A circumpolar parasite: Evidence of a cryptic undescribed species of sucking louse, Linognathus sp., collected from Arctic foxes, Vulpes lagopus, in Nunavut (Canada) and Svalbard (Norway).

The North has experienced unprecedented rates of warming over the past few decades, impacting the survival and development of insects and the pathogens that they carry. Since 2019, Arctic foxes from Canada (Nunavut) have been observed with fur loss inconsistent with natural shedding of fur. Adult lice were collected from Arctic foxes from Nunavut (n = 1) and Svalbard (n = 2; Norway) and were identified as sucking lice (suborder Anoplura). Using conventional PCR targeting the mitochondrial cytochrome c oxidase subunit 1 gene (cox1), lice from Canada and Svalbard were 100% similar (8 pooled samples from Nunavut and 3 pooled samples from Svalbard), indicating that there is potential gene flow between ectoparasites on Scandinavian and North American Arctic fox populations. The cox1 sequences of Arctic fox lice and dog sucking lice (Linognathus setosus) had significant differences (87% identity), suggesting that foxes may harbour a cryptic species that has not previously been recognised. Conventional PCR targeting the gltA gene for Bartonella bacteria amplified DNA from an unknown gammaproteobacteria from two pooled louse samples collected from Svalbard foxes. The amplified sequences were 100% identical to each other but were only 78% like Proteus mirabilis reported in GenBank (CP053614), suggesting that lice on Arctic foxes may carry unique microorganisms that have yet to be described.

Ecological factors shaping the ectoparasite community assembly of the Azara's Grass Mouse, Akodon azarae (Rodentia: Cricetidae).

Parasites are integral members of the global biodiversity. They are useful indicators of environmental stress, food web structure and diversity. Ectoparasites have the potential to transmit vector-borne diseases of public health and veterinary importance and to play an important role in the regulation and evolution of host populations. The interlinkages between hosts, parasites and the environment are complex and challenging to study, leading to controversial results. Most previous studies have been focused on one or two parasite groups, while hosts are often co-infected by different taxa. The present study aims to assess the influence of environmental and host traits on the entire ectoparasite community composition of the rodent Akodon azarae. A total of 278 rodents were examined and mites (Mesostigmata), lice (Phthiraptera), ticks (Ixodida) and fleas (Siphonaptera) were determined. A multi-correspondence analysis was performed in order to analyze interactions within the ectoparasite community and the influence of environmental and host variables on this assembly. We found that environmental variables have a stronger influence on the composition of the ectoparasite community of A. azarae than the host variables analyzed. Minimum temperature was the most influential variable among the studied. In addition, we found evidence of agonistic and antagonistic interactions between ticks and mites, lice and fleas. The present study supports the hypothesis that minimum temperature plays a major role in the dynamics that shape the ectoparasite community of A. azarae, probably through both direct and indirect processes. This finding becomes particularly relevant in a climate change scenario.

Ectoparasites of dogs (Canis familiaris) from northeastern Nigeria: an epidemiological study.

Ectoparasites of dogs represent an important group of parasites. They often suck blood, cause pruritis, and could serve as vectors of many pathogens of veterinary and public health importance. In northeastern Nigeria, there is a lack of data regarding ectoparasites of dogs. Therefore, this study was undertaken to explore the external parasites of dogs and the associated epidemiological risk factors. A total of 1041 dogs (mean age = 8.5 ± 2.1 months) from residential house visit (54.9%) and those attending veterinary clinic (45.1%) were sampled in northeastern Nigeria. Multivariate logistic regression analysis assessed epidemiological risk factors associated with canine ectoparasitic infections. Of the 1041 dogs screened, 92.5% (963/1047) harbored one or more ectoparasites. Rhipicephalus sanguineus (52.4%), Linognathus setosus (7.8%), Ctenocephalides canis (2.3%), and Otodectes cynotis canis (1.4%) were the significantly encountered tick, lice, fleas, and mite species, respectively. Being female dog (OR = 1.8; p = 0.01), cross (OR = 2.2; p = 0.029), and exotic breeds (OR = 2.4; p = 0.02), < 7 months (OR = 3.1; p = 0.04) and 7-12 months (OR = 2.1; p = 0.01) aged dogs as well as rainy season (OR = 1.9; p = 0.02) were strong predictors for tick infestation. Similarly, cross (OR = 7.2; p = 0.001) and local breeds (OR = 2.8; p = 0.0001), dogs aged > 12 months (OR = 2.5; p = 0.03), and dogs used for hunting (OR = 3.2; p = 0.01) and as security guards (OR = 3.8; p = 0.01) were strongly associated with lice infestation. Results from this study revealed a high prevalence of external parasites parasitizing majority of the sampled dogs. Some of these parasites may serve as vectors of zoonotic pathogens posing public health risks.

