Amphibian cross-fertilization and polyspermy

Area of Science:

• Reproductive biology
• Amphibian fertilization

Background:

• Cross-fertilization studies are crucial for understanding reproductive isolation mechanisms.
• Bufo arenarum (Ba) oocytes were used to investigate fertilization success with homologous and heterologous sperm.

Purpose of the Study:

• To examine the effects of homologous and heterologous insemination on Bufo arenarum oocyte development.
• To investigate the role of timing and cortical granule products in preventing polyspermy during heterologous fertilization.

Main Methods:

• Insemination of Bufo arenarum oocytes with homologous (Ba) and heterologous (Leptodactylus chaquensis, Lch; Bufo paracnemis, Bp) spermatozoa.
• Sequential insemination experiments at different time intervals (30, 60, 300 seconds).
• Artificial activation of oocytes and incubation with cortical granule products.

Main Results:

• Homologous insemination led to normal development; heterologous fertilization resulted in polyspermy and abnormal development.
• Delayed heterologous insemination (300 sec) reduced polyspermy and abnormalities, suggesting a transient fertilization block.
• Permanent polyspermy blockage via oocyte activation or cortical granule products inhibited heterologous sperm penetration.

Conclusions:

• The electrophysiological block to fertilization in Bufo arenarum is transient and can be overcome by heterologous sperm if insemination is delayed.
• Cortical granule products play a significant role in establishing a permanent block against polyspermy, particularly in heterologous fertilization scenarios.