The tale of an endemic shrimp's exceptional osmoregulation and the ancient Athalassic mangrove oasis

The hyperarid mangrove in the Middle East is characterised by the absence of rivers or freshwater inputs and is one of the most extreme settings of this ecosystem on Earth. Endemic to Qatar's hyperarid mangroves, a Palaemon shrimp is uniquely confined to a sole mangrove site in the Arabian Gulf. Within these mangrove channels, we unveiled brine groundwater sources exceeding 70 ppt salinity, contrasting the local marine standard of 42 ppt. Concurrently, a mysid species typically linked to salt pans and groundwater coexists. Stable isotopic analysis implied the existence of a predator-prey dynamic between this mysid species and the studied shrimp. Then, investigating the endemic shrimp's adaptation to extreme salinity, we conducted osmolarity experiments and phylogenetic studies. Our findings demonstrate that this shrimp transitions from hypo- to hyper-osmoregulation, tolerating salinities from 18 to 68 ppt-an unprecedented osmoregulatory capacity among caridean shrimps. This speciation pattern likely arises from the species osmolarity adaptation, as suggested for other Palaemon congeners. Phylogenetic analysis of the studied Palaemon, along with the mangrove's geological history, suggests a profound evolutionary interplay between the ecosystem and the shrimp since the Eocene. This study proposes the hyperarid mangrove enclave as an Athalassic mangrove oasis-a distinctive, isolated ecosystem within the desert landscape.

Molecular evidence and differences in gonopod morphology lead to the recognition of a new species of the freshwater crab genus Candidiopotamon Bott, 1967 (Crustacea, Brachyura, Potamidae) from eastern Taiwan

A new freshwater crab of the potamid genus Candidiopotamon Bott, 1967, is described from eastern Taiwan. Candidiopotamonpenglai sp. nov. is morphologically similar to C.rathbuni (De Man, 1914) from western Taiwan, but can be distinguished by the morphology of the male first gonopod (G1), as well as by their mitochondrial DNA (16S rRNA and COI genes). In the G1 of C.rathbuni, the subterminal segment shows a cline from robust in northern populations to slender in southern populations. In the G1 of C.penglaisp. nov., a distinctly larger and more distally directed keel-like projection is found on the distal inner edge of the terminal segment, with northern populations having an inward-curving subterminal segment and southern populations a straight subterminal segment. The genetic differentiation of the two species of Candidiopotamon within Taiwan is discussed, and morphological differences are compared. A key to the species of Candidiopotamon is also provided.

Phylogenetic evidence and morphological diagnosis for a new species of Parasesarma De Man, 1895 (Decapoda, Brachyura, Sesarmidae) from Sulawesi, Indonesia

A new species of Parasesarma, P. rahayuae n. sp., is described from Sulawesi, Indonesia. Genetically, the new species is distinct from all other known species of Parasesarma and has a close phylogenetic relationship with P. anambas Yeo, Rahayu & Ng, 2004 and P. gemmatum Li, Shih & Ng, 2019. Morphologically, the new species most closely resembles P. anambas and P. gemmatum, but can be distinguished from these two species by the shape of the dactylar tubercles of the male chela and of the male first gonopod. This is the fourth species of Parasesarma recorded from Sulawesi, and with its description, the number of species assigned to the genus Parasesarma is 58.

Molecular phylogeny of Thoracotremata crabs (Decapoda, Brachyura): toward adopting monophyletic superfamilies, invasion history into terrestrial habitats and multiple origins of symbiosis

The Thoracotremata is a large and successful group of "true" crabs (Decapoda, Brachyura, Eubrachyura) with a great diversity of lifestyles and well-known intertidal representatives. The group represents the largest brachyuran radiation into terrestrial and semi-terrestrial environments and comprises multiple lineages of obligate symbiotic species. In consequence, they exhibit very diverse physiological and morphological adaptations. Our understanding of their evolution is, however, largely obscured by their confused classification. Here, we resolve interfamilial relationships of Thoracotremata, using 10 molecular markers and exemplars from all nominal families in order to reconstruct the pathways of lifestyle transition and to propose a new taxonomy corresponding to phylogenetic relationships. The results confirm the polyphyly of three superfamilies as currently defined (Grapsoidea, Ocypodoidea and Pinnotheroidea). At the family level, Dotillidae, Macrophthalmidae, and Varunidae are not monophyletic. Ancestral state reconstruction analyses and divergent time estimations indicate that the common ancestor of thoracotremes already thrived in intertidal environments in the Late Cretaceous and terrestrialization became a major driver of thoracotreme diversification. Multiple semi-terrestrial and terrestrial lineages originated and radiated in the Early Eocene, coinciding with the global warming event at the Paleocene-Eocene Thermal Maximum (PETM). Secondary invasions into subtidal regions and colonizations of freshwater habitats occurred independently through multiple semi-terrestrial and terrestrial lineages. Obligate symbiosis between thoracotremes and other marine macro-invertebrates evolved at least twice. On the basis of the current molecular phylogenetic hypothesis, it will be necessary in the future to revise and recognize seven monophyletic superfamilies and revisit the morphological character states which define them.

