Dow’s Anemone, Anthopleura dowii
Dow’s Anemone, Anthopleura dowii. Underwater photographs taken in Zihuatanejo Bay, Guerrero, March 2018. Photographs courtesy of Ron Woheau, Zihuatanejo. Identifications courtesy of Greg Timms, youtube.com/@Coralmasterdives-PuertoVallarta/videos.
Phylogeny: Dow’s Anemone, Anthopleura dowii (Verrill, 1869), is a member of the Actiniidae Family of True Sea Anemones. The Anthopleura Genus is one of fifty-six genera in the Actiniidae Family, and there are fifty species in the Anthopleura Genus. The species was named in honor of Captain John Melmoth Dow, a Captain for the Pacific Mail Steamship Company. Dow was a prolific amateur naturalist who collected extensively along the Pacific Coast of Mexico and Central America. It is also known as Dow’s Anthopleura and in Mexico as Anthopleura de Dow.
Morphology: Dow’s Anemones have a well-developed pedal disk, which suctions them to the bottom substrate. The pedal disk is around 2.1 cm (0.8 inches) to 2.3 cm (0.9 inches) in diameter. Extending from this disk is a cylindrical column that is around 18 mm in diameter and height. The sides of the column have widely-spaced longitudinal rows of verrucae (warts). Topping the column is the oral disk, which reaches 2.2 cm (0.9 inches) in diameter. The oral disk has up to 134 tentacles arranged in 6 concentric circles. The tentacles are all the same length, reaching around 5 mm. The tentacles are smooth and sticky. The pedal disk and column are olive to brown in color, with whitish verrucae. The oral disk is green, with orange or pink around the mouth. Orange, brown, grey or purple radial lines run from the mouth to the base of the tentacles. The tentacles may be grey, purple or orange, with a dark longitudinal stripe. Orange spots decorate the oral side of the tentacles. Some specimens display white banding around the tentacles. Dow’s Anemones can be distinguished from the similar looking Actiniid Sea Anemone, Isoaulactinia hespervolita by its smaller size and more widely spaced, straighter, rows of verrucae.
Habitat and Distribution: Dow’s Anemones are found attached to rocks and other hard substrates, from the low intertidal zone to depths up to 3 m (10 feet). They are a subtropical to tropical Eastern Pacific species that are found in all waters of the Mexican Pacific Ocean, with the exception that they are absent from the west coast of the Baja Peninsula.
Diet: Dow’s Anemone utilze their stinging tentacles to paralyze prey and pass it to their mouth. Their specific diet has not been formally documented. Similar species in the Anthopleura Genus consume amphipods, copepods, small fish, isopods, invertebrate larvae and marine worms. Dow’s Anemones are also zooxanthellate having a symbiotic relationship with single-cell dinoflagellates, known as zooxanthellae. Zooxanthellae live within certain Coral Polyps, Sea Anemones, Jellyfish, and Nudibranchs. The zooxanthellae produce energy, during daylight, by means of photosynthesis. This energy is passed along to their hosts, sometimes providing up to 90% of the host’s total energy needs. In return, the host provides nutrients, carbon dioxide, and a secure, sunlit, platform for the zooxanthellae.
Predators: Dow’s Anemones protect themselves by use of their stinging tentacles and a sticky mucous layer, but they are still subject to predation. Information related to the predation specific to this species has not been formally documented. Similar species are preyed upon by nudibranchs, sea spiders, sea stars and snails.
Reproduction: Dow’s Anemones are gonochoric (male or female for life). Sexual reproduction is accomplished through broadcast spawning, with the gametes released through the mouth. Fertilization is external. The eggs hatch into planular larva. Asexual reproduction has not been documented in this species.
Ecosystem Interactions: Other than their mutualistic relationship with zooxanthellae, any form of parasitic or symbiotic relationships for Dow’s Anemones have not been formally documented. They do benefit the neighbors by feeding on the larvae of parasitic species.
Human Interaction: Dow’s Anemones have no direct impact on human activities. From a conservation perspective they have not been formally evaluated.
Synonyms: Anthopleura dovii and Bunodactis mexicana.