Dead Host Research Articles

Unpredicted transmission strategy of Gyrodactylus salaris (Monogenea: Gyrodactylidae): survival and infectivity of parasites on dead hosts

The viviparous monogenean Gyrodactylus salaris continues to devastate Norwegian Atlantic salmon populations despite the extreme measures taken to control this pathogen. Increased understanding of parasite biology is needed to develop alternative control and management strategies of wild Atlantic salmon. We have examined temperature-dependent survival of G. salaris, both on and off the host. At 18 degrees C, survival off the host was 1 day, but at 3 degrees C parasites survived for 4 days. However, in contrast to assumptions made by earlier authors, many parasites remained with their host following its death. Ultrastructural evidence indicated that G. salaris individuals can feed on a dead host, and laboratory tests demonstrated that worms on their hosts more than double their life-span compared with individuals maintained off the host. Experimental infections also demonstrated that establishment and subsequent population growth of parasites previously maintained on dead hosts for 3 days, was similar to that of parasites transferred directly between living hosts. Hence, for G. salaris, dead infected hosts may increase the chances of successful transmission and be a potential important infection source in rivers and hatcheries.

ENDOSYMBIOSIS IN ORDOVICIAN–SILURIAN CORALS AND STROMATOPOROIDS: A NEW LINGULID AND ITS TRACE FROM EASTERN CANADA

The earliest known record of lingulid-coral associations is described from Ashgill tabulate corals preserved on Manitoulin Island, Ontario. Lingulid infestation of tabulate corals and stromatoporoids also is locally abundant in Ashgill and Llandovery limestones on Anticosti Island, Québec, and these preserve the new lingulid species Rowellella? anticostiensis inside the cavities of Trypanites borings. In all examples, lingulids appear to nestle in previously formed Trypanites, likely in a dead host coral or stromatoporoid. In some instances in the Silurian of Anticosti, regeneration of host growth while infested by lingulids is evidenced by a new type of compound trace fossil, Klemmatoica linguliforma new ichnogenus and ichnospecies. Similar endosymbiotic relationships previously observed in Silurian corals from Wales and Sweden suggest that the lingulid association with tabulate corals and stromatoporoids was widespread in early Paleozoic shallow marine settings.

Ultrastructural analysis of the behavior of the dimorphic fungus Microbotryum violaceum in fungus-induced anthers of female Silene latifolia flowers

The development of male organs is induced in female flowers of the dioecious plant Silene latifolia by infection with the fungus Microbotryum violaceum. Stamens in a healthy female flower grow only to stage 6, whereas those in an infected female flower develop to the mature stage (stage 12), at which the stamens are filled with fungal teliospores instead of pollen grains. To investigate these host-parasite interactions, young floral buds and fungus-induced anthers of infected female flowers were examined by electron microscopy following fixation by a high-pressure freezing method. Using this approach, we found that parasitic hyphae of this fungus contain several extracellular vesicles and have a consistent appearance up to stage 8. At that stage, parasitic hyphae are observed adjacent to dying sporogenous cells in the infected female anther. At stage 9, an increased number of dead and dying sporogenous cells is observed, among which the sporogenous hyphae of the fungus develop and form initial teliospores. Several types of electron-dense material are present in proximity to some fungi at this stage. The initial teliospores contain two types of vacuoles, and the fungus cell wall contains abundant carbohydrate, as revealed by silver protein staining. The sporogenous cell is probably sensitive to infection by the fungus, resulting in disruption. In addition, the fungus accelerates cell death in the anther and utilizes constituents of the dead host cell to form the mature teliospore.