Characterization of The Complete Mitochondrial Genome of the Bromeliad Crab Metopaulias depressus (Rathbun, 1896) (Crustacea: Decapoda: Brachyura: Sesarmidae)

Metopaulias depressus is a non-marine crab endemic to Jamaica that dwells in rainforest bromeliads and exhibits elaborate active parental care behavior. Current genomic resources on M. depressus are rare, limiting the understanding of its adaptation to terrestrial life in species that evolved from marine ancestors. This study reports the complete mitochondrial genome of M. depressus assembled using Sanger sequencing. The AT-rich mitochondrial genome of M. depressus is 15,765 bp in length and comprises 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, and 22 transfer RNA genes. A single 691 bp-long intergenic space is assumed to be the control region (CR) or D-loop. A set of selective pressure analyses indicate that the entirety of the PCGs experience purifying selection. Cox1, cox2, nad5, cox3, and atp6 experience strong purifying selection, and atp8 experiences weak purifying selection compared to the rest of the PCGs. The secondary structures of most tRNA genes exhibit a standard ‘cloverleaf’ structure, with the exception of trnS1, which lacks the dihydroxyuridine (DHU) arm but not the loop, the trnH gene, which lacks the thymine pseudouracil cytosine (T) loop but not the arm, and trnM, which exhibits an overly developed T loop. A maximum likelihood phylogenetic analysis based on all PCGs indicated that M. depressus is more closely related to the genera Clistocoeloma, Nanosesarma, and Parasesarma than to Chiromantes, Geosesarma, and Orisarma. This study contributes to deciphering the phylogenetic relationships within the family Sesarmidae and represents a new genomic resource for this iconic crab species.

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.

Redescription of the hermit crab Diogenes pugilator (Decapoda: Anomura) reveals the existence of a species complex in the Atlanto-Mediterranean transition zone, resulting in the resurrection of D. curvimanus and the description of a new species

Examination of material from the coasts of the Iberian Peninsula and nearby areas has revealed that more than one species is mixed under the name for the common diogenid hermit crab, Diogenes pugilator. In this study, three species are recognized, primarily on the basis of a combination of morphological characters and live colour patterns. Diogenes pugilator is redescribed on the basis of a neotype selected from near the supposed type locality, as well as specimens from other localities. Diogenes curvimanus is resurrected and the name attributed to a second species, whereas a third morphotype is described as a new species, Diogenes armatus sp. nov.. The last two species are also fully described and differentiating characters among the three species are discussed. Newly generated sequences from two mitochondrial genes and one nuclear gene, and comparative analyses with other available DNA sequences for the genus, are also included. The corresponding molecular phylogenies support the recognition of the three species and suggest the presence of additional unknown species in the D. pugilator species complex. All previous records of D. pugilator should be revised in the light of these new findings. Finally, a comprehensive identification key to the eastern Atlantic and western Mediterranean species of Diogenes is also provided.

Discovery of two new populations of the rare endemic freshwater crab Louisea yabassi Mvogo Ndongo, von Rintelen & Cumberlidge, 2019 (Brachyura: Potamonautidae) from the Ebo Forest near Yabassi in Cameroon, Central Africa, with recommendations for conservation action

The endemic freshwater crab, Louisea yabassi Mvogo Ndongo, von Rintelen & Cumberlidge, 2019, is currently only known from three populations in the biodiversity-rich rainforests of southwestern Cameroon.  The first record of L. yabassi dates back to 1908 from Yabassi, while the other two populations were discovered in December 2019 and March 2020 from the Ebo Forest near Yabassi.  These specimens were initially identified as L. edeaensis (Bott, 1969), but were subsequently assigned to L. yabassi.  The newly-discovered populations of L. yabassi provided important data on its habitat, population structure and geographical distribution, all critical knowledge for conservation measures.  Reported here are the anthropogenic threats to L. yabassi and its rainforest habitat, which include forest destruction, agricultural encroachment, water pollution and firewood collection.  This information is inherently useful in the assessment of the extinction risk of L. yabassi and highlights the importance of implementing strategies for preserving primary rainforest and its associated aquatic habitats in Central Africa.

Conspicuous genetic similarity within a widely distributed and newly described species of Parasesarma De Man, 1895 from Western Pacific oceanic islands, with notes on the allied P. calypso group (Crustacea : Brachyura : Sesarmidae)

Some brachyuran crab species of the Western Pacific appear to be widespread throughout the region and distributed across a large geographic area, without obvious phylogeographic structuring. In the present study, we describe a new species of Parasesarma that appears to be restricted to Western Pacific islands (so far Guam, Palau, Vanuatu, Fiji, Wallis and New Caledonia). Comparisons of partial sequences of the COX1 gene show that individuals of this species, though from relatively isolated and widely separated islands, are monophyletic and, surprisingly, genetically uniform. These results give credence to the hypothesis that these oceanic islands serve as ‘stepping stones’ for the current-mediated dispersal and genetic homogenisation of coastal–littoral marine species. Morphologically, the new species differs most significantly from similar congeners in the tuberculation pattern of the chelar dactyli, whereas genetically it is markedly divergent from other morphologically similar species of Parasesarma, with a minimum COX1 p-distance of 6.9%. With such evidence, the new species is here formally described as Parasesarma daviei sp. nov. It is the fifth species of Parasesarma reported from oceanic islands of the Western Pacific. Compared to other congeners, P. daviei sp. nov. shows a close relationship with a clade including P. calypso. Therefore, P. calypso (De Man, 1895), and three of its former subspecies or varieties were subjected to a closer examination and are here rediagnosed and illustrated. In consequence, we suggest full species status for P. kuekenthali (De Man, 1902), P. lanchesteri (Tweedie, 1936), and P. ellenae (Pretzmann, 1968).

Taxonomic reassessment of Parasesarma (Crustacea: Brachyura: Decapoda: Sesarmidae) based on genetic and morphological comparisons, with the description of a new genus

Parasesarma is a species-rich genus whose representatives are common in wetlands and mangroves of the Indo-Pacific. Morphologically, the genus is heterogeneous and has been postulated to constitute a polyphyletic taxon. In the present study, most species of Parasesarma are re-evaluated phylogenetically, using mitochondrial and nuclear molecular markers. The results show that the majority of the examined species cluster consistently with the type species Parasesarma plicatum. However, some species, among them the tree-climbing Parasesarma leptosoma, are clearly separated from this main clade of Parasesarma, forming a second stable monophyletic group, distinct from other known genera. Based on these results, and with additional support by morphological diagnoses highlighting consistent differences between the two species groups, we propose a new genus for the species clustering around P. leptosoma, proposing the new name Leptarma gen. nov.

