The influence of autospasy on the flight initiation distance of harvestmen

• Grant number: 14/14013-0
• Support Opportunities: Scholarships abroad - Research
• Start date: September 15, 2014
• End date: October 04, 2014
• Field of knowledge: Biological Sciences - Zoology - Animal Behavior
• Principal Investigator: Rodrigo Hirata Willemart
• Grantee: Rodrigo Hirata Willemart
• Host Investigator: Roger Douglas Santer
• Host Institution: Escola de Artes, Ciências e Humanidades (EACH). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Aberystwyth University, Wales

Abstract

Fleeing from predators envolve the detection and decision about when to start fleeing. Two hypotheses that exist in the literature are that (1) prey must flee when the distance of the predator is such that it offers real danger and (2) that the cost of monitoring the predator must also be considered and therefore prey must flee earlier. Therefore, whereas the first predicts fleeing only when the predator is close, the latter predicts early fleeing. Computer generated visual stimuli are an excellent tool to test these hypotheses and also allow - by modifying type of stimulus and velocity of approaching - which causes which reaction. Harvestmen are arachnids very dependent on chemicals to find resources and there is no experimental study on how harvestmen use their pair of median eyes to flee from predators. Since autospasy is common in some species, these are also good models to test a possible relation between the number of legs (which affects locomotion) and flight behavior. In this project we will explore such questions in the harvestman Phalangium opilio. We will first test the reaction of the animals to distinct stimuli. We will then pick on stimulus and use it to compare the behavior of harvestmen with three categories of number of legs. According to hypothesis (1) and considering the greater locomotor activity of individuals with all the legs, we would expect latency to flee to be higher in these individuals. The hypothesis (2) predicts that the latency to flee do not differ between groups since harvestmen would flight early in any case. Additionally, we will have information on the visual capabilities of harvestmen and how these help them to distinguish between different types of stimuli and different velocity of approaches. (AU)