Up-regulation of Pr1, a subtilisin-like protease, during conidiation in the insect pathogen Metarhizium anisopliae

Metarhizium anisopliae exhibits two different developmental patterns under nutrient-deprived conditions: appressorium formation in early stages and conidiation in late stages of pathogenesis in its insect hosts. In this study we isolated genes enriched during mature conidial production under nutrient-deprived conditions in M. anisopliae by using the method of suppression subtractive hybridization. We sequence-identified seven conidiation-associated genes (cag) in M. anisopliae. One of the genes, cag7, encoded an extracellular subtilisin-like protease, Pr1, that plays a fundamental role in cuticular protein degradation. Reverse-transcription polymerase chain reaction (RT-PCR) analysis confirmed that cag cDNAs are expressed during the development of mature conidia under nutrient-deprived conditions. RT-PCR analysis was also performed for Pr1 during infection of greater wax moth larvae (Galleria mellonella). Results showed up-regulation of Pr1 in the infected insect as the mycelia emerge and produce conidia on the surface of the cadaver. It is well documented that Pr1 is produced during the initial stages of transcuticular penetration by M. anisopliae. Here we show that Pr1 is also up-regulated during the final stages of pathogenesis as the fungus emerges from the dead host and subsequently conidiates on the cadaver.

Different mechanisms of transmission of the microsporidium Octosporea bayeri: a cocktail of solutions for the problem of parasite permanence

Periods of low host density impose a constraint on parasites with direct transmission, challenging their permanence in the system. The microsporidium Octosporea bayeri faces such constraint in a metapopulation of its host, the cladoceran Daphnia magna, where ponds frequently lose their host population due to ponds drying out in summer and freezing in winter. We conducted experiments aimed to investigate the mechanisms of transmission of O. bayeri, and discuss how these mechanisms could contribute to the parasite's permanence in the system. Spores accumulate in the fat cells and the ovaries of the host, and vary in morphology, possibly corresponding to 3 different spore types. Horizontal transmission occurred through the release of spores from dead hosts, with the proportion of infected hosts depending on the spore dose. Further, spores are able to persist outside the host both in dry and wet conditions. Vertical transmission occurred to both parthenogenetic and sexual offspring. The former were invariably infected, while the sexually produced resting eggs (= ephippia) had a less efficient transmission. The parasite may be carried by the ephippia, and thus disperse to new ponds together with the host. Together, these mechanisms may allow the parasite to endure periods of harsh environmental conditions both outside and inside the host.

The function of a trypsin-like enzyme in the saliva of Euplectrus separatae larvae

Larvae of the gregarious ectoparasitoid, Euplectrus separatae, a species that parasitizes Pseudaletia separata, migrate from the dorsal to the ventral side of the host larva for pupation 7 days after parasitization. The parasitized host larvae die after the migration. The body mass of the parasitoid larvae increases while that of the host larva drastically decreases. Most of the tissue in the dead host larvae completely collapses. In this study, we examined the cause of host death and how the tissues collapse. Artificial removal of all parasitoid larvae before their migration on day 7 rescued the host larvae, but removal after parasitoid migration did not rescue the hosts. Tissues of the dead host larvae were completely liquefied. Injection of saliva from day 7 parasitoid larvae into host larvae killed the host larvae. High activity of a trypsin-like enzyme was detected in the saliva of day 7 parasitoids. Though phospholipase B and hyaluronidase were also detected in the saliva, commercial phospholipase B and hyaluronidase did not kill the hosts, whereas an injection of commercial trypsin was lethal. The trypsin-injected hosts showed the same tissue collapse as noted in parasitized and saliva-injected hosts. Leupeptin, a trypsin inhibitor, reduced mortality when injected into day 7 hosts (parasitoids were removal following migration). These observations suggest that the day 7 parasitoid larvae release saliva containing a trypsin-like enzyme to digest the host tissues following migration.

