Purple Hydrocorals (Stylaster californicus) are a distinct species in that they are native to the California coast from San Francisco to Baja California, along with the reef habitats and islands found along this range. Because they are endemic to their habitat, they are often called the California hydrocoral. This is one of the few species of coral that is found in California waters.
Hydrocorals are not considered true stony corals but are classified more as soft corals despite actually having a hard skeleton, even containing stinging cells called nematocysts.
The Purple Hydrocoral is aptly named for its brilliant shades of purple but can also be found in varying other colors from red to orange, to salmon, to shades of blue.
Forming a calcium carbonate skeleton structure, much like stony corals, this species grows at a very slow rate, thought to be 1/4 inch per year. The growth patterns vary from lacy formations to a dense network of branches. This hydrocoral grows from 6 to 12 inches in height and has a base that can reach 24 inches across.
In their habitats, they range from small individuals to heavy colonization, depending on food sources and potential damage to the reefs.
Unlike other corals, this Hydrocoral does not need sunlight to survive and feed. Rather they are carnivorous and need zooplankton and other small organic matter found in the water currents to feed.
This species houses minuscule pores along its external structure that contain polyps. These polyps are surrounded by long tentacles that have nematocysts or stinging cells. Each of those individual polyps houses a feeding polyp that has its own set of four short tentacles surrounding its mouth. The long tentacles exist to protect the polyp and to catch prey, which passes to the shorter tentacles at the mouth.
Purple Hydrocoral colonies are found predominantly off Catalina Island in the Farnsworth Bank Marine Conservation Area. They can be found in shallow water, in as little as 15 feet to depths of 368 feet on the sea floor. This hydrocoral prefers the rocky substrate of reef structures, often colonizing in areas of a strong current. It is common to find, but difficult to visualize, a small parasitic snail called Pedicularia californica. They are closely related to cowries and hard to see due to their shell color matching that of the hydrocoral it’s residing on.
This species shares its habitat with many other important fish species, including the Dwarf-red Rockfish, the Squarespot Rockfish, the Rosy Rockfish, the Blackeye Goby, many species of sea anemones, and other soft corals.
Purple Hydrocoral colonies contain both male and female specimens. They can reproduce in two ways. The first way is asexually through fragmentation. This is when segments of the hydrocoral break off from the parent, and a new organism grows from the fragment.
The second way is through sexual reproduction, where the male releases sperm into the water column, and the female houses eggs that then become fertilized. The eggs hatch into larvae that leave the female between late October through November.
Ecological observations have shown that anchor drops from visiting boats are one of the main threats to the Purple Hydrocoral. In places where this species can be found in the largest colonies, like Farnsworth Bank, anchors hitting the sea floor can damage large numbers at a time. This is particularly critical to the California Hydrocoral because it is estimated that they grow at only 1/4 inch per year.
In its native habitats, large amounts of marine debris, including large amounts of debris from commercial fishery waste, such as lines and nets, were found in data observations.
During the 1960s, this Hydrocoral was so abundant that divers tell stories about being able to see a purple glow from the water’s surface. It was shortly thereafter that the populations were decimated in the Farnsworth Bank, off Catalina Island, from divers taking the corals for the tourist and jewelry trades. Sadly, due to its delicate nature, this Hydrocoral did not make good candidates for those trades and was often broken before it could reach the public.
Facts about Purple Hydrocoral
- Purple Hydrocoral is in the phylum Cnidaria, along with all other hydrocorals, jellyfish, corals, and sea anemones. This species falls into the Class Hydrozoa.
- There are at least 48 species in the Stylaster Genus.
- There are at least 350 species in the Cnidaria Phylum.
- Technically the California Hydrocoral have tentacles with specialized cells that can sting, but they are so small humans cannot feel the sting.
- Due to its range along the California coast, this Hydrocoral is often called the California Hydrocoral.
- The most abundant fish species wait amongst this Purple Hydrocoral for commensal species that serve as prey items. A commensal relationship between two species is where one obtains food or benefit and the other neither benefits nor is harmed.
Is there such a thing as purple coral?
Yes, the Purple Hydrocoral is a coral species found in various shades of purple, violet, lavender, and other hues of red, orange, and blue.
How deep can the Purple Hydrocoral be found?
Because the Purple Hydrocoral does not need sunlight to live and eat, it can be found at much deeper depths than most corals. This species can be found from 15 feet to over 300 feet.
How fast does the Purple Hydrocoral grow?
The Purple Hydrocoral grows at a rate of 1/4 inch per year, making it very slow growing. It is also believed that if a branch is broken on the coral, it will take six months before that branch starts to regrow.
Where is the Purple Hydrocoral found?
The native range of the Purple Hydrocoral covers from San Francisco to Baja California. There are dense populations found off southern California and Catalina Island. It has been observed that the largest colonies are found in the shallowest waters.
What do Purple Hydrocorals eat?
The Purple Hydrocoral uses stinging cells and their tentacles to catch prey in the form of zooplankton and other microscopic organic matter.
Can a Purple Hydrocoral sting you?
Technically, the Purple Hydrocoral has stinging nematocysts, but they are so small that they aren’t felt by the human touch. This is the opposite of a close relative, the Fire Coral. The highly venomous sting of this species causes burns, rashes, blisters, itching, and even as much as kidney damage and pulmonary edema.