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Tradeoffs between weaponry and fecundity in snapping shrimp queens vary with eusociality

Weakly eusocial queens must trade off their investment in maintaining their fighting claws or producing eggs

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IMAGE: Allometric measurements for (a) carapace length and (b) chela length on preserved, sponge-dwelling shrimp. view more 

Credit: Bornbusch et al (2018)

Amongst species of colonial snapping shrimp, the capacity for defense versus reproduction in queens varies with the level of cooperation, according to a study published March 14, 2018 in the open-access journal PLOS ONE by Sally Bornbusch from Duke University, USA, and colleagues.

Snapping shrimp in the genus Synalpheus are the only marine organisms that are eusocial, that is, reproduction is skewed to the queens, and colonies defend their territories cooperatively. The degree of eusociality varies amongst Synalpheus species, however, raising the question of whether queens of different species also have different strategies for allocating their resources between defense and reproduction. To find out, Bornbusch and colleagues determined fighting claw mass and egg number of 353 egg-bearing females from 221 colonies of six eusocial snapping shrimp species in the Caribbean.

In queens of snapping shrimp species that are weakly eusocial, the researchers found strong trade-offs between fighting claw mass and egg number. In contrast, this trade-off was smaller or absent in queens of species that are strongly eusocial. In addition, colony size was also a factor: in large colonies of highly eusocial species, trade-offs between queens' weaponry and fecundity were smaller. This work suggests that in snapping shrimp species that are less cooperative, female-female conflict within the colony has selected for queens that retain weapons at a significant cost to fecundity. Conversely, in species that are more eusocial -- notably those with a single queen per colony -- protection by other colony members could be an explanation to a reduction in this cost of weaponry in queens.

"We find that in eusocial Synalpheus shrimp, female-female competition and reproductive skew play a role in shaping a trade-off in queen energy allocation between reproductive success and defense weaponry," says Bornbusch. "These findings suggest that the evolution of eusociality in Synalpheus shrimp has left a signal in the allometry of female reproduction and defense."

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In your coverage please use this URL to provide access to the freely available article in PLOS ONE: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0193305

Citation: Bornbusch SL, Lefcheck JS, Duffy JE (2018) Allometry of individual reproduction and defense in eusocial colonies: A comparative approach to trade-offs in social sponge-dwelling Synalpheus shrimps. PLoS ONE 13(3): e0193305. https://doi.org/10.1371/journal.pone.0193305

Funding: The authors are grateful to the Smithsonian Institution's Caribbean Coral Reef Ecosystem program (ccre.si.edu) and to the National Science Foundation, particularly for grants to J.E.D. (DEB 92-01566, DEB 98-15785, IBN-0131931, IOS-1121716). This research was additionally funded by a College of William and Mary Honors Fellowship and Scion Natural Sciences Individual Grant to S.L.B. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

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