Adult Host Research Articles

Effects of host migration, diversity and aquaculture on sea lice threats to Pacific salmon populations

Animal migrations can affect disease dynamics. One consequence of migration common to marine fish and invertebrates is migratory allopatry-a period of spatial separation between adult and juvenile hosts, which is caused by host migration and which prevents parasite transmission from adult to juvenile hosts. We studied this characteristic for sea lice (Lepeophtheirus salmonis and Caligus clemensi) and pink salmon (Oncorhynchus gorbuscha) from one of the Canada's largest salmon stocks. Migratory allopatry protects juvenile salmon from L. salmonis for two to three months of early marine life (2-3% prevalence). In contrast, host diversity facilitates access for C. clemensi to juvenile salmon (8-20% prevalence) but infections appear ephemeral. Aquaculture can augment host abundance and diversity and increase parasite exposure of wild juvenile fish. An empirically parametrized model shows high sensitivity of salmon populations to increased L. salmonis exposure, predicting population collapse at one to five motile L. salmonis per juvenile pink salmon. These results characterize parasite threats of salmon aquaculture to wild salmon populations and show how host migration and diversity are important factors affecting parasite transmission in the oceans.

A feline immunodeficiency virus vif-deletion mutant remains attenuated upon infection of newborn kittens

This report characterizes lentivirus attenuation associated with a vif mutation by inoculation of newborn kittens with a vif-deleted feline immunodeficiency virus provirus plasmid (FIV-pPPRDeltavif). Virus in peripheral blood, antiviral antibody or CD4 T-cell count alterations were not detected in kittens inoculated with FIV-pPPRDeltavif plasmid, with the exception of one kitten that demonstrated FIV Gag antibody production at 42 weeks after inoculation. In contrast, wild-type FIV-pPPR-infected kittens were viraemic, seropositive and exhibited a decrease in the CD4 T-cell subset in peripheral blood. Interestingly, FIV-specific T-cell proliferative responses detected at 32 and 36 weeks after infection were comparable for both FIV-pPPRDeltavif- and wild-type FIV-pPPR-inoculated kittens and suggested the possibility of a discreet tissue reservoir supporting sustained FIV-pPPRDeltavif expression or replication. Overall, these findings confirmed that the severe virus attenuation for both replication and pathogenicity exhibited by a vif-deleted FIV mutant is similar for both neonatal and adult hosts.

Parasite co-infection and interaction as drivers of host heterogeneity

We examined the hypothesis that the interaction between concomitant infecting parasites modifies host susceptibility, parasite intensity and the pattern of parasite distribution within the host population. We used a 26 year time series of three common parasites in a natural population of rabbits: two gastrointestinal nematodes (Trichostrongylus retortaeformis and Graphidium strigosum) and the immunosuppressive myxoma virus. The frequency distribution of nematodes in the host population and the relationship between host age and nematode intensity were explored in rabbits with either single or dual nematode infections and rabbits infected with the nematodes and myxoma virus. The aggregation of T. retortaeformis and G. strigosum among the rabbits varied with the nature of the co-infection both in male and female hosts. The two nematodes exhibited different age–intensity profiles: G. strigosum intensity increased exponentially with host age while T. retortaeformis intensity exhibited a convex shape. The presence of a secondary infection did not change the age–intensity profile for G. strigosum but for T. retortaeformis co-infection (either both nematodes or myxoma-nematodes) resulted in significantly greater intensities in adult hosts. Results suggest that multi-species infections contributed to aggregation of parasites in the host population and to seasonal variation in intensity, but also enhanced differences in parasitism between sexes. This effect was apparent for T. retortaeformis, which appears to elicit a strong acquired immune response but not for G. strigosum which does not produce any evident immune reaction. We concluded that concomitant infections mediated by host immunity are important in modifying host susceptibility and influencing heterogeneity amongst individual hosts.

Molecular Diagnosis of Kingella kingae Pericarditis by Amplification and Sequencing of the 16S rRNA Gene

Kingella kingae is a fastidious gram-negative bacillus that is considered an emerging pathogen in pediatric settings but remains less common in adults. Here we describe a case of pericarditis in an immunocompetent adult host. The microorganism was identified directly from the clinical sample by molecular techniques, i.e., 16S rRNA gene amplification and sequencing.

