Physophora

Physophora hydrostatica Forskal, 1775
Phylum Cnidaria / Class Hydrozoa / Subclass Siphonophorae / Order Physonecta / Family Physophoridae
Physonect siphonophore, Physophora hydrostatica, Point Lobos CA, Pacific Ocean
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This stunning physonect siphonophore is easily distinguished from any other gelatinous West Coast animal. A conspicuous silvery apical gas-filled float is followed by a set of swimming bells that occupy about half the length. Finger-like dactylozooids, colored with beautiful tinges of orange and violet, attach at the base of the swimming bells. These structures house relatively potent nematocysts that can impart a strong sting on those careless enough to make contact. A mass of feeding gastrozooids and reproductive gonozooids lie inside the ring of dactylozooids. Typical length of the compact swimming bell / dactylozooid portion of the siphonophore is from 8 to 12 cm. Trailing behind are the highly extensible tentacles that usually exceed the length of the rest of the siphonophore. Physophora typically swims slowly with tentacles extended as it drifts for zooplankton prey. Look carefully at the whitish clumps spaced at regular intervals along the tentacles. They resemble swimming copepods as the tentacles are repeatedly contracted and extended. Perhaps this is a method for luring copepod-seeking predators that instead become prey for the siphonophore. Physophora is occasionally seen in surface waters of central California, but never in any great numbers.

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