Sertularia

Sertularia is a genus of small colonial marine hydrozoans in the family Sertulariidae, within the class Hydrozoa of the phylum Cnidaria. Members form delicate, branching colonies that grow along a central stalk or axis, often encrusting hard substrates in shallow to deep marine environments. The colony is composed of individual zooids housed in protective structures called hydrothecae, with feeding polyps projecting their tentacles from these cups. The perisarc, a chitinous or calcareous external sheath, covers and protects the entire colony.

Morphology and growth are characterized by regularly spaced, cup-shaped hydrothecae containing the feeding polyps, and by reproductive units that give rise to the next generation of colonies. Growth occurs through non-reproductive and reproductive zooids; specialized gonangia produce the reproductive products that enable the propagation of the species within the marine community.

Reproduction in Sertularia involves both asexual and sexual processes. Asexual budding enlarges the colony by adding new zooids, while sexual reproduction occurs within specialized gonophores to produce planula larvae that settle as new colonies, sustaining the species and contributing to genetic diversity.

Habitat and distribution are marine and cosmopolitan, though individual species display preferences for particular substrates and depth ranges. Sertularia is commonly found on rocks, shells, seaweeds, and other hard surfaces in temperate to polar waters, often forming conspicuous, fern-like or bottle-branched colonies.

Taxonomically, Sertularia comprises multiple described species within Sertulariidae. Identification relies on colony morphology, hydrothecal shape, and details of internodes, with molecular data increasingly used to support species delimitation and phylogenetic relationships.