Molecular investigation on infection by haemosporidians in three Western Palearctic species of swift (Apodidae) and their ectoparasitic louse flies.

Swifts (Apodidae) are an unusual group of birds that spend most of their lives in flight, landing only when breeding. Although this aerial lifestyle greatly reduces their likelihood of being bitten by vectors and infected by vector-born parasites, swifts can still be heavily infested during breeding by nest-based vectors such as louse flies (Hippoboscidae). Here, we investigated host, vector, and vector-borne parasite relationships in the three most widespread swift species in the Western Palearctic (WP): common swifts (Apus apus), pallid swifts (A. pallidus), and alpine swifts (Tachymarptis melba), their nest-based louse flies (Crataerina pallida and C. melbae) and avian haemosporidians (genera Haemoproteus, Plasmodium, and Leucocytozoon). Studies of haemosporidian infections in Apodidae remain limited, with clear evidence of infection found to date in just four Neotropical and one Australasian species. The possible role of louse flies in transmitting haemosporidian infections has never been tested in swifts. We assessed the occurrence of haemosporidian infection by PCR screenings of DNA from blood samples from 34 common swifts and 44 pallid swifts from Italy, and 45 alpine swifts from Switzerland. We also screened 20 ectoparasitic louse flies present on 20 birds and identified them by both morphological features and cytochrome oxidase subunit 1 (COI) barcodes. Our results provide no evidence of haemosporidian infection in the 123 swifts tested or in the two louse fly species we identified. Our findings are consistent with available knowledge showing no haemosporidian occurrence in WP swift species and that the most likely infection route for these highly aerial species (via louse fly ectoparasites during nesting) is unlikely.

Characterization of the fragmented mitochondrial genome of domestic pig louse Haematopinus suis (Insecta: Haematopinidae) from China.

The domestic pig louse Haematopinus suis (Linnaeus, 1758) (Phthiraptera: Anoplura) is a common ectoparasite of domestic pigs, which can act as a vector of various infectious disease agents. Despite its significance, the molecular genetics, biology and systematics of H. suis from China have not been studied in detail. In the present study, the entire mitochondrial (mt) genome of H. suis isolate from China was sequenced and compared with that of H. suis isolate from Australia. We identified 37 mt genes located on nine circular mt minichromosomes, 2.9 kb-4.2 kb in size, each containing 2-8 genes and one large non-coding region (NCR) (1,957 bp-2,226 bp). The number of minichromosomes, gene content, and gene order in H. suis isolates from China and Australia are identical. Total sequence identity across coding regions was 96.3% between H. suis isolates from China and Australia. For the 13 protein-coding genes, sequence differences ranged from 2.8%-6.5% consistent nucleotides with amino acids. Our result is H. suis isolates from China and Australia being the same H. suis species. The present study determined the entire mt genome of H. suis from China, providing additional genetic markers for studying the molecular genetics, biology and systematics of domestic pig louse.

Fragmented mitochondrial genomes of seal lice (family Echinophthiriidae) and gorilla louse (family Pthiridae): frequent minichromosomal splits and a host switch of lice between seals.

