Dive Dry with Dr. Bill

#298: A Barely Bloody Star

Every time I mention the blood star to divers on the King Neptune or in the dive park, I wonder what kind of image it creates in their minds. This starfish is actually far from gruesome in appearance, and has a certain charm of its own. When I see them underwater, I sense no association with the effects of a pirate's sword and torn flesh. The infamous swashbuckler Captain Blood they are not. They are certainly not an apt symbol to associate with the debauchery of Buccaneer Days at Two Harbors here on Catalina. In fact, they are quite attractive.

If one is not carrying a dive light, this sea star may appear a dull gray. However, once they are illuminated, they are a beautiful orange to red-orange in color. Occasionally tan or purple ones may be observed, and sometimes there are darker bands on the arms. The central disk on this species is relatively small compared to the long, slender arms. Almost all the individuals I have observed had the normal complement of five arms, but ones with four to six arms have been observed. Blood stars are usually about four inches in diameter although they may reach twice that size. The body's upper surface exhibits a network of narrow ridges made up of calcified structures known as ossicles or spicules.

These sea stars lack the pedicellariae possessed by many other starfish to keep larvae and encrusting forms from settling on their upper surfaces. Despite this, I've never observed any real growth on their dorsal surface. Perhaps the network of ossicles prevents settlement by providing too rough a substrate to attach to. I could also speculate and suggest there may be some form of chemical that prevents settlement, but that would just be an over-educated guess!

Although this starfish prefers rocky bottoms from the lower intertidal to depths in excess of 1,300 feet, they are occasionally seen on soft substrate habitats like sandy bottoms. The blood star is recorded from the Aleutian Islands of Alaska to Bahia Tortugas, Baja California. There is also a population in Japanese waters.

I could live on the diet preferred by many sea stars since I love mussels and other bivalves. I'm even fond of raw oysters for a number of reasons I won't go into here! I used to eat them in the bars during my Harvard days... when they were just a quarter each. However, the blood star has some dietary preferences that would make me gag... or worse! They actually feed on bacteria and other organic matter which is trapped in mucus and transferred by cilia to the oral opening. I can't imagine any of my readers would adopt such a feeding mode! Of course in doing so, they provide a valuable service by keeping the bottom and reef surfaces "clean."

I felt better after researching this species a bit further. Scientists noted that they may also feed on bryozoa and sponges by everting their stomach onto these invertebrates and digesting them externally. Still not my "cup of tea." However, others stated they observed them feeding on clams, fish and even other starfish. As you can see from the picture, some appear to want to bite off more than they can chew! At least that's a bit closer to my menu preferences, but I think I'll stick with what I can afford at Vons, and microwave or barbecue at the house.

Many invertebrates, including other starfish, disperse to new habitats through pelagic (open water) larval stages drifting in the plankton. This serves several purposes. It gets them away from the adults so the young 'uns can live their own lives. Then the adults adults can enjoy the "empty nest" syndrome. More importantly, dispersal also improves the genetic diversity of other blood star populations by mixing things up a bit, and helps colonize new habitats.

However, the blood star doesn't always cast its young off to fend for themselves. Development of the young is direct, with no intermediate larval stage between the fertilized egg and the young starfish. Smaller female blood stars actually brood their eggs on the underside of their central disk by arching their body. Apparently only the larger females release their eggs directly into the surrounding water.

Most species including humans have goals that include getting enough food to eat (aka munching), "getting enough" to reproduce their species (mating) and conquering new territory (dispersal). Since the blood star, despite its "gory" name, appears to lack inherent capabilities to "conquer" new habitats; how does it spread to the far corners of the world? Most likely this species gets a free ride to new areas by hitch-hiking on detached and drifting giant kelp plants or other. It may not be a plundering pirate in its travels, but it accomplishes the same goal the easy way!

© 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!

A blood star "on the rocks" so to speak, the rough surface created by the ridhes of ossicles;
the starfish's underside and an individual "biting" off more than it can chew!

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