Red Epizoanthid, Epizoanthus Sp.

Red Epizoanthid, Epizoanthus Sp. Underwater photographs taken in Zihuantanejo Bay, Guerrero, March 2018 and February 2020. Photographs courtesy of Ron Woheau, Zihuantanejo, Guerrero.

Phylogeny: The Red Epizoanthid Epizoanthus sp. is a member of the Epizoanthidae family of Epizoanthids. The genus Epizoanthus is one of two genera in this family. Epizoanthus is a fairly large genus containing eighty-five species. They are known in Mexico as Epizoántido Rojo. The Red Epizoanthid is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

Morphology: Red Epizoanthids have radial symmetry, a hollow digestive cavity, and specialized stinging structures in tentacles surrounding the mouth. Their polyps have a flower-like appearance, with two rows of tentacles located on the disk. The outer surface of the column of Red Epizoanthids is usually encrusted with sand or mud. The disk and tentacles are red to reddish brown in color. The polyps reach a maximum of 2.5 cm (1.0 inch) in height.

Habitat and Distribution:  Red Epizoanthids are found on rocks and on gorgonians from the shallow subtidal zone to depths of 76 m (250 feet). They are found throughout the Gulf of California, and south to, at least, Puerto Vallarta. The specimens shown here, were found south of the documented southern limit, and may be misidentified. Another species, with a common name of Scarlet Epizoanthid, looks similar and is found in the Galapagos Islands. Very little information for either of these species has been published in the scientific literature.

Diet: Red Epizoanthids are suspension feeders. They use their tentacles to capture zooplankton, such as amphipods or fish and invertebrate larva, from the surrounding water. Unlike many zooanthids, Red Epizoanthids are azooxanthellate.

Predators:  Red Epizoanthids are preyed upon by Ivette’s Sea Butterfly Nudibranch, Trivettia papalotla. These burgundy colored nudibranchs are well camouflaged on the epizoanthid.

Reproduction: Red Epizoanthids reproduce  both sexually and asexually. Asexual reproduction involves budding, where new polyps grow from existing ones. Sexual reproduction occurs when gametes are released into the water. The fertilized eggs become planktonic larva, which eventually settle and form new colonies.

Ecosystem Interactions: Information regarding ecosystem interactions of Red Epizoanthids has not been documented. Epizoanthids are known to provide shelter for fish and invertebrates.

Human Interactions: Zoanthids contain palytoxin, a substance that is toxic to humans. However, humans would need to ingest a significant amount of Zoanthid to be affected by this toxin, but there are anecdotal stories of humans affected by handling live specimens. Otherwise, Red Epizoanthids have very little direct impact on human activities. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.