Cuvier, 1804
Description
— Solitary zooids elongate, with slightly convex anterior and a squarely cut off posterior. Test entirely smooth, moderately thick to thin. Muscles (M) 1-3 strongly fused over a wide area in the mid-dorsal region, M8 and M9 are likewise strongly fused. M1-M9 with 136-296 fibres, except for M4 with 14-40 fibres. Number of muscle fibers is due to clinal variation, in the NE Atlantic ranging from 30 to 40 in M4 and from 206 to 281 in M1-M9. Dorsal tubercule is small and C-shaped. Nucleus relatively small, compact, not causing a swelling of the test. Rudimentary elaioblast disappears in a young stage.
— Aggregate zooids: body barrel shaped and typically fusiform, with conical anterior and posterior protuberances of the test that are typically long in relation to the body, giving it a slight asymmetry. Test entirely smooth, moderately thick to thin. Six body muscles; M1-M4 strongly fused over a wide area in mid-dorsal region; M4-M5 laterally fused; M5-M6 strongly fused in the mid-dorsal region. Fibre number of M1-M6 is 25-68 and is due to clinal variation. Dorsal tubercule is a simple slightly arched stick. Nucleus pale green in live specimens, relatively small and oval, not causing a swelling of the test.
Size
Solitary zooid: 22 to 52 mm; Aggregate zooids: 7 to 52 mm (excluding projections).
Depth range
Occurring at depths from surface to ca. 800 m, seems to perform diurnal vertical migration.
Distribution in the North Sea
S. fusiformis is frequently entering the northern North Sea from the NE Atlantic.
World distribution
Cosmopolitan, eurythermic species, occurring from 70°N to 45°S in the Atlantic Ocean, to 45°S in the Indian Ocean and from 50°N to 45°S in the Pacific Ocean. S. fusiformis has the widest distribution of all salp species, and is also one of the most abundant ones.