Salipidae Family of Salps

Three Salps of the Salipidae Family can be found in this website:

Phylogeny: Salps of the Salpidae 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. Salps are in the subphylum Tunicata, the class Thaliacea, and the order Salpida. The Salpidae Family is the only family in this order. The Salpidae Family contains two subfamilies, thirteen genera, and forty-five species. The name Salpidae comes from the Greek and Latin names for a type of elongate fish. This seems to be referring to the elongate shape of these Salps.

Morphology:  Adult Salps are transparent, gelatinous, and sack-like, with two openings (siphons) located at opposite ends of the body. 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. Salps generally have cylindrical or barrel-shaped body, often with posterior projections. They have strong muscle bands that do not completely encircle the body. They are capable of forceful contractions in the body wall, giving them fairly strong swimming ability, though they are still planktonic. They may exist as solitary individuals or as chains of linked individuals. Larval salps have a notochord (a tough, flexible rod which protects the central nerve cord and provides an attachment point for muscles) running down their back, but unlike most tunicates, Salps lack a tailed larval phase.  Individual Salps may reach up to 30 cm (12 inches) in length.

 Habitat and Distribution: Salps are usually found in open water. They generally spend the day in deep water and ascend to the surface at night for feeding. Otherwise, they drift with the currents and are considered plankton. They are found from the surface to depths of 1,500 m (4,920 feet). Salps are found worldwide, primarily in tropical to temperate waters, but they do extend to polar seas. At least twenty-nine species from this family are found in Mexican waters.

Reproduction: Salps have a complex life cycle alternating between a sexual and asexual form. During the asexual phase, budding produces a chain of identical clone cells. Each clone divides itself up, resulting in many tiny salps. These clone chains can reach more than fifty feet in length, and form complex shapes, such as giant wheels or double helixes. These salp clones are linked together and communicate through electrical signals to synchronize their movements. The signals  produce a chain of harmonized light pulses. Each clone in the chain is a sequential hermaphrodite, starting life as a female and then turning into a male. Each female carries one or two eggs.  Mating occurs with chains of older salps that have already transformed into males. Fertilization occurs through spermcasting, with internal fertilization. The female broods her embryo in a placenta-like membrane until the young salp can survive on its own. Released embryos grow into solitary creatures that repeat the asexual/sexual reproduction cycle. By the time she releases her embryo, the mother salp is already turning into a male.

Ecosystem Roles: Salps feed on microflagellates and small diatoms that they filter from the ambient water. In turn they are preyed upon by fish, sea birds, sea turtles, whales and other plankton. Salps can grow astonishingly quickly, up to 5% per hour under proper conditions. They can also reproduce quickly, and are known for massive blooms. During these blooms they quickly consume the available food and may then have a massive die-off. These blooms can have significant impacts on their local environments and other animal species as well.