Review of the pilumnid crab genus Lophoplax Tesch, 1918 from the western Pacific, with descriptions of two new species, and the clarification of the identity of Pseudocryptocoeloma parvus Ward, 1936 (Crustacea: Brachyura).

The taxonomy of the pilumnid crab genus Lophoplax Tesch, 1918, is discussed. Lophoplax sculpta Stimpson, 1858) is redescribed and a neotype is selected in the interests of nomenclatural stability. Two new species allied to L. sculpta are described: L. sordida n. sp. from Indonesia, and L. pannosa n. sp. from Vanuatu. Pilumnus vermiculatus A. Milne-Edwards, 1873, is here transferred to Lophoplax. The poorly known Pseudocryptocoeloma parvus Ward, 1936 (type species of Pseudocryptocoeloma Ward, 1936), known only from Australia thus far, is redescribed and figured; and Pseudocryptocoeloma symmetrinudum Edmondson, 1951 (from Samoa and Japan), is transferred to Lophoplax.

Discovery of Buea bangem Mvogo Ndongo, von Rintelen, Tomedi-Eyango & Cumberlidge, 2020 (Crustacea: Potamoidea: Potamonautidae: Liberonautinae) from Mt. Nlonako Wildlife Reserve, Cameroon.

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Identification and functional characterization of C-type lectins and crustins provide new insights into the immune response of Portunus trituberculatus.

A meticulous understanding of the immune characteristics of aquaculture animals is the basis for developing precise disease prevention and control strategies. In this study, four novel C-type lectins (PtCTL-5, PtCTL-6, PtCTL-7 and PtCTL-8) including a single carbohydrate-recognition domain (CRD), and four novel crustins (Ptcrustin-1, Ptcrustin-2, Ptcrustin-3 and Ptcrustin-4) with a single whey acidic protein (WAP) domain were identified from the swimming crab Portunus trituberculatus. Tissue distribution analysis indicated that most of the target genes were predominantly expressed in the hepatopancreas in all examined tissues, except for Ptcrustin-1 which were mainly expressed in the gills. Our results showed that the eight genes displayed various transcriptional profiles across different tissues. In hemocytes, the PtCTL-7 responded quickly to Vibrio alginolyticus and exhibited much more strongly up-regulation than other three PtCTLs. The Ptcrustin-1 rapidly responded to V. alginolyticus within 3 h in all the three tested tissues. Furthermore, recombinant proteins of PtCTL-5 and PtCTL-8 were successfully obtained, and both of them displayed bacterial binding activities toward V. alginolyticus, V. harveyi and Staphylococcus aureus, and only showed antibacterial activity against V. harveyi. These findings provided new insights into the diverse immune response of P. trituberculatus and laid theoretical foundations for the development of precise disease prevention and control strategies in P. trituberculatus farming. Moreover, the specific anti-V. harveyi activities exhibited by rPtCTL-5 and rPtCTL-8 suggested their promising application prospects for controlling diseases caused by V. harveyi.

Molecular phylogeography reveals multiple Pleistocene divergence events in estuarine crabs from the tropical West Pacific.

Due to the lack of visible barriers to gene flow, it was a long-standing assumption that marine coastal species are widely distributed, until molecular studies revealed geographically structured intraspecific genetic differentiation in many taxa. Historical events of sea level changes during glacial periods are known to have triggered sequential disjunctions and genetic divergences among populations, especially of coastal organisms. The Parasesarma bidens species complex so far includes three named plus potentially cryptic species of estuarine brachyuran crabs, distributed along East to Southeast Asia. The aim of the present study is to address phylogeography and uncover real and hidden biological diversity within this complex, by revealing the underlying genetic structure of populations and species throughout their distribution ranges from Japan to West Papua, with a comparison of mitochondrial COX1 and 16S rRNA gene sequences. Our results reveal that the P. bidens species complex consists of at least five distinct clades, resulting from four main cladogenesis events during the mid to late Pleistocene. Among those clades, P. cricotum and P. sanguimanus are recovered as monophyletic taxa. Geographically restricted endemic clades are encountered in southeastern Indonesia, Japan and China respectively, whereas the Philippines and Taiwan share two clades. As individuals of the Japanese clade can also be found in Taiwan, we provide evidence of a third lineage and the occurrence of a potential cryptic species on this island. Ocean level retreats during Pleistocene ice ages and present oceanic currents appear to be the main triggers for the divergences of the five clades that are here addressed as the P. bidens complex. Secondary range expansions converted Taiwan into the point of maximal overlap, sharing populations with Japan and the Philippines, but not with mainland China.

