Could the latitudinal distributions of Leptuca panacea and L. pugilator be explained by the morphology of the hypertrophied cheliped and its role in thermoregulation?

• Grant number: 25/09894-1
• Support Opportunities: Scholarships abroad - Research Internship - Scientific Initiation
• Start date: March 29, 2026
• End date: July 28, 2026
• Field of knowledge: Biological Sciences - Ecology - Ecosystems Ecology
• Principal Investigator: Tânia Marcia Costa
• Grantee: Ana Carolina Francelino
• Supervisor: Michael Zachary Darnell
• Host Institution: Instituto de Biociências (IB-CLP). Universidade Estadual Paulista (UNESP). Campus Experimental do Litoral Paulista. São Vicente , SP, Brazil
• Institution abroad: The University Of Southern Mississippi, United States
• Associated to the scholarship: 24/17379-7 - Thermal Ecology of Leptuca spp.: Preferences, Thermal Windows, and Thermoregulatory Capacity, BP.IC

Abstract

Currently, the effects of climate change are already being strongly observed, such as the rise in global temperature. Rising temperatures affect various aspects of animal life, from physiology to behavior, as evidenced by global shifts in species distributions toward the poles, a process often referred to as tropicalization. This poleward migration consists of searching for areas that are thermally suitable for their physiology as a strategy to cope with these changes. This effect is more pronounced in ectotherms because their body temperature is regulated by the temperature of the environment. Fiddler crabs are ectotherms found in intertidal areas around the world. The strong sexual dimorphism in these animals shows that the male has a hypertrophied cheliped with agonistic, reproductive and thermoregulatory functions. The morphology of this cheliped can vary both intra- and interspecifically. Studies have already observed that intraspecific variation has a greater capacity for heat exchange and can influence its distribution. Therefore, studying and understanding the thermal ecology of these organisms can help predict how they will cope with rising temperatures. The aim of this study is to analyze whether the different latitudinal distributions of the species Leptuca panacea and L. pugilator can be explained by the morphology and thermoregulatory function of the hypertrophied cheliped of these species, and to compare this between the two species. These species are phylogenetically close and have different latitudinal distributions. This will be assessed by comparing the thermal preference, heat exchange capacity and geometric morphometry of these chelipeds. The thermal preference will be carried out by analysing the amount of time that each animal spends at different temperatures along a thermal gradient. Heat exchange capacity will be investigated by immersing the hypertrophied cheliped in an ice bath in one treatment and in a control treatment in which the cheliped is only exposed to air. Finally, geometric morphometry will be carried out using 7 landmarks on the hypertrophied cheliped to compare between the two species. Thus, we hope that this study will help to observe and compare the thermal ecology of these species in the context of current climate change. (AU)