Life in the Open Ocean. Joseph J. Torres

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Life in the Open Ocean - Joseph J. Torres


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the bracts (Figure 3.28), the gonophores, and the gas‐filled float or pneumatophore (Figure 3.29).

Schematic illustration of siphonophore zooids.

      Sources: (a and c) Adapted from Hyman (1940), figure 148 (p. 470); (b) Bayer and Owre (1968), figure 89 (p. 54).

Schematic illustration of siphonophore nectophores.

      Sources: (a) Hyman (1940), figure 148 (p. 470); (b) Adapted from Pugh (1999), figure 2 (p. 477); (c) Pugh (1999), figure 3.131 (p. 509); (d) Pugh (1999), figure 3.132 (p. 509).

      Gonophores take many shapes, ranging from what appears to be an intact medusa with the sexual organs taking the place of a manubrium to the more rudimentary sacs observed in Figure 3.26c. Gonophores are dioecious, bearing only male or female gametes. The siphonophore colony as a whole is hermaphroditic; male and female gonophores may be found within the same cluster or may be borne separately.

Schematic illustration of siphonophore bracts. Schematic illustration of vertical section of the simple type of pneumatophore of Agalma.

      Source: Adapted from Woltereck (1905).

      Whole Animal Organization

      The stem is divided into two sections, the nectosome and siphosome (formerly siphonosome). In physonect siphonophores (Figure 3.25c and d), the nectosome extends from the base of the float to the bottom of the swimming bells or nectophores. In the calycophorans, lacking a float, the nectosome is apical (Figure 3.25e and f). The cystonects, which lack swimming bells altogether (Figure 3.25a and b), have no nectosome at all.

Schematic illustration of siphonophore colony structure.

      Sources: (a) Hyman (1940), figure 151 (p. 476); (b) Hyman (1940), figure 148 (p. 470); (c) Redrawn from Mayer (1900), plate 32; (d) Adapted from Brusca and Brusca (1990), figure 9 (p. 224).


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