Chemical Defense as a Condition-Dependent Trait in Harvestmen
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The expression of costly traits often depends on the amount of food available to the individuals. Chemical defenses are costly, thus their production should be condition-dependent. Here, we tested the hypothesis that an increase in food availability and an acetate-supplemented diet will increase the production of chemical defenses by the harvestman Magnispina neptunus, which releases alkylated benzoquinones biosynthesized using acetate as a precursor. We manipulated the diet of the individuals and created four experimental groups: well-fed with acetate, well-fed without acetate, poorly-fed with acetate, and poorly-fed without acetate. Well-fed individuals produced secretions with higher mass and concentration of benzoquinones than poorly-fed individuals, but we detected no significant effect of the acetate supplement. Thus, the production of benzoquinones is condition-dependent, and even short periods of dietary restriction may make individuals more vulnerable to predators, imposing fitness consequences to chemically-protected arthropods that biosynthesize their own defensive compounds.
KeywordsBenzoquinone Costs Dietary restriction Food availability Parental care Arachnida Opiliones
We thank S. Rodrigues and R. Crespo for logistical support at LaReMN-UFF, A.H. Januário, A. González, M.F.K. Becker, B.A. Buzatto, N. Chaline, A. Arab, and two anonymous reviewers for comments on the manuscript, and FAPESP (2011/50800-8, 2012/50229-1) and CNPq (306550/2014-8) for financial support.
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