Abstract Thoe Bell, 1836 is amphi-American in distribution and includes small spider crabs with cryptic habits and rare records in the literature and carcinological collections. The taxonomy of the three recent and two fossil species currently known in the genus has been revised. A phylogenetic reconstruction conducted here based on the mitochondrial markers COI and 16S rRNA supports the monophyletic status of Thoe. The resulting phylogeny suggests a western Atlantic to eastern Pacific radiation of the genus.

Abstract Gonopods are phylogenetically important morphological characters, and in several cases providing diagnostic characters to support taxonomic and phylogenetic studies. Relatively few studies, however, have emphasized in-depth descriptions of gonopods, and the functional morphology of these structures are poorly understood. We use SEM to describe and illustrate the two pairs of gonopods (G1 and G2) of nine species of Mithracidae (Majoidea) and of Macrocoeloma trispinosum Latreille, 1825, recently relocated to Epialtidae (Majoidea). The G1 was found to present the typical characteristics of Majoidea: long, with a mesial suture, setae inserted from the base to the distal second third and sensilla in the apical plate; the G2 is always short and conical. The apical region of the G1 was diagnostic for the species analyzed, which could provide important characters for differentiating among the majoids; and also for studying the functional, reproductive, and phylogenetic significance of these structures.

Abstract 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 comprises several lakes, coastal lagoons, and the delta of the Parnaíba River. In total, we found five species: Macrobrachium acanthurus (Wiegmann, 1836), Macrobrachium amazonicum (Heller, 1862), Macrobrachium carcinus (Linnaeus, 1758), Macrobrachium jelskii (Miers, 1877), and Macrobrachium olfersii (Wiegmann, 1836) all of which are new records for the region.