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Brood ball-mediated transmission of microbiome members in the dung beetle, Onthophagus taurus (Coleoptera: Scarabaeidae).

Estes AM, Hearn DJ, Snell-Rood EC, Feindler M, Feeser K, Abebe T, Dunning Hotopp JC, Moczek AP - PLoS ONE (2013)

Bottom Line: Yet one of the most ecologically necessary and evolutionarily successful groups of beetles, the dung beetles (Scarabaeinae) feeds primarily, or exclusively, on dung.Finer level phylotyping analyses based on lepA and gyrB amplicons of cultured isolates placed the isolates closest to Enterobacter cloacae, Providencia stuartii, Pusillimonas sp., Pedobacter heparinus, and Lysinibacillus sphaericus.The use of autoclaved dung for rearing, the presence of microbes in the brood ball and offspring, and identical 16S rRNA sequences in both parent and offspring suggests that the O. taurus female parent transmits specific microbiome members to her offspring through the brood chamber.

View Article: PubMed Central - PubMed

Affiliation: Towson University, Department of Biological Sciences, Baltimore, Maryland, United States of America ; Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.

ABSTRACT
Insects feeding on plant sap, blood, and other nutritionally incomplete diets are typically associated with mutualistic bacteria that supplement missing nutrients. Herbivorous mammal dung contains more than 86% cellulose and lacks amino acids essential for insect development and reproduction. Yet one of the most ecologically necessary and evolutionarily successful groups of beetles, the dung beetles (Scarabaeinae) feeds primarily, or exclusively, on dung. These associations suggest that dung beetles may benefit from mutualistic bacteria that provide nutrients missing from dung. The nesting behaviors of the female parent and the feeding behaviors of the larvae suggest that a microbiome could be vertically transmitted from the parental female to her offspring through the brood ball. Using sterile rearing and a combination of molecular and culture-based techniques, we examine transmission of the microbiome in the bull-headed dung beetle, Onthophagus taurus. Beetles were reared on autoclaved dung and the microbiome was characterized across development. A ~1425 bp region of the 16S rRNA identified Pseudomonadaceae, Enterobacteriaceae, and Comamonadaceae as the most common bacterial families across all life stages and populations, including cultured isolates from the 3(rd) instar digestive system. Finer level phylotyping analyses based on lepA and gyrB amplicons of cultured isolates placed the isolates closest to Enterobacter cloacae, Providencia stuartii, Pusillimonas sp., Pedobacter heparinus, and Lysinibacillus sphaericus. Scanning electron micrographs of brood balls constructed from sterile dung reveals secretions and microbes only in the chamber the female prepares for the egg. The use of autoclaved dung for rearing, the presence of microbes in the brood ball and offspring, and identical 16S rRNA sequences in both parent and offspring suggests that the O. taurus female parent transmits specific microbiome members to her offspring through the brood chamber. The transmission of the dung beetle microbiome highlights the maintenance and likely importance of this newly-characterized bacterial community.

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Brood ball chamber.The brood ball chamber is a unique structure for the transmitted microbiome of dung beetles. (A) The innermost walls of the brood ball chamber with the egg are smooth as compared to the fibrous outer walls. (B) A brood ball is shown broken into 3 pieces. The hollow brood ball chamber is where the egg develops (left). The remainder of the brood ball is filled with cellulose-rich, fibrous dung (center and right). Images C-F are scanning electron micrographs of different portions of the brood ball. (C) Micrograph illustrating the smooth biofilm-like matrix coating the inner wall of the brood ball chamber. (D) Fibrous bits of grass from the cow dung found in the portion of the brood ball away from the chamber. (E) Higher magnification of the smooth biofilm-like matrix that coats the brood ball chamber walls. (F) When the smooth matrix is scraped away, rod shaped microbes in chains (arrows) are found underneath the smooth matrix of the brood ball chamber walls. Other rod-shaped structures in the background remain covered in the biofilm-like matrix (arrowheads). This matrix and microbes are only observed where the mother has prepared the brood ball chamber.
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pone-0079061-g002: Brood ball chamber.The brood ball chamber is a unique structure for the transmitted microbiome of dung beetles. (A) The innermost walls of the brood ball chamber with the egg are smooth as compared to the fibrous outer walls. (B) A brood ball is shown broken into 3 pieces. The hollow brood ball chamber is where the egg develops (left). The remainder of the brood ball is filled with cellulose-rich, fibrous dung (center and right). Images C-F are scanning electron micrographs of different portions of the brood ball. (C) Micrograph illustrating the smooth biofilm-like matrix coating the inner wall of the brood ball chamber. (D) Fibrous bits of grass from the cow dung found in the portion of the brood ball away from the chamber. (E) Higher magnification of the smooth biofilm-like matrix that coats the brood ball chamber walls. (F) When the smooth matrix is scraped away, rod shaped microbes in chains (arrows) are found underneath the smooth matrix of the brood ball chamber walls. Other rod-shaped structures in the background remain covered in the biofilm-like matrix (arrowheads). This matrix and microbes are only observed where the mother has prepared the brood ball chamber.

