Mycobiota in the brood cells of the European beewolf, Philanthus triangulum (Hymenoptera: Crabronidae)

Evolutionary stability of antibiotic protection in a defensive symbiosis

“…In contrast to other insects with defensive microbial symbionts (e.g., leafcutter ants, aphids), beewolves occur in comparatively small aggregations (usually dozens to several hundred individuals), and their nesting sites are often located in disturbed and ephemeral habitats (84,85). Thus, they represent a scarce and unpredictable resource for microbes, and indeed, only common mold fungi that are abundant in the beewolves' nesting environments have been observed to infect the beewolf offspring, while specialized microbial pathogens are unknown (86). Thus, the key for the long-term success of the symbiont-provided antibiotic mixture in beewolves was probably the lack of coevolving pathogens.…”

Nitric oxide radicals are emitted by wasp eggs to kill mold fungi

“…First, provisioned bees without wasp eggs that were kept in artificial brood cells together with bees carrying an egg (but without physical contact) showed significantly delayed fungal growth compared to control bees that were kept alone (Breslow test, day 0–11: Chi square = 7.6 df=1, p=0.006; day 0–3: Chi square = 9.1, df = 1, p=0.003; Figure 2B). Second, when one of the most abundant mold species from infested beewolf brood cells, the fast growing Aspergillus flavus (Engl et al, 2016), was exposed to the volatiles presumably emanating from beewolf eggs on nutrient agar for three days, its growth was entirely inhibited, whereas it thrived in controls (for all observation times 24 hr, 48 hr, 72 hr: binomial test: N = 20, p<0.001, Figure 3). Notably, when the beewolf larvae were removed from the assays shortly after hatching (three days after oviposition), no fungal growth occurred in the exposed areas during another three days.…”

“…Some fungal spores might survive under the bees because they were screened against the gas. Another possibility, namely that strains of the ubiquitous mold fungi that are the main causes of molding in beewolf brood cells (Engl et al, 2016), have evolved resistance against the toxic effects of NO ⋅ /NO 2 ⋅ seems rather unlikely. Ultimately, there will be only weak selection for resistance at all since beewolf brood cells are certainly a rare habitat for the ubiquitous mold fungi (Engl et al, 2018).…”

“…The beewolf egg is laid on one of the bees, the larva hatches after three days, feeds on the bees for six to eight days, then spins a cocoon and either emerges the same summer or hibernates. The warm and humid microclimate in the brood cell promotes larval development but also favors fast growing, highly detrimental fungi (Engl et al, 2016). Without any countermeasures the provisions will be completely overgrown by mold fungi within three days (Figure 1B), and the beewolf larva becomes infested by fungi or starves to death (Strohm and Linsenmair, 2001; Herzner et al, 2011a).…”

Schon immer die gleiche Medizin

“…Sie können also nicht aktiv sicherstellen, dass dieser nicht von vor allem im Boden ubiquitären Schimmelpilzen verdorben wird, wodurch die Larven verhungern müssten oder selbst von den Schimmelpilzen befallen werden könnten. 6) Stattdessen sorgen die Weibchen vor: Sie putzen die gelähmten Bie-nen ausgiebig und entfernen dadurch Schimmelpilzsporen; sie überziehen sie beim Putzen mit einer Schicht aus hydrophoben Kohlenwasserstoffen und verhindern so, dass die Schimmelpilzsporen genügend Wasser zum Wachsen haben. [7][8][9] Zudem geben die Grabwespen ihren Nachkommen prophylaktisch eine Dosis Antibiotika 10,11)sie deponieren Bakterien in deren Brutzelle, die, sobald die Larven sie in ihren Kokon eingesponnen haben, dort einen Substanzcocktail produzieren, der das Wachstum von Schimmelpilzen hemmt (Abbildung 2).…”