Behavioral improvement in a primate Parkinson's model is associated with multiple homeostatic effects of human neural stem cells

Stem cells have been widely assumed to be capable of replacing lost or damaged cells in a number of diseases, including Parkinson's disease (PD), in which neurons of the substantia nigra (SN) die and fail to provide the neurotransmitter, dopamine (DA), to the striatum. We report that undifferentiated human neural stem cells (hNSCs) implanted into 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated Parkinsonian primates survived, migrated, and had a functional impact as assessed quantitatively by behavioral improvement in this DA-deficit model, in which Parkinsonian signs directly correlate to reduced DA levels. A small number of hNSC progeny differentiated into tyrosine hydroxylase (TH) and/or dopamine transporter (DAT) immunopositive cells, suggesting that the microenvironment within and around the lesioned adult host SN still permits development of a DA phenotype by responsive progenitor cells. A much larger number of hNSC-derived cells that did not express neuronal or DA markers was found arrayed along the persisting nigrostriatal path, juxtaposed with host cells. These hNSCs, which express DA-protective factors, were therefore well positioned to influence host TH+ cells and mediate other homeostatic adjustments, as reflected in a return to baseline endogenous neuronal number-to-size ratios, preservation of extant host nigrostriatal circuitry, and a normalizing effect on alpha-synuclein aggregation. We propose that multiple modes of reciprocal interaction between exogenous hNSCs and the pathological host milieu underlie the functional improvement observed in this model of PD.

Horizontal transmission success of Nosema bombi to its adult bumble bee hosts: effects of dosage, spore source and host age

Parasite transmission dynamics are fundamental to explaining the evolutionary epidemiology of disease because transmission and virulence are tightly linked. Horizontal transmission of microsporidian parasites, e.g. Nosema bombi, may be influenced by numerous factors, including inoculation dose, host susceptibility and host population heterogeneity. Despite previous studies of N. bombi and its bumble bee hosts, neither the epidemiology nor impact of the parasite are as yet understood. Here we investigate the influence N. bombi spore dosage (1000 to 500,000 spores), spore source (Bombus terrestris and B. lucorum isolates) and host age (2- and 10-day-old bees) have on disease establishment and the presence of patent infections in adult bumble bees. Two-day-old bees were twice as susceptible as their 10-day-old sisters, and a 5-fold increase in dosage from 100,000 to 500,000 spores resulted in a 20-fold increase in the prevalence of patent infections. While intraspecific inoculations were 3 times more likely to result in non-patent infections there was no such effect on the development of patent infections. These results suggest that host-age and dose are likely to play a role in N. bombi's evolutionary epidemiology. The relatively low levels of horizontal transmission success are suggestive of low virulence in this system.

