|Iasis zonaria (Pallas, 1774)
Phylum Chordata / Subphylum Urochordata / Class Thaliacea / Order Salpida / Family Salpidae
Salps use circular bands of muscles to pump water through the body – this species has the most obvious, distinct bands of any species that visits the Pacific Coast. Solitary individuals have a firm body, length up to 5 cm, with 6 broad muscle bands. Three projections extend dorsally from the posterior end. The mouth is a wide slit, and the gut nucleus forms a relatively small posterior mass. Individuals in the aggregate chains have a firm asymmetric body, length up to 6 cm, with 5 broad muscle bands. The posterior has a single rear projection. The mouth openings of all individuals in the chain are directed dorsally. They are positioned such that the swimming thrust is in line with the chain axis. This creates a more efficient swimming ability that is also characteristic of salps in the genus Salpa. With its relatively strong muscle bands, Iasis is among the fastest of all the salps, and also one of the most cold tolerant. It is relatively abundant in the Atlantic and Indian Oceans, and in the Pacific Ocean north to the Gulf of Alaska to depths of about 200 meters. This species is only rarely encountered in nearshore surface waters of California.
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