A phylogeny based on cytochrome-c oxidase gene sequences identifies sympatric Ichthyophonus genotypes in the NE Pacific Ocean.

In recent decades, evidence has accumulated to suggest that the widespread and highly variable parasite Ichthyophonus hoferi is actually a species complex. Highly plastic morphology and a general lack of defining structures has contributed to the likely underestimate of biodiversity within this group. Molecular methods are a logical next step in the description of these parasites, but markers used to date have been too conserved to resolve species boundaries. Here we use mitochondrial encoded cytochrome-c oxidase (MTCO1) gene sequences and phylogenic analysis to compare Ichthyophonus spp. isolates from several marine and anadromous fish hosts. The resulting phylogeny displays lineage separation among isolates and possible host/niche segregation not previously described. The parasite type that infects Pacific herring Clupea pallasii, Atlantic herring C. harengus, Atlantic salmon Salmo salar, and Pacific staghorn sculpin Oligocottus maculosus (Clade A) is different from that which infects Chinook salmon Oncorhynchus tshawytscha, walleye pollock Gadus chalcogrammus, Greenland halibut Reinhardtius hippoglossoides, and Pacific halibut Hippoglossus stenolepsis (Clade B). MTCO1 sequences confirmed the presence of a more divergent Ichthyophonus sp. isolated from American shad Alosa sapidissima in rivers of eastern North America (Clade C), while American shad introduced to the Pacific Ocean are infected with the same parasite that infects Pacific herring (Clade A). Currently there are no consensus criteria for delimiting species within Ichthyophonidae, but MTCO1 sequences hold promise as a potential species identifying marker and useful epizootiological tool.

Facilitating Reforestation Through the Plant Microbiome: Perspectives from the Phyllosphere.

Tree planting and natural regeneration contribute to the ongoing effort to restore Earth's forests. Our review addresses how the plant microbiome can enhance the survival of planted and naturally regenerating seedlings and serve in long-term forest carbon capture and the conservation of biodiversity. We focus on fungal leaf endophytes, ubiquitous defensive symbionts that protect against pathogens. We first show that fungal and oomycetous pathogen richness varies greatly for tree species native to the United States (n = 0-876 known pathogens per US tree species), with nearly half of tree species either without pathogens in these major groups or with unknown pathogens. Endophytes are insurance against the poorly known and changing threat of tree pathogens. Next, we review studies of plant phyllosphere feedback, but knowledge gaps prevent us from evaluating whether adding conspecific leaf litter to planted seedlings promotes defensive symbiosis, analogous to adding soil to promote positive feedback. Finally, we discuss research priorities for integrating the plant microbiome into efforts to expand Earth's forests.

Annual Recurrences of Viral Hemorrhagic Septicemia Epizootics in Age 0 Pacific Herring Clupea pallasii Valenciennes, 1847.

Throughout a 20 year biosurveillance period, viral hemorrhagic septicemia virus was isolated in low titers from only 6/7355 opportunistically sampled adult Pacific herring, reflecting the typical endemic phase of the disease when the virus persists covertly. However, more focused surveillance efforts identified the presence of disease hot spots occurring among juvenile life history stages from certain nearshore habitats. These outbreaks sometimes recurred annually in the same temporal and spatial patterns and were characterized by infection prevalence as high as 96%. Longitudinal sampling indicated that some epizootics were relatively transient, represented by positive samples on a single sampling date, and others were more protracted, with positive samples occurring throughout the first 10 weeks of the juvenile life history phase. These results indicate that viral hemorrhagic septicemia (VHS) epizootics in free-ranging Pacific herring C. pallasii are more common than previously appreciated; however, they are easily overlooked if biosurveillance efforts are not designed around times and locations with high disease potential.