MICROSPORIDIAN PARASITES OF MOSQUITOES

The Microsporidia are a large diverse group of obligate, intracellular parasites. They are singlecelled eukaryotic microorganisms that have small genomes in the size range of prokaryotic cells and are now thought to be highly evolved fungi (Keeling and Fast 2002). They are exclusive parasites of other eukaryotes and possess a unique and highly specialized mechanism for invading host cells via infectious spores. Spores are the only stage that can exist outside a living host cell and they are the primary vehicles for horizontal transmission between hosts (peroral) and vertical transmission (transovarial) within the host. Spores are diagnostic, especially at the ultrastructural level (Fig. 1), and are distinguished by their small size (2–20 mm), thick walls (consisting of an endospore and exospore), and presence of a unique set of organelles that function as an extrusion apparatus. These include a tightly coiled polar filament (tube) that is attached to an anchoring disc at the anterior pole of the spore, a membranous polaroplast, and a posterior vacuole which collectively function to explosively inoculate the spore content or ‘‘sporoplasm’’ through the polar filament into a host cell to initiate infection. Microsporidia are ubiquitous in nature and exhibit a very broad host range within the animal kingdom. They have been described as parasites in all classes of vertebrates, including humans, and most invertebrates, but are particularly common to arthropods and fish. Microsporidia represent one of the largest and most diverse groups of parasitic organisms associated with mosquito populations in nature. They have been described from 14 different genera worldwide, and it is quite likely that all mosquitoes serve as hosts for one or more of these parasites. The group currently includes a heterogeneous assemblage of over 150 described species from 23 recognized genera, 15 of which are monotypic (only one species is known) (Table 1). Members of these genera exhibit extensive variation in their development and life cycles but generally fall into 2 broad categories. The first includes the monomorphic forms such as Anncaliia (formerly Nosema and then Brachiola) (Franzen et al. 2006) and Vavraia. These microsporidia have comparatively simple life cycles involving only one sporogonic sequence (Fig. 2). They develop asexually (merogony or schizogony) and produce a single spore type that is orally infectious to mosquito larvae. Vertical transmission may additionally occur via oral ingestion of spores on contaminated eggs (transovum), but there is no separate developmental sequence leading to ovarian infection in female hosts. These microsporidia have a very broad host range and are mildly pathogenic to mosquitoes, generally producing low larval mortality. Other genera from which only one developmental sequence has been described include Aedispora, Crepidulospora, Polydispyrenia, Senoma, Trichotosporea, and Tricornia. However, the complete life cycles and modes of transmission of members of these genera have yet to be resolved and they may be polymorphic. The second group includes the true polymorphic forms. These parasites are more common in nature and exhibit some of the most complex life cycles yet described for any microsporidia (Fig. 2). These include elements of asexual (schizogony, merogony, and sporogony) and sexual (karyogamy, gametogenesis, and plasmogamy) reproduction; the formation of multiple spore types in various stages of the host; host sexand tissue-dependent development; and separate developmental sequences leading to vertical (transovarial) and horizontal transmission. Many species, such as Edhazardia aedis, require two successive host generations to complete their life cycle, and at least 4 genera, Amblyospora, Duboscqia, Hyalinocysta and Parathelohania require obligatory development in an intermediate copepod host. These microsporidia generally exhibit higher levels of host specificity and although they do not cause any acute mortality or detectable morbidity in adult female hosts that go on to transmit infections transovarially, they have at least one phase of development that typically kills larval hosts during the last stadium. Mortality in larvae results from destruction of various host tissues and subsequent depletion of essential energy reserves necessary for pupation. The production of entomopathogenic toxins has never been documented. Copyright E 2007 by The American Mosquito Control Association, Inc.

Biological and Distributional Observations on North American Cerambycidae (Coleoptera)

Biological and distributional observations are presented for 166 species/subspecies of North American Cerambycidae representing 100 genera/subgenera in four subfamilies. New or confirmed records include 245 larval hosts, 39 distributions, 66 flower hosts, and 18 adult hosts. The male of Gaurotes thoracica (Haldeman) is described, the holotype deposition of Purpuricenus linsleyi Chemsak is clarified, and comments or corrections to previous literature records for several species are made.

Steel factor responsiveness regulates the high self-renewal phenotype of fetal hematopoietic stem cells

AbstractFetal hematopoietic stem cells (HSCs) regenerate daughter HSCs in irradiated recipients more rapidly than do adult HSCs. However, both types of HSCs divide in vitro with the same cell-cycle transit times, suggesting different intrinsically determined self-renewal activities. To investigate the mechanism(s) underlying these differences, we compared fetal and adult HSC responses to Steel factor (SF) stimulation in vitro and in vivo. These experiments were undertaken with both wild-type cells and W41/W41 cells, which have a functionally deficient c-kit kinase. In vitro, fetal HSC self-renewal divisions, like those of adult HSCs, were found to be strongly dependent on c-kit activation, but the fetal HSCs responded to much lower SF concentrations in spite of indistinguishable levels of c-kit expression. Fetal W41/W41 HSCs also mimicked adult wild-type HSCs in showing the same reduced rate of amplification in irradiated adult hosts (relative to fetal wild-type HSCs). Assessment of various proliferation and signaling gene transcripts in fetal and adult HSCs self-renewing in vitro revealed a singular difference in Ink4c expression. We conclude that the ability of fetal HSCs to execute symmetric self-renewal divisions more efficiently than adult HSCs in vivo may be dependent on specific developmentally regulated signals that act downstream of the c-kit kinase.

