BackgroundMites (Acari) have traditionally been treated as monophyletic, albeit composed of two major lineages: Acariformes and Parasitiformes. Yet recent studies based on morphology, molecular data, or combinations thereof, have increasingly drawn their monophyly into question. Furthermore, the usually basal (molecular) position of one or both mite lineages among the chelicerates is in conflict to their morphology, and to the widely accepted view that mites are close relatives of Ricinulei.ResultsThe phylogenetic position of the acariform mites is examined through employing SSU, partial LSU sequences, and morphology from 91 chelicerate extant terminals (forty Acariformes). In a static homology framework, molecular sequences were aligned using their secondary structure as guide, whereby regions of ambiguous alignment were discarded, and pre-aligned sequences analyzed under parsimony and different mixed models in a Bayesian inference. Parsimony and Bayesian analyses led to trees largely congruent concerning infra-ordinal, well-supported branches, but with low support for inter-ordinal relationships. An exception is Solifugae + Acariformes (P. P = 100%, J. = 0.91). In a dynamic homology framework, two analyses were run: a standard POY analysis and an analysis constrained by secondary structure. Both analyses led to largely congruent trees; supporting a (Palpigradi (Solifugae Acariformes)) clade and Ricinulei as sister group of Tetrapulmonata with the topology (Ricinulei (Amblypygi (Uropygi Araneae))). Combined analysis with two different morphological data matrices were run in order to evaluate the impact of constraining the analysis on the recovered topology when employing secondary structure as a guide for homology establishment. The constrained combined analysis yielded two topologies similar to the exclusively molecular analysis for both morphological matrices, except for the recovery of Pedipalpi instead of the (Uropygi Araneae) clade. The standard (direct optimization) POY analysis, however, led to the recovery of trees differing in the absence of the otherwise well-supported group Solifugae + Acariformes.ConclusionsPrevious studies combining ribosomal sequences and morphology often recovered topologies similar to purely morphological analyses of Chelicerata. The apparent stability of certain clades not recovered here, like Haplocnemata and Acari, is regarded as a byproduct of the way the molecular homology was previously established using the instrumentalist approach implemented in POY. Constraining the analysis by a priori homology assessment is defended here as a way of maintaining the severity of the test when adding new data to the analysis. Although the strength of the method advocated here is keeping phylogenetic information from regions usually discarded in an exclusively static homology framework; it still has the inconvenience of being uninformative on the effect of alignment ambiguity on resampling methods of clade support estimation. Finally, putative morphological apomorphies of Solifugae + Acari...

BackgroundWithin an evolutionary framework of Gastrotricha Marinellina flagellata and Redudasys fornerise bear special interest, as they are the only Macrodasyida that inhabit freshwater ecosystems. Notwithstanding, these rare animals are poorly known; found only once (Austria and Brazil), they are currently systematised as incertae sedis. Here we report on the rediscovery of Redudasys fornerise, provide an account on morphological novelties and present a hypothesis on its phylogenetic relationship based on molecular data.Methodology/Principal FindingsSpecimens were surveyed using DIC microscopy and SEM, and used to obtain the 18 S rRNA gene sequence; molecular data was analyzed cladistically in conjunction with data from 42 additional species belonging to the near complete Macrodasyida taxonomic spectrum. Morphological analysis, while providing new information on taxonomically relevant traits (adhesive tubes, protonephridia and sensorial bristles), failed to detect elements of the male system, thus stressing the parthenogenetic nature of the Brazilian species. Phylogenetic analysis, carried out with ML, MP and Bayesian approaches, yielded topologies with strong nodal support and highly congruent with each other. Among the supported groups is the previously undocumented clade showing the alliance between Redudasys fornerise and Dactylopodola agadasys; other strongly sustained clades include the densely sampled families Thaumastodermatidae and Turbanellidae and most genera.Conclusions/SignificanceA reconsideration of the morphological traits of Dactylopodola agadasys in light of the new information on Redudasys fornerise makes the alliance between these two taxa very likely. As a result, we create Anandrodasys gen. nov. to contain members of the previously described D. agadasys and erect Redudasyidae fam. nov. to reflect this novel relationship between Anandrodasys and Redudasys. From an ecological perspective, the derived position of Redudasys, which is deeply nested within the Macrodasyida clade, unequivocally demonstrates that invasion of freshwater by gastrotrichs has taken place at least twice, in contrast with the single event hypothesis recently put forward.

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Halicyclops hurlberti, a new species of cyclopoid copepod, is described from San Diego, California. Specimens identified by C.D. Marsh as H. aequoreus kept in the US Museum of Natural History were checked and placed in the species H. cf. clarkei Herbst and H. fosteri M.S. Wilson. The description of these two species is being emended.

Two new species of semiterrestrial darwinulid ostracods, both belonging to the pagliolii -lineage of the genus Vestalenula , are described here. Vestalenula botocuda sp. nov ., collected from moist mud in a rain forest remnant, is an enigmatic species, as it combines valve characters of the boteai-lineage with soft part features of the danielopoli-lineage within the genus. Vestalenula irajai sp. nov ., found in several types of semiterrestrial habitats, is closely related to V. pagliolii in its soft part morphology, but has more elongated valves, with straight dorsal and ventral margins running parallel to each other. The description of these new species confirms the relatively high levels of endemicity and diversity in Southern Hemisphere Vestalenula and challenges earlier classifications of this group.

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Five new species and a new genus of terrestrial ostracods from Brazil are described: Callistocypris mckenziei sp. nov., Callistocypris rossettii sp. nov., Terrestricypris wurdigae sp. nov., Caaporacandona shornikovi gen. et sp. nov. and Caaporacandona iguassuensis gen. et sp. nov. This is the first time that Callistocypris Shornikov, 1980 and Terrestricypris Shornikov, 1980 have been found since their original description from the Solomon Islands. The family Terrestricyprididae Shornikov is here lowered to the rank of tribe within the Candoninae; this tribe comprises Terrestricypris, Terrestricandona Danielopol & Betsch, 1980 (from Madagascar) and Caaporacandona gen. nov. Putative heterochronic character evolution within this tribe (in valves A1 and A2) is compared to a parallel evolutionary pathway in another group of terrestrial ostracods, the Mesocypridini. The similarity between the terrestrial ostracod faunas of Brazil and the Western Pacific Islands (including New Zealand) and the dissimilarity between those of Africa and South America is indicated. The putative causality of the prevalence of asexual reproduction in terrestrial ostracods is briefly discussed. © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society, 2005, 145, 145–173.