The influence of seasonal temperature variation on embryonic development in two species of spider crabs (Majoidea).

The aim of this study was to analyze the ecological influence of seasonal temperature variations on embryonic development in two species of Majoidea. Leurocyclus tuberculosus and Libinia spinosa. These species inhabit stable populations in the San José Gulf (42°25'41″S, 64°08'27″O, Patagonia-Argentina) in a wide depth range and seasonal temperature variations from 8 °C to 18 °C. The influence of seasonal temperatures on embryonic development was examined in ovigerous females of both species, through a bioassay in laboratory conditions at 8 °C, 14 °C, and 18 °C from gastrula to hatching. Additionally, monthly female samplings were conducted for one year, characterizing their spatial depth distribution associated with the seawater temperature in the study area and their ovigerous/non ovigerous condition. Laboratory experimental results showed that duration of incubation increased 67 % in L. tuberculosus and 55% in L. spinosa by a decline in temperature from 18 °C to 8 °C with one diapause period. The embryonic development for the 3 assayed temperatures was divided in five periods. The assayed temperatures did not affect the morphology of the embryo, and its growth during each period did not present significant differences among the different temperatures. Field analysis showed significant differences in the spatial distribution of ovigerous females which were associated to the assessed temperatures along the year. This distribution might modulate the development of embryos leading to two spawnings synchronized with the phyto- and zooplankton peaks in the San José gulf. Finally, ecological and potential impact of ocean warming in these species was also addressed.

The first zoeal stage of the yellow land crab Johngarthia lagostoma (Milne Edwards, 1837) (Decapoda: Brachyura: Gecarcinidae).

The objective of this paper is to describe and illustrate the first zoeal stage of the largest land crab of the Tropical Atlantic, Johngarthia lagostoma (Milne Edwards, 1837) (Brachyura: Gecarcinidae). A larval description of J. lagostoma was previously not available. Larvae were obtained from ovigerous females on Rocas Atoll and Fernando de Noronha Archipelago, Brazil. Twenty larvae were randomly chosen to be dissected and described in detail, while 40 others (20 larvae from each island) were measured only. The published description of the congener J. planatus (Stimpson, 1860) larvae was used for a comparison of larval morphology. Some morphological differences between the first zoeal stage of these two species were: The absence or presence of a simple shorter seta on antennule, number of the minute terminal spines on the antenna, setation of the coxal endite of the maxilla, exopod unsegmented of the first and second maxilliped, and a single mid-dorsal seta on first pleonite. These results and differences observed between these species can assist in studies on phylogenetic relationships within the Family Gecarcinidae MacLeay, 1838, as well as in the identification of the larvae of J. Lagostoma in plankton samples from the tropical Atlantic.

Pseudolitochira integra (Miers, 1884) (Crustacea: Brachyura: Pilumnidae): redescribed and illustrated from micro-ct scanning the type female.

The taxonomy of the poorly known pilumnid crab, Pseudolitochira integra (Miers, 1884), has been confused because the original description and figures of the type female have inaccuracies, and the specimen has not been examined in detail since the original publication. Consequently, numerous specimens from the Indo-West Pacific have been incorrectly assigned to P. integra, suggesting that this species is widely distributed. The type female was micro-CT scanned in order to provide video and accurate figures of this rare pilumnid. The female possesses a suite of carapace and pereopodal characters that distinctly distinguish it from other pilumnoid taxa. The species is redescribed, refigured and formally designated as the type species of Pseudolitochira Ward, 1942. The identities of the numerous specimens assigned to P. integra are discussed and the distribution of the species is restricted to the western Indian Ocean for the time being.

emOvilyra/em, a new genus of leucosiid crab (Crustacea: Decapoda: Brachyura) from the West Pacific.