BACKGROUND: The mitochondrial (mt) genomes of 15 species of sucking lice from seven families have been studied to date. These louse species have highly dynamic, fragmented mt genomes that differ in the number of minichromosomes, the gene content, and gene order in a minichromosome between families and even between species of the same genus. RESULTS: In the present study, we analyzed the publicly available data to understand mt genome fragmentation in seal lice (family Echinophthiriidae) and gorilla louse, Pthirus gorillae (family Pthiridae), in particular the role of minichromosome split and minichromosome merger in the evolution of fragmented mt genomes. We show that 1) at least three ancestral mt minichromosomes of sucking lice have split in the lineage leading to seal lice, 2) one minichromosome ancestral to primate lice has split in the lineage to the gorilla louse, and 3) two ancestral minichromosomes of seal lice have merged in the lineage to the northern fur seal louse. Minichromosome split occurred 15-16 times in total in the lineages leading to species in six families of sucking lice investigated. In contrast, minichromosome merger occurred only four times in the lineages leading to species in three families of sucking lice. Further, three ancestral mt minichromosomes of sucking lice have split multiple times independently in different lineages of sucking lice. Our analyses of mt karyotypes and gene sequences also indicate the possibility of a host switch of crabeater seal louse to Weddell seals. CONCLUSIONS: We conclude that: 1) minichromosome split contributes more than minichromosome merger in mt genome fragmentation of sucking lice, and 2) mt karyotype comparison helps understand the phylogenetic relationships between sucking louse species.

Molecular phylogenetics of the avian feather louse Philopterus-complex (Phthiraptera: Philopteridae).

The avian feather louse Philopterus-complex (Phthiraptera: Ischnocera: Philopteridae) currently contains 12 genera that have been grouped together because of shared morphological characteristics. Although previously lumped into a single genus (Philopterus), more recent morphological treatments have separated the group into several different genera. Here we evaluate the status of these genera using DNA sequence data from 118 ingroup specimens belonging to ten genera in the Philopterus-complex: Australophilopterus Mey, 2004, Cinclosomicola Mey 2004, Clayiella Eichler, 1940, Corcorides Mey, 2004, Mayriphilopterus Mey, 2004, Paraphilopterus Mey 2004, Philopteroides Mey 2004, Philopterus Nitzsch, 1818, Tyranniphilopterus Mey, 2004, and Vinceopterus Gustafsson, Lei, Chu, Zou, and Bush, 2019. Our sampling includes 97 new louse-host association records. Our analyses suggest that the genus Debeauxoecus Conci, 1941, parasitic on pittas (Aves: Pittidae), is outside of the Philopterus-complex, and that there is strong support for the monophyly of a group containing the remaining genera from the complex. Some diverse genera, such as Philopterus (sensu stricto) and Mayriphilopterus are supported as monophyletic, whereas the genera Australophilopterus, Philopteroides, and Tyranniphilopterus are not. The present study is the largest phylogenetic reconstruction of avian lice belonging to the Philopterus-complex to date and suggests that further generic revision is needed in the group to integrate molecular and morphological information.

Phylogenomics of Parasitic and Nonparasitic Lice (Insecta: Psocodea): Combining Sequence Data and Exploring Compositional Bias Solutions in Next Generation Data Sets.

The insect order Psocodea is a diverse lineage comprising both parasitic (Phthiraptera) and nonparasitic members (Psocoptera). The extreme age and ecological diversity of the group may be associated with major genomic changes, such as base compositional biases expected to affect phylogenetic inference. Divergent morphology between parasitic and nonparasitic members has also obscured the origins of parasitism within the order. We conducted a phylogenomic analysis on the order Psocodea utilizing both transcriptome and genome sequencing to obtain a data set of 2370 orthologous genes. All phylogenomic analyses, including both concatenated and coalescent methods suggest a single origin of parasitism within the order Psocodea, resolving conflicting results from previous studies. This phylogeny allows us to propose a stable ordinal level classification scheme that retains significant taxonomic names present in historical scientific literature and reflects the evolution of the group as a whole. A dating analysis, with internal nodes calibrated by fossil evidence, suggests an origin of parasitism that predates the K-Pg boundary. Nucleotide compositional biases are detected in third and first codon positions and result in the anomalous placement of the Amphientometae as sister to Psocomorpha when all nucleotide sites are analyzed. Likelihood-mapping and quartet sampling methods demonstrate that base compositional biases can also have an effect on quartet-based methods.[Illumina; Phthiraptera; Psocoptera; quartet sampling; recoding methods.].

