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PubMed2005

Structure of the ovary and the differentiation of follicular epithelium in the pig louse, Haematopinus suis (Insecta: Phthiraptera).

The female reproductive system of the pig louse, Haematopinus suis (Insecta: Phthiraptera) is composed of paired ovaries, lateral oviducts, and a common oviduct that leads into a vagina. Clusters of mycetocytes (= cells filled with symbiotic organisms) are associated with lateral oviducts. Each ovary is composed of five loosely arranged ovarioles of the polytrophic-meroistic type. An individual ovariole is covered by a basal lamina and is composed of a terminal filament, germarium, and vitellarium. The terminal filament is composed of large, disc-shaped cells that are orientated perpendicularly to the long axis ofthe ovariole. The basal part of the terminal filament is separated from the germarium by a well-developed transverse septum. The germarium is short and filled with clusters of oogonial cells. In each cluster the cells arejoined by intercellular bridges, filled with fusomal material. Within the cluster, only one cell, the future oocyte, enters the prophase of the first meiotic division; the other cells differentiate into nurse cells. The basal part ofthe germarium is filled with the somatic prefollicular cells. The boundary between the germarium and the vitellarium is not distinct. The vitellarium contains linearly arranged ovarian follicles in subsequent stages of oogenesis (previtellogenesis, vitellogenesis and choriogenesis). Each follicle consists of an oocyte and 7 nurse cells and is surrounded by follicular cells. During oogenesis the follicular cells diversify, so that ultimately, five morphologically distinct subpopulations of these cells can be distinguished: (1) cells in contact with the nurse cells, (2) anterior cells, (3) mainbody cells, (4) posterior cells, and (5) interfollicular cells. Interestingly, the follicular cells associated with the anterior part of the oocyte, i.e. located in space at the oocyte/nurse cell border (fold cells) are mitotically active throughout previtellogenesis. It might be suggested, in this context, that the separation of the oocyte from the nurse cell compartment is brought about by mitotic divisions, consequent multiplication and centripetal migration of these cells.

Animals↗
PubMed1990

External morphology of the antennae of Damalinia ovis (Phthiraptera: Trichodectidae).

The antennae of adult Damalinia ovis, the sheep louse, were studied using light and scanning electron microscopy. Sensory structures are located on all three antennal segments with the predominant sensilla type being tactile. Nine different types of sensilla are described on the basis of external appearance. One of the sensilla, designated a "pit organ" because of its unusual shape, has not been described previously. A pair of these sensilla are present on each antenna, and their function is unknown. A group of 11 sensilla on the tip of each antenna contains olfactory and chemosensory pegs, and a possible thermohygroreceptor. The antennae are sexually dimorphic, the male having more tactile sensilla, two well-developed terminal hooks, and a different cuticular architecture on the posterior surface of antennal segment 1.

Animals↗
PubMed2006

Patterns in the distribution of avian lice (Phthiraptera: Amblycera, Ischnocera) living on the great grey shrike Lanius excubitor.

The lice parasite community of great grey shrike Lanius excubitor collected in NE Slovakia during 1962-1974 was quantitatively studied. Lice fauna comprised of three species: Docophorulus coarctatus, Bruelia cruciata (Ischnocera) and Lanicanthus camelinus (Amblycera). All these species were previously indicated as characteristic for that host. The prevalence of lice was high--lice were recovered from 96.3% (n=108) host specimens. Distributions of lice on the great grey shrike, a strictly territorial bird, were aggregated, indicating substantial variation in the abundance of lice. Sex ratios of lice were biased towards females and not correlated with the subpopulation size of lice on individual hosts.

Animals↗
PubMed2006

Supergroup F Wolbachia bacteria parasitise lice (Insecta: Phthiraptera).

We studied six species of lice from three of the four suborders of lice. These lice were infected with Wolbachia bacteria from supergroups A and F. This is the first report of an infection of supergroup F Wolbachia in lice. To date, Wolbachia from supergroup F have been found in filarial nematodes, Mansonella spp., and, rarely, in insects. We inferred the phylogeny of the Wolbachia from lice and representatives of all Wolbachia supergroups, with nucleotide sequences from the small subunit ribosomal RNA gene (SSU rRNA). There was no evidence of congruence between the taxon of louse and the Wolbachia bacteria that infect lice. There is no evidence that Wolbachia and their louse hosts co-evolved at least at the level of Wolbachia supergroups. We propose a novel mechanism for the horizontal transfer of Wolbachia between different species of lice from birds: transfer of Wolbachia during phoresis by hippoboscid flies.