The identities of two species of shallow water Southeast Asian and southern Chinese leucosiid crabs Philyra fuliginosa Targioni-Tozzetti, 1877, and P. olivacea Rathbun, 1909, are clarified; and shown to be synonyms. A new genus, Ovilyra, is established for P. fuliginosa, and it is easily distinguished from Philyra s. str. as well as allied genera by possessing an elongate carapace, a narrow and slender male pleon with somites 1 and 2 articulate, and a male first gonopod which has the distal quarter sharply bent with a well developed subdistal process.

Description of a new species of emGlassella/em Campos amp; Wicksten, 1997 from a coastal lagoon, SE Gulf of California (Crustacea, Decapoda, Pinnotheridae).

A new a species of pinnotherid crab in the eastern Pacific coasts is presented. Twenty males and 21 females of small crabs were collected from burrows, presumably from ghost shrimp (Neotrypaea spp.), in sand-mud substrata from the Santa María-La Reforma coastal lagoon, SE Gulf of California. The new species was assigned to the genus Glassella because its morphological characteristics clearly match the amended diagnosis of the genus Glassella by Palacios Theil and Felder (2020) and Felder Palacios Theil (2020), including the presence of a gonopodal plate (GP) inserted in the internal part of the male pleon, similar to that described for most of the species currently grouped into the genus Glassella. The new species is similar to G. miamiensis (McDermott, 2014) from western Atlantic, but it can be distinguished from this and the rest of the species of Glassella by differences in carapace margins and ridges, male pleon outline, and the shape of the GP.

Genetic Identification of all Four Mangrove Mud Crab Species (genus Scylla) Using Multiple Molecular Markers.

Misleading identification and subsequent publications on biological, molecular, and aquaculture data of mangrove mud crab (genus Scylla de Hann 1833) is a major concern in many countries. In this study, multiple molecular markers were used for genetic identification of all four known mud crab species under genus Scylla collected from India, Philippines, Myanmar, Malaysia and Indonesia. Internal Transcribed Spacer (ITS-1), Polymerase chain reaction (PCR)-Restriction Fragment Length Polymorphism (PCR-RFLP) and PCR-based species-specific markers were used to resolve taxonomic ambiguity. PCR-RFLP techniques using NlaIV and BsaJI restriction endonucleases were efficient to differentiate four different mud crab species under genus Scylla with specific fragment profile. The results also justified the use of ITS-1 and PCR-based species-specific markers to identify mud crab species available in many countries quite rapidly and effectively. Several new molecular markers generated during the study are reported here to resolve the taxonomic ambiguity of Scylla species and the results reconfirmed that India is only having two commonly available mud crab species which was reported by the authors earlier.

The Entire Mitochondrial Genome of Macrophthalmus abbreviatus Reveals Insights into the Phylogeny and Gene Rearrangements of Brachyura.