Effect of host age, sex and life stage on the prevalence and abundance of sucking lice on Weddell seal in the Antarctic Peninsula.

Through evolutionary time, seal lice have developed morphological, behavioral, and ecological adaptations to cope with the amphibious lifestyle of their hosts in a co-evolutionary process. Consequently, the dynamics of lice populations are determined by seals behavior. We aim to study the effects of host sex, age class, year, and sampling location, on the prevalence and mean abundance of Antarctophthirus carlinii, on Weddell seals (WS) Leptonychotes wedelli. The study was conducted at two sites in the Antarctic Peninsula, namely, Marambio/Seymour Island (MI) and the Danco Coast (DC). We collected lice from 71 WS: 33 from MI, during the reproductive season, and 38 from DC, during the molting season, between 2014 and 2017. According to our analyses, host age class and sex were the variables that affected prevalence levels of lice on WS. Whereas, age class, year, site, and sex affected lice mean abundance. Juveniles presented higher prevalence and mean abundance than adults, possibly acting as reservoirs for lice as they move through different colonies until they reach reproductive age. Concurrently, seals during molting season were more infested. Unlike nursing, during the molting season seals spend much time ashore forming mixed groups that favor both egg development and lice transmission.

A Novel Mitochondrial Genome Fragmentation Pattern in the Buffalo Louse Haematopinus tuberculatus (Psocodea: Haematopinidae).

Sucking lice are obligate ectoparasites of mammalian hosts, causing serious public health problems and economic losses worldwide. It is well known that sucking lice have fragmented mitochondrial (mt) genomes, but many remain undetermined. To better understand patterns of mt genome fragmentation in the sucking lice, we sequenced the mt genome of the buffalo louse Haematopinus tuberculatus using next-generation sequencing (NGS). The mt genome of H. tuberculatus has ten circular minichromosomes containing a total of 37 genes. Each minichromosome is 2.9-5.0 kb long and carries one to eight genes plus one large non-coding region. The number of mt minichromosomes of H. tuberculatus (ten) is different from those of congeneric species (horse louse H. asini, domestic pig louse H. suis and wild pig louse H. apri) and other sucking lice. Two events (gene translocation and merger of mt minichromosome) are observed in Haematopinus. Compared to other studies, our phylogeny generated from mt genome datasets showed a different topology, suggesting that inclusion of data other than mt genomes would be required to resolve phylogeny of sucking lice. To our knowledge, this is the first report of a ten mt minichromosomes genome in sucking lice, which opens a new outlook into unexplored mt genome fragmentation patterns in sucking lice.

Detection of deltamethrin, cypermethrin and flumethrin efficacy against buffalo lice-Haematopinus tuberculatus.

The cattle and buffalo farm practices have been adopted differently by farmers in India but the infestation of ectoparasites including louse has been advocated in high population of animals across the country. The aim of this study was to identify the louse morphologically and determine the in vitro efficacy of the insecticides deltamethrin, cypermethrin and flumethrin against the buffalo louse, Haematopinus tuberculatus. The present research work was conducted using lice collected from organized buffalo dairy farms of Mhow block, Indore district of Madhya Pradesh, India. The adult's lice were collected from heavily infested regions of the body and tail of buffaloes. Some of the collected adult's lice were preserved for morphological identification in 70% alcohol. Briefly, in vitro treated surface bioassay utilizing a cloth rectangle that allows lice to move freely has been used. The concentrations were prepared as 30, 60, 90 and 120 ppm for deltamethrin and flumethrin, whereas for cypermethrin, 100, 200, 300 and 400 ppm concentrations were prepared in distilled water. The 600 µl of each concentration was spread evenly over a cloth rectangle held in the bottom of a Petri plate. Ten adult lice were used for each concentration in triplicate (n = 30) and the same is maintained for control. The vitality of the louse was assessed at various intervals: 30, 60, 120, 180 and 240 min. The lousicidal efficacy was determined by using in vitro bioassays with deltamethrin, cypermethrin and flumethrin. It is observed that as the concentration of insecticides increases with exposure time, mortality of lice is also increased. The current study reveals that cypermethrin and flumethrin were effective in their recommended doses but in the case of deltamethrin, the lice showed a low level of resistance. Furthermore, this type of study on buffalo louse has not conducted in Mhow region of Madhya Pradesh where heavy infestation of lice occurs on buffalo.

