The association of bacterial agents and flagellated protozoans in the etiopathogenesis of subspectacular abscesses in snakes.

OBJECTIVES: To describe the etiology, clinical pathology, and treatment of subspectacular abscesses (SAs) in 16 snakes. ANIMALS STUDIED: Sixteen snakes from private captive collections that were presented at a veterinary teaching hospital and diagnosed with SAs. PROCEDURES: Exudate was collected from SAs via percutaneous aspiration or by performing a partial spectaculectomy and submitted to direct light microscopic examination and/or microbiological examination. RESULTS: Bacterial isolates were cultured from exudate samples in 12 out of 16 snakes and comprised Pseudomonas aeruginosa isolates that showed identical antimicrobial susceptibility patterns in seven cases. Direct light microscopic examination demonstrated the presence of flagellated protozoa in the exudate in 10 out of 16 snakes and in all of these snakes, concurrent oropharyngeal flagellated protozoan infection could be demonstrated. Combined flagellated protozoan and bacterial SA infection was demonstrated in six snakes. Comparison of small subunit ribosomal RNA gene sequences of flagellated protozoans that were detected in the exudate of SAs from four snakes revealed they represented the parabasalians Monocercomonas colubrorum and Hypotrichomonas acosta in one and three cases, respectively. In all snakes, successful treatment of the SAs was achieved following surgical debridement of the subspectacular space combined with antimicrobial treatment. CONCLUSION: Bacteria as well as flagellates are considered to reach the subspectacular space through ascending infection from the oral cavity via the lacrimal duct. Although opportunistic bacterial infection presumably constitutes the predominant cause of SAs in snakes, the role of flagellate infection in the pathogenesis of this disorder should be further elucidated.

Single cell transcriptomics reveals UAR codon reassignment in Palmarella salina (Metopida, Armophorea) and confirms Armophorida belongs to APM clade.

Anaerobes have emerged in several major lineages of ciliates, but the number of independent transitions to anaerobiosis among ciliates is unknown. The APM clade (Armophorea, Muranotrichea, Parablepharismea) represents the largest clade of obligate anaerobes among ciliates and contains free-living marine and freshwater representatives as well as gut endobionts of animals. The evolution of APM group has only recently started getting attention, and our knowledge on its phylogeny and genetics is still limited to a fraction of taxa. While ciliates portray a wide array of alternatives to the standard genetic code across numerous classes, the APM ciliates were considered to be the largest group using exclusively standard nuclear genetic code. In this study, we present a pan-ciliate phylogenomic analysis with emphasis on the APM clade, bringing the first phylogenomic analysis of the family Tropidoatractidae (Armophorea) and confirming the position of Armophorida within Armophorea. We include five newly sequenced single cell transcriptomes from marine, freshwater, and endobiotic APM ciliates - Palmarella salina, Anteclevelandella constricta, Nyctotherus sp., Caenomorpha medusula, and Thigmothrix strigosa. We report the first discovery of an alternative nuclear genetic code among APM ciliates, used by Palmarella salina (Tropidoatractidae, Armophorea), but not by its close relative, Tropidoatractus sp., and provide a comparative analysis of stop codon identity and frequency indicating the precedency to the UAG codon loss/reassignment over the UAA codon reassignment in the specific ancestor of Palmarella. Comparative genomic and proteomic studies of this group may help explain the constraints that underlie UAR stop-to-sense reassignment, the most frequent type of alternative nuclear genetic code, not only in ciliates, but eukaryotes in general.

Free-living Trichomonads are Unexpectedly Diverse.

The vast majority of the more than 450 described species of Parabasalia are intestinal symbionts or parasites of animals. This endobiotic life-history is presumably ancestral although the root of Parabasalia still needs to be robustly established. The half-dozen putatively free-living species thus far described are likely independently derived from endobiotic ancestors and represent the most neglected ecological group of parabasalids. Thus, we isolated and cultivated 45 free-living strains of Parabasalia obtained from a wide variety of anoxic sediments to conduct detailed morphological and SSU rRNA gene phylogenetic analyses. Sixteen species of trichomonads were recovered. Among them, we described seven new species, three new genera, two new families, and one new order. Most of the newly described species were more or less closely related to members of already described genera. However, we uncovered a new deep-branching lineage without affinity to any currently known group of Parabasalia. The newly discovered free-living parabasalids will be key taxa in comparative analyses aimed at rooting the entire lineage and deciphering the evolutionary innovations involved in transitioning between endobiotic and free-living habitats.