Fetal/neonatal ethanol exposure irreversibly alters immune parameters in young mice (36.28)

Abstract Chronic ethanol ingestion has been shown to impair immune defensive function of adult hosts to invading organisms. Children born to alcoholic mothers are known to have increased incidence and severity of infections, but EtOHÕs effect on the immune system in the fetus/neonate has not been well studied. We have developed a model of fetal/neonatal EtOH exposure in which female mice are maintained on 10% EtOH in the drinking water during breeding and gestation, and then on 12% EtOH during lactation. Pups have successfully been weaned and showed no significant difference in weights from controls through 42 days of age. These pups have been studied at 20 d (weaning) and 42 d (adolescence) for immunological cell numbers and function. Our data showed decreased splenic T and B cells in EtOH pups, but increased pulmonary leukocyte and dendritic cell (DC) numbers. Splenic DC and epidermal Langerhans cells numbers did not change. However, EtOH decreased baseline costimulatory molecule expression on splenic DC and the ability of these DC to stimulate allogeneic T cells, changes that persisted following cessation of EtOH exposure. These results indicate that mice born to EtOH-consuming mothers have immune deficiencies that are persistent following cessation of EtOH exposure. The dissection of T, B cell and DC dysfunction in EtOH pups is in progress.

ECTOPARASITES IN AN URBAN POPULATION OF BIG BROWN BATS (EPTESICUS FUSCUS) IN COLORADO

Ectoparasites of an urban population of big brown bats (Eptesicus fuscus) in Fort Collins, Colorado, were investigated during summers 2002, 2003, and 2004. Eleven species of ectoparasites were found (the macronyssid mite Steatonyssus occidentalis, the wing mite Spinturnix bakeri, the myobiid mites Acanthophthirius caudata and Pteracarus aculeus, the chirodiscid mite Alabidocarpus eptesicus, the demodicid mite Demodex sp., the chigger Leptotrombidium myotis, the soft tick Carios kelleyi, the batfly Basilia forcipata, the batbug Cimex pilosellus, and the flea Myodopsylla borealis). Five species were analyzed by prevalence and intensity (C. pilosellus, M. borealis, L. myotis, S. bakeri, and S. occidentalis) based on 2161 counts of 1702 marked individual bats over the 3 summer study periods. We investigated 4 factors potentially influencing prevalence and intensity: age class of the host, reproductive status of adult female hosts, roosts in which the hosts were found, and abiotic conditions during the year sampled. The macronyssid mite, S. occidentalis, was the most prevalent and abundant ectoparasite. Adult big brown bats had more ectoparasites than volant juveniles for most of the species analyzed. In a sample of known age bats at 1 large colony, bats of 4 yr of age or greater had higher ectoparasite loads of S. occidentalis and S. bakeri when compared with younger bats. Lactating female bats had the highest prevalence and intensities of most ectoparasites. Annual differences in ectoparasite prevalence and intensity were related to temperature and humidity, which can affect the nidicolous species of ectoparasites. Residents of 2 buildings sprayed insecticides in response to Cimex sp., and this appeared to reduce ectoparasitism of S. occidentalis and C. pilosellus present at these buildings. Intensity of S. occidentalis had no influence on annual survival of big brown bats.

Soilborne ascospores and pycnidiospores ofLeptosphaeria maculanscan contribute significantly to blackleg disease epidemiology in oilseed rape (Brassica napus) in Western Australia

