Dive Dry with Dr. Bill

#533: All In One Basket

Although my dives with sharks in the Bahamas were a tremendous thrill, and I obtained a lot of excellent footage during them, it doesn't take an apex predator to heighten my enthusiasm. Years ago I spent a 43 minute dive filming a mantis shrimp out in the open at Hen Rock. When I surfaced with a "yeeha," Capt. Tony Heeter of the King Neptune said "Only you could get so excited about a 'worm.'" Recently, my French dive buddy Anabel in the Bahamas looked on my website at the 500+ columns I've written and e-mailed to say she'd never met someone so obsessed with diving and marine life. Well, it is my passion and I do live my life by "following my bliss."

Anabel and George were my dive buddies on a night dive in the Bahamas at Cave Rock. We were just finishing the dive and preparing to head back to the boat when I spotted a very fuzzy object on the reef. My video lights just barely illuminated it in the distance, but it was unusual enough for me to swim over to check it out. As I approached with camera rolling, it slowly resolved into something that made my blood stir. I was filming my first basket star!

Back in my Harvard undergrad days I studied under an echinoderm expert, Dr. H. Barraclough Fell. "Barry" was a real mentor to me (along with E. O. Wilson) and I found these spiny skinned critters to be of great interest. I'm referring to the phylum that contains the starfish (or sea stars for the PC crowd), the sea urchins, sea cucumbers and brittle stars. Of course those are only the groups divers most commonly encounter. While a student of Steven Jay Gould's, I discovered a new species of helicoplacoid (a fossil echinoderm) which no modern day SCUBA diver ever encounters unless they have a time machine (and if they did, where would they get an air fill?)..

I've also filmed other echinoderm relatives such as the crinoids in Belize and again in the Bahamas. This group was much more abundant in ancient seas well before Cousteau and Gagne invented the demand regulator and SCUBA evolved. However, this was the very first basket star I've ever filmed so I was indeed thrilled! I felt like one of those avid (and obsessive) bird photographers checking off another species on their life list.

The giant basket star (Astrophyton muricatum) is actually in the same class of echinoderms as the brittle stars you can see hiding under rocks in the dive park. It is considered common throughout Florida and the Caribbean, but is rarely observed by the average diver. During the day, these long-armed critters coil up into tight balls and may hide in the rocky reef or attach to gorgonians (soft corals). At night they open up, extending their long, highly differentiated arms to feed.

The basket star munches by extending its complex "arms" to face the current and trapping plankton as it drifts through the reef. Our local brittle stars can feed in a similar way, burying their central disks in a kelp holdfast or under the sand and extending their arms to trap plankton. An interesting fact about the echinoderms is that they do not use blood to transport nutrients and oxygen to their tissues. Instead they use their water vascular system (which starts with the tube feet in starfish, sea urchins, etc.) to transport these vital needs to the various tissues and organs.

At night in my video lights the giant basket star appeared tan, probably because it was overexposed due to the contrast with the dark background. During the day they may be tan to brown to orange in color. Juveniles may be tan and lavender, but some individuals are black in color. The tiny central disk where the primary organs are located may be a mere 1-1 1/2 inches in diameter while the armspread may be 1-1 1/2 feet! This species is found at depths of about 20 to 90 feet.

Well, even though I've chalked up another interesting critter on my marine biology "life list," I'm not about to retire yet. According to the World Register of Marine Species (WoRMS), there are about 216,000 recognized marine species world-wide. I figure I still have about 215,000 left to go and I don't plan to give up until I finally chalk up a real mermaid. If she is the last "species" on my list, I'm sure the taxonomists will discover more, or by that time I can finally dive the seas on Mars!

© 2013 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Basket star extended to feed and close-up of arms; basket star contracting in response to my video lights.

This document maintained by Dr. Bill Bushing.
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