Mentions: Onthophagus adults fly to a fresh dung pad where they use scoop-like mouthparts to filter the liquid portion of the dung for associated microbes [38] (Figure 1). Females then tunnel vertically in the soil underneath the dung pad where they form a series of brood balls for their offspring. Females move dung down to the ends of the tunnel where they pack dung into an oval brood ball with a brood chamber at one end of the brood ball (Figure 1). The female meticulously constructs a brood chamber lined with her own saliva where a single egg [39] is laid on top of a pedestal made of the adult female's own excrement [31,39] (Figure 1 A and G and 2 A). The entire juvenile portion of the life cycle - all 3 larval instars as well as pupation - occurs within this brood ball chamber [31,39] (Figure 1A-H). The larva hatches from the egg. Using its heavily sclerotized, toothed mandibles [38], the first instar larva immediately feeds on the dung pedestal, and then methodically alternates feeding on the solid, cellulose-rich portion of dung of the brood ball wall and its own excrement (Figure 1H) until pupation [31] (Figure 1E). Larvae pupate inside a pupation chamber constructed out of late larval fecal matter and left-over brood ball material in the remains of the brood ball (Figure 1E). After ~ 8 days at 25 °C the pupa ecloses into the filial adult, which remains inside the pupation chamber for at least several days until fully sclerotized. During dry or winter seasons, pupae will remain in their pupation chamber until the appropriate weather conditions are present. At this point during the breeding and nesting season, the adult digs to the soil surface to find food and mate [39] (Figure 1F).


Brood ball-mediated transmission of microbiome members in the dung beetle, Onthophagus taurus (Coleoptera: Scarabaeidae).

Estes AM, Hearn DJ, Snell-Rood EC, Feindler M, Feeser K, Abebe T, Dunning Hotopp JC, Moczek AP - PLoS ONE (2013)

Brood ball chamber.The brood ball chamber is a unique structure for the transmitted microbiome of dung beetles. (A) The innermost walls of the brood ball chamber with the egg are smooth as compared to the fibrous outer walls. (B) A brood ball is shown broken into 3 pieces. The hollow brood ball chamber is where the egg develops (left). The remainder of the brood ball is filled with cellulose-rich, fibrous dung (center and right). Images C-F are scanning electron micrographs of different portions of the brood ball. (C) Micrograph illustrating the smooth biofilm-like matrix coating the inner wall of the brood ball chamber. (D) Fibrous bits of grass from the cow dung found in the portion of the brood ball away from the chamber. (E) Higher magnification of the smooth biofilm-like matrix that coats the brood ball chamber walls. (F) When the smooth matrix is scraped away, rod shaped microbes in chains (arrows) are found underneath the smooth matrix of the brood ball chamber walls. Other rod-shaped structures in the background remain covered in the biofilm-like matrix (arrowheads). This matrix and microbes are only observed where the mother has prepared the brood ball chamber.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3815100&req=5

