Tide Pools Bloom With Sea Flowers
Peering into Laguna tidepools, one often comes across what resembles a large, green, petaled flower. In fact, the Starburst sea anemone (Anthopleura sola) is not a flower nor even a plant, but actually a predatory marine animal that is related to sea jellies, corals and sea pens. Although the lifespan of the anemone is unknown, they are thought to be able to live around 150 years. The geographical range of Starburst anemones is from Central California to Baja California. In Laguna Beach, they inhabit rocks submerged in the tidepools near the mussel beds in the mid and low intertidal zone where waves and currents continually provide fresh water. Although located in fairly close proximity to other individuals, they are considered a solitary species that will defend its territory from other anemones.
The Starburst anemone exhibits radial symmetry, with an adhesive pedal disc (foot) which is used to attach to solid surfaces, a thick stalk which consists of a fleshy tubular body capped with an array of conical tentacles that surround its striped oral disc (mouth). It can reach a maximum width of six inches at its broadest point and is estimated to grow an in diameter every 10 years. When underwater and open and depending on the amount of sunlight it is exposed to, the color ranges from bright blue-green, olive-green to almost white. Contributing to the green color is a photosynthetic algae living within the anemone. Living symbiotically, the single-celled algae is protected from its predators and in return, provides nutrients to the anemone. When the water recedes and the tentacles fold inward, the color is an olive green and the stalk is covered with an assortment of shells, shell bits, sand and other debris, which is thought to reflect the sun and protect the anemone from dehydration. The anemone does not have a brain and has a primitive nervous system comprised of nerve cells arranged in a nerve net that allows it to respond to stimuli.
Starburst anemones are either male or female and reach sexual maturity between five to 10 years of age. They can reproduce asexually or sexually. Asexual reproduction occurs when the anemone divides itself in half to create two smaller anemones. Sexual reproduction occurs through broadcast spawning and external fertilization during one spawning event that happens when the water warms up in late summer or early fall. The thousands of pelagic larvae that are produced float in the currents before settling in mussel beds where they develop into anemones. Once settled, although they are considered sessile (stationary) in their home range, if needed, they can move to get to a better food environment or escape predation in a hostile environment.
Carnivores and scavengers, anemones feed on basically any small marine organism alive or dead that fall within their grasp. Because they have a slow metabolism, they only need to feed a couple of times per month. Like all members of the cnidarian phylum, within their tentacles are thousands of nematocysts, stinging cells that contain venom. With their tentacles outstretched, they remain motionless in water until coming in contact with prey. Once touched by a venomous tentacle, the victims become immobilized allowing the tentacles to transport them to the anemone’s mouth to be eaten. The mouth is also used to expel any undigested portions. The nematocysts are also used for defense from their predators, which include primarily the Wentle Trap, a tiny gastropod, sea stars and nudibranchs. There are indications that they were cooked and eaten by indigenous peoples in ancient times, but today they are not considered a food source. However, medical research is being conducted on their tissue for possible beneficial effects for heart and tumor medications. Easily found in Laguna during the current negative tides, they are not considered threatened on any conservation list but like other marine invertebrates, they are vulnerable to human disturbance, ocean acidification and climate change.
Mia Davidson and artist Jan Sattler are residents of Laguna Beach and year-round ocean swimmers who want to remind you that Laguna Beach is a state marine reserve, where collecting or fishing is forbidden.
