Читать книгу Life in the Open Ocean - Joseph J. Torres - Страница 116

The Chondrophora is a legacy taxonomic ranking for a unique group of hydrozoans commonly known as “By‐the‐Wind Sailors.” The name is still widely used to refer to them and will be used here. There are two genera delineating the two morphs within the group: with and without sails (Figure 3.38). Together they form the Porpitidae, a family now classified within the suborder Capitata in the order Athecata and subclass Hydroidolina.

Before any of the present schemes, the chondrophora were considered to be highly specialized members of the Siphonophora. A glance at Figure 3.38 will show you why. They are small colonies of zooids attached to the underside of a chitinous float and are most often encountered in flotillas of varying size. The flotillas form a mini‐ecosystem that is exploited by a number of molluscan species taking advantage of the “moving island” as a substrate and source of food. A chance encounter with a raft of Velella is one of the real treats of being at sea.

The reason for classification changes over the years is a shift in what was considered the dominant life stage. If the medusa is considered as the primary taxonomic determinant, the “by the wind‐sailors” group most closely align with the anthomedusae (Athecata). The best known life stage, the “by the wind‐sailors” themselves, is considered to be an aberrant or highly specialized polypoid stage.