Two new species of Geosesarma De Man, 1892 (Crustacea: Brachyura: Sesarmidae) from Palawan, the Philippines

Two new and relatively large species of semi-terrestrial sesarmid crabs of the genus Geosesarma De Man, 1892, are described from Palawan Island, Philippines. They are distinguishable from congeners by the characteristic structure of their carapace, chelipeds, ambulatory legs and male first gonopods. Aspects of their ecology are briefly discusse

Description of a new genus and species of Pseudothelphusidae Ortmann, 1893 (Decapoda: Brachyura) from Panama, and new records and remarks on the zoogeography of Trichodactylus quinquedentatus Rathbun, 1893 (Trichodactylidae) in Central America

A collection of freshwater crabs from Central America resulted in the description of a new genus and two new species of pseudothelphusid crabs from Panama, and the record of the trichodactylid Trichodactylus quinquedentatus Rathbun, 1893 from Honduras and Panama. A new monotypic genus, Emberacarcinus n. gen., is erected to accommodate Potamocarcinus darienensis Magalhães, Campos & Turkay, 2013. The two new species and can be distinguished from their respective congeners by the structures of the male first gonopods: Ptychophallus bilobatus n. sp. has a bilobed mesial process whereas Potamocarcinus tapirrhynchus n. sp. exhibits a mesial process as a stout, rounded projection obliquely directed apical-cephalically and partially fused to the mesial lobe of the apical crest. The taxonomic affinities of both species with their closest congeners are treated, and the zoogeographic implication of the new records of T. quinquedentatus in Central America is discussed. © The Author(s) 2019

Geometric morphometric analysis in female freshwater crabs of Sarawak (Borneo) permits addressing taxonomy-related problems

The taxonomy of freshwater crabs requires a paradigm change in methodological approaches, particularly in investigations that use morphological techniques. The traditional morphometric approach (two-dimensional measurements) tends to be inappropriate for the identification of freshwater crabs due to their variable external morphology and lack of gonopods (conventionally used for the identification of male crabs) in females. In this study, we explore the potential use of the geometric morphometric technique for identification of female freshwater crabs, and identify taxonomic key characteristics of species. The shape of the carapace could be a good characteristic for the identification of female crabs, especially when the geometric morphometric technique is used. It was observed that the shape of the carapace has an advantage over the shape of the pleon and chela because its relatively flat orientation allows more consistent and easier data preparation for geometric morphometric analysis. The geometric morphometric technique is inexpensive, relatively less time consuming to employ, and accurate. This technique is convenient when dissection to examine the gonopods is not possible, which can damage the specimen in the case of endangered or rare species. Since the technique was used herein for only two species, more compelling and extensive evidence is needed before the reliability of the method can be proven

Benchmarking global biodiversity of decapod crustaceans (Crustacea: Decapoda)

A new assessment of the global biodiversity of decapod Crustacea (to 31 December 2022) records 17,229 species in 2,550 genera and 203 families. These figures are derived from a well-curated dataset maintained on the online platform DecaNet, a subsidiary of the World Register of Marine Species (WoRMS). Distinct phases are recognised in the discovery process (as measured by species descriptions) corresponding to major historical and geopolitical time periods, with the current rate of species descriptions being more than three times higher than in the Victorian age of global exploration. Future trends are briefly explored, and it is recognised that a large number of species remain to be discovered and described

Alain Crosnier’s role in modern carcinology: exploration, international collaboration, and taxonomy

Este artículo contiene 8 páginas, 5 figuras.The French carcinologist and oceanographer Alain Crosnier (1930–2021) had a most influential role in modern carcinology. This tribute reviews his contributions to organising oceanographic expeditions; expanding collections of specimens, particularly from the deep sea; and supporting international collaboration for taxonomic investigations of the rich collections of material obtained from these expeditions. His expertise and enthusiasm also extended to the publication of the results of these investigations.Peer reviewe

