Multi-predator chemical deterrence and visual signaling in harvestmen (Arachnida, Opiliones)

• Grant number: 21/02098-4
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: March 01, 2022
• End date: May 31, 2023
• Field of knowledge: Biological Sciences - Zoology - Animal Behavior
• Principal Investigator: Rodrigo Hirata Willemart
• Grantee: Nathalia Ximenes Gonçalves
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Almost all harvestmen (Arachnida, Opiliones) species produce chemical secretions that vary in nature and some harvestmen species have conspicuous coloration, the latter being putative signals. However, up to now, the effectiveness of those different compounds has not been compared in the light of a wide range of selective pressures predators might exert. And even though bright colors have been suggested to be aposematic, this has not been assessed either. Therefore, our goals are to investigate (1) whether chemical compounds differ in predator taxa deterrence and (2) whether harvestmen signal chemical effectiveness through conspicuous body coloration to their visually guided predators. To test if different chemical compounds deter distinct predators, we will conduct a meta-analysis considering defensive secretions in arthropods, and an experiment using harvestmen secretions (quinone, phenol and ketone)presented to distinct predators. We will use a color vision model to evaluate how harvestmen(in the family Gonyleptidae) are perceived by predators. To assess if there is a correlation between signal conspicuousness and chemical effectiveness, we will use data from literatureand the results from color vision modeling. We expect that chemical compounds will vary in effectiveness according to the predator habitat and habit, and according to specific chemical traits of each chemical defense. We also expect that the more effective is the harvestmen chemical defense, the more conspicuous it will be.