Baculoviruses in populations of western spruce budworm.

Population studies of western spruce budworm, Choristoneura occidentalis, revealed that a baculovirus, ChocNPV, was widespread in outbreak populations over a broad geographical area of British Columbia, Canada although the rate of mortality was usually low (<5%). Elevated levels of ChocNPV-related mortality (≈20%) were found when western spruce budworm populations reached high densities (≈300 larvae per kg of Douglas-fir foliage) and contributed to declines in population densities in these areas. A subsample from budworm collections examined using a multiplex-PCR assay showed ChocNPV was the most prevalent virus but also often occurred in combination with a granulovirus, ChocGV and a cypovirus, CoCPV.

Cytology of Leidyana canadensis (apicomplexa: eugregarinida) in Lambdina fiscellaria fiscellaria larvae (lepidoptera: geometridae).

The eugregarine Leidyana canadensis infects the larval gut of the eastern hemlock looper, Lambdina fiscellaria fiscellaria. Guts of infected larvae were chemically fixed, embedded in epoxy resin, and sectioned for light and electron microscopy to describe the cytology of L. canadensis and its pathology in the larval host. Oocysts of L. canadensis are ingested by larval hemlock looper. Trophozoites emerge from the oocysts, pass through the peritrophic membrane into the ectoperitrophic space, and attach to the epithelium of the midgut by means of an apical epimerite. The epimerite does not actually penetrate the affected epithelial cell; instead, it causes an invagination of the plasma membrane of the cell. The center of the epimerite contains membrane cisternae, and mitochondria line its periphery. Microtubules and mitochondria in the host cell cytoplasm surround the epimerite. At the light microscopic level, there appeared to be septa between the epimerite and the protomerite and between the protomerite and the deutomerite; however, in the electron microscope, no septa were evident. Only differences in the concentrations and nature of the inclusions in the cytoplasms of these three regions were apparent. The deutomerite contains a single nucleus in the central-posterior area. After an undetermined period, the epimerite detaches from the host gut epithelium and is withdrawn into the protomerite, and the trophozoites float freely in the ectoperitrophic space before differentiating into gamonts. Division of the single, large nucleus into numerous small nuclei appears to occur prior to syzygy. Gamonts pair and a cyst wall is laid down around them, forming a gametocyst. Oocysts are extruded from mature gametocysts, in chains, through sporoducts.

Choristoneura fumiferana granulovirus: sequence analysis and 5' characterization of ORF891.

A gene located immediately upstream of the granulin gene of Choristoneura fumiferana (ChfuGV) granulovirus was identified, sequenced and named ORF891. The determined, putative open reading frame (ORF) of 891 bp encodes an estimated 34.6 kDa protein. The 5' end transcript of the gene was mapped and analysed. A putative promoter region organization of ChfuGV ORF891 contains a consensus late baculovirus promoter element, TAAG, and two putative early TATA boxes similar to the promoters of ORF909 of Cryptophlebia leucotreta granulovirus (ClGV). Sequence comparisons of ChfuGV ORF891 with ClGV ORF909 and Cydia pomonella granulovirus (CpGV) ORF124R showed respective homologies of 60.9 and 63.9% for nucleotides and 46.3% and 49.3% for amino acids. Homology of ChfuGV ORF891 with ME53 ORF of Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) was 68.2% for nucleotides but a total lack of homology for amino acid sequences. Two zinc finger motifs are also associated with ChfuGV ORF891.

A nuclear polyhedrosis virus from the obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera:Tortricidae).

A nuclear polyhedrosis virus (CrMNPV) has been isolated from larvae of the obliquebanded leafroller Choristoneura rosaceana (Harris) collected near St. Quentin in northwest New Brunswick, Canada. Restriction endonuclease digestion-gel electrophoresis of this virus, using a number of different endonucleases and whole CrMNPV genome Southern hybridization, have shown it to be different but similar to the equivalent virus from the spruce budworm Choristoneura fumiferana (Clem.) (CfMNPV). The polyhedrin gene of CrMNPV has been isolated, cloned, and sequenced and shown to have a predicted amino acid sequence only two amino acids different from the CfMNPV polyhedrin. In bioassays against spruce budworm larvae, CrMNPV had little pathogenicity to that host.

Identification and sequence analyses of the granulin gene of Choristoneura fumiferana granulovirus.

The nucleotide sequence of the granulin gene of Choristoneura fumiferana granulovirus (CfGV) was determined. The gene encodes a protein of 248 amino acids with a predicted Mr of 29.299 kDa. The granulin genes of Trichoplusia ni, Pieris brassicae and Cryptophlebia leucotreta granuloviruses showed homologies ranging from 76.7-80.5% for nucleotide sequences and 84.2-88.3% for amino acid sequences when compared to CfGV. The secondary structure of CfGV granulin protein, including the hydrophilic (polar) and hydrophobic (basic) regions, was predicted and found to be similar to other granulins. A very late baculovirus promoter motif, ATAAG, was found within the putative promoter region of the CfGV granulin gene.

