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Nanomia cara PROFILE Systematics: Phylum: Cnidaria • Class: Hydrozoa • Subclass: Siphonophora Order: Physonectae • Family: Agalmidae Genus: Nanomia • Species: cara 
Nanomia cara is a colonial animal belonging to the Class Hydrozoa, Subclass Siphonophora. These gelatinous fauna are not true jellyfish, which comprise a distinct class of Phylum Cnidaria, the Scyphozoa. Siphonophores are an integrated colonoal assemblage of highly specialized medusoid and polypoid forms. One member of this class is the familiar Portuguese Man-of-war (Physalia physalis). Unlike the man-of-war, which possesses a large gas-filled float and is designed for life at the ocean surface, Nanomia is adapted for swimming and feeding deeper in the water column. At the top of the colony is a gas-filled structure (=pneumatophore), which is smaller than the float of Physalia but similarly used to confer a degree of buoyancy to the colony. Nanomia can inflate and deflate the pneumatophore, allowing the colony to 
ascend or descend within the water column. A Pacific Ocean congener (belonging to the same genus), Nanomia bijuga,
reportedly can migrate vertically as much as 300 meters in under an hour. The apical
float is connected to the rest of the colony by a long stem. The stem is hollow
(=gastrovascular cavity) and serves to anchor several different organs.
Just behind the pneumatophore lie a series of muscular swimming bells (=nectophores) that provide locomotion. Further along the stem of the colony are clusters of specialized organs (each a colonial individual). The largest structures are digestive bodies (=gastrozooids and palpons). The gastrozooids have a flexible mouth that expands to engulf prey. Adjacent to these stomachs are muscular tentacles (=dactylozooids) with branches (=tentilla) that extend to capture prey and then contract to bring prey in contact with the gastrozooid. The tentacles also defend against predators. The tentilla are armed with cnidocytes that contain nematocysts (=the stinging cells). These cells are capsules (see insert) that discharge barbed tubes whenever the dactylozooid comes into contact with anything foreign. Once triggered, the tubes sting by penetrating the prey's flesh and releasing a neurotoxin that is usually lethal. Click here to view behavior sequence in Flash 5 format. Other structures are specialized for reproduction (=gonozooids). These polyps release eggs and sperm into the ocean in order to produce successive generations. Often overlooked are the delicate, diaphanous bracts. There are often 50 or more of these structures packed along the length of the stem and they provide a kind of protective armor and additional floatation. 
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