EXPERIMENTAL EVIDENCE THAT BOTH PARTIES BENEFIT IN A FACULTATIVE PLANT–SPIDER MUTUALISM

Spiders are known to influence plant fitness, and vice versa. Yet, it has not been appreciated that these facultative relationships can be mutualistic. I examined the interaction between Phryganoporus candidus , a subsocial Australian spider, and the ex- trafloral nectary-bearing shrub Acacia ligulata to explore variability in mutualistic inter- actions over a three-year period. Spiders enhanced seed production by reducing seed pre- dation by heteropterans, wasps, and weevils. Because spider colonies occupy only a fraction of a plant's volume, average benefits ranged from 0.4 to 6% increases in whole-plant seed production. These benefits were strongest in years of low seed production, suggesting that spiders may buffer plants against female reproductive failure. To evaluate benefits for spiders, I established experimental spider colonies on three common hosts. Spider perfor- mance (persistence and prey capture rates) on live A. ligulata and live hopbush Dodonaea viscosa exceeded that on dead acacia, suggesting that live hosts are more beneficial than dead hosts. Stable-isotope analyses demonstrated that colonies living on the three hosts differed substantially in diet, providing a possible mechanism for the observed differential suitability of hosts. However, the analyses were unable to establish conclusively that A. ligulata extrafloral nectar was an important reward for spiders. Variability in the A. ligulata- P. candidus system suggests that plant-spider associations, like other facultative protection relationships, likely vary along a continuum from antagonism to mutualism.

Ephemera strigata imagoes are the likely source of a parasitic nematode infection of fish

Ephemera strigata imagoes are the likely source of a parasitic nematode infection of fish

Strategy for orchard use of Bacillus thuringiensis while minimizing impact on Choristoneura rosaceana parasitoids

AbstractTrials were conducted to study how spring Bacillus thuringiensis Berliner subsp. kurstaki treatments on apple may be timed to maximize the survival of parasitoids of the obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), found in the southern interior of British Columbia, Canada. Orchard collections verified that second through fourth instar obliquebanded leafrollers were found in varying proportions from pink through the petal fall stage of apple development when spring B. thuringiensis treatments are applied vs. lepidopteran pests. Laboratory‐reared second through fourth instar obliquebanded leafrollers, unparasitized and parasitized by one of three native parasitoid species, were fed untreated apple leaves or leaves treated with B. thuringiensis. The highest mortality of unparasitized obliquebanded leafrollers occurred when fourth instars were exposed to B. thuringiensis‐treated leaves; B. thuringiensis‐induced mortality in the unparasitized second and third instars was less than 50%. The consumption of B. thuringiensis‐treated leaves by host larvae significantly increased the percentage of dead host larvae in all parasitized and unparasitized treatments. However, because of the low susceptibility of this leafroller species to B. thuringiensis, relatively high numbers (38–43%) of three obliquebanded leafroller parasitoid species were able to survive the consumption of B. thuringiensis by second and third instar host larvae. Fourth instar obliquebanded leafrollers were found at the full bloom and petal fall stage of apple development in the orchard, at which time B. thuringiensis treatments are recommended for optimal leafroller control. The highest parasitoid mortality due to host mortality was recorded in Apophua simplicipes Cresson (Hymenoptera: Ichneumonidae) and Macrocentrus linearis (Nees) (Hymenoptera: Braconidae), when the hosts were treated as fourth instars. Both of these parasitoids emerge from fifth and sixth instar obliquebanded leafrollers. Bacillus thuringiensis did not have as negative an impact on Apanteles polychrosidis Viereck (Hymenoptera: Braconidae), which emerges when the host is in the fourth instar. When leafroller mortality and parasitism were combined, the B. thuringiensis treatment did not significantly increase host elimination above that of parasitism alone, except for larvae parasitized by A. simplicipes that were in the fourth instar. The consumption of B. thuringiensis by unparasitized larvae was shown to slow larval development.

