CD8alpha and CD8beta in Atlantic halibut, Hippoglossus hippoglossus: cloning, characterization and gene expression during viral and bacterial infection

CD8 is expressed on cytotoxic T-cells where it functions as a co-receptor for the TCR by binding to MHC class I proteins that present peptides on the cell surface. In this study we describe the cloning and sequencing of full length cDNAs encoding CD8alpha and CD8beta from Atlantic halibut (Hippoglossus hippoglossus L.) and subsequent isolation and characterization of the CD8alpha and CD8beta genes. The predicted halibut CD8alpha and CD8beta proteins are similar to those of mammals and other fish. Real time RT-PCR revealed that the highest levels of CD8 mRNA were found in the thymus, while some expression was also seen in the spleen, the gills, and the anterior and posterior kidney. In situ hybridization confirmed that the halibut thymus contained numerous CD8alpha and CD8beta expressing cells, while the anterior kidney had no CD8alpha positive cells but only a few CD8beta expressing cells. Only moderate changes in CD8 mRNA expression in other organs during either nodavirus or Vibrio anguillarum infection were observed. Both CD8alpha and CD8beta were significantly (P<0.05) down-regulated in spleen at 48h compared to their levels at 12h post-infection with nodavirus and V. anguillarum.     

Protection against Atlantic halibut nodavirus in turbot is induced by recombinant capsid protein vaccination but not following DNA vaccination

Fish nodaviruses (betanodaviruses) are small, non-enveloped icosahedral single-stranded positive-sense RNA viruses that can cause viral encephalopathy and retinopathy (VER) in a number of cultured marine teleost species, including Atlantic halibut (Hippoglossus hippoglossus). A recombinant protein vaccine and a DNA vaccine were produced, based on the same capsid-encoding region of the Atlantic halibut nodavirus (AHNV) genome, and tested for protection in juvenile turbot (Scophthalmus maximus). Vaccine efficacy was demonstrated in the fish vaccinated with recombinant capsid protein but not in the DNA-vaccinated fish, despite the fact that in vivo expression of the DNA vaccine-encoded antigen was confirmed by RNA in situ hybridisation and immunohistochemistry. Combined DNA and recombinant vaccine administration did not improve the effect of the latter. Surprisingly, fish vaccinated with 50 microg recombinant protein demonstrated a threefold lower survival rate than the two groups that received 10 microg recombinant protein. Neither the recombinant protein vaccine nor the DNA vaccine induced anti-viral antibodies 9 weeks after immunisation, while antibodies reactive with the recombinant protein were detectable mainly in fish vaccinated with 50 microg recombinant protein. The study also demonstrates evidence of viral replication inside the myocytes of intramuscularly challenged fish.     

The functional and numerical response of Typhlodromips swirskii (Acari: Phytoseiidae) to the factitious prey Suidasia medanensis (Acari: Suidasidae) in the context of a breeding sachet

The whitefly and thrips predator Typhlodromips swirskii (Athias-Henriot) (Acari: Phytoseiidae) can be reared on the factitious astigmatid mite Suidasia medanensis (Oudemans) (Acari: Suidasiidae). The predator–prey relationship allows the system to be incorporated into a breeding sachet which releases predators into a crop over several weeks ensuring predator presence on arrival of the target pests and increased predator numerical response on the crop through immigration from the breeding sachet. This study investigated whether the prey preference and functional and numerical response of T. swirskii to different development stages of S. medanensis can provide understanding of the predator–prey interactions sustaining such a breeding sachet. T. swirskii elicited a strong preference to egg stages of S. medanensis, exhibited a Type II functional response and increased oviposition rate with increasing prey density. The relevance of these attributes to a balanced breeding sachet is discussed.     

