ELECTRIC IMPEDANCE OF HIPPONOE EGGS.

Area of Science:

• * Cellular Electrophysiology
• * Marine Biology
• * Biophysics

Background:

• * Understanding the electrical properties of cell membranes is crucial for comprehending cellular function.
• * Echinoderm eggs serve as a model system for studying fertilization and early development.

Purpose of the Study:

• * To measure the alternating current (AC) resistance and capacity of Hipponoë esculenta eggs.
• * To investigate how fertilization and swelling affect egg membrane electrical properties.
• * To develop a method for determining egg volume concentration in suspensions.

Main Methods:

• * AC resistance and capacity measurements across a frequency range (1.08 kHz to 2.32 MHz).
• * Suspensions of unfertilized, fertilized, and swollen unfertilized eggs were analyzed.
• * A novel method for measuring egg volume concentration was employed.

Main Results:

• * Unfertilized egg membranes are non-conducting at low frequencies with a static capacity of 0.87 µF/cm².
• * Internal resistance of unfertilized eggs is 11 times that of seawater.
• * Fertilized eggs show 2.5x higher membrane capacity than unfertilized eggs, with increased internal resistance.
• * Egg membrane capacity decreases linearly with surface area when eggs swell in dilute seawater (down to 75% in 40% seawater).

Conclusions:

• * Fertilization significantly alters the electrical properties of the echinoderm egg membrane.
• * Egg membrane capacitance is sensitive to changes in cell volume and hydration.
• * The findings provide insights into the biophysical changes occurring during fertilization and osmotic stress.