How do cephalochordates reproduce?

Cephalochordates, such as amphioxus, reproduce exclusively through sexual means; asexual reproduction does not occur. These animals are dioecious, meaning the sexes are separate, though males and females are identical in outward appearance.123

The reproductive process involves the following steps:

• Gonad Development: The gonads develop in the wall of the atrial cavity, a space that receives water after it passes over the gills. They consist of 24 or more pairs of ovaries or testes that lack ducts.23
• Spawning: When the gonads are ripe, they rupture, spilling eggs or sperm directly into the atrium. These gametes are then carried out into the sea by the water flowing from the cavity.23
• Fertilization: Fertilization occurs externally in the water.13
• Development: After fertilization, the eggs develop into microscopic, ciliated larvae. These larvae are carried by ocean currents for several weeks before they metamorphose into the adult form and settle into the substrate to complete their life history.31

Breeding frequency depends on the environment, occurring several times a year in tropical regions but only once annually in temperate areas.3