Phylogeographic and evolutionary history analyses of the warty crab Eriphia verrucosa (Decapoda, Brachyura, Eriphiidae) unveil genetic imprints of a late Pleistocene vicariant event across the Gibraltar Strait, erased by postglacial expansion and admixture among refugial lineages

Background

The Pleistocene cyclic sea-level fluctuations are thought to have markedly affected the distribution and genetic architecture of Atlanto-Mediterranean biota. Despite the acknowledged key role played by these historical events in shaping population genetic structure of marine species, little is still known about the processes involved in shaping the spatial distribution of genetic variation within intertidal species. We intended in this study to reconstruct the phylogeography of a common and widely distributed coastal species across the East Atlantic and Mediterranean Sea (the warty crab Eriphia verrucosa), aiming to unravel potential microevolutionary processes likely involved in shaping its genetic polymorphism. For this purpose, a total of 155 specimens of E. verrucosa from 35 locations across the entire distribution range were analyzed by comparing a 453 basepairs region of the mitochondrial gene cytochrome oxidase subunit 1 (Cox1).

Results

Our results unveiled the prevalence of high genetic connectivity among East Atlantic and Mediterranean populations, with noticeable genetic distinctiveness of the peripheral population from the Azores. Spatio-temporal patterns of genetic diversification and demographic history allowed retrieving genetic imprints of late Pleistocene vicariant event across the Gibraltar Strait followed by subsequent postglacial expansion events for both the East Atlantic and Mediterranean regions. Integrative evidences from the outcomes of comparison of regional genetic diversification, as well as evolutionary and biogeographic histories reconstructions, support the existence of potential glacial refugia for E. verrucosa in the East Atlantic and western Mediterranean. Our results also revealed low levels of genetic variability along with recent demographic and spatial expansion events for eastern Mediterranean warty crabs, suggesting that the eastern areas within the distribution range of the species might have been recently colonized from putative glacial refugia.

Conclusions

These findings provide new insights into the phylogeography and evolutionary history of a common but poorly studied Atlanto-Mediterranean decapod species. Specifically, they contribute to the understanding of the impact of historical processes on shaping contemporary population genetic structure and diversity in intertidal marine species.

Electronic supplementary material

The online version of this article (10.1186/s12862-019-1423-2) contains supplementary material, which is available to authorized users.

Phylogeography of Potamon ibericum (Brachyura: Potamidae) identifies Quaternary glacial refugia within the Caucasus biodiversity hot spot

Refugia are critical for the maintenance of biodiversity during the periods of Quaternary climatic oscillations. The long-term persistence of refugial populations in a large continuous refugium has resulted in a homogenous pattern of genetic structure among populations, while highly structured evolutionary lineages characterize the restriction of refugial populations to smaller subrefugia. These mechanisms have resulted in the identification of hot spots of biodiversity within putative glacial refugia. We studied phylogeography of Potamon ibericum (Brachyura: Potamidae) in the drainages of the western Caucasus biodiversity hot spot (i.e., Colchis and the Caucasus) to infer spatial genetic structure and potential refugia for a freshwater crab in this region. These areas have traditionally considered as a refugium due to the presence of Tertiary relict species. We integrated population genetic data and historical demographic analysis from cytochrome oxidase subunit I sequences and paleoclimatic data from species distribution modeling (SDM). The results revealed the lack of phylogeographic structure and provided evidence for demographic expansion. The SDM presented a rather homogenous and large refugium that extended from northeast Turkey to Colchis during the last glacial period. In contrast to these findings, previous phylogeographic study on P. ibericum of the eastern Caucasus biodiversity hot spot (i.e., Hyrcania) identified multiple independent refugia. By combining these results, we explain the significance of this important western Palearctic hot spot of biological diversity in shaping the geographic distribution of intraspecific genetic diversity in a freshwater taxon.

A journey on plate tectonics sheds light on European crayfish phylogeography

Crayfish can be used as model organisms in phylogeographic and divergence time studies if reliable calibrations are available. This study presents a comprehensive investigation into the phylogeography of the European stone crayfish (Austropotamobius torrentium) and includes samples from previously unstudied sites. Two mitochondrial markers were used to reveal evolutionary relationships among haplogroups throughout the species' distributional range and to estimate the divergence time by employing both substitution rates and geological calibration methods. Our haplotype network reconstruction and phylogenetic analyses revealed the existence of a previously unknown haplogroup distributed in Romania's Apuseni Mountains. This haplogroup is closely related to others that are endemic in the Dinarides, despite their vast geographical separation (~600 km). The separation is best explained by the well-dated tectonic displacement of the Tisza-Dacia microplate, which started in the Miocene (~16 Ma) and possibly carried part of the A. torrentium population to the current location of the Apuseni Mountains. This population may thus have been isolated from the Dinarides for a period of ca. 11 m.y. by marine and lacustrine phases of the Pannonian Basin. The inclusion of this geological event as a calibration point in divergence time analyses challenges currently accepted crayfish evolutionary time frames for the region, constraining the evolution of this area's crayfish to a much earlier date. We discuss why molecular clock calibrations previously employed to date European crayfish species divergences should therefore be reconsidered.

Parapatric genetic divergence among deep evolutionary lineages in the Mediterranean green crab, Carcinus aestuarii (Brachyura, Portunoidea, Carcinidae), accounts for a sharp phylogeographic break in the Eastern Mediterranean

BACKGROUND

Recently, population genetic studies of Mediterranean marine species highlighted patterns of genetic divergence and phylogeographic breaks, due to the interplay between impacts of Pleistocene climate shifts and contemporary hydrographical barriers. These factors markedly shaped the distribution of marine organisms and their genetic makeup. The present study is part of an ongoing effort to understand the phylogeography and evolutionary history of the highly dispersive Mediterranean green crab, Carcinus aestuarii (Nardo, 1847), across the Mediterranean Sea. Recently, marked divergence between two highly separated haplogroups (genetic types I and II) of C. aestuarii was discerned across the Siculo-Tunisian Strait, suggesting an Early Pleistocene vicariant event. In order to better identify phylogeographic patterns in this species, a total of 263 individuals from 22 Mediterranean locations were analysed by comparing a 587 basepair region of the mitochondrial gene Cox1 (cytochrome oxidase subunit 1). The examined dataset is composed of both newly generated sequences (76) and previously investigated ones (187).

