Anthoathecata

Anthoathecata is an order of the class Hydrozoa, which are marine invertebrates belonging to the phylum Cnidaria. This order is distinguished by the absence of a true, free-swimming medusa stage in its life cycle. Instead, the reproductive polyps, known as gonophores, are typically sessile and develop directly from the hydroid colony. The polyps within Anthoathecata can exist in various forms, including solitary individuals or colonial structures. These colonies can exhibit diverse growth patterns, such as branching, encrusting, or forming complex, upright structures.

The feeding polyps, or hydranths, in Anthoathecata are often specialized for capturing prey, with tentacles surrounding the mouth. The gonophores, while sessile, are responsible for producing gametes. Fertilization can occur externally or internally, leading to the development of a planula larva. This larva then settles on a substrate and metamorphoses into a new hydroid colony, thus completing the life cycle without a free-swimming medusa. Anthoathecata includes a wide range of species, from small, inconspicuous hydroids to larger, more noticeable forms. Their ecological roles vary, but many are predators, feeding on small invertebrates and plankton.