Frequency-dependent viscosity of salmon ovarian fluid has biophysical implications for sperm-egg interactions ...

• Main Author: Graziano, Marco
• Format: Dataset
• Language: English
• Published: Dryad 2022
• Subjects: FOS Biological sciences; cryptic female choice; Mate choice; Female reproductive fluid; Viscoelasticity; Sperm competition; Sexual selection; Canada; Atlantic salmon; Newfoundland
• Online Access: https://dx.doi.org/10.5061/dryad.z8w9ghxfm; https://datadryad.org/stash/dataset/doi:10.5061/dryad.z8w9ghxfm

Gamete-level sexual selection of externally fertilising species is usually achieved by modifying sperm behaviour with mechanisms thought to alter the chemical environment in which gametes perform. In fish this can be accomplished through the ovarian fluid, a substance released with the eggs at spawning. While its biochemical effects in relation to sperm energetics have been investigated, the influence of the physical environment in which sperm compete remains poorly explored. Our objective was therefore to gain insights on the physical structure of this fluid and potential impacts on reproduction. Using soft-matter physics approaches of steady-state and oscillatory viscosity measurements, we subjected salmon ovarian fluids to variable shear stresses and frequencies resembling those exerted by sperm swimming through the fluid near eggs. We show that this fluid, which in its relaxed state is a gel-like substance, displays a non-Newtonian viscoelastic and shear-thinning profile, where the viscosity decreases ... : Sample collection and preliminary measurements Wild anadromous Atlantic salmon were collected in early September from a fish ladder at Grand Falls (48° 55' N, -55° 39' W) during their up-stream spawning migration on the Exploits River (Newfoundland, Canada). Following previous protocols (Rooke et al., 2019), fish were transferred to covered, outdoor tanks next to the river, and experienced ambient temperatures and light. Over two weeks in early November, females were assessed for ovulation using gentle abdominal pressure, fish were then anaesthetised using a solution of 2ml/L clove oil, measured for length and weight, and stripped of eggs after drying the urogenital pore. Each female’s eggs (and associated ovarian fluid) were kept in sealed glass jars, enclosed with bubble wrap, and placed in a cooler of wet ice for transport to the laboratory. Each egg batch was separated from its ovarian fluid using a fine mesh net (Purchase & Rooke, 2020) within 10 hours of stripping. For each ovarian fluid we ...