Ludwig Buckup in recognition of his dedication and contributions to the development of Carcinology Checklist of the species of Macrobrachium Spence Bate , 1868 ( Decapoda : Caridea : Palaemonidae ) from the lower Parnaíba River basin , Piauí , Brazil

We present herein the results of a brief field survey of species of Macrobrachium Spence Bate, 1868 in three points of the northern portion of the lower Parnaíba River basin. The northern region of the lower Parnaíba River basin is part of the Environmental Protection Area Delta do Parnaíba and Nauplius, 26: e2018017 All content of the journal, except where identified, is licensed under a Creative Commons attribution-type BY. orcid.org/0000-0003-0560-3559 original arTiCle CORRESPONDING AUTHOR William Santana willsantana@gmail.com SUBMITTED 31 October 2017 ACCEPTED 30 May 2018 PUBLISHED 13 August 2018 Guest Editors Alessandra Angélica de Pádua Bueno and Sandro Santos DOI 10.1590/2358-2936e2018017 orcid.org/0000-0001-6937-0841 orcid.org/0000-0002-7623-2663 orcid.org/0000-0002-3114-3704 orcid.org/0000-0003-3086-4419

inTroduCTion Macrobrachium Spence Bate, 1868 is a very successful group of palaemonid shrimps found in freshwater and estuarine habitats in the tropical and subtropical regions of the world (Holthuis, 1952;Valencia and Campos, 2007).Nowadays, Macrobrachium is considered the most speciose genus of the subfamily Palaemoninae, with 243 species, 55 of which are found in the Americas and 17 in Brazil (Fransen and De Grave, 2009;Pileggi and Mantelatto, 2012).
Macrobrachium shrimps are very important commercially, with several species fished and farmed around the world (Holthuis, 1980;Moraes-Riodades and Valenti, 2001).Likewise, they play an important role in the food chain and other ecological processes of the freshwater fauna (Magalhães, 2001).Nevertheless, information about some species is scarce, especially for those that are smaller and of little commercial interest and for species with restricted distributional areas and low abundance (Barros and Braun, 1997).
The northern portion of the lower Parnaíba River basin is part of the Environmental Protection Area Delta do Parnaíba, which comprises several lakes and coastal lagoons (ICMBIO, 2017).The costal region's peculiar conditions and diverse ecosystems led to the region's categorization as one of the priority areas for conservation actions as well as sustainable use and sharing of the Brazilian biodiversity (LIMA/ COPPE/UFRJ, 2006).However, the northeast region's freshwater biodiversity remains almost unexplored (Rocha, 2003), and the crustacean fauna in the habitats of the lower Parnaíba River basin is nearly unknown.We presented herein the results of a brief field survey of species of Macrobrachium in three points of the northern portion of the lower Parnaíba River basin, state of Piauí, Brazil.
It is important to notice that three (M.acanthurus, M. amazonicum, and M. olfersii) of the five species found in