Blackleg disease (Leptosphaeria maculans) causes severe yield losses in oilseed rape (Brassica napus) worldwide from the development of cankers in the crown of the plant and, in Western Australia, also from seedling death following early infections. Although most aspects of the epidemiology of this disease are relatively well described, the role of soilborne ascospores and pycnidiospores in the disease epidemic remains unknown. Three separate experiments were undertaken to define the role for soilborne ascospores and pycnidiospores of the blackleg pathogen in the disease epidemiology of oilseed rape. Both spore types were able to cause seedling death, even after the spores had remained in a plant growth medium for up to 21 days before sowing. The most severe seedling death occurred where seeds were sown 7 days before infestation (59 and 40% seedlings dead for pycnidiospores and ascospores, respectively) or at 14 days before infestation (53 and 32% seedlings dead for pycnidiospores and ascospores, respectively). For pycnidiospores in moist sand, there was significantly more seedling death for sowings 7, 14 or 21 days after infestation compared with concurrent sowing and infestation. For pycnidiospores, allowing the sand to dry between infestation and sowing, significantly reduced mortality for seedlings, but not for ascopsores. For ascospores, adding a 20-mm layer of uninfested sand over the top of the infested sand reduced seedling death. A buried slide assay indicated that both ascospores and pycnidiospores were capable of germination in the sand with lengths of germ tubes similar to those observed on control slides incubated in a sterile moist chamber. To our knowledge, this is the first study to indicate a clear role for soilborne inoculum in the epidemiology of blackleg disease. It is postulated that this role will be of high relative importance in the disease epidemiology in situations where the ascospore showers have been low or restricted to a short period at the beginning of growing season. However, soilborne inoculum could also play a significant role in the disease epidemiology in situations where one or more major ascospore showers have occurred just before or during the early stages of sowing and/or seedling development. The findings, in relation to soilborne pycnidiospore infestations, are further evidence that blackleg, at least in Australia, is a polycyclic disease. Our findings may also explain the responses of canola seedlings to the application of fungicides to soil or seed in reducing blackleg severity and improving seedling survival in blackleg-affected fields in previous studies in Western Australia. The implications for field management of this disease in Australia include a greater need for the application of fungicidal seed or fertiliser treatments and/or utilisation of higher levels of seedling and/or adult host resistance in situations where soilborne inoculum is present.

The Response Specificity of Trichogramma Egg Parasitoids towards Infochemicals during Host Location

Parasitoids are confronted with many different infochemicals of their hosts and food plants during host selection. Here, we investigated the effect of kairomones from the adult host Pieris brassicae and of cues present on Brussels sprout plants infested by P. brassicae eggs on the behavioral response of the egg parasitoid Trichogramma evanescens. Additionally, we tested whether the parasitoid’s acceptance of P. brassicae eggs changes with different host ages. The wasps did not discriminate between olfactory cues from mated and virgin females or between mated females and males of P. brassicae. T. evanescens randomly climbed on the butterflies, showing a phoretic behavior without any preference for a certain sex. The parasitoid was arrested on leaf parts next to 1-day-old host egg masses. This arrestment might be due to cues deposited during oviposition. The wasps parasitized host eggs up to 3 days old equally well. Our results were compared with former studies on responses by T .brassicae showing that T. evanescens makes less use of infochemicals from P. brassicae than T. brassicae.

Migration of neural precursor cells derived from olfactory bulb in cochlear nucleus exposed to an augmented acoustic environment

The regeneration of the auditory neural system remains a challenge in hearing restoration. Acoustic signals may induce a site-specific cell replacement in the auditory system. This hypothesis was tested with grafted implantation of neural precursor cells (NPCs) along the cochlear nucleus in the adult host followed by an augmented acoustic stimulation. NPCs were obtained from the olfactory bulbs at embryonic day 14–16 and were transplanted into the inside border of cochlear nucleus. The labeled cells survived at least 2 weeks, verified by Hoechst 33342 fluorescence, and by immunostaining for a neuronal marker. In some cases NPCs had migrated directionally to the root of the auditory nerve. This observation demonstrates the survival and migration of NPCs from the olfactory bulb (OB) along the adult auditory nerve in an augmented acoustic environment following implantation.

Kairomones Extracted from Rice Yellow Stem Borer and their Influence on Egg Parasitization by Trichogramma japonicum Ashmead

Host location and acceptance by egg parasitoids can be mediated by close-range host stimuli. In this study, we tested the response of Trichogramma japonicum Ashmead to cuticular extracts of adult and larval rice yellow stem borer (YSB), Scripophaga incertulas Walker. We also studied the wasps' response to extracts from YSB larval frass. Laboratory bioassays revealed that hexane extracts of the adult host body stimulate ovipositor probing of T. japonicum. Extracts of larval frass also stimulated parasitization. In contrast, host larval cuticular extracts had no effect on parasitization rates. Fractionation of the crude extracts of adult YSB cuticular extracts was performed using silica gel chromatography, followed by bioassays of the individual fractions to test their effects on wasp behavior. Analyses of the most active fractions by gas chromatography-mass spectrometry revealed that the extract contained saturated long chain alkanes and alkenes, with carbon numbers ranging from C20 to C32. Hydrocarbons were applied onto host eggs to test their effects on parasitization rates. Treatments of eggs with docosane, tetracosane, pentacosane, and eicosane enhanced host egg parasitization, while pentadecane, hexadecane, and nonadecane deterred oviposition.