Brachyuran crabs comprise the most species-rich clades among extant Decapoda and are divided into several major superfamilies. However, the phylogeny of Brachyuran remains controversial, comprehensive analysis of the overall phylogeny is still lacking. Complete mitochondrial genome (mitogenome) can indicate phylogenetic relationships, as well as useful information for gene rearrangement mechanisms and molecular evolution. In this study, we firstly sequenced and annotated the complete mitogenome of Macrophthalmus abbreviatus (Brachyura; Macrophthalmidae). The mitogenome length of M. abbreviatus is 16,322 bp, containing the entire set of 37 genes and a control region typically observed in Brachyuran mitogenomes. The genome composition of M. abbreviatus was highly A+T biased 76.3% showing positive AT-skew (0.033) and negative GC-skew (- 0.351). In M. abbreviatus mitogenome, most tRNA genes were folded into the clover-leaf secondary structure except trnH, trnS1 and trnC, which was similar to the other species in Macrophthalmidae. Phylogenetic analysis showed that all families form a monophyletic, and Varunidae and Macrophthalmidae clustered into a monophyletic clade as sister groups. Comparative analyses of rearrangement among Brachyura revealed that Varunidae (Grapsoidea) and Macrophthalmidae (Ocypodoidea) had the same gene order, which reinforced the result of phylogeny. The combined results of two aspects revealed that the polyphyly of Ocypodoidea and Grapsoidea were well supported. In general, the results obtained in this research will contribute to further studies on molecular based for the classification and gene rearrangements of Macrophthalmidae or even Brachyura.

The complete mitochondrial genome of the sand bubbler crab Scopimera globosa and its phylogenetic position.

The mitochondrial genome has become commonly used for the molecular phylogenetic analysis of animals. Most phylogenetic studies on brachyurans using mitogenome sequences have indicated the paraphyly of superfamilies Grapsoidea and Ocypodoidea but taxon sampling remains limited. The phylogenetic position of Scopimera has been tested in several previous studies using nuclear and/or mitochondrial DNA sequences, but the phylogenetic relationship within the family remains to be resolved. We newly sequenced the complete mitochondrial genome of the sand bubbler crab Scopimera globosa (Ocypodoidea: Dotillidae). Scopimera globosa was clustered with Ilyoplax despite the morphological similarity between Scopimera and Dotilla. The mitochondrial gene order of S. globosa was unique, whereas that of other genera in the family was the same. These results suggest that phylogenetic analysis based on mitogenome sequences and gene order comparison would provide a more robust phylogeny of Dotillidae.

The complete mitochondrial genome of the red-jointed brackish-water fiddler crab Minuca minax (LeConte 1855) (Brachyura: Ocypodidae): New family gene order, and purifying selection and phylogenetic informativeness of protein coding genes.

Minuca minax is a semi-terrestrial crustacean that commonly lives in low salinity, riverine habitats along the shores of the eastern United States. This study reports, for the first time, the complete mitochondrial genome of M. minax. The AT-rich mitochondrial genome of M. minax is 15,937 bp in length and comprised of 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, and 22 transfer RNA genes. A single 737 bp long intergenic space is assumed to be the D-loop. Most of the PCGs and tRNA genes are encoded in the L-strand. The gene order observed in the mitochondrial genome of M. minax is new although almost identical to that reported in confamiliar species. In all other confamiliar species to which M. minax is compared, the positions of the trnQ gene and the trnI gene are switched. KA/KS ratios calculated for all mitochondrial PCGs show values of <1, indicating that these PCGs are evolving under purifying selection. A maximum likelihood phylogenetic analysis (concatenated PCGs [n = 13], 15 species) supports the monophyly of the subfamilies Ocypodinae and Gelaminidae. Mitochondrial PCGs have enough phylogenetic information to reveal relationships supporting higher taxonomic levels within this family. The knowledge of a complete mitochondrial genome from the red-jointed brackish-water fiddler crab M. minax contributes to the better understanding of meta-population connectivity and the mechanisms involved in the adaptation of marine organisms to near-limnic conditions.

Phylogenetic relationships of Grapsoidea and insights into the higher phylogeny of Brachyuran.

Decapoda is one of the most diverse crustacean orders, and has become an important research subject. However, the phylogenetic relationships among the main lineages of Decapoda remain uncertain, especially in the order Brachyura. Herein, we sequenced the whole mitochondrial genome of V. litterata and constructed a phylogenetic tree to understand its phylogenetic relationships with other species. The results showed that the mitochondrial genome of V. litterata was generally similar to mitogenomes of Metazoa reported in the literature, with a size of 16,247 bp, 37 genes, and a control region. Both AT-skew and GC-skew were negative, indicating more abundant Cs and Ts than Gs and As. The gene arrangement of V. litterata is identical to those of Eriocheir hepuensis, Cyclograpsus granulosus, Hemigrapsus sanguineus, Helicana wuana, and Helice tientsinensis but differs from the pancrustacean ground pattern and typical arrangement of Brachyuran crabs. Phylogenetic reconstruction showed that V. litterata belongs to the Varunidae.

