Standard Methods for Dissection of Varroa destructor Females

Varroa destructor (Anderson and Trueman) is known as a major pest of Apis mellifera L, especially in the Northern Hemisphere where its effects can be deleterious. As an obligate parasite, this mite relies entirely on its host to reproduce and complete its cycle. Studies focusing on isolated organs are needed to better comprehend this organism. To conduct such targeted molecular or physiological studies, the dissection of V. destructor mites is crucial as it allows the extraction of specific organs. Here, we propose a technical article showing detailed steps of females V. destructor dissection, illustrated with pictures and videos. These illustrated guidelines will represent a helpful tool to go further in V. destructor research.

Chrysomyxa abietis (needle rust of fir).

C. abietis is a microcyclic rust fungus; an obligate parasite completing its life cycle on species of Picea (spruce). Only the current year's needles of Picea are infected and those needles are shed early. Reported from northern Europe and Asia, the fungus is a Regulated Pest for the USA. It is absent from North America, where susceptible species are native, and Australia and New Zealand, where they are introduced. Although usually not a significant problem in its native range, because conditions are not favourable for heavy infections every year (Smith et al., 1988; Hansen, 1997), this rust could be more damaging as an invasive in other temperate areas. Due to the fact that small amounts of infection may be overlooked, accidental introduction could occur through importation of infected seedlings or young trees.

Thekopsora areolata (cherry spruce rust).

T. areolata is a heteroecious rust fungus; an obligate parasite with stages of its life cycle on cones of Picea species and leaves of Prunus spp. Reported from Europe and Asia, the fungus is a Regulated Pest for the USA. It is absent from North America, where susceptible species are native or introduced, and Australia and New Zealand, where such species are introduced. Although usually not a major problem in its native range, this rust could be more damaging as an invasive in other temperate areas. Due to the fact that small amounts of infection may be overlooked, accidental introduction could occur through importation of infected cones carrying aeciospores. The one known introduction to North America involved a tree of Prunus sp. in a garden, from which there was no documented spread.

Isolation and Characterization of Rhizophydiales sp. (Chytridiomycota), Obligate Parasite of Planktothrix agardhii in a Laurentian Great Lakes Embayment

Planktothrix agardhii dominates the cyanobacterial harmful algal bloom community in Sandusky Bay, Lake Erie (USA) from May through September. This filamentous cyanobacterium is host to a known obligate parasite; the chytrid Rhizophydium sp. During the 2018 bloom season, by utilizing dilution and single filament isolation techniques, 7 chytrid and 12 P. agardhii strains were isolated from Sandusky Bay. These 7 chytrids and a selection of P. agardhii hosts were then characterized with respect to infection rates. Infections by the isolated chytrids were specific to Planktothrix planktonic species and were not found on other filamentous cyanobacterial taxa present in the bay (Aphanizomenon sp. and Cuspidothrix sp.). Even among the potential P. agardhii host strains, individual chytrid isolates had different degrees of infectivity and showed preference for different host isolates, suggesting possible ecological partitioning even within the same sample population. Examining mechanisms of chytrid pathogenesis, the zoospores displayed a swarming pattern to attack and fracture the host filament and create new infection sites at the trichome termini. Infections by these parasitic chytrids also led to a release of intracellular microcystin toxins from the hosts. Additionally, infections were dependent on media type, highlighting the importance of media choice on experimental outcomes. Media in which chytrid swarming was observed closely matched the ionic strength of the natural environment. Understanding pathogenesis by fungal parasites will assist future efforts aimed at determining environmental factors favoring loss mechanisms for Planktothrix agardhii-dominated blooms. IMPORTANCE Whereas many studies have focused on the factors contributing to the establishment and persistence of cyanobacterial harmful algal blooms (cHABs), few studies have examined bloom pathogenesis. Chytrid fungi infect cyanobacteria and stimulate food web interactions through manipulation of previously hard to digest filaments and the release of nutrients to support heterotrophic microbes. Specifically, chytrids infective on filamentous Planktothrix agardhii exhibit a species-specific infection that fragments trichomes into shorter units that can be consumed more easily by grazers. Chytrid zoospores also serve as a high-quality food source for the lower food web. Understanding host-pathogen relationships and mechanisms of pathogenesis on cyanobacteria will be necessary to effectively model the ecology of cHABs.

Sheep Bot Fly Oestrus ovis Linnaeus (1761) (Insecta: Diptera: Oestridae)

The sheep bot fly, Oestrus ovis, is an obligate parasite found all over the world. It cannot complete its life cycle without parasitizing the nasal passages, frontal and maxillary cavities, and sinuses of sheep. Unlike other flies, females do not lay eggs, instead depositing droplets containing live larvae into the nostrils of sheep. This 4-page fact sheet written by Hannah A. Sholar and Jennifer L. Gillett-Kaufman and published by the UF/IFAS Entomology and Nematology Department describes the life cycle of the pest and its veterinary significance and management. https://edis.ifas.ufl.edu/in1267

Complete Genome Sequence of Strain PM004, a Novel Cultured Member of the Human Oral Microbiome from the Candidate Phylum Saccharibacteria (TM7)

Strain PM004 is a cultured representative of human microbial taxon 955, a bacterium from the phylum Saccharibacteria. It is an obligate parasite with a genome of <0.9 Mb and can be grown in coculture with its host, Pseudopropionibacterium propionicum. The complete genome sequence is presented here.

Complete Genome Sequence of Strain AC001, a Novel Cultured Member of the Human Oral Microbiome from the Candidate Phylum Saccharibacteria (TM7)

Strain AC001 is a cultured representative of human microbial taxon 488, a bacterium from the candidate phylum Saccharibacteria. It is an obligate parasite with a genome of <0.9 Mb and grows in coculture with its host, Pseudopropionibacterium propionicum. The complete genome sequence is presented here.

Neobarya peltigerae. [Descriptions of Fungi and Bacteria].

A description is provided for Neobarya peltigerae, an apparently obligate parasite on Peltigera species. Some information on its habitat, dispersal and transmission, and conservation status is given, along with details of its geographical distribution (Asia (Russia), Europe (Austria, Russia (Karachay-Cherkess Republic), Spain, UK)).

Neobarya xylariicola. [Descriptions of Fungi and Bacteria].

A description is provided for Neobarya xylariicola, which is an apparently obligate parasite of Xylaria species. Some information on its habitat, dispersal and transmission, and conservation status is given, along with details of its geographical distribution (North America (USA (Oregon)), Europe (France, UK)). No evaluation has been made of any possible positive economic impact of this fungus (e.g. as a recycler, as a source of useful products, as a provider of checks and balances within its ecosystem, etc.). Also, no reports of negative economic impacts have been found.