Functional Morphology and Reaction to Stimuli in Two Classes of Echinoderms

Farnaz Anwar and Abby El-Shafei

Upon observation in Discovery Bay, sea stars and brittle stars have been most commonly found under rocks, or more specifically in the absence of light. Two of the classes of Echinoderms, Class Asteroidea and Class Ophiuroidea, are differentiated by the attachment of their arms relative to the central disk. Our research was brought about by our interest in the implications of the functional morphology for these classes of Echinoderms. We analyzed both to see if functional morphology would play a role in the total displacement of the organisms when presented with light, sunscreen, and a failed predator simulation. Each organism was placed at the origin of the experimental tank for a timed duration as it was presented with one of the aforementioned stimuli. The results support the idea that the difference in functional morphology of Class Asteroidea and Class Ophiuroidea play a role in their total displacement. More specifically, the functional morphology of Class Ophiuroidea gives the organisms of this class an advantage when movement is needed to avoid discomfort and predators. Moreover, if an organism has a larger mass, it is more probable that it will be able to move a farther distance than one with a smaller mass if given the same amount of time to do so.

Organisms of the Class Asteroidea and Class Ophiuroidea found in Discovery Bay.