Abstract
During ovipositioning, avian eggshells become susceptible to bacterial and fungal growth and studies have shown that a community of these microorganisms, or microflora, is maintained on eggshells throughout the incubation process. To determine the possible role of these microorganisms on embryonic development, it is first important to understand the composition of the microbial community present on the surface of the egg. A limited amount of studies have been published in this area; thus, the objective of this study was to broaden this area of study and determine what bacterial communities are found on the surface of naturally-incubated House Wren eggs across three stages of incubation (pre, early, and late) as defined by egg temperature. Our data uniquely suggest that the eggshell microflora is dynamic and that this may be regulated by temperature fluctuations due to intermittent incubation behavior. Using culture-based techniques, 46 different bacterial species were identified belonging to 13 bacterial families and 20 genera. The majority of bacteria belonged to the Pseudomonas, Staphylococcus, Stenotrophomonas, or Burkholderia genera and have been previously associated with avian eggs and nests. Bacteria within the Pseudomonas genus were the most predominant and we hypothesize that their maintenance may be linked to their ability to produce antibiotic substances called bacteriocins. The bacterial composition of the microflora isolated in this study also suggests that avian egg microfloras are derived from environmental origins.
Highlights
The primary role of avian incubation, whether intermittent or continuous, is to supply optimal conditions to the egg to maintain embryonic development in regard to temperature, humidity, and gas exchange [1]
The affect this behavior has on the microflora maintained on eggshells likely varies for different avian species; we monitored the attentiveness of the female House Wren on the nest and the average egg temperature throughout the incubation period of several House Wrens within different nests and over multiple years
The data show that increases in female attentiveness correlate with increases in the average egg temperature, consistent with patterns observed in other passerine species [23]
Summary
The primary role of avian incubation, whether intermittent or continuous, is to supply optimal conditions to the egg to maintain embryonic development in regard to temperature, humidity, and gas exchange [1]. This is exemplified by numerous studies that have shown a dramatic decrease in viability in the absence of incubation [2,3,4,5]. The bacteria may have an environmental origin and be introduced to eggs via nest materials, which has been shown to be important for fungal associations [13, 14]
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