In cirroteuthid and stauroteuthid octopods, portions of the web between the arms have a special modification called the secondary web. This secondary web allows the arm to extend orally while the expanded primary web, inflated by surounding a large volume of water, remains aborally positioned. The definitions of the primary and secondary webs are illustrated in the arm and web cross-sections below left. Below right is a photograph taken of a cirrate near the ocean floor. The upcurved arms clearly show the secondary web which, incorrectly, appears as a membrane separate from the web.
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Figure. Left - Cross-sections of the arms and web of Stauroteuthis syrtensis, which has a secondary web, and Cirroctopus glacialis, which lacks a secondary web. Drawings modified from Vecchione and Young (1997). Right - Posterior view of a cirrate with arms spread. Photograph from Roper and Brundage (1972).
Roper, C.F.E. and Brundage Jr., W. 1972. Cirrate octopods with associated deep-sea organisms: new biological data based on deep benthic photographs (Cephalopoda). Smithsonian Contributions to Zoology, 121:1-46.
Vecchione, M. and R. E. Young. 1997 Aspects of the functional morphology of cirrate octopods: locomotion and feeding. Vie Milieu 47(2):101-110.
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University of Hawaii, Honolulu, HI, USA
National Museum of Natural History, Washington, D. C. , USA
Katharina M. Mangold (1922-2003)
Laboratoire Arago, Banyuls-Sur-Mer, France
Page copyright © 2001 , , and Katharina M. Mangold (1922-2003)
Page: Tree of Life
Cephalopod Primary and Secondary Webs
Richard E. Young, Michael Vecchione, and Katharina M. Mangold (1922-2003).
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