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Gregarines from the families Dactylophoridae and Trichorhynchidae parasitize exclusively centipedes and have a distinct morphology among other terrestrial eugregarines, but their evolutionary relationships have not yet been studied with molecular methods. Here we obtain rDNA operon sequences for the dactylophorids and trichorhynchids. We describe a new species Trichorhynchus efeykini sp. n. from a scutigeromorph Thereuopoda longicornis from Vietnam. Phylogenetic analyses with combined SSU, 5.8S and LSU rDNA dataset support the previously proposed separation of Trichorhynchus to the Trichorhynchidae based on morphology and recover the dactylophorids and trichorhynchids as sister groups in a monophyletic clade. This clade appears sister to the clade of the Actinocephaloidea and Stylocephaloidea, and represents a new major lineage of terrestrial gregarines that we designate as a new superfamily Dactylophoroidea. [ABSTRACT FROM AUTHOR]

The phylum Nematoda remains very poorly sampled for mtDNA, with a strong bias toward parasitic, economically important or model species of the Chromadoria lineage. Most chromadorian mitogenomes share a specific order of genes encoded on one mtDNA strand. However, the few sequenced representatives of the Dorylaimia lineage exhibit a variable order of mtDNA genes encoded on both strands. While the ancestral arrangement of nematode mitogenome remains undefined, no evidence has been reported for Enoplia, the phylum's third early divergent major lineage. We describe the first mitogenome of an enoplian nematode, Campydora demonstrans, and contend that the complete 37‐gene repertoire and both‐strand gene encoding are ancestral states preserved in Enoplia and Dorylaimia versus the derived mitogenome arrangement in some Chromadoria. The C. demonstrans mitogenome is 17,018 bp in size and contains a noncoding perfect inverted repeat with 2013 bp‐long arms, subdividing the mitogenome into two coding regions. This mtDNA arrangement is very rare among animals and instead resembles that of chloroplast genomes in land plants. Our report broadens mtDNA taxonomic sampling of the phylum Nematoda and adds support to the applicability of cox1 gene as a phylogenetic marker for establishing nematode relationships within higher taxa. Research Highlights: Genes are encoded on both strands in the mitochondrial genome of enoplid nematode Campydora demonstrans.The coding portion of C. demonstrans mitochondrial genome is subdivided in two regions by two arms of a long noncoding inverted repeat.cox1 gene can serve as a suitable phylogenetic marker for resolving within‐higher‐taxon relationships among nematodes. [ABSTRACT FROM AUTHOR]

Parasitic life-strategies in the phylum Nematoda (roundworms) are remarkably diverse and intricate in terms of evolution and taxonomy. By analysing novel rDNA data obtained on rare host-associated groups with unusual biology, we reveal paraphyly of the last major taxon with uncertain higher-rank classification that united solely parasitic nematodes (Marimermithida) to show that primarily marine parasitism only emerged independently and repeatedly in a few free-living lineages. We report secondary seaward ingression of land-based parasites (Mermithida) via invading hosts in the subtidal zone to illustrate the host-borne scenario of oceanic fish and mammal colonization by primarily terrestrial parasites (Spiruria). We also present the first molecular data on marine nematodes from unicellular hosts (foraminiferan protozoans) to demonstrate the independent origins of exploitative nematode associations at a microscopic scale. We argue that, in contrast with primarily intestinal associations arising from saprotrophy and commensalism, non-intestinal host capture (colonization of host body cavity or internal organs) is likely to be a primary route of transition to truly exploitative parasitism in roundworms. Predispositions to host capture in nematode morphology, ecology and life cycles imply its evolution as part of innate pre-adaptations to crossing environmental boundaries to enable multiple successful transitions to parasitism in the phylum history. [ABSTRACT FROM AUTHOR]

Metchnikovellidae are a group of unusual microsporidians that lack some of the defining ultrastructural features characteristic of derived Microsporidia and are thought to be oneof their earliest-branching lineages. The basal position of metchnikovellids was never confirmed bymolecular phylogeny in published research, and thus far no genomic data for this group were available. In this work, we obtain apartialgenomeof metchnikovellidAmphiamblys sp.using multiple displacement amplification, next-generation sequencing, and metagenomic binning approaches. The partial genome, which we estimate to be close to 90% complete, displays genome compaction on par with gene-dense microsporidian genomes, but contains an unusual repertoire of unique repeat elements. Phylogenetic analyses of multigene datasets place Amphiamblys sp. as the first branch of the microsporidian lineage following the divergence of amitochondriate microsporidian Mitosporidium. We find evidence for amitochondrial remnant presumably functionally equivalent to a mitosome in Amphiamblys sp. and the common enzymatic complement for microsporidian anaerobic metabolism. Comparativegenomicanalyses identify the conservationof components for clathrin vesicle formationasoneof thekey features distinguishing themetchnikovellid from its highly derived relatives. The presented data confirm the notion of Metchnikovellidae as a less derivedmicrosporidian group, and provide an additional stepping stone for reconstruction of an evolutionary transition from the early diverging parasitic fungi to derived Microsporidia. [ABSTRACT FROM AUTHOR]

The evolutionary and ecological importance of predatory flagellates are too often overlooked. This is not only a gap in our understanding of microbial diversity, but also impacts how we interpret their better-studied relatives. A prime example of these problems is found in the alveolates. All well-studied species belong to three large clades (apicomplexans, dinoflagellates, and ciliates), but the predatory colponemid flagellates are also alveolates that are rare in nature and seldom cultured, but potentially important to our understanding of alveolate evolution. Recently we reported the first cultivation and molecular analysis of several colponemid-like organisms representing two novel clades in molecular trees. Here we provide ultrastructural analysis and formal species descriptions for both new species, Colponema vietnamica n. sp. and Acavomonas peruviana n. gen. n. sp. Morphological and feeding characteristics concur with molecular data that both species are distinct members of alveolates, with Acavomonas lacking the longitudinal phagocytotic groove, a defining feature of Colponema. Based on ultrastructure and molecular phylogenies, which both provide concrete rationale for a taxonomic reclassification of Alveolata, we establish the new phyla Colponemidia nom. nov. for the genus Colponema and its close relatives, and Acavomonidia nom. nov. for the genus Acavomonas and its close relatives. The morphological data presented here suggests that colponemids are central to our understanding of early alveolate evolution, and suggest they also retain features of the common ancestor of all eukaryotes. [ABSTRACT FROM AUTHOR]

A complete mitochondrial genome sequence of amphipodaEulimnogammarus vittatusDybowsky, 1874 from Lake Baikal was obtained using next-generation sequencing approach. Mitochondrial DNA with the length of 15,534 bp contains 13 protein-coding genes, 2 ribosomal RNA, 23 transfer RNA and non-coding sequences: a putative control region and 7 intergenic spacers. A brief comparative analysis of mitochondrial genomes ofE. vittatusand its sister speciesEulimnogammarus verrucosuswas performed. [ABSTRACT FROM PUBLISHER]

In this study, we present a complete mitochondrial genome of a deep-water amphipodaBrachyuropus grewingkii(Dybowsky, 1874) from Lake Baikal. A circular mitochondrial DNA has 17,118 bp in length and contains 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, a putative control region, and five intergenic spacers. An extended control region and altered positions of some tRNA genes distinguish mitochondrial genome ofB. grewingkiifrom the mitochondrial genomes described for other Baikalian amphipoda species. [ABSTRACT FROM AUTHOR]