Pyrosomatidae Family of Pyrosomes
One Pyrosome of the Pyrosomatidae Family can be found in this website:
Giant Fire Pyrosome, Pyrostemma spinosum. A representive Pyrosome of the Pyrosomatidae Family.
Phylogeny: Pyrosomes of the Pyrosomatidae Family, like humans and other complex organisms, are in the phylum Chordata. This means that they have a notochord (a primitive spine), a dorsal, tubular, nerve chord, a post-anal tail, and pharyngeal slits (filter feeding organs). In many animals, these traits are only present during their embryonic or larval stage of development. For example, in humans the pharyngeal slits are only present during the embryonic stage of development and transition to form the jaw and inner ear structures, the tail disappears completely. In bony fish the pharyngeal slits transition to form the gill arches. Pyrosomes are in the subphylum Tunicata, the class Thaliacea, and the order Pyrosomatida. The Pyrosomatidae Family is the only family in this order. The Pyrosomatidae Family contains two subfamilies, three genera, and eight species. The name Pyrosomatidae comes from the Greek words meaning “fire-body”, and refers to the bioluminescence emitted by these tunicates.
Morphology: Pyrosomes are colonial tunicates, made up of individuals known as zooids. The zooids are held together within a transparent test (gelatinous body covering). Adult tunicates are essentially sack-like, with two openings (siphons). Water flows in one siphon, is filtered through the body, and flows out the other siphon. This water movement is used for respiration, feeding, waste removal, and limited propulsion. The intake siphon of individual zooids opens on the external side of the body wall. The outflow siphon opens on the interior wall. This design builds pressure inside the body sack, which is released though the open end, providing propulsion. This propulsion is primarily used for daily vertical migration. Flexing of the body wall and cilia move water through the siphons. Pyrosomes can produce bright bioluminescent flashes. Pyrosome larvae are tadpole-like and display all of the Chordate traits. As they metamorphose, they lose their spine, tail, and nervous system. Aggregate blankets of pyrosomes may reach up to 20 m (65 feet) in length.
Habitat and Distribution: Pyrosomes are found in open water. They generally spend the day in deep water and ascend to the surface at night for feeding. Some are found at depths exceeding 3,000 m (9,840 feet). Otherwise, they drift with the currents and are considered plankton. Pyrosomes are found worldwide in temperate to tropical waters. At least three species from this family are found in Mexican waters.
Reproduction: 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. Colonies are able to self fertilize from one end of the tube to the other.
Ecosystem Roles: Pyrosomes 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. They are preyed upon by sea birds, fish, sea turtles, whales and other plankton. Pyrosomes commensally host shrimp and other crustaceans, which ride and shelter inside the pyrosome. Pyrosomes play an important role in distributing nutrients from shallower waters where they feed to deep water where their wastes and, ultimately, their bodies settle.