|Wonderful image by Judt on Flickr|
|SEM pic from Dearborn et al., 1991|
Forceps-like Pedicellariae are formidible and numerous. Below are some close up pictures of these tiny structures on two well-known species on the North American Pacific coast: the giant sunflower star (Pycnopodia helianthoides) and the ochre star (Pisaster ochraceus).
Pedicellariae are typically present around the spines in retractable rosettes or pompons, numbering in the THOUSANDS! These could be extended or retracted like gun batteries if the animal felt threatened.
Pedicellariae are smaller in other forcipulate asteroids but can be quite effective.
During the days of my halcyon youth when I worked as a docent at touch tidepools at Steinhart Aquarium and Monterey Bay Aquarium, people with hairy arms had to exercise some care not to completely apply the surface of the ochre star (Pisaster) lest you wanted all of the thousands of little claws to tear off all your arm hair!
|Image by Judt|
2. Bivalve PedicellariaeStarfish in the Goniasteridae and the related Oreasteridae have a different type of pedicellariae. These are flattened and more "lip-like" and can be VERY abundant on the surface of some species.
And if we want to take those bivalve pedicellariae to extremes.. here's a genus and species of deep-sea goniasterid I described a few years back from New Caledonia..called Akelbaster
And here is a closeup showing several tinier bivalve pedicellariae on the surface of a tropical oreasterid fron Singapore: Anthenea aspera. The pedicellariae are the tiny little white clamp-shaped structures..
Very neat looking-but again the question: WHAT DO THEY DO??
Do they use them to protect themselves from small, annoying crustacean predators? Do they aid in feeding? Some weird biophysics thing we've not figured out yet???
3. Cholocariform or "Other"?
Scientists have been observing pedicellariae for literally 100s of years (they were originally described as animals! if you can believe it!) but a good understanding of these structures has been elusive! Its weird stuff like this which makes echinoderms such a joy to study...