Gregarine single-cell transcriptomics reveals differential mitochondrial remodeling and adaptation in apicomplexans.

BACKGROUND: Apicomplexa is a diverse phylum comprising unicellular endobiotic animal parasites and contains some of the most well-studied microbial eukaryotes including the devastating human pathogens Plasmodium falciparum and Cryptosporidium hominis. In contrast, data on the invertebrate-infecting gregarines remains sparse and their evolutionary relationship to other apicomplexans remains obscure. Most apicomplexans retain a highly modified plastid, while their mitochondria remain metabolically conserved. Cryptosporidium spp. inhabit an anaerobic host-gut environment and represent the known exception, having completely lost their plastid while retaining an extremely reduced mitochondrion that has lost its genome. Recent advances in single-cell sequencing have enabled the first broad genome-scale explorations of gregarines, providing evidence of differential plastid retention throughout the group. However, little is known about the retention and metabolic capacity of gregarine mitochondria. RESULTS: Here, we sequenced transcriptomes from five species of gregarines isolated from cockroaches. We combined these data with those from other apicomplexans, performed detailed phylogenomic analyses, and characterized their mitochondrial metabolism. Our results support the placement of Cryptosporidium as the earliest diverging lineage of apicomplexans, which impacts our interpretation of evolutionary events within the phylum. By mapping in silico predictions of core mitochondrial pathways onto our phylogeny, we identified convergently reduced mitochondria. These data show that the electron transport chain has been independently lost three times across the phylum, twice within gregarines. CONCLUSIONS: Apicomplexan lineages show variable functional restructuring of mitochondrial metabolism that appears to have been driven by adaptations to parasitism and anaerobiosis. Our findings indicate that apicomplexans are rife with convergent adaptations, with shared features including morphology, energy metabolism, and intracellularity.

Molecular and Morphological Diversity of the Oxymonad Genera Monocercomonoides and Blattamonas gen. nov.

Oxymonads are a group of flagellates living as gut symbionts of insects or vertebrates. They have several unique features, one of them being the absence of mitochondria. Diversity of this group is seriously understudied, which is particularly true for small species from the family Polymastigidae. We isolated 34 strains of oxymonads with Polymastigidae-like morphology from 24 host species and unused cesspits and sequenced the SSU rRNA gene. Our strains formed two clades in the phylogenetic tree with Streblomastix strix branching between them. This topology was also supported by a three-gene phylogenetic analysis. Despite considerable genetic differences between the clades, light and electron microscopy revealed only subtle differences. The larger clade is considered genus Monocercomonoides and the isolates belonging here were classified into three new species (including the first potentially free-living species), two previously described species, and three unclassified lineages. The smaller clade, here described as Blattamonas gen. nov., consists of three newly described species. Concomitantly with the description of Blattamonas, we elevate the Monocercomonoides subgenus Brachymonas to the genus level. Our study shows that, despite their conserved morphology, the molecular diversity of Polymastigidae-like oxymonads is broad and represents a substantial part of the diversity of oxymonads.

Wing reduction influences male mating success but not female fitness in cockroaches.

Although cockroaches (Blattodea s. str.) exhibit high proportion of species with reduced wings, the underlying evolutionary forces remain unclear. Wing reduction in insects is generally considered advantageous for females and a trade-off between investment into the flying apparatus and reproduction is predicted to explain its evolution. However, what if the wing maintenance is an important issue for males' fitness? Males raise wings during the ritualized courtship which is viewed as an unavoidable movement unveiling the tergal glands for female access. We, however, propose a novel male mating success hypothesis suggesting that male wings are essential for their successful mating. We tested these two competing, but not mutually exclusive hypotheses in the cockroach Eublaberus distanti. We found no effect of female wing loss on any of the measured fecundity characteristics despite that alatectomized females histolyzed flight muscles. On the contrary, alatectomized males did not histolyze wing muscles, but experienced a markedly decreased mating success. Our findings, therefore, provide the first evidence on the crucial mechanical role of wings on male mating success. Consequently, selection for the retention of wings in males rather than for their reduction in females can explain the evolution of sexual wing dimorphism in cockroaches and other insects.