Few people would mention siphonophores when asked what they thought would be a top predator in the depths of the ocean.  Take an excursion into Monterey Canyon and you will likely find that this group of hydrozoans is well represented and includes a number of ecologically important and often quite massive predators.  Praya is among the more prevalent siphonophores in midwater habitats.  Calycophoran siphonophores like Praya lack the distinctive apical gas float of physonects.  It can attain astounding stem lengths of up to 40 or 50 meters, and is probably the longest organism in Monterey Canyon.   You may encounter a Praya near the surface, but typically it will only be a section that at most may be 2 to 3 meters long, but usually less.  It may include the relatively large paired transparent swimming bells that are located at the anterior end in intact specimens.  Trailing behind the swimming bells is the stem, which is made up of repeated units known as cormidia.  Each incorporates gonozooids (for reproduction), gastrozooids (for feeding) and dactylozooids (nematocyst bearing structures).  Cormidia that break free (eudoxids) serve a reproductive role.   Praya is among the more commonly  encountered siphonophores in surface waters of central California, and is distinguished by the bright yellowish color of zooids in the stem.  Avoid any contact with the thin tentacles - they pack a fairly powerful nematocyst punch.

All photographs © David Wrobel and may not be used or copied without permission!

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