ABSTRACT
The hitherto undescribed brittlestar species Ophiothrix n. sp. (Ophiotrichidae) occurs in association with the rock-boring sea urchin Echinometra lucunter (L.) in the rocky intertidal zone of the Santa Marta region (Colombia). Observations of different size specimens and histological investigations of gonad development revealed that Ophiothrix n. sp. is a protandric hermaphrodite. Individuals from 1.5 to about 3.5 mm disc diameter have testes whereas specimens from about 4.6 to the maximum size of 7.0 mm have ovaries. The intermediate-size specimens have transitional gonads. Large females appear to brood their embryos throughout the year. The embryos are brooded externally on the oral region. A typical pelagic ophiuroid larva does not occur.