RESULTS

Our results unveiled the occurrence of a highly divergent haplogroup (genetic type III) in the most north-eastern part of the Mediterranean Sea. Divergence between the most distinct type III and the common ancestor of both types I and II corresponds to the Early Pleistocene and coincides with the historical episode of separation between types I and II. Our results also revealed strong genetic divergence among adjacent regions (separating the Aegean and Marmara seas from the remaining distribution zone) and confirmed a sharp phylogeographic break across the Eastern Mediterranean. The recorded parapatric genetic divergence, with the potential existence of a contact zone between both groups in the Ionian Sea and notable differences in the demographic history, suggest the likely impact of paleoclimatic events, as well as past and contemporary oceanographic processes, in shaping genetic variability of this species.

CONCLUSIONS

Our findings not only provide further evidence for the complex evolutionary history of the green crab in the Mediterranean Sea, but also stress the importance of investigating peripheral areas in the species' distribution zone in order to fully understand the distribution of genetic diversity and unravel hidden genetic units and local patterns of endemism.

[Acute dystonia in a patient with an elevated clozapine level due to an infection]

Acute dystonia is a side-effect associated with the use of antipsychotics. We describe the case of a 75-year-old patient with late-onset schizophrenia who used clozapine. During a hospital admission due to pneumonia, she developed a form of acute dystonia consisting of a rotational torticollis, which disappeared rapidly after treatment with biperiden. Blood examination showed an increase of the clozapine level, probably due to the infection. This case report shows that acute dystonia, although very rare, can occur during treatment with clozapine; therefore awareness is needed of the circumstances that can alter clozapine levels.

Molecular systematics reveals multiple lineages and cryptic speciation in the freshwater crayfish Parastacus brasiliensis (von Martens, 1869) (Crustacea : Decapoda : Parastacidae)

The characterisation of intraspecific genetic diversity in representatives of the South American crayfish genus Parastacus Huxley, 1879 is here carried out for the first time by comparing populations of Parastacus brasiliensis (von Martens, 1869) as currently defined. Phylogenetic reconstructions based on mitochondrial and nuclear markers indicate the existence of multiple lineages, of which only one can be considered as P. brasiliensis sensu stricto. In addition, there are seven other lineages, one of which is the subspecies Parastacus brasiliensis promatensis Fontoura & Conter, 2008, which is here elevated to species level. We thereby increase to 14 the number of recognised species within Parastacus in South America. Genetic distances among P. brasiliensis sensu stricto and the lineages ‘A’, ‘B’ and ‘C’ increase with geographical distances, suggesting isolation by distance as an important driver of diversification, and eventually speciation, in these burrowing crayfishes. Parastacus brasiliensis occurs mainly in the Guaíba Lake basin and studied populations show limited connectivity and gene flow, probably due to habitat fragmentation. On the basis of genetic and distribution data, the conservation status of P. brasiliensis sensu stricto is confirmed as Near Threatened (NT). These findings lead us to encourage the establishment of preservation areas for isolated populations. The importance of preserving the newly recognised distinct gene pools in order to maintain overall genetic diversity is emphasised.

Systematics and phylogeography of the Australasian mangrove crabs Parasesarma semperi and P. longicristatum (Decapoda : Brachyura : Sesarmidae) based on morphological and molecular data

Parasesarma semperi (Bürger, 1893) was first described from Bohol in the Philippines and is considered to be widely distributed in Southeast Asia. Parasesarma longicristatum (Campbell, 1967) was originally described as a subspecies of P. semperi from Queensland, Australia, and later recognised as a full species. In this study, we re-examine specimens of the two species from across their entire geographic range using genetic markers, a morphometric analysis, and traditional morphological characters. Previous taxonomic species diagnoses were found to be unreliable, but morphometric principle component analyses consistently separate the two species, with the length to width ratio of the propodus of the fourth pereiopod being of particular importance. Genetic data corresponding to the mitochondrial genes COI, ND1 and 16S confirmed a close sister relationship between the two species, forming reciprocally monophyletic groups. Both species have high haplotype diversities and high intraspecific gene flow.

Morphological and molecular evidence for a new species of freshwater crab of the genus <i>Sudanonautes</i> Bott, 1955 (Brachyura: Potamoidea: Potamonautidae) from Cameroon, with notes on its ecology

A new species of freshwater crab of the genus Sudanonautes Bott, 1955, is described from the tropical rainforests of Edea and Tiko in southern Cameroon, Central Africa. Sudanonautes tiko n. sp. is recognized by a unique combination of characters of the carapace, thoracic sternum, chelipeds, and male first gonopod, and by distinct mtDNA sequences for two loci (COI and 16S rRNA). A diagnosis, illustrations, and a tree of phylogenetic relationships based on mtDNA sequences are provided, along with a comparison to similar species from the region. Brief notes are provided on the ecology of the new species and of three other species of Sudanonautes collected during this study.

