Hydractiniidae Family of Hydrocorals

One Hydrocoral of the Hydractiniidae Family can be found in this website:

Staghorn Hydrocoral, Janaria mirabilis. A representative of the Hydractiniidae Family of Hydrocorals.

Phylogeny: Hydrocorals of the Hydractiniidae Family, like sea anemones, hard corals, and jellyfish, are in the phylum Cnidaria. They are in the subphylum Medusozoa, the class Hydrozoa, the subclass Hydoidolina, the order Anthoathecata and the suborder Filifera. The Hydractiniidae Family is one of twenty-five families in this suborder. The Hydractiniidae Family contains sixteen genera and around one hundred twelve species. The name Hydractiniidae comes from a combination of Greek words meaning something like “water snake anemone-like thing” or “water anemone”. Species in this family are also known as  Calcified Hydroids.

Morphology: Hydractiniid Hydrocorals are athecate, meaning that in their polyp stage they are unprotected by a holster, in contrast to thecate polyps. Hydrocorals are colonial organisms that consist of four types of multi-cellular, interdependent, animals (zooids). Like hard corals, they build a calcareous skeleton however they grow slowly and do not significantly contribute to reef building. They may exist as an encrusting, interconnecting mat or a branching hydrocoral. Like other corals, the mouth is surrounded by tentacles that have nematocysts (or cnidocysts) that are capable of delivering a toxic sting in order to capture prey or repel predators.

Habitat and Distribution:  Hydractiniid Hydrocorals are found attached to algae, gastropod shells and rocks, from the intertidal zone to depths up of 200 m (655 feet). They are found globally, in  temperate to tropical seas. At least three species from this family are found in Mexican waters.

Reproduction:  Hydractiniid Hydrocoral colonies are gonochoric (either male or female for life). Each has specialized sexual polyps that produce eggs or sperm. Sexual reproduction occurs through broadcast spawning, with internal fertilization. The zygote develops into a planular larva inside the gonophore. When the planula find suitable habitat it metamorphoses into a founder polyp. The founder polyp then reproduces asexually by budding. These buds eventually break away as a genetic clone of the founder.

Ecosystem Roles:  Hydractiniid Hydrocorals primarily consume amphipods and other plankton from the surrounding water. Since their polyps are immovable these corals reside in locations that have moving water caused by wave action and currents. In turn they are preyed upon by crabs, fish, gastropods, starfish and polychaete worms.