First record of Potimirim potimirim ( Müller , 1881 ) ( Crustacea , Decapoda , Atyidae ) from Rio Grande do Norte , northeastern Brazil

Potimirim potimirim (Müller, 1881), a species of coastal freshwater shrimp, is recorded for the first time from the state of Rio Grande do Norte, northeastern of Brazil, where it was collected in a small tributary of the Potengi River. This record extends the distribution of this species about 220 km north along Brazilian coast. New records, such as this, reinforce the need for greater research efforts in the northeastern freshwater ecosystems of Brazil to provide better understand the region’s biodiversity and establish better parameters for conservation actions.

The family Atyidae De Haan, 1849 is a group of mainly freshwater shrimps of about 469 species belonging to over 40 genera and distributed worldwide (De Grave & Fransen 2011).Despite the large diversity of this group, the Neotropical Region has just 19 known species (De Grave et al. 2008).
Limnic ecoregions are large areas of hydrographic basins that present distinct assembles of freshwater species (Abell et al. 2008).Potimirim potimirim occurs in four of the nine freshwater ecoregions on Brazilian east coast: Northeastern Caatinga and Coastal Drainages, Northeastern Atlantic Forest, Ribeira de Iguape, and Southeastern Atlantic Forest.
This species is an important component of limnic ecosystems, playing a fundamental role in transport and retention of detritus, in nutrient cycling (Covich et al. 1999;Crowl et al. 2001), and in promoting sediment resuspension (Moulton et al. 2004).Moreover, this species cleans hard substrates, exerting a negative influence on periphyton (Souza & Moulton 2005).
We record here, for the first time, the presence of P. potimirim from the state of Rio Grande do Norte, northeastern Brazil.
Our collections were made in 2013 and 2014 from a small tributary of the Potengi River, Rio Grande do Norte, Brazil (Figures 1 and 2) in accordance to federal environmental laws (Collection license SISBIO-IBAMA #28314-1).Shrimps were captured in a permanent, low-energy, firstorder stream (energy order scale, sensu Cardoso et al. 2006) with clear water.In the area sampled, the stream ranges from 1.5 m to 3.0 wide and 20 cm to 80 cm deep.Along most of its course it is shaded by native forest.The stream's substrate is composed by muddy, organic material and a large amount of submerged leaf litter (leaves, twigs, and fruits from the surrounding vegetation).
Our diurnal samples were made using sieves with 2-mm mesh.Collected specimens were identified according to Melo (2003) and Müller (1892).A digital caliper (0.01 mm precision) was used to measure specimens' total length (TL, post-orbital margin to posterior dorsal margin of telson) and cephalothorax length (CL, post-orbital margin to posterior dorsal margin of carapace).
The sex of each specimen was determined by the presence or absence of the male sexual appendix, which is positioned at the second pair of pleopods.Any egg mass present in ovigerous females were classified according to their stage of development: stage 1, eggs homogeneously colored, with absence of visible pigmentation of the eyes; stage 2, eye pigmentation slightly visible; or stage 3, eyes completely developed (Herrera-Correal et al. 2013).Finally, specimens were fixed in 70% ethanol.These were deposited in the carcinological collection of the Grupo de Estudos de Ecologia e Fisiologia de Animais Aquáticos, Universidade Federal do Rio Grande do Norte (GEEFAA/UFRN), Brazil.
We conducted a literature review to find other occurrence data for P. potimirim.When records were not georeferenced, we approximated geographic coordinates using Google Earth® software (version 7.1.2.2041).The map was created using the ArcMap 10.  much longer than first pair of carpus; merus of pereiopods 3-5 armed with three distal spines on ventral surface; dactyl of third and fourth pair of pereiopods with seven spines.Preanal carina on acute format; presence of 20 spines on uropods' diaeresis (Müller 1892;Melo 2003).Lima & Oshiro (2002) and Lima et al. (2006) remarked that first-order rivers, with unconstrained substrate and high density of submerged leaf litter, were suitable habitat for this species.We were observed these same characteristics at our site in the Potengi River basin.
The presence of females with eggs in late stages of development in this stream, about 18 km from the mouth of Potengi River, suggests that this stream may be a spawning ground.We suppose that salinity does not influence egg eclosion.Based on ecological data from Lima & Oshiro (2002) and our observations, we believe that P. potimirim prefers streams with reduced salinity for spawning.However, additional samples from along the length of the stream and observing females with eggs in other stages of development are needed to confirm this supposition.
The presence of P. potimirim in the states of Pernambuco, Alagoas, and now Rio Grande do Norte suggests that may also occur in Paraíba and Ceará because these states are also within the Northeastern Caatinga and Coastal Drainages ecoregion (Abell et al. 2008).TL = 26.44mm;CL = 6.39mm, (GEEFAA/UFRN 357).
Diagnosis: Rostrum reaching the second antennular article, narrow and sharp, with slightly down-curved top edge.Top median carina unarmed and three teeth on ventral surface.Carapace smooth, anterior margin with a suborbital tooth; pterygostomian spine present in the anteroventral angle of the carapace's edge.Absence of epipodite on base of fourth and fifth pereiopods; carpus of second pair of pereiopods almost as long as propodus, and Our record of P. potimirim from a tributary of Potengi River increases its known range and represents the northernmost occurrence on the Brazilian coast (Table 1).Among the bioecologic studies of this species, the study of population structure by Lima et al. (2006) is outstanding, as is study on the evolution of reproduction in the genus by Grilli et al. (2014).Nevertheless, the biology of P. potimirim is not well known, likely because of the low commercial interest in the species.Thus, we emphasize the need for further research that will provide a better understanding of the biodiversity of Brazil's coastal aquatic ecosystems.This will allow for more effective and better targeted conservation actions.