Do fiddler crabs use vision to guide themselves under water? The effect of the variation of the tides in antipredatory responses of Leptuca thayeri

• Grant number: 20/15680-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2021
• End date: July 20, 2023
• Field of knowledge: Biological Sciences - Zoology - Animal Behavior
• Principal Investigator: Tânia Marcia Costa
• Grantee: Caio Augusto Paula
• Host Institution: Instituto de Biociências (IB-CLP). Universidade Estadual Paulista (UNESP). Campus Experimental do Litoral Paulista. São Vicente , SP, Brazil

Abstract

The fiddler crabs are territorial animals, caves builders, which live in between tides areas. They were considered active only during low tide, however, some species are also actives during high tide. Besides the ecological relevance of the fiddler crabs, they are a significant part of the alimentation of some estuarine birds. Therefore, in this project, we will perform laboratory tests to assess if the variation of the tides, between high and low, can affect the behavioural response of the fiddler crab Leptuca thayeri to a visual stimulus of the model of the predator, the little blue heron Egretta caerulea. To assess the effect of the predator we will perform three types of treatments at high tide and the same three at low tide: 1) model of the predator, 2) polystyrene ball, 3) without any object (control treatment). During the experiments, the terrariums will be observed for 10 minutes (two observations of 5 minutes each, separated by the offer of visual stimulus), considering 5 minutes of pre-stimulus and 5 minutes of post-stimulus. We will test if the crabs modify its behavior in different tides, analysing the variable responses: escape from visual stimulus; latency to the first reaction; crabs hiding in their burrows; latency to hide for the first time; latency in the burrow; remain in the border of the burrow; and enter and exit the burrow. The data will be calculated based on delta (post-stimulus deducted pre-stimulus) of the differents answers given by the crabs in the distinct tides, in the replicated observations. The data will be checked about normality and homoscedasticity, being submitted afterwards according to the results to one of the tests (variance test, Kruskal-Wallis test). (AU)