High fertilization success in a surface-brooding Caribbean gorgonian

Area of Science:

• Marine Biology
• Reproductive Ecology
• Gorgonian Corals

Background:

• The Caribbean gorgonian Pseudopterogorgia elisabethae exhibits external fertilization with eggs retained on the colony surface.
• Spawning events are crucial for coral reproduction, but success can be limited by sperm availability and environmental factors.

Purpose of the Study:

• To investigate fertilization success in Pseudopterogorgia elisabethae during natural spawning events.
• To assess the relationship between spawning duration, male spawning activity, and fertilization rates.
• To evaluate the ecological advantages of surface brooding in enhancing reproductive efficiency.

Main Methods:

• Observation of spawning events over six days in December 2001 on San Salvador Island, Bahamas.
• Collection of eggs for fertilization success analysis.
• Correlation analysis between fertilization success, spawning duration, male spawning, male gonad index, and proximity of male colonies.

Main Results:

• High fertilization success (>90%) was observed during most of the spawning period, with overall success exceeding 66%.
• Fertilization success correlated with male spawning activity but not with male gonad index or proximity of male colonies.
• Surface brooding effectively captures sperm, extending the temporal window for egg-sperm encounters.

Conclusions:

• Surface brooding in Pseudopterogorgia elisabethae is an efficient reproductive strategy that maximizes fertilization success.
• This mechanism mitigates the need for extremely high sperm densities, thereby reducing the risk of polyspermy.
• Surface brooding allows for temporal summation of fertilization across variable sperm availability.