Exploring the Influence of Viscosity on Spermatozoa Motility and Behavioral Dynamics

• Grant number: 25/08877-6
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: November 01, 2025
• End date: April 30, 2026
• Field of knowledge: Biological Sciences - Physiology - Compared Physiology
• Principal Investigator: Renata Guimarães Moreira Whitton
• Grantee: Evander Matos Penchel
• Supervisor: Serhii Boryshpolets
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: University of South Bohemia in Ceske Budejovice (USB), Czech Republic
• Associated to the scholarship: 24/08477-5 - Effects of ibuprofen, diclofenac and their mixture on the seminal quality parameters of Astyanax lacustris (Characiformes: Characidae), BP.MS

Abstract

In natural environments, the reproductive fluids (RF), such as ovarian fluid and seminal plasma, exhibit higher viscosities than water due to their complex biochemical makeup, which may affect the hydrodynamic environment where fish gametes fertilization takes place. Notably, ovarian fluid (OF) exhibits properties that enhance sperm velocity and motility duration. This research will investigate how fluid viscosity influences sperm motility and behavior in externally fertilizing species. To mimic the viscosity of the fertilization environment, artificial viscous media (AVM) will be created by the use of methylcellulose (MC) and polyvinylpyrrolidone (PVP) at varying concentrations. Sperm samples will be collected from the natural breeding season of different fish species. Then, motility parameters in AVM will be video-recorded using digital microscopy. Additionally, microcapillary experiments will be employed to observe sperm behavior across viscosity boundaries, hence shedding light on the hydrodynamic challenges that sperm encounter in heterogeneous environments. Video records will be analyzed using the CASA (Computer-Aided Sperm Analysis) plugin for ImageJ, and the data will be statistically analyzed. The findings will be critical for deciphering species-specific viscous adaptations and will be important in studies that aim to evaluate the effects of contaminants present in the water on seminal quality, reinforcing that externally fertilizing species will be studied.