Comparative study of the morphology of the female seminal receptacles of Ilia nucleus and Persephona mediterranea (Decapoda, Brachyura, Leucosiidae)

Because of the poor knowledge of the morphology of the female reproductive organs of most brachyuran crabs, this study investigated two Atlantic representatives of the family Leucosiidae, Ilia nucleus (Linnaeus, 1758) and Persephona mediterranea (Herbst, 1794), using histological methods and magnetic resonance imaging (MRI). While the vagina conforms to the concave type, the arrangement of the two chambers of the seminal receptacle differs strongly from that of other eubrachyuran sperm storage organs. Both chambers are oriented laterally within the crab's body. This is in contrast to the dorso-ventral orientation described in most other known brachyuran crabs. The lateral chamber is covered by cuticle, whereas the medial chamber is covered by a holocrine glandular epithelium. The oviduct connection is located ventrally, posterior to the vagina. The oviduct orifice is characterized by a transition from the epithelium lining the oviduct to the seminal receptacle's holocrine glandular epithelium. Moreover, muscle fibres are attached to the oviduct orifice and to the sternal cuticle. This musculature can be interpreted as an important feature in the fertilization and egg-laying process by supporting and controlling the inflow of eggs into the seminal receptacle lumen. The results of this study are compared to the morphology of the seminal receptacle of another leucosiid crab, Ebalia tumefacta (Montagu, 1808), and to those of other known eubrachyuran crabs.

New data on the taxonomy, ecology, and conservation of the rediscovered <i>Louisea</i> <i>edeaensis</i> (Bott, 1969) (Brachyura: Potamoidea: Potamonautidae), an endangered freshwater crab from Cameroon

The rare and endangered Cameroonian potamonautid freshwater crab Louisea edeaensis (Bott, 1969) was recently rediscovered during a biological inventory of the freshwater decapods of southern Cameroon. The previous record dated back more than 100 years. The new specimens allow an updated diagnosis of the species based on comparisons of important taxonomic characters. Photographs of the carapace, gonopods, third maxillipeds, and chelipeds of the largest adult male specimen from Lake Ossa, Cameroon are provided, as are the first photographs of living specimens. The conservation implications of the new data on habitat, population structure, distribution, and threats for this rare and endangered species are discussed.

Genetic and Morphological Differentiation of the Semiterrestrial Crab Armases angustipes (Brachyura: Sesarmidae) along the Brazilian Coast

The genetic and morphometric population structures of the semiterrestrial crab Armases angustipes from along the Brazilian coast were examined. The influence of the Central South Equatorial Current on larval dispersal of A. angustipes also was evaluated. Six populations were sampled from estuarine areas in São Luis do Maranhão, Maranhão; Natal, Rio Grande do Norte; Maceió, Alagoas; Ilhéus, Bahia; Aracruz, Espírito Santo; and Guaratuba, Paraná. Patterns of genetic differentiation were assessed using DNA sequence data corresponding to parts of the mitochondrial cytochrome c oxidase subunit 1. Geometric morphometric techniques were used to evaluate morphological variation in shape and size of the carapace and right cheliped propodus. Our results revealed low genetic variability and lack of phylogeographic structure; geometric morphometrics showed statistically significant morphological differentiation and geographic structuring. Our data indicate the absence of possible barriers to gene flow for this mobile species, and no clear correlation of morphological or genetic variation with ocean currents and/or geographic distance. Our results also suggest that historical geological and climatological events and/or possible bottleneck effects influenced the current low genetic variability among the populations of A. angustipes.

Unravelling population genetic structure with mitochondrial DNA in a notional panmictic coastal crab species: sample size makes the difference

Background

The extent of genetic structure of a species is determined by the amount of current gene flow and the impact of historical and demographic factors. Most marine invertebrates have planktonic larvae and consequently wide potential dispersal, so that genetic uniformity should be common. However, phylogeographic investigations reveal that panmixia is rare in the marine realm. Phylogeographic patterns commonly coincide with geographic transitions acting as barriers to gene flow. In the Mediterranean Sea and adjoining areas, the best known barriers are the Atlantic-Mediterranean transition, the Siculo-Tunisian Strait and the boundary between Aegean and Black seas. Here, we perform the so far broadest phylogeographic analysis of the crab Pachygrapsus marmoratus, common across the north-eastern Atlantic Ocean, Mediterranean and Black seas. Previous studies revealed no or weak genetic structuring at meso-geographic scale based on mtDNA, while genetic heterogeneity at local scale was recorded with microsatellites, even if without clear geographic patterns. Continuing the search for phylogeographic signal, we here enlarge the mtDNA dataset including 51 populations and covering most of the species’ distribution range.

Results

This enlarged dataset provides new evidence of three genetically separable groups, corresponding to the Portuguese Atlantic Ocean, Mediterranean Sea plus Canary Islands, and Black Sea. Surprisingly, hierarchical AMOVA and Principal Coordinates Analysis agree that our Canary Islands population is closer to western Mediterranean populations than to mainland Portugal and Azores populations. Within the Mediterranean Sea, we record genetic homogeneity, suggesting that population connectivity is unaffected by the transition between the western and eastern Mediterranean. The Mediterranean metapopulation seems to have experienced a relatively recent expansion around 100,000 years ago.

Conclusions

Our results suggest that the phylogeographic pattern of P. marmoratus is shaped by the geological history of Mediterranean and adjacent seas, restricted current gene flow among different marginal seas, and incomplete lineage sorting. However, they also caution from exclusively testing well-known biogeographic barriers, thereby neglecting other possible phylogeographic patterns. Mostly, this study provides evidence that a geographically exhaustive dataset is necessary to detect shallow phylogeographic structure within widespread marine species with larval dispersal, questioning all studies where species have been categorized as panmictic based on numerically and geographically limited datasets.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-016-0720-2) contains supplementary material, which is available to authorized users.

Comparative analyses of olfactory systems in terrestrial crabs (Brachyura): evidence for aerial olfaction?

