Teredo navalis takes about five weeks to develop from eggs to metamorphosing larvae. They spend half of this time in the mother’s gill chamber until they are released into the water as free-swimming larvae. As the larvae develop, they transition from being small and white to large and dark gray. Fertilized eggs develop into cilia-covered larvae, referred to as trochophores. Over time, cilia are seen covering only the velum in larvae, now called veligers. The velum serves as an organ participating in movement and feeding. A shell appears about the same time in development as the velum and becomes bivalved after formation. Older veligers are released into the water. During this free-swimming stage, the siphons, gills, and foot develop. Once shipworms attach onto a wooden substrate, metamorphosis is observed.
Sexes alternate in T. navalis. Young are hermaphrodites while adults are either male or female. Usually, organisms are male first and then become female later. A second male to female phase may occur but shipworms normally do not live long enough for completion of the second phase.
Development - Life Cycle: metamorphosis