Palaeopascichnida is a problematic group of extinct organisms that is globally distributed in Ediacaran sequences of Avalonia, Baltica, Siberia, South China and Australia. The fossils related to Palaeopascichnida consist of serially or cluster-like arranged, millimetre- to centimetre-scale globular or allantoid chambers, which are characterized by substantial differences in preservation, leading to no consistent diagnosis for these organisms. Here we integrate morphometric variation, stratigraphic distribution and habitat settings of more than 1200 specimens from all known fossil localities. The results of the morphological analysis demonstrate variation in chamber shape and size, and allow us to recognize six valid species within the group. Statistical analysis of the specimen distribution with respect to sedimentary environments indicates a significant difference in palaeoecological settings between species, making a significant contribution to the evolution and systematic palaeontology of these problematic organisms and perspective on their use in Neoproterozoic biostratigraphy. Our revision and systematic study sheds new light on one of the least studied groups of the late Ediacaran biota.

Two new genera and six new species of benthic amphipods from the soft sediments of the Perdido Fold Belt region, western Gulf of Mexico, are described. Morphological comparisons of the new species with description of their congeners resulted in the determination of one new genus and one new species of the family Melitidae as Dentimelita lecroyae gen. nov., sp. nov., one new genus and four new species of the family Pardaliscidae as Pardaliscella perdido sp. nov., Paraeperopeus longirostris gen. nov., sp. nov., Pardaliscoides ecosur sp. nov. and Tosilus cigomensis sp. nov., and one new species of the family Unciolidae as Neohela winfieldi sp. nov. The occurrence of the newly described amphipods in the Perdido Fold Belt region represented new geographic range extensions for the genera, including new records of Neohela in the Gulf of Mexico, Pardaliscella and Pardaliscoides in the western Atlantic and Tosilus in the Atlantic.

The taxonomy of the 10 recognized Neoechinorhynchus species associated with emydid turtles is complex due to the morphological conservatism. In the present study, specimens of N. emyditoides from northern and southeastern Mexico exhibit great phenotypic plasticity on its diagnostic characteristics. We sequenced three molecular markers: the internal transcribed spacers ITS1, ITS2 and 5.8S gene, the D2 + D3 domains of the large subunit from nuclear DNA and cytochrome c oxidase subunit I (cox1) from mitochondrial DNA. Sequences of the nuclear molecular markers were aligned and compared with other congeneric species associated with emydids available in GenBank. Phylogenetic analyses supported the polyphyly of Neoechinorhynchus. The species from emydids formed a clade, which was subdivided into five subclades that correspond with each species analysed (N. pseudemydis, N. chrysemydis, N. emydis, N. schmidti and N. emyditoides). To understand better the genetic structure of N. emyditoides a haplotype network was inferred with 29 cox1 sequences, revealing the presence of 13 haplotypes, two of which were shared and 11 were unique. The high values of fixation index, Fst (0.4227–0.8925) detected between the two populations from southeastern and the two from northern Mexico indicated low genetic flow among the populations. Our data suggest that the Neoechinorhynchus species associated with emydid turtles diversified in the eastern USA and that of N. emyditoides expanded its distribution range reached southeastern Mexico.

The taxonomy of species of Bivesicula Yamaguti, 1934 is analysed for samples from holocentrid, muraenid and serranid fishes from Japan, Ningaloo Reef (Western Australia), the Great Barrier Reef (Queensland), New Caledonia and French Polynesia. Analysis of three genetic markers (cox1 mtDNA, ITS2 and 28S rDNA) identifies three strongly supported clades of species and suggests that Bivesicula as presently recognized is not monophyletic. On the basis of combined morphological, molecular and biological data, 10 species are distinguished of which five are proposed as new. Bivesicula Clade 1 comprises seven species of which three are effectively morphologically cryptic relative to each other; all seven infect serranids and four also infect holocentrids. Bivesicula Clade 2 comprises three species of which two are effectively morphologically cryptic relative to each other; all three infect serranids and one also infects a muraenid. Bivesicula Clade 3 comprises two known species from apogonids and a pomacentrid, and forms a clade with species of Paucivitellosus Coil, Reid & Kuntz, 1965 to the exclusion of other Bivesicula species. Taxonomy in this genus is made challenging by the combination of low resolving power of ribosomal markers, the existence of regional cox1 mtDNA populations, exceptional and unpredictable host-specificity and geographical distribution, and significant host-induced morphological variation.

