of Aegla under threat or almost 70% of the 82 species evaluated.This proportion represents a significant increase in relation to previous assessments for the genus Aegla, which estimated nearly half of the present value (Bond-Buckup et al., 2008;Pérez-Losada et al., 2009).Considering the most recent conservation status assessment for each species, from the 32 species previously assessed as LC, only 20 kept the same status; nine species changed the category to some level of threat and three have deficient data.Twenty-nine species kept the same threat category, but seven previously threatened species raised the threat level.Only one species changed from a threat category to NT status (Tab.1).
The high rate of endemism presented by many aeglid species, in association with habitat loss/fragmentation or even climatic events, has led many populations to decline (Maia et al., 2013;Bueno et al., 2014).Forty years ago, many species were found in several streams and rivers within a basin, but currently, most of them are restricted to low order creeks (Bond-Buckup and Buckup, 1994).
Threats to conservation of aeglids and other freshwater organisms in southern South America
Known species of the genus Aegla Leach, 1820, distribution, previous and current conservation status assessments according to IUCN (2012) Red List categories (CR -critically endangered; EN -endangered; VU -vulnerable; NT -near threatened; LC -least concern; DD -deficient data; EX -extinct and NE -not evaluated).The numbers in parentheses, after the name and author of the species, indicate their location in the maps of figures 2 and 3. Cont.

Species Country: Hydrographic basin (main rivers)
Previous assessment (Reference)

Diversity and conservation of Aeglidae
Nauplius, 25: 2017011 derive from different sources: removal of riparian forest, causing siltation (Magris et al., 2010); habitat modification, fragmentation and destruction (Cumberlidge et al., 2009;Reid et al., 2013); freshwater contamination with agricultural pesticide (Magris et al., 2010;Negro et al., 2015;Stehle and Schulz, 2016); construction of dams that alter the flow and sometimes the temperature of the water as well (Olsson, 2015); urban and agricultural activities which modify the physical and chemical characteristics of water bodies and freshwater biota composition (Milesi et al., 2008;Hepp and Santos, 2009;Hepp et al., 2010;Magris et al., 2010); invasive species (Palaoro et al., 2013;Loureiro et al., 2015), among others.Threats to the family Aeglidae, specifically, have been identified and listed, as the use of biocides in wine and fruit farms in Chile, silviculture of exotic species, largescale cultivation of potatoes and apples with extensive use of pesticides, and hog raising activities along southern rivers in Brazil (Bond-Buckup et al., 2008), beyond severe deforestation in Paraguay (Satterlee et al., 2012).Irrigated rice crops are responsible for the entrance of great amount of pesticides into the hydric systems (Bhuiyan and Castañeda, 1995), what may constitute a threat to aeglids in southern Brazil, Uruguay, Paraguay and northwestern Argentina.These activities, although doubtless important, negatively impact the aquatic environment, and it is imperative that they respect the principle of sustainability (Santos et al., 2012).In Argentina, the exotic golden mussel Limnoperna fortunae Dunker, 1857 was reported to settle on Aegla platensis Schmitt, 1942 affecting its populations (Darrigran and Damborenea, 2006).In Bolivia, anthropic activity and indiscriminate extraction by local people affect populations of Aegla septentrionalis Bond-Buckup & Buckup, 1994(Flores, 2010), the only aeglid species occurring in that country.
It should also be taken into account that many aeglid species present a narrow distribution, and two species with a relatively wide distribution, Aegla longirostri Bond-Buckup & Buckup, 1994 and Aegla platensis, may represent a complex of cryptic species as supported by genetic and morphogeometric evidence (Bartholomei-Santos et al., 2011;Marchiori et al., 2014;2015).If this is true, so the distribution area of each cryptic species will be narrower than the "grouped" species, which can result in different conservation status for each cryptic species, the reason for which data were considered deficient for these two current recognized species.
Our assessment of the conservation status of all the currently known species of Aeglidae is worrisome, with 70% of the species under some level of threat and 20% critically endangered.Measures to protect the aeglid fauna are urgent, such as the frequent monitoring of water quality in systems where the threatened species occur, following-up the species to obtain information on possible population fluctuation or decline, protecting and restoring habitats, and information spreading among the population on the importance of water courses for conserving the native fauna, as well as encouraging agricultural practices that do not harm the water quality.
Aeglids live preferentially in clean waters (Bond-Buckup and Buckup, 1994), presenting a high demand for oxygen (Dalosto and Santos, 2011), and thus making these crustaceans potential good indicators of water quality.Policies for continental water quality control will help to protect not only the aeglids but also the limnetic fauna as a whole.

Figure 2 .
Figure2.Distribution of Aegla Leach, 1820 in Argentina, Bolivia, Chile, and Paraguay (see Tab. 1 for the corresponding species number).In areas with less species diversity, we used a larger font size to facilitate the localization in the map.However, where diversity is high, to avoid overlapping the numbers, we reduced the font size, and if necessary we used a point with a line indicating the respective number.