To the sound of the applause of waves (a sound most beachgoers are more familiar with than waves of applause), the major characters in the drama assemble themselves at the rock center. This is a rather deep presentation that has a lot of action. The plot is rather basic though - some romance, some humor, suspense, tragedy - but all with a happy ending, at least for most involved. And the whole show is done with such artistic grace, with colorful ostrich plumes (or what bears a close resemblance to such), swaying to and fro through it all.
Yes, it truly is not being too theatrical to say that along the sea coast of Southern California, the showy world of the Ostrich Plume Hydroid and the animals which live on it provides some fine entertainment. And it is educational and quite a cultural experience as well.
That is especially the case if you are into the diving culture. But people who promote the beach walking culture can likewise enjoy the Ostrich Plume Hydroid and Co., for this group performs all the way for matinee style tidepools down to several hundred feet deep, and all along the our Pacific coast.
The star attraction to this show, which by necessity holds center stage, the ostrich plume hydroid (Aglaophenia spp.) is actually a whole troupe in itself. Yet, even though it is a colonial animal, it has its act down so well that it functions in perfectly choreographed coordination. Set like a swaying curtain against the current, the entire chorus of small mouths can be opened at once to provide a harmonious filter feeding of plankton. And by having an interconnected digestive system, as long as some succeed, there will be not starving artists in the group.
Most hydroids have dramatically amazing method of reproduction, which involves an alternation of generation, or an amazing change in acts. The more often seen attached stage produces a free-swimming mini-jellyfish resembling state, which in turn produces the attached version. This mind-boggling complicated procedure has received many wild reviews by researchers. But the hydroids which direct this type of production need to be calm water varieties, as the tender jellyfish-like phase would be easily torn to bits, not by critics, but by rough water.
The ostrich plume hydroid, however, likes to be where the action is - along rocky coastlines where it is constantly waved at (and not by doting fans, but by real, crashing waves). Yet the highly acclaimed production of this showy hydroid also has its intermission period of alternation of generation. But its changing of sets is done behind the scenes. Special corbulae, or private booths, are set up along the branches of the ostrich plume hydroid - prudently with the ones for the males and for the females being separate from each other. Moreover, when the Ostrich Plume Hydroid does produce an encore generation of offspring that are able to "hit the road" and fend for themselves, they often do not travel very far. In fact, very often they will set up their own feathery colony on the same rock as their parents, making a multimedia, multi-plumed extravaganza.
On its own, the ostrich plume hydroid has many features like these that have kept numerous scientists well enthralled, but it also has a supporting cast of other co-stars. Most of these do tend to blend into the background, though, so a person needs to know what to look for, in order to have the fun of exploring what to most other people may seem to be little more than some old seaweed.
Tiny skeleton shrimps (Caprella spp.) dance and twist all about, in almost clown-like movements. These miniature acrobatic amphipods have hooks towards their tail-ends by which they can securely attach themselves to the hydroid's branches.
Sea spiders or pycnogonids are even harder to spot, but probably more
rewarding when found. Several types of this bizarre class of entirely marine arthropods hang around the hydroid colony. One, Ammothea hilgendorfi, is rather common and really, really wants to be part of the ostrich plume hydroid scene. In fact, this little critter can be said to be truly into the hydroid, for by means of its sharp, pointed appendages, its larvae enter into the colony and live within the ostrich plume hydroid's own tissues.
Two frilly sea slugs or nudibranchs also find the ostrich plume hydroid's production is heavy duty enough, something that they can really get their teeth (or at least their scraping molluscan tooth-like radulae), into. The spotted dirona (Dirona picta) and stubby bushy-backed nudibranchs (Dendronotus subramosus) both have costumes to match the fern-like hydroid on which they feed.
But even with such predatory fanfare, the ostrich plume hydroid just can't seem to be able to resist being in the limelight - when it gets dark, it will even biolumenesce.
There are other types of ostrich plume hydroid colonies found around the world, all basically variations of the ones found at the rock centers (or the mid-tide sections of the rocky shore), of coastal Southern California. The supporting casts differ from place to place, some being better orchestrated with more invertebrates than others. Some may even put people on the edge of their seats - and beyond! In the tropical Western Pacific, one type of showy ostrich plume hydroid has stinging cells that are venomous to humans. People who happen to sit on one of those colonies will more than likely be stirred to give that particular ostrich plume hydroid's performance an instant standing ovation!
1. Hydroid colony
2. Corbula
3. Skeleton shrimp
4. Sea spider
5. Spotted dirona nudibranch
6. Stubby bushy-backed nudibranch
7. Opaleye
8. Bay mussel
9. Buckshot barnacle
10. Gooseneck barnacle
11. Aggregated anemone
12. Tidepool sculpin
13. Rough limpet
14. Thatched barnacle
15. Tube snail
16. Coralline algae
17. Mossy chiton
18. Sponge
19. Hermit crab
20. Sea lettuce
Nancy Vander Velde is a regular contributor to California Diving News. She has also illustrated several books.
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