Infraorder
Remarks.This is the first record of this species from the lower Parnaíba River basin and the northern portion of the state of Piauí, with only one documented previous record in the state from the municipality of Jaicós (Ferreira et al., 2010).This species can be differentiated from its congeners through a combination of characters of the rostrum and telson (Valencia and Campos, 2007): rostrum slightly sinuous and apex somewhat curved upward, usually overreaching scaphocerite; upper margin of rostrum with 8-12 teeth, with proximal teeth closer to each other, including 1-3 teeth completely postorbital; lower margin of rostrum with 4-7 teeth; telson terminal margin ending in sharp midpoint, with 2 pairs of spinules laterally, inner pair overreaching midpoint.Distribution.In Brazil, this species has been recorded in the states of Acre, Roraima, Rondônia, Amapá, Amazonas, Pará, Maranhão, Piauí, Ceará, Rio Grande do Norte, Paraíba, Pernambuco, Bahia, Tocantins, Goiás, Mato Grosso, Mato Grosso do Sul, Minas Gerais, São Paulo and Paraná (Melo, 2003;Pileggi et al., 2013;Pimentel and Magalhães, 2014;present work).
Remarks.Ramos-Porto and Coelho (1998) as well as Melo (2003) cited the occurrence of M. amazonicum from Piauí, however, they did not mention the material examined and locality.This is the first record of M. amazonicum from the lower Parnaíba River basin.
According to Magalhães et al. (2005), adults of M. amazonicum are easily recognized by the long and sinuous rostrum, which is arched over the orbits and obliquely curved upward distally.Telson somewhat conical, tapering gradually toward to the tip, ending in an acute median point with no distinct discontinuity, with two pairs of spines in the posterior half of the lateral margins, inner pair not overreaching the apex of the telson.In immature and juvenile specimens these characters can be misleading, especially in comparisons with M. jelskii.However, the telson of M. jelskii have a distinct posterior margin, with a clear discontinuity between the lateral margins and the median point, and the inner pair of spines of the posterolateral margins is always longer than the median point of the telson (Magalhães et al., 2005).
Remarks.As for M. amazonicum, Ramos-Porto and Coelho (1998) and Ferreira et al. (2010) cited the occurrence of M. carcinus in Piauí but without mention the material examined and locality.This is the first documented record of M. carcinus in the Parnaíba River basin.Macrobrachium carcinus is the most important freshwater species economically and socially in the Brazilian northeast region.Populations of this species are in decline in several Brazilian hydrographic basins due to over-exploitation and habitat loss (Almeida et al., 2008).However, no studies about population estimation quantify the population reduction of this species, which motivated the categorization of this species as Insufficient Data in the last evaluation of the threatened crustacean species of the Brazilian fauna (Mantelatto et al., 2016), although most fishermen agree that this species is threatened in at least some regions (Almeida et al., 2008).In addition, the practice of uncontrolled cultivation of other Macrobrachium species in nonnative areas, with the possibility of species dispersal, may represent a future concern for local biodiversity (Mantelatto et al., 2016).Macrobrachium carcinus is easily recognizable through its short rostrum and the carpus of the second pereopod distinctly shorter than the merus, and with a single, large, triangular tooth on the cutting edges of the dactyl and propodus.Distribution.In Brazil, this species has been recorded in the states of Acre, Amapá, Amazonas, Pará, Maranhão, Piauí, Ceará, Rio Grande do Norte, Paraíba, Pernambuco, Alagoas, Sergipe, Bahia, Mato Grosso, Espírito Santo, Rio de Janeiro, Minas Gerais, São Paulo, Paraná, Santa Catarina) (Melo, 2003;Pileggi et al., 2013;present work).
Remarks.This is the first record of M. jelskii in the Parnaíba River basin.M. jelskii is commonly found in sympatry with M. amazonicum.Here we found both species in Prata Lagoon, though M. jelskii was more abundant than M. amazonicum (cf.material examined).Also, see remarks section regarding M. amazonicum for characters to differentiate between these species.Distribution.In Brazil, this species has been recorded in the states of Amapá, Piauí, Ceará, Rio Grande do Norte, Alagoas, Sergipe, Bahia, Minas Gerais, Espírito Santo, São Paulo and Santa Catarina (Barros and Braun, 1997;Müller et al., 1999;Melo, 2003;Pimentel and Magalhães, 2014;present work).
Remarks.This is the first record of M. olfersii in the lower Parnaíba River basin, although Ferreira et al. (2010) mentioned the occurrence of this species in Piauí when discussing an indeterminate specimen from the Piauí River without a precise locality [material deposited at the Museu Nacional (MNRJ 2574)].Macrobrachium olfersii can be easily differentiated through its almost straight and relatively short rostrum, and the strong second pair of pereopods with chelae of unequal sizes and gaping fingers and a dense pubescence on the palm and cutting edges.