Abstract
Simple SummaryCarpenter ants are important to ecosystem services as they assist in the breakdown of course woody debris when excavating wood for nests. Feeding on a variety of carbohydrate and protein sources, they have an infrabuccal filter that limits passage of large food particles to their gut. A variety of yeasts have been found associated with the infrabuccal pocket and the nests of these ants. The yeast Schwanniomyces polymorphus is associated with the carpenter ant Camponotus vicinus. To examine a possible nutritional association between this yeast and ant, we reared small sub-colonies of defaunated and non-defaunated C. vincus brood on several artificial diets where various nutritional components were removed. Part of the testing involved exposure of brood to these diets and cells of S. polymorphus. Dietary treatments that were augmented with yeast generally had deleterious effects on brood development compared to diets without yeast. However, increased brood weight and increased number of adult ants from initial brood was observed in non-defaunated ants fed a diet where B vitamins and sterols were absent, but augmented with live yeast. The results suggest a supplemental role for this yeast in ant nutrition and development.The yeast Schwanniomyces polymorphus is associated with the infrabuccal pocket in the carpenter ant Camponotus vicinus (Hymenoptera: Formicidae), but its role in ant development is poorly defined. The potential effects of this yeast on brood development were examined on sets of larval groups and workers over a 12 week period. Worker–larval sets were fed variations of a completely artificial, holidic diet and exposed or not exposed to live S. polymorphus. Worker–larval sets in half of the experiment were defaunated using a two-step heat and chemical process. Brood development and number of adult ants produced were significantly affected by the heat/chemical defaunation process. Compared to worker–larval groups fed a basal, complete diet, all treatments resulted in no or deleterious larval development. Brood weights and number of worker ants produced from the original larval sets at initiation were significantly higher in non-defaunated ant groups fed a diet lacking both B vitamins and cholesterol and exposed to live S. polymorphus. We propose that this yeast may help ants to more efficiently assimilate nutrients when fed nutrient-deficient diets, particularly those deficient in sterols.
Highlights
This appeared noticeable in diets lacking both B vitamins and cholesterol after 4 weeks
Live yeast-exposed ants fed this same diet had higher brood weights, suggesting that the yeast conferred some nutritional advantage to a diet lacking both B vitamins and cholesterol
Exposure to live Schwanniomyces polymorphus showed a positive effect on brood weights and number of worker ants produced in only one of the diet treatments exposed to yeast
Summary
Carpenter ants generally nest in wood, they do not use it as a food source. The majority of Camponotus species play an important role in Holarctic forest ecosystems where they aid in the breakdown of woody debris through their nesting habits and feed omnivorously on plant exudates and live arthropod prey including pest insects. Carpenter ants do not ingest solid food particles as workers possess a buccal filter or infrabuccal pocket that limits the passage of large food particles to the gut [4,5,6,7,8]. Incoming food filtered by the infrabuccal pocket forms a pellet that is squeezed by muscular action, and any liquid produced passes to the midgut before the pellet is evacuated. Previous studies observed Gram-negative bacteria and yeast species in the infrabuccal pocket and galleries of Camponotus vicinus Mayr; the potential function, if any, of these organisms has not been examined [8,9,10]
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