Male reproductive strategies in two species of spider crabs, Leurocyclus tuberculosus and Libinia spinosa.

Reproductive strategies vary according to season length, individual reproductive traits, and factors associated with the social context such as density and sex ratio of the individuals. The social context predicts the intensity of sexual selection due to its effect on mate choice and intra-sexual competition. Moreover, it exacerbates the costs derived from sexual conflict and allows for the existence of alternative reproductive tactics to counteract such costs. However, these mechanisms are still underexplored in many animal taxa. Majoidea "spider crabs" show a diversity of life history, and behavioral and morphological adaptations for reproduction, which have evolved as an outcome of competition to maximize reproductive success. We aimed to analyze in this study, male reproductive strategies through mating behavior under different social contexts, density of individuals, and males size differences in two species of "spider crabs", Leurocyclus tuberculosus and Libinia spinosa. The experiments were as follows: one female and one male per aquarium (Experiment 1); a female and three males of similar sizes per aquarium (Experiment 2); and a female and three males of distinct sizes per aquarium (Experiment 3). The experiments showed that mating behavior and duration of mate guarding differ between species and among different social contexts. The presence of males with similar or different sizes showed a relevant different behavior, the female copulated with more than one male when males were similar in size (E2), and copulated only with the largest male when males were different in size (E3). In mate guarding, the shape and the use of the chelipeds had an important role: the male of Leurocyclus tuberculosus grasped the female with the chelipeds and did not fight with other males, but the male of Libinia spinosa surrounded the female with the chelipeds and fought with other males. The longest duration of mate guarding was during precopulatory guarding. Precopulatory guarding was present in all the experiments and its duration did not present significant differences among the experiments. However, in both species, the experiments differ in the duration of postcopulatory guarding until spawning. Gonopod morphology revealed important differences between species and are probably associated with sperm competition. The experiments under distinct social contexts linked to the use and shape of the chelipeds and the morphology of the gonopods, could allow to understand the functional significance of the different reproductive strategies.

Eocarcinus praecursor Withers, 1932 (Malacostraca, Decapoda, Meiura) is a stem group brachyuran.

Beginning with the description by Withers in 1932, Eocarcinus praecursor from the Jurassic has long been considered the oldest representative of the Brachyura. In 2010 Feldmann and Schweitzer re-investigated the specimens of E. praecursor and expressed doubts about the brachyuran nature of this species. Among other characters, the suspected existence of small chelae in the 2nd or 3rd pereopods led them to the conclusion that E. praecursor must be removed from the Brachyura and rather be seen as a representative of the Anomala. However, Anomala also do not possess chelae on the 2nd and 3rd pereopods. This contradiction and other aspects initiated a new investigation of E. praecursor. It can be shown that neither the 2nd nor the 3rd pereopods of E. praecursor are chelate. Furthermore, there are no other derived characters shared with anomalans. By contrast, there are a number of apomorphies shared with Brachyura such as the shape and articulation of the large chelae and the attachment points of the last two pereopods. However, not all apomorphies of the crown group are present yet. Thus, E. praecursor is a stem group representative, which allows statements about individual steps in the evolution of the set of characters of the crown group Brachyura.

Characterization of the complete mitochondrial genome of Helice latimera and its phylogenetic implications in Brachyura.