Adaptations to a terrestrial lifestyle occurred convergently multiple times during the evolution of the arthropods. This holds also true for the "true crabs" (Brachyura), a taxon that includes several lineages that invaded land independently. During an evolutionary transition from sea to land, animals have to develop a variety of physiological and anatomical adaptations to a terrestrial life style related to respiration, reproduction, development, circulation, ion and water balance. In addition, sensory systems that function in air instead of in water are essential for an animal's life on land. Besides vision and mechanosensory systems, on land, the chemical senses have to be modified substantially in comparison to their function in water. Among arthropods, insects are the most successful ones to evolve aerial olfaction. Various aspects of terrestrial adaptation have also been analyzed in those crustacean lineages that evolved terrestrial representatives including the taxa Anomala, Brachyura, Amphipoda, and Isopoda. We are interested in how the chemical senses of terrestrial crustaceans are modified to function in air. Therefore, in this study, we analyzed the brains and more specifically the structure of the olfactory system of representatives of brachyuran crabs that display different degrees of terrestriality, from exclusively marine to mainly terrestrial. The methods we used included immunohistochemistry, detection of autofluorescence- and confocal microscopy, as well as three-dimensional reconstruction and morphometry. Our comparative approach shows that both the peripheral and central olfactory pathways are reduced in terrestrial members in comparison to their marine relatives, suggesting a limited function of their olfactory system on land. We conclude that for arthropod lineages that invaded land, evolving aerial olfaction is no trivial task.

Characterization of fossilized relatives of the White Spot Syndrome Virus in genomes of decapod crustaceans

Background

The White Spot Syndrome Virus (WSSV) is an important pathogen that infects a variety of decapod species and causes a highly contagious disease in penaeid shrimps. Mass mortalities caused by WSSV have pronounced commercial impact on shrimp aquaculture. Until now WSSV is the only known member of the virus family Nimaviridae, a group with obscure phylogenetic affinities. Its isolated position makes WSSV studies challenging due to large number of genes without homology in other viruses or cellular organisms.

Results

Here we report the discovery of an unusually large amount of sequences with high similarity to WSSV in a genomic library from the Jamaican bromeliad crab Metopaulias depressus. De novo assembly of these sequences allowed for the partial reconstruction of the genome of this endogenized virus with total length of 200 kbp encompassed in three scaffolds. The genome includes at least 68 putative open reading frames with homology in WSSV, most of which are intact. Among these, twelve orthologs of WSSV genes coding for non-structural proteins and nine genes known to code for the major components of the WSSV virion were discovered. Together with reanalysis of two similar cases of WSSV-like sequences in penaeid shrimp genomic libraries, our data allowed comparison of gene composition and gene order between different lineages related to WSSV. Furthermore, screening of published sequence databases revealed sequences with highest similarity to WSSV and the newly described virus in genomic libraries of at least three further decapod species. Analysis of the viral sequences detected in decapods suggests that they are less a result of contemporary WSSV infection, but rather originate from ancestral infection events. Phylogenetic analyses suggest that genes were acquired repeatedly by divergent viruses or viral strains of the Nimaviridae.

Conclusions

Our results shed new light on the evolution of the Nimaviridae and point to a long association of this viral group with decapod crustaceans.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-015-0380-7) contains supplementary material, which is available to authorized users.

Phylogeography of the sand dune ant Mycetophylax simplex along the Brazilian Atlantic Forest coast: remarkably low mtDNA diversity and shallow population structure

BACKGROUND

During past glacial periods, many species of forest-dwelling animals experienced range contractions. In contrast, species living outside such moist habitats appear to have reacted to Quaternary changes in different ways. The Atlantic Forest represents an excellent opportunity to test phylogeographic hypotheses, because it has a wide range of vegetation types, including unforested habitats covered predominantly by herbaceous and shrubby plants, which are strongly influenced by the harsh environment with strong wind and high insolation. Here, we investigated the distribution of genetic diversity in the endemic sand dune ant Mycetophylax simplex across its known range along the Brazilian coast, with the aim of contributing to the understanding of alternative phylogeographic patterns. We used partial sequences of the mitochondrial gene cytochrome oxidase I and nuclear gene wingless from 108 specimens and 51 specimens, respectively, to assess the phylogeography and demographic history of this species. To achieve this we performed different methods of phylogenetic and standard population genetic analyses.

RESULTS

The observed genetic diversity distribution and historical demographic profile suggests that the history of M. simplex does not match the scenario suggested for other Atlantic Forest species. Instead, it underwent demographic changes and range expansions during glacial periods. Our results show that M. simplex presents a shallow phylogeographic structure with isolation by distance among the studied populations, living in an almost panmictic population. Our coalescence approach indicates that the species maintained a stable population size until roughly 75,000 years ago, when it underwent a gradual demographic expansion that were coincident with the low sea-level during the Quaternary. Such demographic events were likely triggered by the expansion of the shorelines during the lowering of the sea level.

CONCLUSIONS

Our data suggest that over evolutionary time M. simplex did not undergo dramatic range fragmentation, but rather it likely persisted in largely interconnected populations. Furthermore, we add an important framework about how both glacial and interglacial events could positively affect the distribution and diversification of species. The growing number of contrasting phylogeographic patterns within and among species and regions have shown that Quaternary events influenced the distribution of species in more ways than first supposed.

Cannabis use is a better indicator of poor mental health in women than in men: a cross-sectional study in young adults from the general population

Cannabis use is a known risk factor for a range of mental health problems, but less is known on the association with general mental health. We aim to explore the relationship between cannabis use and general mental health. We did a cross-sectional online survey of 1,929 young adults aged 18-30 years. Participants reported socio-demographic data, substance use and the Symptom Checklist-90 (SCL-90). Monthly cannabis use was associated with a higher total score on the SCL-90, both in a crude (OR 1.94, 95% CI 1.57-2.38) and fully adjusted model (OR 1.48, 95% CI 1.07-2.03). The association between cannabis and mental health was stronger in women and weekly users, and was independent of age at first use of cannabis. We conclude that moderate cannabis use is associated with general mental health problems in young adulthood. This relationship is independent of age at first use and of other risk factors, and is strongest in women.

Change in cannabis use in the general population: a longitudinal study on the impact on psychotic experiences

OBJECTIVE

To prospectively assess the relationship between cannabis use and psychotic experiences over time.

METHOD

In a longitudinal design, young adults aged 18-27years (N=705) gave online information on cannabis use and completed the Community Assessment of Psychic Experiences (CAPE). These measures were repeated after an interval ranging from six months to five years.

