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First detection of the larval chalkbrood disease pathogen Ascosphaera apis (Ascomycota: Eurotiomycetes: Ascosphaerales) in adult bumble bees.

Maxfield-Taylor SA, Mujic AB, Rao S - PLoS ONE (2015)

Bottom Line: Queens that died during rearing or that did not lay eggs within one month of capture were dissected, and tissues were examined microscopically for the presence of pathogens.The identity of the fungus was confirmed using molecular markers and phylogenetic analysis.Thus, the discovery of A. apis in adult bumble bees in the current study has important implications for commercial production of bumble bee colonies and highlights potential risks to native bees via pathogen spillover from infected bees and infected pollen.

View Article: PubMed Central - PubMed

Affiliation: Department of Crop and Soil Science, Oregon State University, Corvallis, Oregon, United States of America.

ABSTRACT
Fungi in the genus Ascosphaera (Ascomycota: Eurotiomycetes: Ascosphaerales) cause chalkbrood disease in larvae of bees. Here, we report the first-ever detection of the fungus in adult bumble bees that were raised in captivity for studies on colony development. Wild queens of Bombus griseocollis, B. nevadensis and B. vosnesenskii were collected and maintained for establishment of nests. Queens that died during rearing or that did not lay eggs within one month of capture were dissected, and tissues were examined microscopically for the presence of pathogens. Filamentous fungi that were detected were plated on artificial media containing broad spectrum antibiotics for isolation and identification. Based on morphological characters, the fungus was identified as Ascosphaera apis (Maasen ex Claussen) Olive and Spiltoir, a species that has been reported earlier only from larvae of the European honey bee, Apis mellifera, the Asian honey bee, Apis cerana, and the carpenter bee Xylocopa californica arizonensis. The identity of the fungus was confirmed using molecular markers and phylogenetic analysis. Ascosphaera apis was detected in queens of all three bumble bee species examined. Of 150 queens dissected, 12 (8%) contained vegetative and reproductive stages of the fungus. Both fungal stages were also detected in two workers collected from colonies with Ascosphaera-infected B. nevadensis queens. In this study, wild bees could have been infected prior to capture for rearing, or, the A. apis infection could have originated via contaminated European honey bee pollen fed to the bumble bees in captivity. Thus, the discovery of A. apis in adult bumble bees in the current study has important implications for commercial production of bumble bee colonies and highlights potential risks to native bees via pathogen spillover from infected bees and infected pollen.

No MeSH data available.


Related in: MedlinePlus

Stages of A. apis colonization of abdominal tissue of B. vosnesenskii.(A) Healthy tissues. (B) Near complete colonization with cleistothecia (darkened areas) visible. (C) Complete colonization; internal organs no longer visible. (D) Internal spore balls visible in cleistothecia (400X).
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pone.0124868.g001: Stages of A. apis colonization of abdominal tissue of B. vosnesenskii.(A) Healthy tissues. (B) Near complete colonization with cleistothecia (darkened areas) visible. (C) Complete colonization; internal organs no longer visible. (D) Internal spore balls visible in cleistothecia (400X).

Mentions: In infected adults of all three bumble bee species, the entire body cavity was filled with white spongy mycelia that were not visible externally. Bumble bee organs were unrecognizable while cleistothecia that are typical in the genus Ascosphaera were detected throughout the abdomen (Fig 1). Morphological characteristics of the fungus were a near perfect match for those previously described for A. apis [4]. Measurements of A. apis microscopic structures made in this study are as follows: Cleistothecia globose 34–85 μm (n = 25, average: 57.57, median: 57.09) in diameter with a thin and friable wall 1.3–1.86 μm (n = 12, average: 1.58, median: 1.6) that breaks down upon disturbance. At maturity, cleistothecia packed with globose spore masses 9–18 μm in diameter. Ascospores are hyaline and measuring 1.87 × 3.45 μm on average (n = 25, min: 1.5 × 2.88 μm, max: 2.17 × 4 μm).