The Magnitude of Global Marine Species Diversity

Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results: There are ∼226,000 eukaryotic marine species described. More species were described in the past decade (∼20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ∼170,000 synonyms, that 58,000–72,000 species are collected but not yet described, and that 482,000–741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7–1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions: Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century

A new strategy for enhancing imputation quality of rare variants from next-generation sequencing data via combining SNP and exome chip data

Background: Rare variants have gathered increasing attention as a possible alternative source of missing heritability. Since next generation sequencing technology is not yet cost-effective for large-scale genomic studies, a widely used alternative approach is imputation. However, the imputation approach may be limited by the low accuracy of the imputed rare variants. To improve imputation accuracy of rare variants, various approaches have been suggested, including increasing the sample size of the reference panel, using sequencing data from study-specific samples (i.e., specific populations), and using local reference panels by genotyping or sequencing a subset of study samples. While these approaches mainly utilize reference panels, imputation accuracy of rare variants can also be increased by using exome chips containing rare variants. The exome chip contains 250 K rare variants selected from the discovered variants of about 12,000 sequenced samples. If exome chip data are available for previously genotyped samples, the combined approach using a genotype panel of merged data, including exome chips and SNP chips, should increase the imputation accuracy of rare variants. Results: In this study, we describe a combined imputation which uses both exome chip and SNP chip data simultaneously as a genotype panel. The effectiveness and performance of the combined approach was demonstrated using a reference panel of 848 samples constructed using exome sequencing data from the T2D-GENES consortium and 5,349 sample genotype panels consisting of an exome chip and SNP chip. As a result, the combined approach increased imputation quality up to 11 %, and genomic coverage for rare variants up to 117.7 % (MAF < 1 %), compared to imputation using the SNP chip alone. Also, we investigated the systematic effect of reference panels on imputation quality using five reference panels and three genotype panels. The best performing approach was the combination of the study specific reference panel and the genotype panel of combined data. Conclusions: Our study demonstrates that combined datasets, including SNP chips and exome chips, enhances both the imputation quality and genomic coverage of rare variants

The genetic architecture of type 2 diabetes

The genetic architecture of common traits, including the number, frequency, and effect sizes of inherited variants that contribute to individual risk, has been long debated. Genome-wide association studies have identified scores of common variants associated with type 2 diabetes, but in aggregate, these explain only a fraction of heritability. To test the hypothesis that lower-frequency variants explain much of the remainder, the GoT2D and T2D-GENES consortia performed whole genome sequencing in 2,657 Europeans with and without diabetes, and exome sequencing in a total of 12,940 subjects from five ancestral groups. To increase statistical power, we expanded sample size via genotyping and imputation in a further 111,548 subjects. Variants associated with type 2 diabetes after sequencing were overwhelmingly common and most fell within regions previously identified by genome-wide association studies. Comprehensive enumeration of sequence variation is necessary to identify functional alleles that provide important clues to disease pathophysiology, but large-scale sequencing does not support a major role for lower-frequency variants in predisposition to type 2 diabetes

Actaea grimaldii, a new species of reef crab from Papua New Guinea (Crustacea, Brachyura, Xanthidae)

A new species of xanthid crab, <em>Actaea grimaldii</em>, is described from the coral reefs of Papua New Guinea. This species has a distinctive red and white coloration and is closest to <em>Actaea spinosissima </em>Borradaile, 1902, from the Indian Ocean. However, the new species can be distinguished by the arrangement of spines on the carapace, chelipeds and ambulatory legs, and the structure of the male gonopods. <em>Actaea grimaldii</em> sp. nov. has also been confused with <em>A. polyacantha</em> (Heller, 1861), but differs markedly in the carapace armature

New species of pinnotherid crabs from Southeast Asia and Papua New Guinea (Crustacea: Decapoda: Brachyura)

Ahyong, Shane T., Ng, Peter K.L. (2020): New species of pinnotherid crabs from Southeast Asia and Papua New Guinea (Crustacea: Decapoda: Brachyura). Zootaxa 4816 (3): 333-349, DOI: https://doi.org/10.11646/zootaxa.4816.3.