Queens stay, workers leave: caste-specific responses to fatal infections in an ant

URN to cite this document: urn:nbn:de:bvb:355-epub-384035

Giehr, Julia and Heinze, Jürgen (2018) Queens stay, workers leave: caste-specific responses to fatal infections in an ant. BMC Evolutionary Biology 18 (1), pp. 1-11.

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Date of publication of this fulltext: 01 Mar 2019 11:54

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Other URL: http://doi.org/10.1186/s12862-018-1320-0, https://bmcevolbiol.biomedcentral.com/articles/10.1186/s12862-018-1320-0

Abstract

Abstract

Background
The intense interactions among closely related individuals in animal societies provide perfect conditions for the spread of pathogens. Social insects have therefore evolved counter-measures on the cellular, individual, and social level to reduce the infection risk. One striking example is altruistic self-removal, i.e., lethally infected workers leave the nest and die in isolation to prevent the spread of a contagious disease to their nestmates. Because reproductive queens and egg-laying workers behave less altruistically than non-laying workers, e.g., when it comes to colony defense, we wondered whether moribund egg-layers would show the same self-removal as non-reproductive workers. Furthermore, we investigated how a lethal infection affects reproduction and studied if queens and egg-laying workers intensify their reproductive efforts when their residual reproductive value decreases (“terminal investment”).

Results
We treated queens, egg-laying workers from queenless colonies, and non-laying workers from queenright colonies of the monogynous (single-queened) ant Temnothorax crassispinus either with a control solution or a solution containing spores of the entomopathogenic fungus Metarhizium brunneum. Lethally infected workers left the nest and died away from it, regardless of their reproductive status. In contrast, infected queens never left the nest and were removed by workers only after they had died. The reproductive investment of queens strongly decreased after the treatment with both, the control solution and the Metarhizium brunneum suspension. The egg laying rate in queenless colonies was initially reduced in infected colonies but not in control colonies. Egg number increased again with decreasing number of infected workers.

Conclusions
Queens and workers of the ant Temnothorax crassispinus differ in their reaction to an infection risk and a reduced life expectancy. Workers isolate themselves to prevent contagion inside the colony, whereas queens stay in the nest. We did not find terminal investment; instead it appeared that egg-layers completely shut down egg production in response to the lethal infection. Workers in queenless colonies resumed reproduction only after all infected individuals had died, probably again to minimize the risk of infecting the offspring.

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Item type:

Article

Date:

27 December 2018

Institutions:

Biology, Preclinical Medicine > Institut für Zoologie > Zoologie/Evolutionsbiologie (Prof. Dr. Jürgen Heinze)

Projects:

Open Access Publizieren (DFG)

Identification Number:

Value	Type
10.1186/s12862-018-1320-0	DOI

Keywords:

Altruism, self-removal, lethal infection, disease management; Terminal investment; Ants; Temnothorax

Dewey Decimal Classification:

600 Technology > 610 Medical sciences Medicine

Status:

Published

Refereed:

Yes, this version has been refereed

Created at the University of Regensburg:

Yes

Item ID:

38403

Owner only: item control page

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