Knowing the minds of many of my readers, I'm sure some of you have a totally inappropriate idea of what this column is going to be about. Rather than titillate your prurient interest today, my subject will be "G" rated... for the most part. Sorry to disappoint you, readers. I know I'm not living up to my reputation for "munching" and "mating" today. However, Mom now reads these columns and...

The subject of this column is the aggregated nipple sponge. The first time I saw this species, I had no clue as to what it was. All I saw were white nubs projecting slightly out of the bottom substrate. In fact it wasn't until I dove La Jolla Shores a few years back that I understood what I had been observing. There I encountered this "critter" (hard to think of a sponge that way) in fairly intact condition. My highly trained and analytical mind quickly realized that I was seeing the same species. However, the ones from Catalina waters appear to have had their "nipples" nibbled, apparently by fish, rendering them quite different from their intact relatives.

When I began diving deep (130-200 ft) in our waters, I started seeing this sponge in intact condition. I put two and two together, resulting in a lucky seven. The ones I observed off La Jolla, and at greater depths here, had probably not been munched on by fish or other predators! A few weeks ago we were diving a site adjacent to the Empire Landing Quarry that Capt/Mayor Bob calls Hal's Point. I decided to explore the site at moderate (for me) depth and found a number of sponges on the rocks and even the sandy bottom there, providing me with new images to share with you.

When I began researching this species, I was surprised to find it was not listed in the primary scientific guide to invertebrates that I use. I did find it in Dan Gotshall's guide to invertebrates. In Dan's description, he listed the distribution as the Aleutian Islands to San Nicholas Island to the north and west of us. He also stated its depth distribution as low intertidal to at least 50 feet.

Given that additional information, I quickly surmised that this is a cold water species. Certainly anything that could tolerate the waters off the Aleutians was no "warm water wussy." I'm surprised Dan did not seem to be aware of this species' presence off San Diego where I've found it in normal recreational SCUBA diving depths. Although I've seen it as shallow as 70-80 feet here off Catalina, it seems to be far more abundant at depths deeper than that. It may be yet another example of "submergence" where a normally cold water species will be found in deeper, colder water further south. Perhaps I should contact Dan and let him know of its presence off Catalina.

Dan's description of the species referred to it as having "breast shaped" individuals. Now my memory isn't as good as it used to be, but I don't think I can recall any human breast that looked like this sponge! The genus it belongs to, Polymastia, refers to many "masts." Those of you familiar with the word for the surgical treatment of breast cancer, mastectomy, will see the common origin due to the medical term for breast, "masto." What one observes when they see this species is a group of these projecting tubules that may cover an area up to 2-3 feet across. Reports from the Monterey Bay Marine Sanctuary indicate they reach more than six feet across there. The masses I see off Catalina are usually 1-2 feet across.

The individual sponges are only about half an inch in diameter at their base, and just an inch or so tall. If you look at the tip of each "nipple," you can see a hole which is called the osculum. This serves to exhaust the water the sponge filters in its search for food in the form of organic matter and small plankton. The huge barrel and other sponges of tropical waters are very efficient at filtering plankton from the water, in part the reason for the great visibility in those warmer waters. I only wish our local sponges were as efficient in removing the plankton here, but then it wouldn't serve as the base for the food chains and webs that support life in our temperate kelp forests.

Sponges are far more interesting than most people think. Although they are really collections of interacting specialized cells, and don't move about and exhibit complex behavior, they do pose interesting questions for investigation. For example, their structural composition often involves hard calcium carbonate or silicon-based spicules for support (and as key indicators for identifying each species). Some can give a good "sting" to a diver who touches them. Others contain toxins meant to discourage predators, some of which can affect humans as well. I'll be "talking" about some of the other interesting sponge species in future columns.

By the way, some more prudish cultures (apparently the Canadians in British Columbia) refer to this species as the aggregating vase sponge. I've never been known for being a prude so I'll stick with the name given it by scientists here. You may not realize they often have slightly warped minds if you translate some of the Latin and Greek scientific names they give new species! But then again, maybe you already know this. After all, you're reading my columns!

© 2008 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 and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. 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," "Gentle Giants: Giant Sea Bass," "Common Fish and Invertebrates of the Sea of Cortez" or the new "Sharks and Rays of Southern California" DVD's. Yes, take Dr. Bill home with you... we'll both be glad you did!

The aggregating nipple sponge showing entire groups; close up
of the nipples showing osculum, a nibbled specimen.

This document maintained by Dr. Bill Bushing.
Material and images © 2008 Star Thrower Educational Multimedia