First detection of the larval chalkbrood disease pathogen Ascosphaera apis (Ascomycota: Eurotiomycetes: Ascosphaerales) in adult bumble bees.

Maxfield-Taylor SA, Mujic AB, Rao S - PLoS ONE (2015)

Stages of A. apis colonization of abdominal tissue of B. vosnesenskii.(A) Healthy tissues. (B) Near complete colonization with cleistothecia (darkened areas) visible. (C) Complete colonization; internal organs no longer visible. (D) Internal spore balls visible in cleistothecia (400X).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401763&req=5

pone.0124868.g001: Stages of A. apis colonization of abdominal tissue of B. vosnesenskii.(A) Healthy tissues. (B) Near complete colonization with cleistothecia (darkened areas) visible. (C) Complete colonization; internal organs no longer visible. (D) Internal spore balls visible in cleistothecia (400X).
Mentions: In infected adults of all three bumble bee species, the entire body cavity was filled with white spongy mycelia that were not visible externally. Bumble bee organs were unrecognizable while cleistothecia that are typical in the genus Ascosphaera were detected throughout the abdomen (Fig 1). Morphological characteristics of the fungus were a near perfect match for those previously described for A. apis [4]. Measurements of A. apis microscopic structures made in this study are as follows: Cleistothecia globose 34–85 μm (n = 25, average: 57.57, median: 57.09) in diameter with a thin and friable wall 1.3–1.86 μm (n = 12, average: 1.58, median: 1.6) that breaks down upon disturbance. At maturity, cleistothecia packed with globose spore masses 9–18 μm in diameter. Ascospores are hyaline and measuring 1.87 × 3.45 μm on average (n = 25, min: 1.5 × 2.88 μm, max: 2.17 × 4 μm).

Bottom Line: Queens that died during rearing or that did not lay eggs within one month of capture were dissected, and tissues were examined microscopically for the presence of pathogens.The identity of the fungus was confirmed using molecular markers and phylogenetic analysis.Thus, the discovery of A. apis in adult bumble bees in the current study has important implications for commercial production of bumble bee colonies and highlights potential risks to native bees via pathogen spillover from infected bees and infected pollen.

View Article: PubMed Central - PubMed

Affiliation: Department of Crop and Soil Science, Oregon State University, Corvallis, Oregon, United States of America.

ABSTRACT
Fungi in the genus Ascosphaera (Ascomycota: Eurotiomycetes: Ascosphaerales) cause chalkbrood disease in larvae of bees. Here, we report the first-ever detection of the fungus in adult bumble bees that were raised in captivity for studies on colony development. Wild queens of Bombus griseocollis, B. nevadensis and B. vosnesenskii were collected and maintained for establishment of nests. Queens that died during rearing or that did not lay eggs within one month of capture were dissected, and tissues were examined microscopically for the presence of pathogens. Filamentous fungi that were detected were plated on artificial media containing broad spectrum antibiotics for isolation and identification. Based on morphological characters, the fungus was identified as Ascosphaera apis (Maasen ex Claussen) Olive and Spiltoir, a species that has been reported earlier only from larvae of the European honey bee, Apis mellifera, the Asian honey bee, Apis cerana, and the carpenter bee Xylocopa californica arizonensis. The identity of the fungus was confirmed using molecular markers and phylogenetic analysis. Ascosphaera apis was detected in queens of all three bumble bee species examined. Of 150 queens dissected, 12 (8%) contained vegetative and reproductive stages of the fungus. Both fungal stages were also detected in two workers collected from colonies with Ascosphaera-infected B. nevadensis queens. In this study, wild bees could have been infected prior to capture for rearing, or, the A. apis infection could have originated via contaminated European honey bee pollen fed to the bumble bees in captivity. Thus, the discovery of A. apis in adult bumble bees in the current study has important implications for commercial production of bumble bee colonies and highlights potential risks to native bees via pathogen spillover from infected bees and infected pollen.

No MeSH data available.


Related in: MedlinePlus