Animals↗
PubMed1991

The distribution of lice (Phthiraptera) on poultry (Gallus domesticus).

The distribution of three amblyceran (Menacanthus stramineus, Menacanthus cornutus, Menopon gallinae) and five ischnoceran species (Lipeurus lawrensis tropicalis, Lipeurus caponis. Goniocotes gallinae, Goniodes gigas, Goniodes dissimilis) on poultry was determined. The preferred sites of these species on the host body were recorded.

Animals↗
PubMed1991

Genetic variation in the Heterodoxus octoseriatus group (Phthiraptera): a test of Price's model of parasite evolution.

Most of the genetic variation in the H. octoseriatus group is present as fixed gene differences between species which have been described on morphological criteria. Based on allozymes, the taxonomic status of some species was challenged. There was insufficient evidence, however, to demonstrate that these were not 'good' biological species. Overall, the limited intraspecific variation was present as fixed gene differences among lice from different hosts and from different colonies of hosts; heterozygotes were rare. Two predictions derived from Price's model of parasite evolution were met: populations of lice were genetically homogeneous and, where genetic markers were present, we found substantial genetic variation among populations. These data contrast with those for endoparasitic helminths, where, in general, the amount of genetic variation is similar to that of free-living invertebrates.

Animals↗
PubMed1993

Systematic relationships among pocket gopher chewing lice (Phthiraptera: Trichodectidae) inferred from electrophoretic data.

Multilocus starch-gel electrophoresis was used to obtain electrophoretic data for maximum parsimony, phenetic, and component analysis of systematic relationships among 14 species of pocket gopher chewing lice and two outgroup species. Pocket gopher lice studied included taxa representing seven of the 25 species complexes in Geomydoecus, and two of the four species complexes of Thomomydoecus. In pairwise comparisons, 12 of the 14 pocket gopher lice were characterized by two or more fixed genetic differences, and each nominal species possessed at least one fixed difference. These electrophoretic results are consistent with previous morphological analysis of species-level taxonomy. A maximum-parsimony analysis of the electrophoretic data yielded 80 trees, each with a length of 78 steps and a consistency index of 0.83. The strict consensus tree and the UPGMA phenogram of genetic distances indicate that five species of lice from Central American pocket gophers (Orthogeomys) form a clade distinct from lice hosted by North American pocket gophers (Geomys, Thomomys, and Cratogeomys). Other louse clades receiving reasonable support in bootstrap parsimony analysis include: (Thomomydoecus wardi, Th. minor); (Geomydoecus scleritus, G. mobilensis); (G. panamensis, G. setzeri); and (G. cherriei, G. costaricensis). The systematic results of this electrophoretic study are generally consistent with the boundaries of louse species complexes described previously.

Alleles↗
PubMed1989

Feeding of the chewing louse Damalinia ovis (Schrank) (Phthiraptera:Trichodectidae) on sheep.

The possibility that Damalinia ovis ingests intact epidermis could explain economically important irritation behaviour by infested sheep. To test this, feeding lice were observed on sheep by hand lens and macrophotography and on light and scanning electron microscope preparations. Aspects of feeding behaviour were described, particularly an epidermal ingestion posture. Louse ingesta were examined in paraffin and frozen sections. Lipid-covered stratum corneum squames were identified in crop, midgut, rectum and faeces. Nucleated keratinocytes from inner epidermal strata were not seen, neither were wool fibres. Vertical frozen sheep skin sections, with feeding lice cryofixed by liquid nitrogen, showed mandibles engaged in the outer stratum corneum of the epidermis. The epidermal origin of some ingesta was confirmed by confirming lice over sheep whose skin was stained with Oil Red O, whose colour was seen in crop, midgut, rectum and faeces of harvested lice. Lipase was found in louse midgut. It was concluded that sebaceous secretions may form an important component of the D. ovis diet. The relative contribution from loose scurf or from stratum corneum squames was not determined. Mechanical stimuli by feeding lice did not seem to be the source of host irritation. The role of sensitising agents in louse brei filtrates was investigated with inconclusive results. Intradermal injections of louse faeces did not elicit a demonstrable response.

Animals↗
PubMed1997

Egg shells of mallophagans and anoplurans (Insecta: Phthiraptera): morphogenesis of specialized regions and the relation to F-actin cytoskeleton of follicular cells.

