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!
[ Apolemia ] [ Calycophoran ] [ Forskalia ] [ Nanomia ] [ Physophora ] [ Praya ]