Giant Fire Pyrosome, Pyrostremma spinosum
Giant Fire Pyrosome, Pyrostremma spinosum. Two photographs of a “chunk” collected at the time of the encounter in coastal waters off Point Palmilla, Baja California Sur, March 2018.
Giant Fire Pyrosome, Pyrostremma spinosum. Small cluster photographed three hours after collection in a controlled environment.
Giant Fire Pyrosome, Pyrostremma spinosum. One gallon of densely packed animal in salt water that was frozen for storage and later study. Identification courtesy of Linsey Sala, Scripps Institution of Oceanography, La Jolla, California.
Phylogeny: The Giant Fire Pyrosome, Pyrostremma spinosum (Herdman, 1888) is a member of the Pyrosomatidae Family of Pyrosomes. The genus Pyrostremma is one of three genera in this family, and there are two species within this genus.
Morphology: Giant Fire Pyrosomes are large tubular colonies that can be up to 20 meters (65 feet) in total length and 1.2 meters (4,0 feet) in diameter. They are soft and either transparent (feeding stage) or reddish-pink (agitated stage) in color. The initial colonies are semi-globular and dome-shaped with a thick opaque test. As they mature, the colonies become cylindrical or cone-shaped and composed of hundreds of thousands of individuals known as zooids all connected via sharing tissues. Each massive colony originates from a single zooid that rapidly multiplies via cloning into a meshed colony growing outwards in concentric circles. Each zooid is a few millimeters in size but embedded in a common gelatinous tunic that is similar to a butterfly net with a wide mouth that tapers to a closed end that joins all individuals. The external surface of the test is covered with blunt, spine-like pyramids of fairly rigid jelly, with one pyramid next to the oral siphon of each zooid. The zooids have the ability to regenerate damaged areas. They lack any common nerves for communication and they communicate via the ability to produce light, which travels through the colony in waves with each individual zooid producing light that can be seen from several meters. These bioluminescent flashes give these animals their name Pyro soma, meaning ”fire body” in ancient Greek.
Habitat and Distribution: Giant Fire Pyrosomes are found in open waters within the tropical and temperate zones of the Atlantic, Indian, and Pacific Oceans. They are normally found at depths between 460 m (1,500 feet) and 300 m (10,000 feet), but venture closer to the surface to feed. In Mexican waters, they are rare, but found on both coasts.
Diet: E ach zooid of the Giant Fire Pyrosome is exposed to both the inside and the outside of the “tunic” and are filter feeders that take in water through a mouth on the outside of the body, pass it through a filtration system removing microscopic phytoplankton and small microzooplankton and oxygen on which they feed, and then they expel it on the inside of the cone. They are planktonic with movements largely controlled by oceanic currents, tides and waves but are generally found far out at sea as their food source is smaller and thus more digestible and the mineral balance is better. They do have the ability to move via the water stream generated by the feedings and are vertical migrators moving up in the water column to feed during the night and retreating to depths to avoid predation during daylight hours.
Predators: Giant Fire Pyrosomes are preyed upon by numerous Sea Turtles and Ocean Sunfish, Mola mola. When under attack, disturbed or under stress they “light up”, changing from a transparent white to a pinkish red and they stop feeding. This allows them to sink down to much greater depths in the water column for safety. Small starter colonies of this species are also eaten by birds, whales, jellies, and fish.
Reproduction: Giant Fire Pyrosomes are simultaneous hermaphrodites ( having both male and female reproductive organs). They can reproduce asexually, through cloning or budding off small starter colonies, or sexually. Sexual reproduction requires that the animals be in close proximity. Sexual reproduction is a complex process whereby a fertilized ovum develops to a “nurse-like” form, termed a “cyathozooid. In the tetrazooid stage, the cyathozooid produces four ascidiozooids through gemmation. The ascidiozooids are the parents of the subsequent asexually produced colony.
Ecosystem Interactions: Giant Fire Pyrosomes commensally host shrimp and other crustaceans, which ride and shelter inside the pyrosome. Because Giant Fire Pyrosomes filter out much smaller organisms than most filter feeders, they play an important role in distributing nutrients from shallower waters where they feed to deep water where their wastes and, ultimately, their bodies settle.
Human Interactions: Giant Fire Pyrosomes have no direct impact on human activities. From a conservation perspective they have not been formally evaluated however, while rare, they have a wide distribution and should be consider to be of Least Concern.
Synonyms: Propyrosoma spinosum, Pyrosoma spinosum, Pyrosoma excelsior, and Pyrosoma sedentarum.
Details on the Encounter. On April 12, 2018, I was fishing in 105 m (350 feet) water in a traditional Mexican Panga in coastal waters just south of San José del Cabo, Baja California Sur, about 3 miles due south of the Los Cabos Westin (23.00oN, 113.00oW). I observed something large in the water, about the size of our 7 m (22 feet) Panga, that was pink in color. The call from my very knowledgeable Captain was “a large piece of plastic.” I asked him to have a closer look. We slowly inched closer and I saw a 180 kg (400 lb) sea turtle depart. He apparently had brought this long ribbon-like pink “sheet” to the surface on which he had been munching away. The turtle split and I grabbed whatever it was with a paw. It was a gelatinous goo composed of perhaps tens of billions of identical appearing individuals all linked together. We estimated its total size to be 8 inches by 14 feet as it slowly sank out of view. I was able to break off a portion very easily, that was perhaps 8 inches by 2 feet. See photograph above. Unfortunately I failed to get an on-site photo of the intact animal as it quickly sunk out of sight.
An excellent video of this species is available on YouTube that was taken in Australian waters. You can see it at the at the beginning of https://www.youtube.com/watch?v=5EQGA_4BZ5s.