Frequent tRNA gene translocation towards the boundaries with control regions contributes to the highly dynamic mitochondrial genome organization of the parasitic lice of mammals.

BACKGROUND: The typical single-chromosome mitochondrial (mt) genome of animals has fragmented into multiple minichromosomes in the lineage Mitodivisia, which contains most of the parasitic lice of eutherian mammals. These parasitic lice differ from each other even among congeneric species in mt karyotype, i.e. the number of minichromosomes, and the gene content and gene order in each minichromosome, which is in stark contrast to the extremely conserved single-chromosome mt genomes across most animal lineages. How fragmented mt genomes evolved is still poorly understood. We use Polyplax sucking lice as a model to investigate how tRNA gene translocation shapes the dynamic mt karyotypes. RESULTS: We sequenced the full mt genome of the Asian grey shrew louse, Polyplax reclinata. We then inferred the ancestral mt karyotype for Polyplax lice and compared it with the mt karyotypes of the three Polyplax species sequenced to date. We found that tRNA genes were entirely responsible for mt karyotype variation among these three species of Polyplax lice. Furthermore, tRNA gene translocation observed in Polyplax lice was only between different types of minichromosomes and towards the boundaries with the control region. A similar pattern of tRNA gene translocation can also been seen in other sucking lice with fragmented mt genomes. CONCLUSIONS: We conclude that inter-minichromosomal tRNA gene translocation orientated towards the boundaries with the control region is a major contributing factor to the highly dynamic mitochondrial genome organization in the parasitic lice of mammals.

A new symbiotic lineage related to Neisseria and Snodgrassella arises from the dynamic and diverse microbiomes in sucking lice.

The phylogenetic diversity of symbiotic bacteria in sucking lice suggests that lice have a complex history of symbiont acquisition, loss, and replacement throughout their evolution. These processes have resulted in the establishment of different, phylogenetically distant bacteria as obligate mutualists in different louse groups. By combining metagenomics and amplicon screening across several populations of three louse species (members of the genera Polyplax and Hoplopleura) we describe a novel louse symbiont lineage related to Neisseria and Snodgrassella, and show its independent origin in the two louse genera. While the genomes of these symbionts are highly similar, their respective distributions and status within lice microbiomes indicate that they have different functions and history. In Hoplopleura acanthopus, the Neisseriaceae-related bacterium is a dominant obligate symbiont present across several host populations. In contrast, the Polyplax microbiomes are dominated by the obligate symbiont Legionella polyplacis, with the Neisseriaceae-related bacterium co-occurring only in some samples and with much lower abundance. The results thus support the view that compared to other exclusively blood feeding insects, Anoplura possess a unique capacity to acquire symbionts from diverse groups of bacteria.

Disentangling lousy relationships: Comparative phylogenomics of two sucking louse lineages parasitizing chipmunks.

