Ritteriella retracta

Taxon-Order: 
Salpida

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Distribution: 
Occurs between 60° N and 40° S.
Size: 
Aggregate generation: to 39 mm; solitary generation: to 70 mm
Diet: 
Filter feeders; phytoplankton and other small particles.
Predators: 
Medusae, siphonophores, ctenophores, heteropods, sea turtles, marine birds and many fish.
Useful Facts or Characters: 

The aggregate generation zooid possesses a thin, flacid tunic and body muscle bands 1-4 and 5-6 meet dorsally.  Body muscle bands 1-2 are fused nearly all the way out to the lateral side compared to body muscle bands 3-4 that are fused dorsally for about 25% of their length.  The solitary generation zooid also posesses a thin tunic and has 10-18 body muscle bands.  

Natural History: 

There are two other species of Ritteriella that overlap in distribution with R. retracta: R. picteti and R. amboinensis closely resemble R. retracta but vary in the number of muscle fibers within body muscle bands.

References: 

Bone, Q. (1998) The biology of pelagic tunicates. Oxford University Press, Oxford.

van Soest, R.W.M. (1974) A revision of the genera Salpa Forskal, 1775, Pegea Savigny, 1816, and Ritteriella Metcalf, 1919 (Tunicata, Thaliacea). Beaufortia 22: 153-191.

Wrobel, D. and Mills, C. (1998) Pacific Coast pelagic invertebrates:  a guide to the common gelatinous animals. Sea Challengers, Monterey Bay Aquarium, Monterey, CA.

Yount, J.L. (1954) The taxonomy of the Salpidae (Tunicata) of the central Pacific Ocean. Pacific Science 8: 276-330.