RESULTS

A decrease in cannabis use was associated with a decrease in total psychotic experiences (β=-0.096, p=0.01) after adjustment for a range of potential confounders. An increase in cannabis use was associated with increased positive symptoms at follow-up (β=0.07, p=0.02), but was not significantly associated with increases in Negative and Depression symptom scores, nor with the total number of psychotic experiences.

CONCLUSION

In the first study to the association of change in cannabis use and psychotic experiences over time in the general population, we found an association between changes in cannabis use and changes in the frequency of psychotic experiences. While this does not prove a causal relationship between cannabis use and psychosis, our findings are consistent with studies suggesting that cessation of cannabis use may be beneficial in terms of reducing psychotic experiences.

Transisthmian differentiation in the tree-climbing mangrove crab Aratus H. Milne Edwards, 1853 (Crustacea, Brachyura, Sesarmidae), with description of a new species from the tropical eastern Pacific

The tree-climbing mangrove crab Aratus pisonii (H. Milne Edwards, 1837) (Brachyura, Sesarmidae) is considered to have a transisthmian distribution, due to its presence in mangroves of the Western Atlantic as well as the Eastern Pacific. We here present evidence, based on the morphologies of male gonopods and on genetic data, that populations from these two coastlines are morphologically and genetically distinct and require the description of a new species, Aratus pacificus n. sp., as the sister-species of Aratus pisonii. The corresponding speciation event can be regarded as the outcome of differentiation following the closure of the Isthmus of Panama. As these coastal brackish species were probably among the last ones to become separated, the speciation can thus be dated to a time frame of no more than 3.1 million years.

Monophyly and phylogenetic origin of the gall crab family Cryptochiridae (Decapoda : Brachyura)

The enigmatic gall crab family Cryptochiridae has been proposed to be phylogenetically derived from within the Grapsidae (subsection Thoracotremata), based on the analysis of 16S mtDNA of one cryptochirid, Hapalocarcinus marsupialis, among a wide array of thoracotremes, including 12 species of the family Grapsidae. Here, we test the monophyly and phylogenetic position of Cryptochiridae using the same gene, but with an extended representation of cryptochirids spanning nine species in eight of 21 genera, in addition to further thoracotreme representatives. The results show that gall crabs form a highly supported monophyletic clade within the Thoracotremata, which evolved independently of grapsid crabs. Therefore, the Cryptochiridae should not be considered as highly modified Grapsidae, but as an independent lineage of Thoracotremata, deserving its current family rank. Further molecular and morphological studies are needed to elucidate the precise placement of the cryptochirids within the Eubrachyura.

Cannabidiol as a potential treatment for psychosis

Although cannabis use is associated with an increased risk of developing psychosis, the cannabis constituent cannabidiol (CBD) may have antipsychotic properties. This review concisely describes the role of the endocannabinoid system in the development of psychosis and provides an overview of currently available animal, human experimental, imaging, epidemiological and clinical studies that investigated the antipsychotic properties of CBD. In this targeted literature review we performed a search for English articles using Medline and EMBASE. Studies were selected if they described experiments with psychosis models, psychotic symptoms or psychotic disorders as outcome measure and involved the use of CBD as intervention. Evidence from several research domains suggests that CBD shows potential for antipsychotic treatment.

Cigarette smoking and cannabis use are equally strongly associated with psychotic-like experiences: a cross-sectional study in 1929 young adults

BACKGROUND

Cannabis use is associated with increased risk for psychotic-like experiences (PLEs) and psychotic disorders. It remains unclear whether this relationship is causal or due to confounding.

METHOD

A total of 1929 young adults aged 18-30 years participated in a nationwide internet-based survey in The Netherlands and gave information on demographics, substance use and parental psychiatric illness and completed the Community Assessment of Psychic Experiences (CAPE).

RESULTS

Cigarette smoking and cannabis use were equally strongly associated with the frequency of PLEs in a fully adjusted model (β = 0.098 and 0.079 respectively, p < 0.05). Cannabis use was associated with distress from PLEs in a model adjusted for an elaborate set of confounders excluding smoking (β = 0.082, p < 0.05). However, when cigarette smoking was included in the model, cannabis use was not a significant predictor of distress from PLEs. Cigarette smoking remained associated with distress from PLEs in a fully adjusted model (β = 0.107, p < 0.001).

CONCLUSIONS

Smoking is an equally strong independent predictor of frequency of PLEs as monthly cannabis use. Our results suggest that the association between moderate cannabis use and PLEs is confounded by cigarette smoking.

Cannabis use as an indicator of risk for mental health problems in adolescents: a population-based study at secondary schools

BACKGROUND

Although the association between cannabis use and a wide range of psychiatric symptoms is fairly well established, it is not clear whether cannabis use is also a risk factor for general mental health problems at secondary school. Method A total of 10 324 secondary school children aged 11-16 years, participating in an ongoing Public Health Service School Survey, gave information on demographics, substance use, school factors and stressful life events and completed the Strengths and Difficulties Questionnaire (SDQ).

RESULTS

Cannabis use in the past month was associated with a clinically relevant score on the SDQ [unadjusted odds ratio (OR) 4.46, 95% confidence interval (CI) 3.46-5.76]. Other risk factors associated with poor psychosocial functioning were: a low level of education, alcohol use, cigarette smoking, hard drug use, frequent truancy, an unfavourable school evaluation, feeling unsafe at school, being victimized, frequent absence due to illness, a mentally ill parent, molestation by a parent, financial problems and feeling distressed by an adverse event. In a full model adjusting for these risk factors, cannabis was not significantly associated with mental health problems, although an association at trend level was apparent. Of these risk factors, regular alcohol use, cigarette smoking, hard drug use, frequent truancy, an unfavourable school evaluation and frequent absence due to illness were also associated with cannabis use.

