Dive Dry with Dr. Bill

#222: Coffee Beans... But Not from Starbucks

When I first started teaching at the Catalina Island School for Boys in 1969, I wanted to involve my students in real marine biological research. I contacted Dr. Barry Fell, my mentor at Harvard, to see what we might do to assist in his work on the dispersal of marine life. He suggested we sample drifting logs for attached marine critters. I guess being from New Zealand, he wasn't aware of how dry our southern California climate was. Not many forests on the mainland, or drifting logs in our waters.

Instead, I suggested we might look at drifting giant kelp "rafts" that could transport marine life from the mainland to the island, or between the islands in our Channel Islands offshore archipelago. He had done similar work in the sub-Antarctic waters and discovered giant kelp might be responsible for transporting sea urchins up to 7,000 miles. Thus started a seven year research effort in which my students sampled kelp rafts drifting along our coast, and out in the Channel, and logged data sheets listing the many species found on them. It took me two decades before I actually published the research, but when I did Dr. Wheeler North (an icon in the field of giant kelp research) called my paper "groundbreaking." At first I thought he meant he was going to take a shovel and bury it six feet under.

One of the critters we discovered on those drifting kelp "rafts" intrigued me because it had a beautifully sculpted shell. Since I was straight from Boston and new to our waters, I checked the field guides and discovered it was a coffee bean. These are a type of snail that somewhat resembles a cowrie. I haven't seen many since then, but did find an empty shell recently on the rocky finger reef just past the Jacques-Yves Cousteau memorial plaque in the Casino Point Dive Park. It brought back fond memories of the days when I was conducting the research with my students.

I checked my field guides and none of the standard ones had this coffee bean (also known as Solander's trivia... so perhaps I was playing "Trivia" Pursuit with the field guides). I then checked my Sea of Cortez marine invertebrates guide and there it was. No wonder... its distribution is listed as from southern California throughout the outer Baja coast and Sea of Cortez south to Peru. This species is at the northernmost end of its range here. Perhaps with global warming we will see an increase in this species, just as they have noticed an increase in southern species at Monterey based on studies over the last 75 years. By the way, I was pleased to see so many of our community attend the free screening of my Harvard classmate, Al Gore's "An Inconvenient Truth." As a coastal community, the predicted rise in sea level could have significant impacts on us. Personally, I'm looking forward to diving the coral reefs that will appear as the kelp forests decline... NOT!

Oops, I digress (not unusual for me). Back to the coffee bean. Its tan to brown shell grows to a length of one-half to three-fourths of an inch. It has a depression along its peak flanked by a series of small raised white spots that have elevated, sculpted ribs running from them down the side. The underside has a slit running the length of the shell through which the soft mantle and other body parts extend... and into which it withdraws if threatened. One has to wonder about the reasons for the ornateness of this shell. Does it serve an adaptive function, or is it simply evolution carried to an ornamental extreme?

Although little is known about these coffee beans (I even checked the Starbuck's web site in vain), scientists in Europe have studied related species. These feed on tunicates, very advanced but often overlooked invertebrates (by humans, not the coffee beans). They apparently creep up to the tunicate, use their tiny jaw to bite the individual zoids and their home. Then they use their scraping radula to slurp up the rest of the body parts. Gory, I know... but these tiny snails are vicious predators... not like your garden variety vegetarian slug!

So much for the munching, what about the mating? Scientists know that the sexes are separate in coffee beans, so there are males and females. Their mating behavior has not been observed to my knowledge... and I'm sure they prefer to keep it this way. I don't intend to pry! The eggs are laid in tunicate colonies, which one would assume was to provide food for the youngsters. However, the eggs hatch into a drifting larval form known as an echinospira, or "spiny coil." It then travels with the currents until it grows big enough to settle out of the water, and begin life on the rocky bottom. So, the young coffee bean larvae don't start munching on tunicates right away.

© 2007 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays. Please help me climb out of self-imposed poverty... buy my "Munching and Mating in the Macrocystis," "Great White Sharks of Guadalupe," "Calimari Concupiscence: Mating Squid, " "Playful Pinnipeds: California Sea Lions," "Belize It or Not: Western Caribbean Invertebrates, Fish and Turtles" or "Gentle Giants: Giant Sea Bass" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!

The live coffee bean from the 1970's, and the coffee bean shell
discovered in the dive park both underwater and topside.

This document maintained by Dr. Bill Bushing.
Material and images © 2006 Star Thrower Educational Multimedia