Gonothecae

Gonothecae are specialized reproductive structures found in certain colonial marine invertebrates, most notably in the phylum Cnidaria, specifically within the Hydrozoa class. These structures are essentially modified zooids, or individual polyps within a colony, that are dedicated to the production and protection of gametes (eggs and sperm). They are typically tubular or vase-shaped and are secreted by the surrounding polyp tissue.

The primary function of a gonotheca is to house and safeguard the developing reproductive cells. In some species, the gonotheca may contain gonads directly, while in others, it may serve as an incubation chamber for planula larvae, the free-swimming larval stage. The arrangement and morphology of gonothecae can vary significantly between different hydrozoan species, sometimes appearing singly or in clusters, and can be a distinguishing taxonomic feature.

Unlike gastrozooids (feeding polyps) or dactylozooids (defensive polyps), gonothecae are solely focused on reproduction. They represent a division of labor within the colonial organism, allowing for efficient production of the next generation. The release of gametes or larvae from the gonotheca is a crucial step in the life cycle of these invertebrates.