Macrobrachium amazonicum (Heller, 1862)

Macrobrachium amazonicum (Heller, 1862) View in CoL

( Fig. 3A–D View Figure 3 )

Material examined. Brazil, Piauí: Portinho Lagoon, 20.ii.2014, 60 specimens [ CZDP ( F2 ) 0054]. Idem, 19.vii.2014, 65 specimens [ CZDP ( F2 ) 0060]. Idem, 19.vii.2014, 3 males ( LSZ 030 ). Parnaíba River , 04.iii.2013, 40 specimens [ CZDP ( F2 ) 0057]. Prata Lagoon, 20.xii.2014, 100specimens [ CZDP ( F2 ) 0059] .

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).