gonozooids

Gonozooids are specialized reproductive zooids found in some colonial animals, notably certain bryozoans and hydrozoans such as siphonophores. In colonies composed of many genetically identical individuals called zooids, different units perform different tasks. Gonozooids are the reproductive branch, forgoing feeding or defense to focus on producing offspring.

In bryozoans, gonozooids often arise as modified autozooids and typically lack a full digestive apparatus. They bear brooding structures such as ovicells, in which fertilized eggs develop into larvae. The larvae are released when ready, enabling dispersal and colonization of new substrates. The presence and arrangement of gonozooids vary among species and influence the colony’s reproductive strategy.

In siphonophores, a colonial cnidarian group, gonozooids are distinct zooids that bear the reproductive gonophores, the structures that release larvae or medusae. Here too, gonozooids specialize for reproduction rather than feeding or defense.

Gonozooids illustrate the division of labor in modular animals and show how colonies coordinate growth and reproduction through specialization of individual zooids. Their study informs understanding of colonial organization, life history, and evolutionary adaptations in bryozoans and hydrozoans.