Reproductive strategies and adaptations for survival among obligatory microsporidian and fungal parasites of mosquitoes: a comparative analysis of Amblyospora and Coelomomyces.

Amblyospora (Microsporida: Amblyosporidae) and Coelomomyces (Chytridiomycetes: Blastocladiales) have independently evolved a diverse array of unique and highly specialized mechanisms that have allowed them to more fully exploit their mosquito hosts and the aquatic environment that their hosts inhabit. Amblyospora and Coelomomyces both have complex life cycles that include obligatory development in an intermediate microcrustacean host and 2 mosquito generations for completion. Amblyospora is polymorphic with 3 separate and distinct developmental sequences, asexual and sexual reproduction, and aspects of both vertical (transovarial) and horizontal transmission. Infective stages of Coelomomyces are motile, a temporal gating mechanism coordinates gamete release, and, even though there is no transovarial transmission, infection of primary host ovaries is important in dissemination of the fungus to new habitats. The intent of this review is to examine how these and other strategies and adaptations facilitate parasite reproduction within the host(s) and enhance transmission and survival between hosts.

On thymidine incorporation by the cultured chick pineal gland.

Explanted chick pineal glands exhibited a cycle in thymidine incorporation when cultured either under a cycle of illumination or in constant darkness. This cycle appeared to be entrained to the light cycle under which the birds were maintained. The incorporation reflected gene replication in a small fraction of the cell population that was largely, but not entirely, located in the stroma of the gland. Glands cultured with colchicine for 28 h contained a very small number of cells showing metaphase chromosomes.

An unusual virus from the parasitic wasp Cotesia melanoscela.

Certain strains of the braconid parasitoid Cotesia melanoscela carry two different viruses within their ovaries, one of which (here designated CmV2) is apparently not a polydnavirus. Virus replication occurs in the ovarian calyx and in some other tissues of both male and female parasitoids; as yet, no replication has been observed in the testis, however. In addition, CmV2 is one of only two parasitoid viruses known to replicate in host insect larvae, and we not show that this virus is also capable of replicating in vitro; the virus is nevertheless nonpathogenic for gypsy moth larvae. The virus is not transmissible per os, either to host animals or to larvae of parasitoid strains lacking it. CmV2 is stably maintained within strains carrying it apparently by a vertical transmission mode involving the maternal line; transmission via the male germ line could not be demonstrated. While purification of the virus was not achieved, preliminary work allows us to suggest the genome consists of a single double-stranded DNA molecule of approximately 125 kb.

Development and structure of the resting sporangium wall in Coelomomyces dodgei and modification during dehiscence.

The mature resting sporangium (RS) wall of Coelomomyces dodgei (Chytridiomycetes; Blastocladiales) consists of three principal layers: (I) an outer pigmented layer (1.8-2.2 microns) that contains polysaccharide, (II) a middle electron translucent layer (1.3-1.6 microns) comparatively free of polysaccharide, and (III) an inner layer (125 nm) rich in polysaccharide that surrounds the meiospores. These layers develop successively between the hyphal coat of the RS initial and its plasma membrane. Prior to meiospore formation, a convex discharge plug that later becomes the dehiscence vesicle forms beneath the inner layer along the preformed dehiscence slit in the outer wall. As dehiscence begins, the RS wall opens along the dehiscence slit, exposing the middle layer which then becomes the rigid outer refractile layer above the dehiscence vesicle. During dehiscence, the discharge plug swells out through the slit, and expands to form the dehiscence vesicle. Meiospores become active as the vesicle expands and are released through tears in the vesicle that result from continued expansion and lysis. Melanized areas observed along the dehiscence slit of RS that initiated dehiscence in the larval hemocoel indicate that the host's defense system is functional but does not recognize the parasite's hyphal coat as foreign, possibly because it lacks any significant level of polysaccharide.

Microfungal variations relative to post-fire changes in soil environment.

Soils of three Picea mariana-Cladina stellaris woodland sites, aged 2, 104 and 137 years after fire, were sampled at 3 cm intervals to 9 cm depth for soil microfungi. Mortierella, Mucor, Penicillium and Trichoderma were the most frequently isolated genera. The species composition of the microfungi remained much the same across the age gradient. Direct and indirect gradient analyses of the microfungal species and 14 soil environmental factors indicate that the frequencies of occurrence of the microfungi are influenced by environmental factors primarily related to the build-up of the organic layer and its destruction by fire.