Molecular and morphological differentiation between two Miocene-divergent lineages of Amazonian shrimps, with the description of a new species (Decapoda, Palaemonidae, Palaemon)

Abstract

Palaemon carteri (Gordon, 1935) and Palaemon ivonicus (Holthuis, 1950) are morphologically similar species of South American freshwater shrimps. Past studies have questioned the taxonomic status of both species, which are supposed to have partially sympatric geographic distributions in the Amazon basin. We analyzed a 550 bp fragment of the mitochondrial 16S rRNA gene from these Amazonian Palaemon species as well as from 11 palaemonids as the outgroup. Additionally, we checked diagnostic characters of the genus and family as well as other morphological characters that have been little explored before. Palaemon carteri and Palaemon ivonicus are allocated in two sister lineages, with wide genetic divergence and little morphological differentiation. The divergence time between these lineages was estimated as approximately 10 million years ago. Both molecular and morphological data support the taxonomic validity of both Palaemon carteri and Palaemon ivonicus, refuting the hypothesis of synonymy. In addition, a new species, Palaemon yuna sp. n., closely related to Palaemon ivonicus, is described. Our findings indicate that these species can be differentiated using the projection of the anterolateral margin and anterolateral spine of the first antennular segment, shape of the rostrum, and relative size of the appendix masculina.

Mitogenome phylogenetics in the genus Palaemon (Crustacea: Decapoda) sheds light on species crypticism in the rockpool shrimp P. elegans

“…The genus Palaemon Weber, 1795 is the third most species-rich genus of the family Palaemonidae Rafinesque, 1815 [ 1 , 2 ], with marine, estuarine and freshwater shrimps and prawns worldwide distributed in tropical and temperate regions. Palaemon currently comprises 88 species, given the recent synonymization of the genera Palaemonetes Heller, 1869, Coutierella Sollaud, 1914 and Exopalaemon Holthuis, 1950 with Palaemon [ 2 ], and five new described species [ 3 – 6 ].…”

Freshwater shrimps (Crustacea, Decapoda, Caridea, Dendrobranchiata) from Roraima, Brazil: species composition, distribution, and new records

“…The richness found in the Branco River basin is 75% similar to that verified for the Negro River basin. With the exception of E. wrzesniowskii, all species herein listed from the Branco River basin were also listed from the Negro River basin, considering that the record of Palaemonetes carteri in Magalhães and Pereira (2007) currently refers to P. yuna (see Carvalho et al 2014).…”

“…Four species of the genus Palaemon occur in the Amazon basin (Carvalho et al 2014). According to these authors, the lineage occurring in the Negro River basin is P. yuna, whose distribution was herein extended into the Branco River basin (Fig.…”

“…However, in a study on the morphological and molecular differentiation of two species of Palaemon from the Amazon basin, Carvalho et al (2014) concluded that the populations distributed in the Negro River basin were distinct and described a new species, Palaemon yuna, from this basin. The records presented herein indicate that the distribution of this species also encompasses the Branco River basin.…”

“…P2 similar in shape and size, overreaching scaphocerite with approximately half of the distal part of carpus. (Carvalho et al 2014; this study). The distribution in Roraima is depicted in Figure 11.…”