Tantulocaridans: Tantulocarida

Very little is known about the behavior of tantulocaridans, especially about how they find and attach themselves to their hosts. After leaving their mothers, larvae spend some time burrowing on the sea bottom before attaching themselves to a crustacean living on or near the ocean bottom.

Tantulocaridans have a very strange double life cycle. Part of the life cycle involves sac-shaped females that can produce larvae without mating. These larvae are released into the sea fully formed and are capable of attaching themselves to a new host. As the larvae develop, they lose all of their thoracic and abdominal segments and become adult females that also reproduce without males. Their now sacklike bodies expand to make room for the eggs and larvae developing inside.

In the life cycle that requires mating, the larvae attach themselves to their host with their mouthparts. As they feed and grow, a sacklike structure begins to grow near the rear of the body. In this sac, the larva will become an adult male or female. Mature adults escape into the sea when the sac breaks open. These males and females have never been observed alive, but it is believed that males are good swimmers and actively search for females. Fertilized eggs are thought to develop inside the expandable cephalothorax of the female.