Chemical Composition and Antimicrobial Activity of the Essential Oil of Ruta chalepensis L. Growing Wild in Lebanon

The essential oils (EOs) isolated from the fresh aerial parts of Ruta chalepensis L. collected in North Lebanon were obtained by solvent‐free microwave extraction (Milestone®), yielding 0.12% EO from both the leaves and a mixture of stems and leaves. The EOs were characterized by GC/MS analysis, and 27 components were identified, which were primarily ketones (88.0–93.2%). The main components were nonan‐2‐one and undecan‐2‐one. The antimicrobial activity of the EOs against a Gram‐positive and a Gram‐negative bacterium, a yeast, and a dermatophyte was evaluated using the broth‐microdilution technique and expressed as minimal inhibitory concentration (MIC). The EOs revealed moderate in vitro antifungal activity against Trichophyton rubrum and Candida albicans.     

Faecal avoidance and the risk of infection by nematodes in a natural population of reindeer

We tested whether Svalbard reindeer (Rangifer tarandus platyrhynchus) minimise the risk of gastro- intestinal nematode infection by avoiding patches with a high density of faeces. This experiment was performed in preferred summer foraging habitat. The possibility that reindeer assess infection risk on the basis of faecal contamination levels across plant communities was determined by measuring the distribution of faeces in seven plant communities, and nematode developmental success in two plant communities with contrasting soil moisture content. We explored whether variation within individual reindeer in the levels of infection by gastro-intestinal nematodes was related to their diet. Reindeer avoided pastures where faecal contamination was increased, and thereby potentially reduced the risk of becoming infected by Trichostrongyle nematodes. Dung density was inversely related to soil moisture content, with high densities of faeces in dry plant communities and low densities in wet communities. However, nematode developmental success was positively related to soil moisture content, and was highest in the wetter sites. Thus, by avoiding dry areas with high dropping densities, reindeer would tend to feed in wetter areas where nematodes thrive. Therefore, dung density may be an unreliable predictor of the risk of infection. The absence of a strong relationship between an individual’s infection level and its diet might be due to the unpredictability of pasture infection level. Received: 8 July 1999 / Accepted: 20 January 2000     

Absence from the nest due to human disturbance induces higher nest predation risk than natural recesses in Common Eiders Somateria mollissima

Human disturbance of nesting birds may cause reduced breeding success. It is therefore necessary to assess the impact of disturbance to identify steps that minimize negative impacts. We carried out a study of nesting success at two adjacent colonies of Common Eider Somateria mollissima on the islands of Grindøya and Håkøya in northern Norway between 2006 and 2011. Over the study period, nesting success was consistently higher on Håkøya (69–82%) than on Grindøya (35–60%). Between 2009 and 2011 we used camera monitoring of individual nests to identify determinants of nest survival and predation, focusing in particular on the effect of departures from the nest due to human disturbance, which differed between the colonies due to a long‐term research project on Grindøya. Overall, absence of Common Eiders from nests due to disturbance increased the predation risk by a factor of 6.42 for an increase of one additional daily disturbance. In contrast, absence due to natural recesses did not increase nest losses. Under high levels of human disturbance, camera monitoring indicated that the main cause of breeding failure was predation, primarily by Hooded Crows Corvus cornix, but also to some extent Great Black‐backed Gulls Larus marinus. The presence of cameras did not increase the predation risk. Both the presence of researchers and the sight of Common Eider females conspicuously departing from nests are likely to have provided cues to these predators. We suggest management trials to reduce nesting disturbance through the guarding of unoccupied nests to mitigate the effects of human disturbance on reproductive success.     