Leptosphaeria doliolum . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Leptosphaeria doliolum . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Although the fungus appears on dry stems of its hosts, which are mainly herbaceous, it is not known to cause any pathological symptoms. HOSTS: Plurivorous; recorded hosts include: Achillea, Ambrosia, Anaphalis, Angelica, Apocynum, Aralia, Arctium, Asclepias, Asparagus, Aster, Bauhinia, Brassica, Clematis, Cirsium, Curcuma, Daucus, Erigeron, Eupatorium, Ficus, Foeniculum, Helianthus, Heracleum, Hieracium, Lactuca, Lathyrus, Lavandula, Pastinaca, Phytolacca, Poa, Polymnia, Potentilla, Rubus, Salvia, Senecio, Smilax, Solanum, Solidago, Sonchus, Spiraea, Thymus, Urtica and Vernonia . GEOGRAPHICAL DISTRIBUTION: AFRICA: Sierra Leone. NORTH AMERICA: Canada (Alberta, British Colombia, Manitoba, Nova Scotia, Ontario, Quebec), USA (Illinois, Michigan, Missouri, New York, North Dakota, Tennessee, Washington). ASIA: Armenia, Bhutan, Brunei, China (Hunan, Yunnan), India, Iran, Kazakhstan, Kirgizstan, Pakistan, Russia (Far East, Siberia), Taiwan (CHEN & HSIEH, 1994), Uzbekistan. AUSTRALASIA: Australia. EUROPE: Belgium, Czech Republic, Denmark (Faeroe Islands), Estonia, France, Finland, Germany, Great Britain, Greece, Italy, Latvia, Netherlands, Poland, Romania, Russia (European), Spain, Sweden, Switzerland. TRANSMISSION: Conidia and ascospores are dispersed by wind and rain-splash; the fungus presumably overwinters on dead host tissue and the ascospores are dispersed in the next favourable season.

Leptosphaeria fusispora . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Leptosphaeria fusispora . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Although the fungus appears on the dry stems of its hosts, it is not known to cause any pathological symptoms. HOSTS: Capparis, Genista, Lythrum, Onobrychis, Polygonum and Thalictrum . GEOGRAPHICAL DISTRIBUTION: NORTH AMERICA: USA (New York, Virginia). EUROPE: Austria, France, Germany, Italy,? Poland (PETRAK, 1925). TRANSMISSION: Ascospores are dispersed by wind and rain-splash; the fungus presumably overwinters on dead host tissue and the ascospores are dispersed in the next favourable season.

Leptosphaeria orthrosanthi . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Leptosphaeria orthrosanthi . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Although the fungus appears on dry leaves of its host, it is not known to cause any pathological symptoms. HOSTS: Orthrosanthus chimboracensis ( Iridaceae ). GEOGRAPHICAL DISTRIBUTION: SOUTH AMERICA: Venezuela TRANSMISSION: Ascospores are dispersed by wind and rain-splash; the fungus presumably overwinters on dead host tissue and the ascospores are dispersed in the next favourable season.

Leptosphaeria purpurea . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Leptosphaeria purpurea . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Although the fungus appears on dry stems of its hosts, which are mainly herbaceous, it is not known to cause any pathological symptoms. HOSTS: Artemisia, Betonica, Carduus, Cirsium, Cnicus, Clinopodium, Helianthus, Satureja and Senecio . GEOGRAPHICAL DISTRIBUTION: NORTH AMERICA: Canada (Quebec, Ontario), USA (New York). ASIA: Pakistan. EUROPE: Austria, Belgium, Czech Republic, Germany, Great Britain, Hungary, Slovak Republic, Sweden. TRANSMISSION: Conidia and ascospores are dispersed by wind and rain-splash; the fungus presumably overwinters on dead host tissue and the ascospores are dispersed in the next favourable season.

Leptosphaeria rubicunda . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Leptosphaeria rubicunda . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Although the fungus appears on dry stems of its hosts, which are mainly herbaceous, it is not known to cause any pathological symptoms. HOSTS: Apiaceae indet., Dipsacus sylvestris, Leonurus, Lythrum salicaria and Sambucus nigra . GEOGRAPHICAL DISTRIBUTION: NORTH AMERICA: Canada (Ontario), USA (New York). EUROPE: Czech Republic, Germany, Great Britain, Hungary, Italy. TRANSMISSION: Ascospores are dispersed by wind and rain-splash; the fungus presumably overwinters on dead host tissue and the ascospores are dispersed in the next favourable season.

