I originally started "Dive Dry with Dr. Bill" with the intention of making money, not much but enough to pay my bills. Instead, I've been depleting my retirement account a lot earlier than expected! However, I've sure been enjoying "the ride" and I hope you, my readers and viewers, have as well. This year I have to face reality and make some money or... So I put my thinking cap on and found a way to gather in a few dollars... at least on video tape!
Dive buddy Andrea and I were scheduled to dive La Jolla Shores in the San Diego area during the monthly "Wrinkles' Dive" sponsored by ScubaBoard, a web site I'm very active on. This would be my first dive on the California mainland in 37 years. My last dive there was in August of 1969 and the visibility was so poor I never went back. When we arrived at The Shores, we learned that conditions were great. Visibility was in the 30-40 ft range, so we got directions from some local members and headed out to the "North Wall."
I've been reading reports of the "Walls" at The Shores for a number of years. I had expected the kind of rocky reef walls that I've dived in places like Belize and Southeast Asia. I'm thinking rocky or coral walls that drop nearly straight down to 5,000 feet or more. The North Wall turned out to be a mud hill instead. Initially we were a bit disappointed, but headed up the wall to the soft bottom habitats that dominate off this sandy beach. I started noticing a few individuals of a critter I'd been seeking... the sand dollar. Okay, so Vons and my mortgage bank won't accept them in payment, but I could finally get this species on tape!
Sand dollars are actually a form of sea urchin. They are close relatives of the spiny sea urchins found on Catalina's rocky reefs. However, they carry very short spines on their surface, which offer little protection compared to the long, sharp spines of most sea urchins. The sand dollar found off our coast is known from Alaska to Baja California. It frequents sandy bottoms from the low intertidal to about 130 ft. Large "beds" of sand dollars are frequently observed. They often bury themselves in the sand, or "stand" on edge so they can feed.
Although usually a brownish color, these urchins may be reddish brown, dark purple, lavender or gray in color. They reach a diameter of about four inches. Beach combers often find their skeletons, called tests, on sandy beaches in our State. The shape and structure of the test can vary depending on whether the sand dollar lives in cold or cool water, or on wave swept beaches or the more quiet waters of bays. When the water is not too rough, they often bury about 1/3rd of the test into the sand and extend perpendicularly or at an angle from the bottom. It is said they migrate towards shore during the calmer summer months and into deeper water for protection during the winter storm season.
Sand dollars feed using several different strategies. Organic matter and small organisms may be trapped from the water by the spines and then transferred to the mouth. Drift algae may be held by the tube feet. Small animals may also be trapped with the spines on the lower surface. The jaws, known as the "doves" in specimens sold in souvenir shops, are used to chew the food. These urchins often take in a fair amount of sand with their food. One source states that this sand may be retained inside the body to serve as a form of weight belt! In turn, sand dollars are eaten by sheephead, starry flounder and a species of sea star. When the sea star approaches, the sand dollars react by burying into the sand to escape.
Males and females look alike, and are present in roughly equal numbers in the population. They are sexually mature at about four years. Females produce 350,-380,000 eggs each. Although reproduction peaks from May to July in our waters, it may happen throughout the summer months. Fertilization occurs externally with the eggs and sperm cast into the surrounding water. The developing larvae disperse in the plankton. Lab experiments suggest development may take 68-162 days depending on water temperature and other conditions. The adults generally live 6-10 years, but may reach the ripe old age of 13... barely into their teen age years! Scientists determine their age through growth rings on the test.
Although these sand dollars won't pay my mortgage or buy my morning pan dulce at Vons, they may help bring in some cash in the future. Sand dollars were one species I needed to get on film to complete a future DVD on the echinoderms. I know all of you will rush to buy that DVD when it comes out... right? In addition to this critter, I filmed twelve other species for the first time on my two dives with Andrea at The Shores. That alone made my first mainland dive in decades very successful.
The following day Andrea and I tried to dive Shaw's Cove in Laguna Beach with another friend, Heather. Although the surf was high, we were able to get out past the breakers. When we descended, the visibility was 1-3 feet and we quickly aborted that dive. It served to remind me why I hadn't dived the mainland in such a long time. However, we plan to make a return trip to dive La Jolla Shores and film a number of other species my dive friends see there. Ready to guide us, Missy?
© 2006 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!
Sand dollar lying flat on sand; on edge feeding; a
group of sand dollars
from a bed, the more typical purple sea urchin.
This document maintained by
Dr. Bill Bushing.
Material and images © 2006 Star Thrower Educational Multimedia