Cold Shock Compromises the Electrically Mediated Block to Polyspermy in Lytechinus variegatus Eggs

Area of Science:

• Reproductive biology
• Cellular physiology
• Marine biology

Background:

• Polyspermy, the fertilization of an egg by multiple sperm, is typically prevented by blocks to fertilization.
• The fast block to polyspermy in sea urchin eggs involves a rapid electrical depolarization of the egg membrane.

Purpose of the Study:

• To investigate the effect of low-temperature exposure on polyspermy in Lytechinus variegatus eggs.
• To elucidate the underlying electrophysiological mechanisms by which cold shock influences fertilization.

Main Methods:

• Eggs of Lytechinus variegatus were exposed to low temperatures prior to insemination.
• Electrophysiological recordings were used to monitor the egg's membrane potential during the fertilization response.

Main Results:

• Cold shock significantly increased the incidence of polyspermy.
• Electrophysiology revealed that cold shock attenuated the fertilization potential, resulting in a subthreshold depolarization.
• This impaired electrical response was insufficient to activate the fast block to polyspermy.

Conclusions:

• Low-temperature exposure creates a vulnerability in the electrical barrier preventing polyspermy.
• Cold shock disrupts the egg's action potential, compromising the fast block mechanism.
• Environmental temperature is a critical factor influencing fertilization success in sea urchins.