DOI: 10.3897/asp.83.e153079

Authors: Edvanda A. Souza-Carvalho, Célio Magalhães, Fabrício L. Carvalho, Fernando L. Mantelatto

Abstract: Abstract The generic system of the Neotropical crabs of the subfamily Trichodactylinae H. Milne Edwards, 1853 has remained quite stable over the last 30 years, but the recognition or not of the genus Mikrotrichodactylus Pretzmann, 1968 has been a matter of debate: erected as a subgenus, it was treated with generic status in Rodríguez’ classificatory system but some subsequent works considered it a junior synonym of Trichodactylus Latreille, 1828. Based on this scenario, an integrative analysis based on molecular (using two mitochondrial, 16S rRNA and COI, and one nuclear, Histone 3, genes) and morphological (using diagnostic characters traditionally used on the identification of the family) data was performed in order to clarify the phylogenetic position of the genera within Trichodactylinae. The inferred phylogeny recovered three great lineages within Trichodactylinae with high support values in both Bayesian Inference and Maximum Likelihood phylogenetic analyses, corroborated the non-monophyletic status of Trichodactylus, and confirmed the full generic status of Mikrotrichodactylus. A taxonomic rearrangement of Trichodactylinae is proposed but the positioning of “Trichodactylus” quinquedentatus Rathbun, 1893 remains doubtful and was treated herein as a taxon inquirendum et incertae sedis. This taxon seems to be closer related to Rodriguezia Bott, 1969, and Avotrichodactylus Pretzmann, 1968; however, more data are needed before additional taxonomic adjustments concerning its positioning within the subfamily is proposed. In the current proposal, Trichodactylus is composed by four species, Mikrotrichodactylus by six species, Avotrichodactylus and Rodriguezia by three each, in addition to “Trichodactylus” quinquedentatus.

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DOI: 10.3897/asp.82.e115268

Authors: Nielson Felix Caetano França, Célio Magalhães, Fernando Luis Mantelatto

Abstract: The taxonomic status of the freshwater crab Dilocarcinus septemdentatus (Herbst, 1783) is still not well established. Currently, the main issue involves synonymization with D. spinifer H. Milne Edwards, 1853, based on a variation of the angulation of the gonopod apex. These species are distributed along rivers and lakes in northern South America, with disjunct occurrences in central-west Brazil and Argentina. Due to these inconsistencies, an integrative approach was performed to elucidate these questions, with morphological (including NanoCT-Scan) and molecular analysis (Maximum Likelihood Trees, Bayesian Inference, Genetics Distance Matrix, and Haplotype Network), based on mitochondrial markers COI and 16S rRNA. Both analysis revealed and supported the existence of a species complex under the name of D. septemdentatus. Based on the results obtained, we propose the revalidation of D. spinifer, the description of a new species, and the redescription of D. septemdentatus s. str., with a neotype designation for this species. The hypothesis that this species complex originated in the Pebas System, an extensive mega wetland system that existed along the lowlands of Western Amazonia from late Oligocene to late Miocene (c. 23–11 mya) is discussed.

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DOI: 10.3897/asp.81.e111799

Authors: Hossein Ashrafi, Kristin M. Hultgren

Abstract: Abstract The alpheid snapping shrimp genus Synalpheus Spence Bate, 1888, is a prominent component of arthropod diversity found in coral reefs. Notably, Synalpheus is the only genus of marine organisms known to exhibit eusocial behavior. Although eusociality has evolved at least four times independently in Synalpheus, all described eusocial species are from the West Atlantic, with only a single study documenting possibly eusocial species from Indonesia. In 2008, during an expedition to Madagascar organized by the Florida Museum of Natural History (FLMNH), a diverse array of sponge-dwelling species was collected, including two species of Synalpheus exhibiting colonial behavior. Through detailed examination of these specimens, we have confirmed that these two species are eusocial and represent new eusocial species of Synalpheus outside of the West Atlantic. Consequently, we provide the first official documentation of eusocial species from the Western Indian Ocean and present their taxonomic descriptions and their phylogenetic relationships with other species of the genus in this study.

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DOI: 10.3897/asp.79.e70234

Authors: Lucas A. Jennings, April M. H. Blakeslee, Krista A. McCoy, Donald C. Behringer, Jamie Bojko

Abstract: Abstract This study provides a broad phylogenetic analysis for the Eubrachyura, with the inclusion of three new Panopeidae mitochondrial genomes: Eurypanopeus depressus (flatback mud crab) (15,854bp), Panopeus herbstii (Atlantic mud crab) (15,812bp) and Rhithropanopeus harrisii (Harris, or ‘white-fingered’ mud crab) (15,892bp). These new mitogenomes were analyzed alongside all available brachyuran mitochondrial genomes (n = 113), comprising 80 genera from 29 families, to provide an updated phylogenetic analysis of the infra-order Brachyura (“true crabs”). Our analyses support the subsection Potamoida within the Eubrachyura as the sister group to Thoracotremata. The family Panopeidae aligns with the family Xanthidae to form the Xanthoidea branch, which is supported by current morphological and genetic taxonomy. A unique gene arrangement termed ‘XanGO’ was identified for the panopeids and varies relative to other members of the subsection Heterotremata (within the Eubrachyura) via a transposition of the trnV gene. This gene arrangement is novel and is shared between several Xanthoidea species, including Etisus anaglyptus (hairy spooner crab), Atergatis floridus (brown egg crab), and Atergatis integerrimus (red egg crab), suggesting that it is a conserved gene arrangement within the Xanthoidea superfamily. Our study further reveals a need for taxonomic revision of some brachyuran groups, particularly the Sesarmidae. The inclusion of panopeid mitogenomes into the greater brachyuran phylogeny increases our understanding of crab evolution and higher level Eubrachyuran systematics.

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