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This checklist is the fifth and last compilation on the decapod crustaceans reported to So Paulo (Brazil) coastal area, resulting from long-term multidisciplinary projects, which combined morphological analyses and molecular techniques. The current research includes 75 decapod species, herein referred as shrimps/lobsters-like (shrimps, ghost-shrimps, lobsters, and related groups), reported to So Paulo coastal area. These species occur in marine, estuarine, and amphidromous habitats and are classified into 21 families as follow: Aristeidae (2 spp., 2 genera), Atyidae (4 spp., 2 genera), Axianassidae (1 sp., 1 genus), Callianassidae (1 sp., 1 genus), Callichiridae (6 spp., 4 genera), Crangonidae (1 sp., 1 genus), Glyphocrangonidae (1 sp., 1 genus), Luciferidae (2 spp., 2 genera), Nephropidae (4 spp., 2 genera), Palaemonidae (15 spp., 9 genera), Palinuridae (2 spp., 1 genus), Pandalidae (1 sp., 1 genus), Pasiphaeidae (1 sp., 1 genus), Penaeidae (10 spp., 6 genera), Sergestidae (3 spp., 3 genera), Sicyoniidae (4 spp., 1 genus), Scyllaridae (5 spp., 3 genera), Solenoceridae (4 spp., 3 genera), Stenopodidae (2 spp., 1 genus), and Upogebiidae (6 spp., 1 genus). We generated new sequences of cytochrome oxidase subunit I (barcode region) and 16S genes (51 and 54, respectively) of 54 species. Our examination concluded that 75 shrimps/lobsters-like species are reported to the So Paulo coast. We excluded Leander tenuicornis (Palaemonidae), Penaeus setiferus (Penaeidae), Philocheras gorei (Crangonidae), and Rhynchocinetes typus (Rhynchocinetidae) from this list.

A freshwater palaemonid shrimp from the São Francisco river basin in Brazil has been found to be a new species and is herein nominated as Macrobrachium veredensis sp. nov. It is morphologically similar to M. brasiliense (Heller, 1862), which is found in many rivers of South America. However, M. veredensis sp. nov. has a smooth carapace and few spinules on the second pereopods, while M. brasiliense has the anterolateral surface of the carapace with small spinules and the palm of the second pereopods with spines, spinules and setae. Despite their similar morphology with these subtle differences, the remarkable genetic different evidenced in DNA analysis. Molecular analyses were based on 43 sequences with 528 base pairs (bp) for 16S rDNA, and 16 new sequences with 581bp, without pseudogenes, for COI mtDNA. The nucleotide divergence between M. veredensis sp. nov. and M. brasiliense (7.0-8.5% for 16S and 11.8-12.5% for COI.), the phylogenetic topology and the haplotype network configuration and it is endemism to a region of the São Francisco river basin support the recognition of a new taxon.

DNA barcoding has emerged as an efficient tool for taxonomy and other biodiversity fields. The vast and speciose group of decapod crustaceans is not an exception in the current scenario and comparing short DNA fragments has enabled researchers to overcome some taxonomic impediments to help broadening knowledge on the diversity of this group of crustaceans. Brazil is considered as an important area in terms of global marine biodiversity and some regions stand out in terms of decapod fauna, such as the São Paulo coastline. Thus, the aim of this study is to obtain sequences of the mitochondrial markers (COI and 16S) for decapod crustaceans distributed at the São Paulo coastline and to test the accuracy of these markers for species identification from this region by comparing our sequences to those already present in the GenBank database. We sampled along almost the 300 km of the São Paulo coastline from estuaries to offshore islands during the development of a multidisciplinary research project that took place for 5 years. All the species were processed to obtain the DNA sequences. The diversity of the decapod fauna on the São Paulo coastline comprises at least 404 species. We were able to collect 256 of those species and sequence of at least one of the target genes from 221. By testing the accuracy of these two DNA markers as a tool for identification, we were able to check our own identifications, including new records in GenBank, spot potential mistakes in GenBank, and detect potential new species.

Macrobrachium olfersii is an amphidromous freshwater prawn, widespread along the eastern coasts of the Americas. This species shows great morphological modifications during ontogenesis, and several studies have verified the existence of a wide intraspecific variation. Because of this condition, the species is often misidentified, and several synonyms have been documented. To elucidate these aspects, individuals of M. olfersii from different populations along its range of distribution were investigated. The taxonomic limit was established, and the degree of genetic variability of this species was described. We extracted DNA from 53 specimens of M. olfersii, M. americanum, M. digueti and M. faustinum, which resulted in 84 new sequences (22 of 16S mtDNA, 45 of Cythocrome Oxidase I (COI) mtDNA, and 17 of Histone (H3) nDNA). Sequences of three genes (single and concatenated) from these species were used in the Maximum Likelihood and Bayesian Inference phylogenetic analyses and COI sequences from M. olfersii were used in population analysis. The genetic variation was evaluated through the alignment of 554 bp from the 16S, 638 bp from the COI, and 338 bp from the H3. The rates of genetic divergence among populations were lower at the intraspecific level. This was confirmed by the haplotype net, which showed a continuous gene flow among populations. Although a wide distribution and high morphological intraspecific variation often suggest the existence of more than one species, genetic similarity of Caribbean and Brazilian populations of M. olfersii supported them as a single species.