pone-0079061-g002: Brood ball chamber.The brood ball chamber is a unique structure for the transmitted microbiome of dung beetles. (A) The innermost walls of the brood ball chamber with the egg are smooth as compared to the fibrous outer walls. (B) A brood ball is shown broken into 3 pieces. The hollow brood ball chamber is where the egg develops (left). The remainder of the brood ball is filled with cellulose-rich, fibrous dung (center and right). Images C-F are scanning electron micrographs of different portions of the brood ball. (C) Micrograph illustrating the smooth biofilm-like matrix coating the inner wall of the brood ball chamber. (D) Fibrous bits of grass from the cow dung found in the portion of the brood ball away from the chamber. (E) Higher magnification of the smooth biofilm-like matrix that coats the brood ball chamber walls. (F) When the smooth matrix is scraped away, rod shaped microbes in chains (arrows) are found underneath the smooth matrix of the brood ball chamber walls. Other rod-shaped structures in the background remain covered in the biofilm-like matrix (arrowheads). This matrix and microbes are only observed where the mother has prepared the brood ball chamber.
Mentions: Onthophagus adults fly to a fresh dung pad where they use scoop-like mouthparts to filter the liquid portion of the dung for associated microbes [38] (Figure 1). Females then tunnel vertically in the soil underneath the dung pad where they form a series of brood balls for their offspring. Females move dung down to the ends of the tunnel where they pack dung into an oval brood ball with a brood chamber at one end of the brood ball (Figure 1). The female meticulously constructs a brood chamber lined with her own saliva where a single egg [39] is laid on top of a pedestal made of the adult female's own excrement [31,39] (Figure 1 A and G and 2 A). The entire juvenile portion of the life cycle - all 3 larval instars as well as pupation - occurs within this brood ball chamber [31,39] (Figure 1A-H). The larva hatches from the egg. Using its heavily sclerotized, toothed mandibles [38], the first instar larva immediately feeds on the dung pedestal, and then methodically alternates feeding on the solid, cellulose-rich portion of dung of the brood ball wall and its own excrement (Figure 1H) until pupation [31] (Figure 1E). Larvae pupate inside a pupation chamber constructed out of late larval fecal matter and left-over brood ball material in the remains of the brood ball (Figure 1E). After ~ 8 days at 25 °C the pupa ecloses into the filial adult, which remains inside the pupation chamber for at least several days until fully sclerotized. During dry or winter seasons, pupae will remain in their pupation chamber until the appropriate weather conditions are present. At this point during the breeding and nesting season, the adult digs to the soil surface to find food and mate [39] (Figure 1F).

Bottom Line: Yet one of the most ecologically necessary and evolutionarily successful groups of beetles, the dung beetles (Scarabaeinae) feeds primarily, or exclusively, on dung.Finer level phylotyping analyses based on lepA and gyrB amplicons of cultured isolates placed the isolates closest to Enterobacter cloacae, Providencia stuartii, Pusillimonas sp., Pedobacter heparinus, and Lysinibacillus sphaericus.The use of autoclaved dung for rearing, the presence of microbes in the brood ball and offspring, and identical 16S rRNA sequences in both parent and offspring suggests that the O. taurus female parent transmits specific microbiome members to her offspring through the brood chamber.

View Article: PubMed Central - PubMed

Affiliation: Towson University, Department of Biological Sciences, Baltimore, Maryland, United States of America ; Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.

ABSTRACT
Insects feeding on plant sap, blood, and other nutritionally incomplete diets are typically associated with mutualistic bacteria that supplement missing nutrients. Herbivorous mammal dung contains more than 86% cellulose and lacks amino acids essential for insect development and reproduction. Yet one of the most ecologically necessary and evolutionarily successful groups of beetles, the dung beetles (Scarabaeinae) feeds primarily, or exclusively, on dung. These associations suggest that dung beetles may benefit from mutualistic bacteria that provide nutrients missing from dung. The nesting behaviors of the female parent and the feeding behaviors of the larvae suggest that a microbiome could be vertically transmitted from the parental female to her offspring through the brood ball. Using sterile rearing and a combination of molecular and culture-based techniques, we examine transmission of the microbiome in the bull-headed dung beetle, Onthophagus taurus. Beetles were reared on autoclaved dung and the microbiome was characterized across development. A ~1425 bp region of the 16S rRNA identified Pseudomonadaceae, Enterobacteriaceae, and Comamonadaceae as the most common bacterial families across all life stages and populations, including cultured isolates from the 3(rd) instar digestive system. Finer level phylotyping analyses based on lepA and gyrB amplicons of cultured isolates placed the isolates closest to Enterobacter cloacae, Providencia stuartii, Pusillimonas sp., Pedobacter heparinus, and Lysinibacillus sphaericus. Scanning electron micrographs of brood balls constructed from sterile dung reveals secretions and microbes only in the chamber the female prepares for the egg. The use of autoclaved dung for rearing, the presence of microbes in the brood ball and offspring, and identical 16S rRNA sequences in both parent and offspring suggests that the O. taurus female parent transmits specific microbiome members to her offspring through the brood chamber. The transmission of the dung beetle microbiome highlights the maintenance and likely importance of this newly-characterized bacterial community.

Show MeSH
Related in: MedlinePlus