While no direct information was found on the mating system of T. navalis, it can be inferred to be polygynandrous. Males release sperm into the water, which females pick up via the incurrent siphon. This occurs on multiple occasions, as females spawn 3 to 4 times per season.
Mating System: polygynandrous (promiscuous)
Reproduction typically occurs in the summer months when temperatures reach 15 degrees Celsius. Females spawn 3 to 4 times per season, each time releasing 1 to 5 million larvae. Teredo navalis embryos spend the first 2 to 3 weeks in the mother’s gill chamber. They are then released into the water as free-swimming veligers. Released larvae are 88 by 75 microns with a depth of 55 to 57 microns. They reach sexual maturity 6 to 8 weeks after inhabiting wood.
As mentioned previously, shipworms alternate between sexes during their life. When larvae mature, half of their gonads become spermatocytes, the other half ovocytes. Usually, spermatocytes multiply faster and are released earlier.
Breeding interval: Shipworms spawn 3 to 4 times each season
Breeding season: Breeding season is usually in the summer
Range number of offspring: 1,000,000 to 5,000,000.
Range gestation period: 2 to 3 weeks.
Range time to independence: 2 to 3 weeks.
Range age at sexual or reproductive maturity (female): 6 to 8 weeks.
Range age at sexual or reproductive maturity (male): 6 to 8 weeks.
Key Reproductive Features: seasonal breeding ; simultaneous hermaphrodite; sequential hermaphrodite (Protandrous ); sexual ; fertilization (Internal ); broadcast (group) spawning; viviparous
Females carry offspring in gill chambers during early development. When larvae reach the advanced veliger stage, they are released into the water. There is no evidence that mothers assist veligers in finding wooden substrates to inhabit.
Parental Investment: female parental care ; pre-hatching/birth (Protecting: Female); pre-weaning/fledging (Protecting: Female)