CONCLUSIONS

The association between cannabis use and poor psychosocial functioning in adolescence is due, at least in part, to confounding by other risk factors. Thus, cannabis use can best be viewed as an indicator of risk for mental health problems in adolescence.

Exploring Pandora's box: potential and pitfalls of low coverage genome surveys for evolutionary biology

High throughput sequencing technologies are revolutionizing genetic research. With this “rise of the machines”, genomic sequences can be obtained even for unknown genomes within a short time and for reasonable costs. This has enabled evolutionary biologists studying genetically unexplored species to identify molecular markers or genomic regions of interest (e.g. micro- and minisatellites, mitochondrial and nuclear genes) by sequencing only a fraction of the genome. However, when using such datasets from non-model species, it is possible that DNA from non-target contaminant species such as bacteria, viruses, fungi, or other eukaryotic organisms may complicate the interpretation of the results. In this study we analysed 14 genomic pyrosequencing libraries of aquatic non-model taxa from four major evolutionary lineages. We quantified the amount of suitable micro- and minisatellites, mitochondrial genomes, known nuclear genes and transposable elements and searched for contamination from various sources using bioinformatic approaches. Our results show that in all sequence libraries with estimated coverage of about 0.02–25%, many appropriate micro- and minisatellites, mitochondrial gene sequences and nuclear genes from different KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways could be identified and characterized. These can serve as markers for phylogenetic and population genetic analyses. A central finding of our study is that several genomic libraries suffered from different biases owing to non-target DNA or mobile elements. In particular, viruses, bacteria or eukaryote endosymbionts contributed significantly (up to 10%) to some of the libraries analysed. If not identified as such, genetic markers developed from high-throughput sequencing data for non-model organisms may bias evolutionary studies or fail completely in experimental tests. In conclusion, our study demonstrates the enormous potential of low-coverage genome survey sequences and suggests bioinformatic analysis workflows. The results also advise a more sophisticated filtering for problematic sequences and non-target genome sequences prior to developing markers.

Cannabis use at a young age is associated with psychotic experiences

BACKGROUND

Cannabis use is associated with psychosis and a range of subclinical psychiatric symptoms. The strength of this association depends on dosage and age at first use. The current study investigates whether level of cannabis exposure and starting age are associated with specific profiles of subclinical symptoms.

METHOD

We collected cross-sectional data from a young adult population sample by administering an online version of the Community Assessment of Psychic Experiences (CAPE). Cannabis exposure was quantified as the amount of Euros spent on cannabis per week and the age of initial cannabis use. The primary outcome measure was the odds ratio (OR) to belong to the highest 10% of scores on the total CAPE and the positive-, negative- and depressive symptom dimensions.

RESULTS

In 17 698 adolescents (mean age 21.6, s.d.=4.2 years), cannabis use at age 12 years or younger was strongly associated with a top 10% score on psychotic experiences [OR 3.1, 95% confidence interval (CI) 2.1-4.3] and to a lesser degree with negative symptoms (OR 1.7, 95% CI 1.1-2.5). The OR of heavy users (>€25/week) for negative symptoms was 3.4 (95% CI 2.9-4.1), for psychotic experiences 3.0 (95% CI 2.4-3.6), and for depressive symptoms 2.8 (95% CI 2.3-3.3).

CONCLUSIONS

Early start of cannabis use is strongly associated with subclinical psychotic symptoms and to a lesser degree with negative symptoms, while smoking high amounts of cannabis is associated with increased levels of all three symptom dimensions: psychotic, negative and depressive. These results support the hypothesis that the impact of cannabis use is age specific.

Association between cannabis and psychiatric hospitalization

OBJECTIVE

To investigate the relationship between cannabis use and mental health.

METHOD

A cross-sectional analysis in a sample of 17 698 individuals with a mean age of 22 years (SD: 4.2). Participants provided information on the amount and initial age of cannabis use and history of psychiatric hospitalizations through a web-based questionnaire. To quantify Δ(9) -tetrahydrocannabinol exposure, we operationalized cannabis use as the amount of money spent on cannabis per week over the last month. The odds ratio of having a history of psychiatric hospitalizations was the primary outcome measure.

RESULTS

We found a dose-response relationship between the amount of cannabis use and the odds for psychiatric hospitalization. Adjusted odds ratios for hospitalization increased with the amount of cannabis consumed from 1.6 (95% CI: 1.1-2.3) in incidental users to 6.2 (95% CI: 4.3-8.9) in heavy users (>€25/week). Our data suggested that concomitant drug use was an intermediate factor. Exposure to cannabis before the age of 12 years was found to carry a 4.8 (95% CI: 2.9-7.8) times increased odds for past psychiatric hospitalizations.

CONCLUSION

We conclude that early and heavy uses of cannabis are each and independently associated with poor mental health in its users.

Adaptive radiation and ecological diversification of Sulawesi's ancient lake shrimps

Ancient lakes are natural laboratories for the study of adaptive radiation. Recently, two lake systems on the Indonesian island Sulawesi have emerged as promising new model systems. A species flock of atyid freshwater shrimps in the Malili lake system comprises 15 colorful endemic taxa. Mitochondrial DNA data suggest two independent colonizations by riverine ancestors. Only one colonization event led to subsequent radiation into 14 species, while the second clade comprises just one species. The vast majority of species (n= 12) are habitat specialists, which are confined to the larger Malili clade and include all taxa with species-specific color patterns and a restricted distribution within the five connected Malili lakes. Morphological, genetic, and ecological data are consistent with the existence of an adaptive radiation in the Malili lakes, involving the habitat-specific diversification of trophic morphology. In addition to testing criteria for the recognition of an adaptive radiation, an ancestral state reconstruction reveals an equal probability for either a riverine generalist or a lacustrine specialist as ancestor of the large Malili clade, which is interpreted as indicative of an early stage of habitat specialization within this radiation. Finally, our results suggest that species diversification may have been primarily driven by ecological specialization and allopatric speciation.