Salpojen

Salpojen, also known as salpidae, is a family of marine tunicates belonging to the subphylum Tunicata. These organisms are commonly referred to as "sea squirts" due to their tendency to expel water forcefully when disturbed. Salpojen are pelagic, meaning they live freely in the open ocean rather than attached to substrates like many other tunicates.

Salpojen exhibit a unique life cycle that includes both a sessile (stationary) larval stage and a pelagic adult stage. The larvae are free-swimming and resemble tadpoles, with a notochord, tail, and pharyngeal slits. Once they settle on a substrate, they undergo metamorphosis into adults, losing their larval features and developing a barrel-shaped body with two siphons—one for intake and one for expulsion of water. Some species, however, retain a pelagic lifestyle throughout their adult stage, forming long chains or colonies.

These organisms play a significant ecological role in marine ecosystems. As filter feeders, they contribute to nutrient cycling by processing large volumes of seawater, removing plankton and other particles. Salpojen are also a key food source for various marine predators, including fish, whales, and seabirds. Their abundance and distribution vary by region, with some species thriving in polar waters while others prefer temperate or tropical zones.

Salpojen are classified into several genera, including *Salpa*, *Thalia*, and *Pegea*, each with distinct morphological and behavioral adaptations. Some species exhibit remarkable regenerative abilities, capable of regenerating lost body parts or even entire individuals through a process called "budding." This adaptability has made them a subject of interest in biological research, particularly in studies of regeneration and evolutionary biology.