Taxonomy and ecology of coral reef tube worms (Serpulidae, Spirorbidae) in the Sudanese Red Sea

Thirty-two species of calcareous tube-dwelling polychaetes (Families Serpulidae and Spirorbidae) are recorded from coral reefs in the Sudanese Red Sea. Twenty-two species belong to the family Serpulidae, and 10 to the family Spirorbidae. Brief descriptions and illustrations of tubes and opercula are included. Factors affecting settlement, post-settlement survival, and the ecological distribution of these species are discussed. Grazing by fish and echinoids results in the removal of many larvae and young tube worms from exposed surfaces in shallow waters, but unchecked growth of green filamentous algae can inhibit larval settlement. Tube worms die when tubes become clogged with sediment or overgrown by encrusting epibiota. Some species have tube or opercular adaptations that may reduce the effects of competition and predation by epifauna. Post settlement mortality is greater among the Spirorbidae than the Serpulidae. This may be due to the small size of the spirorbids or to the oxygen requirements of the brooded embryos. In the Sudanese Red Sea spirorbids occurred at depths less than 50 m, while the serpulids were found at all depths from the intertidal to below 80 m.