The evolution of obligate parasites is often interpreted in light of their hosts' evolutionary history. An expanded approach is to examine the histories of multiple lineages of parasites that inhabit similar environments on a particular host lineage. Western North American chipmunks (genus Tamias) have a broad distribution, a history of divergence with gene flow, and host two species of sucking lice (Anoplura), Hoplopleura arboricola and Neohaematopinus pacificus. From total genomic sequencing, we obtained sequences of over 1100 loci sampled across the genomes of these lice to compare their evolutionary histories and examine the roles of host association in structuring louse relationships. Within each louse species, clades are largely associated with closely related chipmunk host species. Exceptions to this pattern appear to have a biogeographic component, but differ between the two louse species. Phylogenetic relationships among these major louse clades, in both species, are not congruent with chipmunk relationships. In the context of host associations, each louse lineage has a different evolutionary history, supporting the hypothesis that host-parasite assemblages vary both across the landscape and with the taxa under investigation. In addition, the louse Hoplopleura erratica (parasitizing the eastern Tamias striatus) is embedded within H. arboricola, rendering it paraphyletic. This phylogenetic result, together with comparable divergences within H. arboricola, indicate a need for taxonomic revision. Both host divergence and biogeographic components shape parasite diversification as demonstrated by the distinctive diversification patterns of these two independently evolving lineages that parasitize the same hosts.

The interplay between host biogeography and phylogeny in structuring diversification of the feather louse genus Penenirmus.

Parasite diversification is influenced by many of the same factors that affect speciation of free-living organisms, such as biogeographic barriers. However, the ecology and evolution of the host lineage also has a major impact on parasite speciation. Here we explore the interplay between biogeography and host-association on the pattern of diversification in a group of ectoparasitic lice (Insecta: Phthiraptera: Penenirmus) that feeds on the feathers of woodpeckers, barbets, and honeyguides (Piciformes) and some songbirds (Passeriformes). We use whole genome sequencing of 41 ingroup and 12 outgroup samples to develop a phylogenomic dataset of DNA sequences from a reference set of 2395 single copy ortholog genes, for a total of nearly four million aligned base positions. The phylogenetic trees resulting from both concatenated and gene-tree/species-tree coalescent analyses were nearly identical and highly supported. These trees recovered the genus Penenirmus as monophyletic and identified several major clades, which tended to be associated with one major host group. However, cophylogenetic analysis revealed that host-switching was a prominent process in the diversification of this group. This host-switching generally occurred within single major biogeographic regions. We did, however, find one case in which it appears that a rare dispersal event by a woodpecker lineage from North America to Africa allowed its associated louse to colonize a woodpecker in Africa, even though the woodpecker lineage from North America never became established there.

I've got you under my skin: inflammatory response to elephant seal's lice.

Seals (Phocidae) undergo an annual cycle of moulting that implies hair regeneration, and in the case of southern elephant seals, it also involves the superficial strata of the epidermis. Therefore, surviving the moulting period is crucial for their obligate and permanent ectoparasites. Throughout evolutionary time, sucking lice (Echinophtiriidae) have developed morphological, behavioural and ecological adaptations to cope with the amphibious lifestyle of their hosts. Lepidophthirus macrorhini, the Southern elephant seal louse species, faces the additional challenge of surviving attached to the host during the moulting period. Since lice live on the skin, L. macrorhini has developed a unique survival strategy by piercing the skin of their host, thus keeping them protected from moulting. During fieldwork in Patagonia and Antarctica, skin samples with lice within were collected for histological analysis to assess whether these parasites caused damage to the host. Lice generate an inflammatory process in the host's dermis, and these lesions could alter the normal chemical and mechanical protective properties of the skin facilitating secondary infections. Further studies that analyse the potential pathogens in those skin lesions are necessary to properly assess the real impact of ectoparasites on their host health.

Molecular detection of Rickettsia in ectoparasites (Siphonaptera and Phthiraptera) of domestic and feral pigs from Argentina.

Rickettsioses are distributed among a variety of hematophagous arthropods, and represent an emergent threat. The presence of rickettsial bacteria in ectoparasites collected from pigs from Argentina is still unknown. This study investigated the presence and identity of Rickettsia spp. in fleas, Pulex irritans, and sucking lice, Haematopinus suis, of domestic and feral pigs, Sus scrofa, from Central-Northern Argentina, through the genes gltA and ompB. Rickettsial bacteria were detected in 50% of fleas and 24% of lice. The BLASTn analysis of the ompB gene fragments in P. irritans samples showed identities 99% and 100% with R. felis. Positive samples of H. suis were 99% similar with species from the spotted fever group, future amplifications of a more polymorphic fragment of the ompB gene will allow to corroborate the identity of the Rickettsia species present in these lice samples. The Rickettsia spp. reported in the present study are having eventually been associated with cases of human diseases, and the circulation of these agents in arthropods has already been reported in several countries. Therefore, the identification of circulating pathogenic agents, such as reported in this study, is crucial for development of preventive measures for the control of ectoparasite-borne rickettsiosis diseases. Further studies, using serology techniques, will be allow to explore the ability of pigs as a possible Rickettsia reservoir and its role as part of transmission cycle of Rickettsia spp. in the studied scenarios.