Organogenesis of Pancreatic Anlagen Allografted in Rats

Aims To study the possibility of revascularization, growth, and differentiation of embryonic pancreatic anlagen transplanted to adult hosts. While transplantations of pancreas and islets are the main methods to cure diabetes mellitus, the donor source is in shortage. So it’s necessary to find a new source for transplantation. Methods The pancreas from embryonic day 14.5 (E14.5) and 15.5 (E15.5) Lewis rat embryos were implanted into either intraperitoneal or subrenal capsular site of healthy Lewis rats. at 3 weeks or 6 weeks after implantation, the pancreatic anlagen in the host rats were resected for size measurements, as well as histopathologic and immunohistochemical examinations. Results Three weeks after implantation into the renal-capsular site, the size of both E14.5 and E15.5 pancreatic anlagen had enlarged 10- to 15-fold with differentiation of acinar components upon histological examination. Moreover, increasing numbers of β cells and islets stained positive for insulin, and newly generated vessels were observed around the tissues. Continued proliferation of the endocrine islets in E14.5 pancreatic anlagen grafts was observed after another 3 weeks, whereas further proliferation in the E15.5 pancreatic anlagen graft was not seen. Additionally fibrosis appeared in the exocrine component of both E14.5 and E15.5 pancreatic anlagen at this time point. When implanted into intraperitoneal site, enlarged E15.5 pancreatic anlagen with proliferatels β cells were also observed after 3 weeks. However, both the size of the pancreatic anlagen and the proliferation of the β cells were much less than that in the subrenal capsular site. Conclusions The allografted E14.5 and E15.5 pancreatic anlagen revascularised and grew into tissues that were structurally similar to normal mature rats pancreatic tissue. Adequate embryonic age for the transplantation of pancreatic anlagen is 14.5 and 15.5 days old. Subrenal capsula is a more suitable site than the peritoneal cavity for implantation of pancreatic anlagen.

New Distribution and Adult Host Records for longhorned Beetles (Cerambycidae) from Iowa

Thirty-nine species of Cerambycidae are recorded for the first time from Iowa. New state records for the Cerambycidae are: Analeptura lineola (Say), Anelaphus pumilus (Newman), Astylopsis collaris (Haldeman), Astylopsis sexguttata (Say), Ataxia brunnea Champlain and Knull, Ataxia hubbardi Fisher, Bellamira scalaris (Say), Centrodera decolorata (Harris), Centrodera sublineata LeConte, Clytoleptus albofasciatus (Laporte and Gory), Clytus ruricola (Olivier), Dorcaschema wildii Uhler, Encyclops caerulea (Say), Goes pulcher (Haldeman), Goes pulverulentus (Haldeman), Grammoptera exigua (Newman), Grammoptera haematites (Newman), Heterachthes quadrimaculatus Haldeman, Leptura subhamata Randall, Lepturges pictus (LeConte), Lepturges regularis (LeConte), Mecas cineracea Casey, Micranoplium unicolor (Haldeman), Monochamus carolinensis (Olivier), Neoclytus approximatus (LeConte), Neoclytus mucronatus mucronatus (Fabricius), Neoclytus scutellaris (Olivier), Oberea ocellata Haldeman, Obrium maculatum (Olivier), Oncideres cingulata cingulata (Say), Saperda imitans Felt and Joutel, Stenocorus cinnamopterus (Randall), Stenocorus vittiger (Randall), Strangalia bicolor (Swederus), Trachysida mutabilis (Newman), Trigonarthris minnesotana (Casey), Typocerus confluens Casey, Typocerus deceptus Knull, and Xestoleptura octonotata (Say). New adult host records are given for Brachyleptura circumdata (Olivier), Charisalia americana (Haldeman), C. ruricola, Goes debilis LeConte, G. exigua, G. haematites, Neoalosterna capitata (Newman), S. vittiger, T. minnesotana, and T. confluens.

