Pyrosoma
Encyclopedia
Pyrosomes, genus
Pyrosoma, are free-floating colonial tunicate
s that live usually in the upper layers of the open ocean in warm seas, although some may be found at greater depths. Pyrosomes are cylindrical or conical shaped colonies made up of hundreds to thousands of individuals, known as zooids. Colonies
range in size from less than one centimeter to several meters in length.
Each zooid is only a few millimeters in size, but is embedded in a common gelatinous tunic that joins all of the individuals. Each zooid opens both to the inside and outside of the "tube", drawing in ocean water from the outside to its internal filtering mesh called the branchial basket, extracting the microscopic plant cells on which it feeds, and then expelling the filtered water to the inside of the cylinder of the colony. The colony is bumpy on the outside, each bump representing a single zooid, but nearly smooth, though perforated with holes for each zooid, on the inside.
Pyrosomes are plankton
ic, which means that their movements are largely controlled by currents, tides and waves in the oceans. On a smaller scale, however, each colony can move itself slowly by the process of jet propulsion, created by the coordinated beating of cilia in the branchial baskets of all the zooids, which also create feeding currents.
Pyrosomes are brightly bioluminescent
, flashing a pale blue-green light that can be seen for many tens of meters. The name Pyrosoma comes from the Greek (pyro = "fire", soma = "body"). Pyrosomes are closely related to salp
s, and are sometimes called "fire salps." Sailors on the ocean are occasionally treated to calm seas containing many pyrosomes, all luminescing on a dark night.
“I have just watched the moon set in all her glory, and looked at those lesser moons, the beautiful Pyrosoma, shining like white-hot cylinders in the water” (T.H. Huxley, 1849).
Pyrosomes often exhibit waves of light passing back and forth through the colony, as each individual zooid detects light and then emits light in response. Each zooid contains a pair of light organs located near the outside surface of the tunic, which are packed with luminescent organelles that may be intracellular bioluminescent bacteria. The waves of bioluminescence that move within a colony are apparently not propagated through neurons, but by a photic process. Flashing zooids not only stimulate other zooids within the colony to bioluminesce, but nearby colonies will also display bioluminescence in response. Colonies bioluminesce in response to mechanical stimulation (touch), as well as to light.
are accepted as valid by the World Register of Marine Species:
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Pyrosoma, are free-floating colonial tunicate
Tunicate
Tunicates, also known as urochordates, are members of the subphylum Tunicata, previously known as Urochordata, a group of underwater saclike filter feeders with incurrent and excurrent siphons that is classified within the phylum Chordata. While most tunicates live on the ocean floor, others such...
s that live usually in the upper layers of the open ocean in warm seas, although some may be found at greater depths. Pyrosomes are cylindrical or conical shaped colonies made up of hundreds to thousands of individuals, known as zooids. Colonies
Colony (biology)
In biology, a colony reference to several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defense or the ability to attack bigger prey. Some insects live only in colonies...
range in size from less than one centimeter to several meters in length.
Each zooid is only a few millimeters in size, but is embedded in a common gelatinous tunic that joins all of the individuals. Each zooid opens both to the inside and outside of the "tube", drawing in ocean water from the outside to its internal filtering mesh called the branchial basket, extracting the microscopic plant cells on which it feeds, and then expelling the filtered water to the inside of the cylinder of the colony. The colony is bumpy on the outside, each bump representing a single zooid, but nearly smooth, though perforated with holes for each zooid, on the inside.
Pyrosomes are plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
ic, which means that their movements are largely controlled by currents, tides and waves in the oceans. On a smaller scale, however, each colony can move itself slowly by the process of jet propulsion, created by the coordinated beating of cilia in the branchial baskets of all the zooids, which also create feeding currents.
Pyrosomes are brightly bioluminescent
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
, flashing a pale blue-green light that can be seen for many tens of meters. The name Pyrosoma comes from the Greek (pyro = "fire", soma = "body"). Pyrosomes are closely related to salp
Salp
A salp or salpa is a barrel-shaped, planktonic tunicate. It moves by contracting, thus pumping water through its gelatinous body...
s, and are sometimes called "fire salps." Sailors on the ocean are occasionally treated to calm seas containing many pyrosomes, all luminescing on a dark night.
Bioluminescence
Although many planktonic organisms are bioluminescent, pyrosome bioluminescence is unusual in its brilliance and sustained light emission, and evoked the following comment when seen by scientist T.H. Huxley at sea:“I have just watched the moon set in all her glory, and looked at those lesser moons, the beautiful Pyrosoma, shining like white-hot cylinders in the water” (T.H. Huxley, 1849).
Pyrosomes often exhibit waves of light passing back and forth through the colony, as each individual zooid detects light and then emits light in response. Each zooid contains a pair of light organs located near the outside surface of the tunic, which are packed with luminescent organelles that may be intracellular bioluminescent bacteria. The waves of bioluminescence that move within a colony are apparently not propagated through neurons, but by a photic process. Flashing zooids not only stimulate other zooids within the colony to bioluminesce, but nearby colonies will also display bioluminescence in response. Colonies bioluminesce in response to mechanical stimulation (touch), as well as to light.
Species
The following speciesSpecies
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
are accepted as valid by the World Register of Marine Species:
- Pyrosoma aherniosum Seeliger, 1895
- Pyrosoma atlanticumPyrosoma atlanticumPyrosoma atlanticum is a pelagic species of marine colonial tunicate in the class Thaliacea. It is found in temperate waters worldwide. The name of the genus comes from the Greek words "pyros" meaning "fire" and "soma" meaning "body", referring to the bright bioluminescent light sometimes emitted...
Péron, 1804 - Pyrosoma godeauxi van Soest, 1981
- Pyrosoma ovatum Neumann, 1909
- Pyrosoma spinosum