Fragmented mitochondrial genomes evolved in opposite directions between closely related macaque louse Pedicinus obtusus and colobus louse Pedicinus badii.

We report for the first time the fragmented mitochondrial (mt) genomes of two Pedicinus species: Pedicinus obtusus and Pedicinus badii, and compared them with the lice of humans and chimpanzees. Despite being congeneric, the two monkey lice are distinct from each other in mt karyotype. The variation in mt karyotype between the two Pedicinus lice is the most pronounced among the congeneric species of sucking lice observed to date and is attributable to the opposite directions between them in mt karyotype evolution. Two of the inferred ancestral mt minichromosomes of the higher primate lice merged as one in the macaque louse whereas one of the ancestral minichromosomes split into two in the colobus louse after these two species diverged from their most recent common ancestor. Our results showed that mt genome fragmentation was a two-way process in the higher primate lice, and minichromosome merger was more common than previously thought.

Mitochondrial Genome Fragmentation Unites the Parasitic Lice of Eutherian Mammals.

Organelle genome fragmentation has been found in a wide range of eukaryotic lineages; however, its use in phylogenetic reconstruction has not been demonstrated. We explored the use of mitochondrial (mt) genome fragmentation in resolving the controversial suborder-level phylogeny of parasitic lice (order Phthiraptera). There are approximately 5000 species of parasitic lice in four suborders (Amblycera, Ischnocera, Rhynchophthirina, and Anoplura), which infest mammals and birds. The phylogenetic relationships among these suborders are unresolved despite decades of studies. We sequenced the mt genomes of eight species of parasitic lice and compared them with 17 other species of parasitic lice sequenced previously. We found that the typical single-chromosome mt genome is retained in the lice of birds but fragmented into many minichromosomes in the lice of eutherian mammals. The shared derived feature of mt genome fragmentation unites the eutherian mammal lice of Ischnocera (family Trichodectidae) with Anoplura and Rhynchophthirina to the exclusion of the bird lice of Ischnocera (family Philopteridae). The novel clade, namely Mitodivisia, is also supported by phylogenetic analysis of mt genome and cox1 gene sequences. Our results demonstrate, for the first time, that organelle genome fragmentation is informative for resolving controversial high-level phylogenies.

Enhancement of sciatic nerve regeneration with dual delivery of vascular endothelial growth factor and nerve growth factor genes.

BACKGROUND: Peripheral nerve injury is one common clinical disease worldwide, in which sciatic nerve is anatomically the most challenging to regenerate given its length and large cross-sectional area. For the present, autologous nerve grafting remains to be the most ideal strategy when treating with sciatic nerve injury. However, this method sacrifices healthy nerves and requires highly intensive surgery, still calling for other advanced alternatives for nerve grafting. RESULTS: In this study, we utilized previously well-established gene delivery system to dually deliver plasmid DNA (pDNA) encoding vascular endothelial growth factor (VEGF) and nerve growth factor (NGF), exploring therapeutics for sciatic nerve injury. Low-molecular-weight branched polyethylenimine (bPEI) was constructed as the backbone structure of gene vectors, and it was further crosslinked to synthesize degradable polycations via the conjugation of dialdehydes. Potential synergistic effect between VEGF and NGF proteins were observed on rat sciatic nerve crush injury model in this study. CONCLUSIONS: We concluded that dual delivery of plasmid VEGF and NGF as gene therapy could enhance sciatic nerve regeneration.