Characithecium (Monogenoidea, Dactylogyridae) is a genus containing nine species that live on the gills of a characid clade containing genera Astyanax, Andromakhe, Psalidodon and Oligosarcus (Characiformes, Characidae) in South and Central America. Earlier studies suggest a tight coevolutionary history between these parasites and their hosts mainly due to the phylogenetic proximity between these genera of fish. Hence, this study explores phylogenetic relationships, species limits and extrinsic factors (geography and ecology) explaining parasite prevalence. To understand the evolutionary history of the genus, we constructed a time-calibrated phylogenetic hypothesis, which includes eight of the nine known species of Characithecium sampled from a broad spectrum of host species. The phylogeny supports the monophyly of Characithecium, with its most recent common ancestor dating from the Miocene. Using generalized mixed-yule coalescent and Bayesian Poisson tree process methods, species delimitation analyses suggested fewer species than the proposed delimitation based on morphology alone, recovering four and six entities, respectively. The results indicate that species of Characithecium have wider geographical and host distribution and higher prevalence on Oligosarcus species compared to Astyanax and Psalidodon. Correlation between parasite prevalence and biotic and abiotic traits, based on generalized linear models, indicates that the frequency of occurrence of different species of Characithecium is associated with distinct factors, such as host genus, high altitudes, rivers and streams, and different ecoregions. Our results suggest that species of Characithecium are highly opportunistic, exploring resources in different manner as our data reveal the ability of these parasites to explore a diverse environment of variable biotic (e.g. hosts) and abiotic features.

Two species of lichenicolous fungi are described as new to science: Lichenotubeufia etayoi Zhurb. (on Trachyderma), with light orange perithecia up to 360 μm diam., non-fasciculate excipular hairs, and 10–13-septate ascospores, 110–162 × 3–5 μm; and L. tibellii Zhurb. (on Coccocarpia), with light orange perithecia up to 275 μm diam., non-fasciculate excipular hairs, and 5–12-septate ascospores, 50–100 × 3–4.5 μm. An updated key to the species of Lichenotubeufia is provided.

This study describes a new species of Hypotrachyna subgenus Parmelinopsis from the south-eastern Cerrado (Brazilian savannah), a biodiversity hotspot. The species is especially common in open vegetation, including urban environments. Hypotrachyna neohorrescens sp. nov. is morphologically and chemically similar to H. horrescens. Nevertheless, phylogenetic analyses of the nuITS and mtSSU regions revealed that H. neohorrescens is a distinct species and closely related to the North American H. mcmulliniana, differing by the size of the laciniae and ascospores.

We report specimens of monorchiids infecting Haemulidae from the waters off Japan and Australia; these specimens represent five species of Helicometroides Yamaguti, 1934, three of which are unambiguously new. Helicometroides murakamii n. sp. infects Diagramma pictum pictum from off Minabe, Japan; Helicometroides gabrieli n. sp. infects Plectorhinchus chrysotaenia from off Lizard Island, Australia; and Helicometroides wardae n. sp. infects Plectorhinchus flavomaculatus and Plectorhinchus multivittatus from off Heron Island, Australia. Helicometroides murakamii n. sp. and H. gabrieli n. sp. conform to the most recent diagnosis of Helicometroides in lacking a terminal organ, but H. wardae n. sp. possesses a terminal organ with distinct, robust spines; despite this morphological distinction, the three form a strongly-supported clade in phylogenetic analyses. We also report specimens morphologically consistent with Helicometroides longicollis Yamaguti, 1934, from D. pictum pictum from off Minabe, Japan, and Diagramma pictum labiosum on the Great Barrier Reef, Australia. Genetic analyses of ITS2 rDNA, 28S rDNA and cox1 mtDNA sequence data for the Japanese specimens reveal the presence of two distinct genotypes. Specimens of the two genotypes were discovered in mixed infections and are morphologically indistinguishable; neither genotype can be associated definitively with H. longicollis as originally described. We thus identify them as H. longicollis lineage 1 and 2, pending study of further fresh material. Genetic analyses of specimens from the Great Barrier Reef are consistent with the presence of only H. longicollis lineage 1. This species thus has a range that incorporates at least Australia and Japan, localities separated by over 7000 km.

Approximately one-third of individuals in a major depressive episode will not achieve sustained remission despite multiple, well-delivered treatments. These patients experience prolonged suffering and disproportionately utilize mental and general health care resources. The recently proposed clinical heuristic of ‘difficult-to-treat depression’ (DTD) aims to broaden our understanding and focus attention on the identification, clinical management, treatment selection, and outcomes of such individuals. Clinical trial methodologies developed to detect short-term therapeutic effects in treatment-responsive populations may not be appropriate in DTD. This report reviews three essential challenges for clinical intervention research in DTD: (1) how to define and subtype this heterogeneous group of patients; (2) how, when, and by what methods to select, acquire, compile, and interpret clinically meaningful outcome metrics; and (3) how to choose among alternative clinical trial design options to promote causal inference and generalizability. The boundaries of DTD are uncertain, and an evidence-based taxonomy and reliable assessment tools are preconditions for clinical research and subtyping. Traditional outcome metrics in treatment-responsive depression may not apply to DTD, as they largely reflect the only short-term symptomatic change and do not incorporate durability of benefit, side effect burden, or sustained impact on quality of life or daily function. The trial methodology will also require modification as trials will likely be of longer duration to examine the sustained impact, raising complex issues regarding control group selection, blinding and its integrity, and concomitant treatments.