The egg shells of investigated phthirapterans consist of three basic elements: an anterior operculum, a main egg shell and a posterior hydropyle. In some species these elements show further regional specializations: bristles and projections that facilitate attachment to feathers of the host, micropyles and aeropylar openings. All of the egg shell specializations are formed by distinct subpopulations of follicular cells. Staining with rhodamine-conjugated phalloidin has revealed that these subpopulations significantly differ in the distribution of microfilaments (F-actin). In this respect four morphological categories of the follicular cells have been distinguished: (1) cells devoid of processes and microvilli, with basal arrays of microfilaments, responsible for the secretion of a flat chorion; (2) cells devoid of processes and microvilli, separated by intercellular spaces, with basal arrays of microfilaments, responsible for the secretion of attachment structures; (3) cells equipped with actin-containing processes, responsible for the formation of micropyles or aeropyles, and (4) cells equipped with bundles of microvilli, responsible for the formation of hydropyles.

Actins↗
PubMed1997

Density and distribution of cattle lice (Phthiraptera:Haematopinidae, Linognathidae, Trichodectidae) on six steers.

The density and distribution of four species of cattle louse, Bovicola bovis (L.). Haematopinus eurysternus (Nitzsch), Linognathus vituli (L.), and Solenopotes capillatus (Enderlein), were elucidated from the hides of six slaughtered steers. Adult and nymphal lice were first removed from one hide by hand and the location of each specimen mapped. The remaining lice were removed by a detergent wash, and KOH dissolution of hide and hair. Lice from the remaining five hides were removed using KOH dissolution of cattle hair and subsequent filtration of the effluent. Bovicola bovis was most abundant, followed by H. eurysternus, L. vituli and S. capillatus. Significant variation was observed in B. bovis, H. eurysternus and L. vituli population densities. Solenopotes capillatus population densities did not differ significantly. All species were contagiously distributed, i.e. 'clumped', suggesting species dependent predilection sites. Predilection sites were ranked according to louse density to facilitate the development of field sampling strategies. Additional biological data were gathered on sex and life stage ratios for each species.

Animals↗
PubMed2004

Phylogeny of "Philoceanus complex" seabird lice (Phthiraptera: Ischnocera) inferred from mitochondrial DNA sequences.

The Philoceanus complex is a large assemblage of lice that parasitise procellariiform seabirds (petrels, albatrosses, and their relatives). We obtained mitochondrial 12S rRNA and cytochrome oxidase I DNA sequences from 39 species from diverse hosts and localities. Resolution of deeper relationships between genera was limited, however there is evidence for two major clades, one hosted by albatrosses, the other by petrels. Based on our results, the genera hosted by albatrosses are excellent candidates for detailed analysis of cospeciation. Our results also suggest that a previous estimate of a 5-fold difference in the relative rate of sequence evolution in lice and their avian hosts is an artefact of limited taxonomic sampling.

Animals↗
PubMed2002

Louse (Insecta: Phthiraptera) mitochondrial 12S rRNA secondary structure is highly variable.

Lice are ectoparasitic insects hosted by birds and mammals. Mitochondrial 12S rRNA sequences obtained from lice show considerable length variation and are very difficult to align. We show that the louse 12S rRNA domain III secondary structure displays considerable variation compared to other insects, in both the shape and number of stems and loops. Phylogenetic trees constructed from tree edit distances between louse 12S rRNA structures do not closely resemble trees constructed from sequence data, suggesting that at least some of this structural variation has arisen independently in different louse lineages. Taken together with previous work on mitochondrial gene order and elevated rates of substitution in louse mitochondrial sequences, the structural variation in louse 12S rRNA confirms the highly distinctive nature of molecular evolution in these insects.

Animals↗
PubMed1995

Increased susceptibility to Bacillus thuringiensis associated with pyrethroid resistance in Bovicola (Damalinia) ovis (Phthiraptera Mallophaga: possible role of monooxygenases.

A comparison of the toxicity of Bacillus thuringiensis (Berliner) to pyrethroid-susceptible and -resistant strains of Bovicola (Damalinia) ovis showed that B. thuringiensis and pyrethroid toxicity were inversely related. The B. ovis strain with an apparent monooxygenase-mediated pyrethroid resistance mechanism was significantly more susceptible to B. thuringiensis. Susceptibility to B. thuringiensis in both the pyrethroid-susceptible and -resistant strains was significantly reduced after administration of the monooxygenase inhibitor piperonyl butoxide. Susceptibility to B. thuringiensis in the pyrethroid-susceptible strain was significantly enhanced after administration of a monooxygenase inducer, sodium phenobarbital. These results suggest that monooxygenases may be important in increasing the toxicity of B. thuringiensis against B. ovis. We discuss the potential use of B. thuringiensis to control pyrethroid-resistant lice.

Animals↗