Mass spawning by two brittle star species,Ophioderma rubicundum and O. Squamosissimum (Echinodermata: Ophiuroidea), at the Flower Garden Banks, Gulf of Mexico

The Flower Garden Banks National Marine Sanctuary in the northwestern Gulf of Mexico hosts a large number of corals that reproduce via mass spawning in the late summer. Other reef invertebrates participate in this annual event, including sponges and christmas tree worms. In this report we describe the participation of hundreds of the brittle stars Ophioderma rubicundum Lütken and O. squamosissimum Lütken in the year 2000 mass spawning event. O. rubicundum spawned mostly on the 7th evening after the August full moon, while O. squamosissimum spawned only on the 8th evening. In both instances females were observed to release eggs approximately 30 min after the first males had been sighted releasing sperm. Males of O. rubicundum formed large aggregates, while males of O. squamosissimum were more solitary. Females were solitary in both species. In a sample of eggs collected immediately upon release from a female O. squamosissimum, one was found to be fertilized and cleaving, implying that like gonochoric corals, female brittle stars may use internal fertilization.