Epizootics of wild fish induced by farm fish.

The continuing decline of ocean fisheries and rise of global fish consumption has driven aquaculture growth by 10% annually over the last decade. The association of fish farms with disease emergence in sympatric wild fish stocks remains one of the most controversial and unresolved threats aquaculture poses to coastal ecosystems and fisheries. We report a comprehensive analysis of the spread and impact of farm-origin parasites on the survival of wild fish populations. We mathematically coupled extensive data sets of native parasitic sea lice (Lepeophtheirus salmonis) transmission and pathogenicity on migratory wild juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon. Farm-origin lice induced 9-95% mortality in several sympatric wild juvenile pink and chum salmon populations. The epizootics arise through a mechanism that is new to our understanding of emerging infectious diseases: fish farms undermine a functional role of host migration in protecting juvenile hosts from parasites associated with adult hosts. Although the migratory life cycles of Pacific salmon naturally separate adults from juveniles, fish farms provide L. salmonis novel access to juvenile hosts, in this case raising infection rates for at least the first approximately 2.5 months of the salmon's marine life (approximately 80 km of the migration route). Spatial segregation between juveniles and adults is common among temperate marine fishes, and as aquaculture continues its rapid growth, this disease mechanism may challenge the sustainability of coastal ecosystems and economies.

A tritrophic analysis of host preference and performance in a polyphagous leafminer

AbstractThe optimal oviposition theory predicts that oviposition preferences of phytophagous insects should correlate with host suitability for their offspring. As plant host suitability depends not only on its quality as food, but also on its provision of enemy‐free space, we examined the relationship between adult host preference and offspring performance for the leafminer Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae) on various host plants, considering also the interaction with natural enemies. Preference and offspring performance were assessed through observational field data and laboratory experiments in central Argentina. Field data suggested a positive host preference – performance linkage, as the leafminer attained larger body size on the crops where it was more abundant. Laboratory trials supported these results: Vicia faba L. (Fabaceae) was the preferred host in the laboratory as well as in the field, performance of L. huidobrensis being also best on this host, with highest survival rates and shortest development time. The actively feeding larval stage showed the largest plant‐related effects. Higher overall parasitism rates were found on plants from which smaller leafminers were reared, reinforcing the preference–performance linkage. On the other hand, the main parasitoid Phaedrotoma scabriventris Nixon (Hymenoptera: Braconidae) reached larger body size, and caused higher mortality rates on crops where the leafminer was larger. Changes in abundance of particular parasitoid species could thus modify overall parasitism trends.

Drosophila brain tumor metastases express both neuronal and glial cell type markers

Loss of either lgl or brat gene activity in Drosophila larvae causes neoplastic brain tumors. Fragments of tumorous brains from either mutant transplanted into adult hosts over-proliferate, and kill their hosts within 2 weeks. We developed an in vivo assay for the metastatic potential of tumor cells by quantifying micrometastasis formation within the ovarioles of adult hosts after transplantation and determined that specific metastatic properties of lgl and brat tumor cells are different. We detected micrometastases in 15.8% of ovarioles from wild type host females 12 days after transplanting lgl tumor cells into their abdominal cavities. This frequency increased significantly with increased proliferation time. We detected micrometastases in 15% of ovarioles from wild type host females 10 days after transplanting brat tumor cells into their abdominal cavities. By contrast, this frequency did not change significantly with increased proliferation time. We found that nearly all lgl micrometastases co-express the neuronal cell marker, ELAV, and the glial cell marker, REPO. These markers are not co-expressed in normal brain cells nor in tumorous brain cells. This indicates deregulated gene expression in these metastatic cells. By contrast, most of the brat micrometastases expressed neither marker. While mutations in both lgl and brat cause neoplastic brain tumors, our results reveal that metastatic cells arising from these tumors have quite different properties. These data may have important implications for the treatment of tumor metastasis.