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Dive Dry with Dr. Bill

#391: Starry, Starry Day

Catalina Islanders are very familiar with local artist Danny Peterson. Why even a dive bum like me has three of his paintings in my house. Some of Danny's work features scenes reminiscent of Van Gogh's "starry, starry night" as made popular in the song "Vincent" by Don McLean. I recently had a dive experience that had some similarities... except it was on a "starry, starry day" as I dove the waters off Santa Cruz Island as a guest of Rod and the Roddenberry Dive Team.

A thick green plankton bloom did reduce visibility to something other than a normal "day" down under, but my heart was illuminated by visions of several sea stars I rarely if ever see out here in Catalina waters. Of course we old timers refer to these as starfish since our finely tuned mental capacities are fully capable of discerning the difference between a star "fish" and a real "fish." I guess those raised with the new math may not be so capable and must be reminded that the echinoderms or "spiny skinned" critters are not directly related to garibaldi or great white sharks.

My first starry encounter was with the sunflower star (Pycnopodia helianthoides). I have never seen this starfish in Catalina waters, although it may well be present in the colder areas towards the west end or on the windward coast. Now I can't imagine anyone reading this column is not familiar with the Beatles' lyric "eight arms to hold you." This sea star triples the threat with 20 to 24 arms. It is an interesting enough critter to spend a future column on so I'll just mention it in passing here. It certainly was one of the more abundant stars in the "constellations" on the reefs off Santa Cruz Island.

Another rare starfish for me was the rainbow star (Orthasterias koehleri) which also appeared at one of the three dive sites we dove on the northwest coast of Santa Cruz Island. It is a beauty with a rose-pink to gray background and bright red bands and patches on the central disk and arms. I recall seeing it only once or twice in Catalina waters, and that was deep on the submerged pinnacle known as Little Farnsworth off the Edison plant on Pebbly Beach Road. This colder water sea star is found from Alaska to southern California so it is at the southernmost end of its range in our region's waters. The minimum ocean temperature of 52-53 degrees Fahrenheit at a mere 60-70 feet off Santa Cruz Island allows them to live in shallower water there vs the deeper depths here. The same goes for several of the other starfish I observed on this trip with the Roddenberry Dive Team.

In this week's column, I want to focus on the leather star (Dermasterias imbricata) which I've never seen in Catalina waters. My only sightings of this species have been in the colder waters of the northern Channel Islands and off San Diego. The one I filmed off Santa Cruz posed nicely for my camera, although the surge kept moving me in and out as I filmed it. Fortunately the still images I captured from the video show it nicely, including the reddish blotches on its surface.

The leather star has a distinctive leather-like skin (hmm... could that be how it got its name?). This is because it lacks the spines often seen on starfish and other spiny skinned echinoderms such as brittle stars and sea urchins. It may reach a diameter of about 10 inches or 250 mm, and some report them up to 12 inches (300 mm). The species is known from Prince William Sound, Alaska, to Sacramento Reef off Baja California, Mexico. In the northern part of its range it may be found in the intertidal, but generally is seen at depths down to 300 feet (90 m) in the southern areas. Fortunately the one I encountered was at a shallow 50-60 feet. People often assume clams, mussels, oysters and its relatives are the primary entrees chosen by starfish. This starfish prefers a different diet that includes sea anemones, sea cucumbers and their relatives, the sea urchins. Based on my observations at the sites we dove, they definitely will not go hungry! I also found that sponges, bryozoans, sea pens, tunicates and even fish eggs were potential food sources giving it a great deal of dietary flexibility.

Many starfish evert their stomach when they feed. It is extruded through the mouth to engulf the prey and begin the process of digestion externally. The leather star apparently feeds in a more socially acceptable manner. It swallows its prey whole and digests it internally. Of course with some munchies it has to be quick to accomplish this. An approaching leather star causes the purple sea urchin to initiate a avoidance response like a jet fighter trying to outmaneuver an incoming missile. They pull in their tender tube feet and then "race" away. One report states that the sea star gives off an odor somewhat similar to garlic which may be what the urchin senses. Scientists believe the chemical is used to ward off predators such as the sunflower star. It also is responsible for another common name, the garlic star. Of course as a creature of the night, especially during full moons, I avoid garlic as well so we have something in common.

The leather star is a broadcast spawner like most of its starfish relatives. Up in the northern part of its range, mating occurs from April to August. The females release yellow eggs which are fertilized by male sperm cast into the water column at the same time. The fertilized eggs and, later, the larvae that emerge from them drift in the water column with the currents. This allows the species to increase gene flow between different populations as well as colonize new areas or replenish populations decimated by natural or human disasters.

Starfish have long been a favorite of many people. Unfortunately one way of showing their appreciation for these spiny skinned critters is to buy dried sea stars from souvenir shops in places like Florida, the Caribbean and even here on Catalina if you look closely around Cabrillo Mole and elsewhere. I may have received a few in my youth when we lived in or vacationed in Florida. Later, in my Harvard days, I spent a lot of my time researching them under echinoderm expert Dr. H. Barraclough "Barry" Fell. I would never buy such a souvenir today, and even hesitate taking obviously dead individuals washed up on beaches. After all, my company name (Starthrower Educational Multimedia) comes from a short story by Loren Eiseley about a man who walks down to the beach early each morning. He picks up every stranded starfish he sees and throws them back into the water for a second chance before less merciful beachcombers awaken. elsewhere (that was just for humor's sake... you did laugh, right?)!

© 2010 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 DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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The cast of "starry, starry day:" leather star and rainbow star; bat star impersonating
the Roddenberry Dive Team's logo and and sunflower star.

This document maintained by Dr. Bill Bushing.
Material and images © 2010 Star Thrower Educational Multimedia