Pinkish-brown Salp, Pegea confoederata

Pinkish-brown Salp, Pegea confoederata, Aggregate Form. Collected with a salmon net off the surface about three miles at sea in coastal waters off San Jose del Cabo, Baja California Sur, June 2019.  Length: 12.0 cm (4.7 inches) and travel in a cube that is flattened on the top and bottom.

The Pinkish-brown Salp, Pegea confoederata (Forskal, 1775), is a pelagic planktonic tunicate that is a member of the Salpidae Family of Salps. The Pegea Genus of Salps has 3 global members.

The Pinkish-brown Salp has a pinkish brown body that is that is entirely covered with a cellulosic transparent matrix, called the tunic, that is composed of greater than 95% of water. They have nipple-like protuberance on the surface of the tunic. The aggregate form has a loose and flabby test and no posterior projections or protuberances. They are unique via having both muscle-band pairs fused in the mid, posterior terminal region being very thick and extended around the nucleus Each muscle pair are short and form a cross. Their gut is compact and closely encircled by the stolon. The solitary form as a pear-shaped test that is smaller posteriorly.

The Pinkish-brown Salp is an epipelagic species that spends the majority of its time near the surface and does not undergo daily vertical migrations that are found at depths up to 182 m (555 feet). The solitary forms reach 12.0 cm (4.7 inches) in length; the aggregate forms reach 15.0 cm (5.9 inches) in length. They collect food that includes bacteria, colloidal masses, and viruses, as small as 0.01 micron in diameter, utilizing a filtration system the removes some of the smallest biological life forms from the passing oceanic water. They have the ability to capture food smaller than its mesh size by optimizing the water flow through a continuously secreted sticky mucus net. The captured sub-micrometer particles are packaged into membrane-bound fecal pellets that are rich in carbon, nitrogen, and phosphorous and contain high amounts of calcium and magnesium which quickly sink to the ocean floor providing for fertilizer for bottom dwelling organisms. They do not vertically migrate and depend on invisibility in the water column to avoid detection by visual predation, especially by animals in the euphotic zone during daylight hours. They have a complex life cycle that is completed within 48 hours. They alternate life stages between aggregated sexual blastozooids or zooids (aggregate form) and solitary asexual oozoids (solitary form). The zooids develop by asexual budding from an elongated stolon within an oozoid and are sequential hermaphrodites that begin life as females, fertilized by males in the same chain, and then embryos develop into oozoids. This rapid and efficient method of asexual reproduction enables their populations to explode during periods when an abundance of food is present. They can reproduce very quickly producing massive quantities that can quickly deplete the food supply and will then quickly die out.

The Pinkish-brown Salp is a common species of Salpidae and is widely distributed being found in the temperate and tropical waters of the Atlantic, Indian and Pacific Ocean. In Mexican waters they are found in all oceanic waters of the Atlantic and the Pacific Ocean.

From a conservation perspective the Pinkish Brown Salp has not been formally evaluated however they one of the most common salpidae and have a wide global distribution and when present they can be found by the billions making them most likely of Least Concern. They are considered to be harmless to Humans.

Synonyms for include Biphora confoederata, Pegea octofora, Salpa confoederata,, Salpa dolium, Salpa femoralis, Salpa informis, Salpa octofora, Salpa quadrata, Salpa scutigera and Salpa vivipara 

Productive discussions and identifications courtesy of Linsey Sala, Scripps Institution of Oceanography, La Jolla, California.