Mitochondrial genomes (mitogenomes) help advance our learning of molecular evolution and phylogenetic relationships. The mitogenome of H. latimera is 16,246 bp in length, which typically contains 37 animal mitogenome genes consisting of 13 protein-coding genes (PCGs), two rRNA genes, and 22 tRNA genes, as well as a control region. The AT content of H. latimera is 69.1%. The A + T skew of the mitogenome of H. latimera was slightly negative (-0.017). The size of Thirteen PCGs is from 162 bp to 1731 bp. Twenty-two tRNA genes ranged from 62 to 73 bp and were highly A + T biased. All tRNA genes owed a typical cloverleaf structure, not including the trnS1 gene lacking a dihydroxyuridine arm. One PCG, two rRNAs, and 12 of the tRNAs were rearranged compared to the pancrustacean gene order. Phylogenetic analysis revealed the locationt of H. latimera among the Varunidae family.

Gene rearrangements in the mitochondrial genome of Chiromantes eulimene (Brachyura: Sesarmidae) and phylogenetic implications for Brachyura.

Complete mitochondrial genome (mitogenome) provides important information for better understanding of gene rearrangement, molecular evolution and phylogenetic analysis. Here we determined the complete mitogenome sequence of Chiromantes eulimene (Brachyura: Sesarmidae) for the first time. The total length is 15,894 bp and includes 13 protein-coding genes (PCGs), 22 transfer RNAs, two ribosomal RNAs, as well as a putative control region. The genome composition is highly A + T biased (75.5%), and exhibits a negative AT-skew (-0.017) and GC-skew (-0.206). All of the 13 PCGs are initiated by the start codon ATN, with an exception (GTG) in ND1. The typical stop codon (TAA or TAG) is detected in ten PCGs, whereas the remaining three PCGs (COI, COII and Cyt b) terminate by an incomplete T. The gene order in C. eulimene mitogenome was rearranged compared with that of the ancestor of Decapoda. The gene order of F-ND5-H changed to H-F-ND5. Like other sesarmid crabs, the I-Q-M gene cluster in the pancrustacean ground pattern became Q-I-M order in C. eulimene genome. Tandem duplication-random loss model and slipped-strand mispairing mechanism are determined as most likely to explain the observed gene rearrangements. Phylogenetic analysis places all Sesarmidae species into one group. Almost all families except Xanthidae, Gecarcinidae and Homolidae form a monophyletic clade and the polyphyly of Eriphioidea, Ocypodoidea and Grapsoidea is well supported. These results will help to better understand the gene rearrangements and evolutionary position of C. eulimene and lay a foundation for further phylogenetic studies of Brachyura.

Characterizing coral reef biodiversity: genetic species delimitation in brachyuran crabs of Palmyra Atoll, Central Pacific.

Coral reefs are highly threatened ecosystems, yet there are numerous challenges in conducting inventories of their vanishing biodiversity, partly because many taxa remain difficult to detect and describe. Genetic species delimitation methods provide a standardized means for taxonomic classification including of cryptic, rare, or elusive groups, but results can vary by analytical method and genetic marker. In this study, a combination of morphological and genetic identification methods was used to estimate species richness and identify taxonomic units in true crabs (Infraorder Brachyura; n = 200) from coral reefs of Palmyra Atoll, Central Pacific. Genetic identification was based on matches between mitochondrial 16S ribosomal RNA (16S rRNA) and/or cytochrome c oxidase subunit I (COI) sequences to GenBank data, while morphological work relied on the taxonomic literature. Broad agreement in the number of candidate species delimited by genetic distance thresholds and tree-based approaches was found, although the multi-rate Poisson tree process (mPTP) was less appropriate for this dataset. The COI sequence data identified 30-32 provisional species and the 16S data revealed 34-35. The occurrence of 10 families, 20 genera, and 19 species of brachyurans at Palmyra was corroborated by at least two methods. Diversity levels within Chlorodiella laevissima indicated possible undescribed or cryptic species in currently lumped taxa. These results illustrate the efficacy of DNA sequences in identifying organisms and detecting cryptic variation, and underscore the importance of using appropriate genetic markers and multiple species delimitation analyses, with applications for future species descriptions.