All Pseudocorynosoma species inhabit freshwater environments of the American continent, but little is known about their life cycles. We report Pseudocorynosoma enrietti (Molfi & Freitas Fernandes, 1953) from natural and experimental specimens in Patagonia and identify the intermediate and definitive hosts of its life cycle for the first time in South America. Adult worms were recovered from Anas platyrhynchos (Linnaeus) and from a new definitive host, Coscoroba coscoroba Molina. Naturally infected amphipods, Hyalella patagonica Ortmann, were collected to obtain cystacanths that were fed to Gallus gallus domesticus (Linnaeus) and Anas platyrhynchos. Specimens of P. enrietti are described in detail using light and scanning electron microscopy. A key to species of the genus Pseudocorynosoma is included. Worms are characterized in both sexes by fore-trunk spines, and genital spines in an isolated field. The proboscis has 19–20 hook rows; males have 9–11 (10) hooks per row and females 7–9 (8). Males with four cement glands similar in size. Eggs elongated, with filaments. Experimental male and female worms were recovered from A. platyrhynchos at seven and 14 days, post-infection.

The Rostania occultata species complex (‘Collema occultatum s. lat.’) is revised in Fennoscandia and found to consist of four species, all epiphytes on deciduous trees: Rostania effusa A. Košuth., M. Westb. & Wedin sp. nov., R. occultata (Bagl.) Otálora et al., R. pallida A. Košuth., M. Westb. & Wedin sp. nov. and R. populina (Th. Fr.) A. Košuth., M. Westb. & Wedin comb. nov. Rostania effusa and R. pallida are newly described from humid habitats in old-growth boreal coniferous forests, usually with a mixture of deciduous trees, and from similar areas in the subalpine birch-dominated forests of Fennoscandia. Rostania effusa is characterized by apothecia with red-brown apothecium discs and an excipulum thallinum with a simple pseudocortex and cubic to oblong, muriform spores. Rostania pallida has apothecia with whitish to pale yellowish discs and an excipulum thallinum with a distinct cellular pseudocortex, and ellipsoid, muriform mature spores that are often constricted at the centre. A lectotype is designated for Collema quadratum J. Lahm ex Körb. The new combination Rostania populina is introduced for the species recognized until now as the variety Rostania occultata var. populina (Th. Fr.) Perlmutter & Rivas Plata. A key to the six species in Rostania s. str. is included.

Based on morphometric, morphological and molecular characterization using partial small subunit 18S ribosomal DNA (rDNA) and the D2/D3 domain of large subunit 28S rDNA, we described a new species Mononchoides kanzakii collected from manure, and the known species Mononchoides composticola Steel, Moens, Scholaert, Boshoff, Houthoofd and Bert, 2011, isolated from the dung beetle Oniticellus cinctus (Fabricius, 1775). Phylogenetic trees based on the evolutionary model (GTR + I + G) were inferred by Bayesian inference algorithms. Mononchoides kanzakii sp. n. is characterized by 28–32 longitudinal ridges, discontinuous at level of stoma; amphidial apertures inconspicuous; metastegostom armed with thorn-shaped dorsal tooth; a flattened, claw-like right subventral tooth, and left subventral denticulate ridge with 12–14 fine denticles delimited by a group of five denticles in females vs. triangular, flattened right subventral tooth, 5–8 prominent denticles at left subventral sector in males; cloacal lips with a distinct rim; and gubernaculum with cuticularized, proximal and distal extensions of equal length, each constituting half of the length of the wider part of gubernaculum.

Two populations of the species Diastolaimus grossus have been obtained from bark of trees in Bosnia and Herzegovina and the Czech Republic. The species is described and characterized in detail using morphological techniques (light and electron scanning microscopy) and morphometrical (Gower General Similarity coefficient of morphological characters) and molecular analyses, including phylogenetic analysis of all related and already sequenced species of the family Chambersiellidae. Morphological and molecular analyses, based on 18S and 28S ribosomal DNA sequences, show that the family Chambersiellidae is polyphyletic, being the subfamily Chambersiellinae related with Cephalobomorpha and Tylenchomorpha, and the subfamily Macrolaiminae is located into Panagrolaimomorpha. The genus Diastolaimus, previously belonging to Macrolaiminae, is transferred to Chambersiellinae. Diastolaimus mexicanus is proposed as a junior synonym of D. grossus.