Evolutionary patterns of volatile terpene emissions across 202 tropical tree species

Plant responses to natural enemies include formation of secondary metabolites acting as direct or indirect defenses. Volatile terpenes represent one of the most diverse groups of secondary metabolites. We aimed to explore evolutionary patterns of volatile terpene emission. We measured the composition of damage‐induced volatile terpenes from 202 Amazonian tree species, spanning the angiosperm phylogeny. Volatile terpenes were extracted with solid‐phase micro extraction and desorbed in a gas chromatography–mass spectrometry for compound identification. The chemical diversity of the terpene blend showed a strong phylogenetic signal as closely related species emitted a similar number of compounds. Closely related species also tended to have compositionally similar blends, although this relationship was weak. Meanwhile, the ability to emit a given compound showed no significant phylogenetic signal for 200 of 286 compounds, indicating a high rate of diversification in terpene synthesis and/or great variability in their expression. Three lineages (Magnoliales, Laurales, and Sapindales) showed exceptionally high rates of terpene diversification. Of the 70 compounds found in >10% of their species, 69 displayed significant correlated evolution with at least one other compound. These results provide insights into the complex evolutionary history of volatile terpenes in angiosperms, while highlighting the need for further research into this important class of compounds.     

Resistance to abomasal nematodes and individual genetic variability in reindeer

Resistance to parasites is believed to have a widespread influence on demographic and adaptive processes. In systems where parasites impose a fitness cost on their host, heterozygotes may be selected because they are more resistant to parasites than homozygotes. Our objective was to assess the relationships between genomewide individual heterozygosity and abomasal nematode burdens in female Svalbard reindeer (Rangifer tarandus platyrhynchus) after the effects of host age, locality, season, and year had been accounted for. Samples were obtained from 306 female reindeer that were culled and genotyped at nine microsatellite loci. Reindeer in our study populations are mainly parasitized by the gastrointestinal nematodes Ostertagia gruehneri and Marshallagia marshalli. The infection intensity of each parasite differed between subpopulations, and among host age classes, seasons and years. We found no significant relationships between abomasal worm burdens, or lumen and mucosa larvae, of either O. gruehneri or M. marshalli and individual heterozygosity (or mean d(2)) alone or in interactions with host age, locality, and year. Although we analysed one of the largest data set available to date on gastrointestinal nematodes of a wild ruminant, we used a typical data set of nine genetic neutral markers that may have had low power to detect heterozygosity-fitness correlations. We conclude that the proportion of the variance in parasite resistance explained by individual heterozygosity for neutral genetic markers is low in Svalbard reindeer and in vertebrates in general, and we suggest that the candidate-gene approach might be more fruitful for further research on gene-fitness correlations.     

A century of conservation: The ongoing recovery of Svalbard reindeer

Several caribou and reindeer (Rangifer tarandus) populations have experienced recent population declines, often attributed to anthropogenic stressors such as harvesting, landscape fragmentation, and climate change. Svalbard reindeer (R. t. platyrhynchus), the wild reindeer subspecies endemic to the high-Arctic Svalbard archipelago, was protected in 1925, after most subpopulations had been eradicated by harvest. Although direct pressure from harvest has ceased, indirect anthropogenic stressors from environmental changes have increased in this climate change hot spot. An assessment of the current distribution and abundance is therefore urgently needed. We combined distance sampling (300 km transects, n = 489 reindeer groups) and total counts (1,350 km², n = 1,349 groups) to estimate the Svalbard reindeer distribution and abundance across its entire range, which we compared with historical data from the literature and radiocarbon-dated bones. Reindeer have now recolonized nearly all non-glaciated land (i.e., areas occupied prior to human presence), and their spatial variation in abundance reflects vegetation productivity. Independent of vegetation productivity, however, recently recolonized areas have lower reindeer densities than areas not subject to past extirpation. This suggests that recovery from past overharvesting is still in progress. These incompletely recovered areas are potential targets for increased monitoring frequency and maintaining strict conservation to follow the Svalbard management goal (i.e., virtually untouched wilderness areas). Because of such ongoing recolonization, possibly combined with vegetation greening effects of recent warming, our status estimate of Svalbard reindeer abundance (22,435 [95% CI = 21,452–23,425]) is more than twice a previous estimate based on opportunistic counts. Thus, although our study demonstrates the successful outcome of strict harvesting control implemented a century ago, current and future population trajectories are likely shaped by climate change. © 2019 The Authors. Journal of Wildlife Management Published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.