On 21 January 2012, students on a UC Davis invertebrate biology class field trip found a siphonophore floating in Bodega Harbor.
Siphonophores are cnidarians — they're related to hydroids, jellyfish, sea anemones, and corals. But they're pelagic (normally found far offshore) and often live deep below the surface, so are unfamiliar to many people.
Siphonophores are very complicated free-swimming colonial animals. They consist of many different units, specialized for locomotion, feeding, defense, or reproduction. They're carnivores, extending long tentacles equipped with powerful stinging cells to capture smaller animals (including small fish). [Look for the yellow-orange strings of tentacles in the photos.] Note that these stinging cells are very potent. If you see a siphonophore and want to take a closer look, it's best not to handle them directly.
The siphonophore pictured below may be Praya dubia. Remarkably, this species is one of the longest animals on Earth. Although this is a small section of one colony (the larger transparent flask-shaped structures are ~1 cm long), some individuals stretch to 40 meters in length! (The longest blue whale recorded was about 33 meters.)
Praya dubia lives in midwater habitats 700-1000 meters deep, so finding one at the surface close to shore is a real treat!