Browsing by Author "Hartfelder, Klaus"
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- ItemThe behavior and reproductive physiology of a solitary progressive provisioning vespid wasp : evidence for a solitary-cycle origin of reproductive castes(University of Chicago Press, 2018-01-05) Kelstrup, Hans C.; Hartfelder, Klaus; Lopes, Tiago Falcon; Wossler, Theresa C.The emergence of queens and workers from solitary antecedents mark a major evolutionary transition in the history of life. The solitary progressive provisioning wasp Synagris cornuta, a member of the subfamily Eumeninae (basal to eusocial vespid wasps), alternates between behavioral states characterized as queenlike and worker-like. Akin to a queen in eusocial wasps, a S. cornuta female initiates construction of a cell into which she oviposits and then, similar to a worker, cares for the brood as it develops. The ovarian groundplan (OGP) hypothesis for caste origins predicts that these behavioral states are associated with cyclical changes in ovarian status, where females performing queenlike tasks have eggs and those performing worker-like tasks possess only small oocytes. Our findings show strong support for the OGP hypothesis: the ovaries of S. cornuta females undergo differential oogenesis depending on the behavioral phase: the largest oocyte in the ovaries of females building a cell progresses faster compared to that of females attending brood. Yet contrary to the OGP hypothesis, neither juvenile hormone nor ecdysteroids is associated with the reproductive cycle. Finally, the cuticular hydrocarbon profile showed no link with ovarian status, suggesting that fertility signals evolved subsequent to the emergence of group living.
- ItemThe role of juvenile hormone in dominance behavior, reproduction and cuticular pheromone signaling in the caste-flexible epiponine wasp, Synoeca surinama(BioMed Central, 2014) Kelstrup, Hans C.; Hartfelder, Klaus; Nascimento, Fabio S.; Riddiford, Lynn M.Background: The popular view on insect sociality is that of a harmonious division of labor among two morphologically distinct and functionally non-overlapping castes. But this is a highly derived state and not a prerequisite for a functional society. Rather, caste-flexibility is a central feature in many eusocial wasps, where adult females have the potential to become queens or workers, depending on the social environment. In non-swarming paper wasps (e.g., Polistes), prospective queens fight one another to assert their dominance, with losers becoming workers if they remain on the nest. This aggression is fueled by juvenile hormone (JH) and ecdysteroids, major factors involved in caste differentiation in most eusocial insects. We tested whether these hormones have conserved aggression-promoting functions in Synoeca surinama, a caste-flexible swarm-founding wasp (Epiponini) where reproductive competition is high and aggressive displays are common. Results: We observed the behavioral interactions of S. surinama females in field nests before and after we had removed the egg-laying queen(s). We measured the ovarian reproductive status, hemolymph JH and ecdysteroid titers, ovarian ecdysteroid content, and analyzed the cuticular hydrocarbon (CHC) composition of females engaged in competitive interactions in both queenright and queenless contexts. These data, in combination with hormone manipulation experiments, revealed that neither JH nor ecdysteroids are necessary for the expression of dominance behaviors in S. surinama. Instead, we show that JH likely functions as a gonadotropin and directly modifies the cuticular hydrocarbon blend of young workers to match that of a reproductive. Hemolymph ecdysteroids, in contrast, are not different between queens and workers despite great differences in ovarian ecdysteroid content. Conclusions: The endocrine profile of S. surinama shows surprising differences from those of other caste-flexible wasps, although a rise in JH titers in replacement queens is a common theme. Extensive remodeling of hormone functions is also evident in the highly eusocial bees, which has been attributed to the evolution of morphologically defined castes. Our results show that hormones which regulate caste-plasticity can lose these roles even while caste-plasticity is preserved.