Leptosphaeria cylindrospora . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Leptosphaeria cylindrospora . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Although the fungus appears on dry stems of its host, it is not known to cause any pathological symptoms. HOSTS: Epilobium ( Onagraceae ). GEOGRAPHICAL DISTRIBUTION: NORTH AMERICA: Canada (Manitoba), USA (Alaska, Arkansas, Colorado, Idaho, Washington). ASIA: Kazakhstan (VASYAGINA et al. , 1987). EUROPE: Czech Republic, Germany, Hungary, Romania (BONTEA, 1955), Sweden, Switzerland. TRANSMISSION: Ascospores are dispersed by wind and rain-splash; the fungus presumably overwinters on dead host tissue and the ascospores are dispersed in the next favourable season.

Leptosphaeria holmskjoeldii . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Leptosphaeria holmskjoeldii . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: On dry cortex or wood. HOSTS: Alnus, Lonicera, Salix and Sorbus . GEOGRAPHICAL DISTRIBUTION: EUROPE: Finland, Germany. TRANSMISSION: Ascospores are dispersed by wind and rain-splash; the fungus presumably overwinters on dead host tissue and the ascospores are dispersed in the next favourable season.

Leptosphaeria planiuscula . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Leptosphaeria planiuscula . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Although the fungus appears on the dry stems of its hosts, it is not known to cause any pathological symptoms. HOSTS: Achillea, Aster, Conyza, Eupatorium, Solidago ( Asteraceae ) and Lepidium ( Brassicaceae ). GEOGRAPHICAL DISTRIBUTION: NORTH AMERICA: Canada (Ontario), USA (Georgia, Kansas, Massachussetts, New Jersey, New York, North Dakota). EUROPE: Austria, Denmark, Germany, Latvia, Poland, Sweden, Switzerland. TRANSMISSION: Ascospores are dispersed by wind and rain-splash; the fungus presumably overwinters on dead host tissue and the ascospores are dispersed in the next favourable season.

Leptosphaeria dryadis . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Leptosphaeria dryadis . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Although the fungus appears on the dead fruits and calyces of its host, it is not known to cause any pathological symptoms. HOSTS: Dryas octopetala ( Rosaceae ). GEOGRAPHICAL DISTRIBUTION: EUROPE: Germany, Iceland, Switzerland. TRANSMISSION: Ascospores are dispersed by wind and rain-splash; the fungus presumably overwinters on dead host tissue and the ascospores are dispersed in the next favourable season.

Leptosphaeria lupinicola . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Leptosphaeria lupinicola . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: On dead herbaceous stems. HOSTS: Lupinus ( Leguminosae ). GEOGRAPHICAL DISTRIBUTION: NORTH AMERICA: USA (California, Colorado). TRANSMISSION: Ascospores are dispersed by wind and rain-splash; the fungus presumably overwinters on dead host tissue and the ascospores are dispersed in the next favourable season.

Effect of Verbenone on Five Species of Bark Beetles (Coleoptera: Scolytidae) in Lodgepole Pine Forests

The response by five species of bark beetles to a range of verbenone doses were tested in bioassays using Lindgren funnel traps baited with attractant semiochemicals. The objective was to determine how these bark beetles respond to verbenone, a purported anti-aggregation pheromone of several economically significant bark beetle species. Catches of Dendroctonus ponderosae Hopkins, a species attacking live trees, were unaffected relative to a control trap (no verbenone) at release rates of 0.2 mg/24 h or less, but were significantly reduced at rates of 1.8 mg/24 h or more. Catches of Ips pini (Say) and I. latidens (LeConte), two opportunistic species normally attacking fresh, dead host material, were gradually reduced with increasing verbenone dose. Verbenone did not affect catches of Hylurgops porosus (LeConte) and Hylastes longicollis Swaine, two species normally associated with bark in contact with the ground, where saprophytic microorganisms quickly invade phloem tissue. The effect by verbenone on catches of the five species was consistent with differences in host-age preference. Catches of species requiring relatively fresh host tissue were reduced by verbenone, whereas catches of species accepting aged tissue were unaffected.