Figure 1: Generalised body plan of Stichopus horrens. (Adapted from: Nichols, 1967)
Stichopus horrens is generally a slow mover and as such has low defensive ability. It is possible that ossicles are a mechanism for defense, or at least for structural support. I found that there were different ossicles located on the dorsal and ventral sides of S. horrens. This is of interest because it is likely that the larger ones positioned ventrally are utilised in locomotion. The ossicles positioned dorsally were of uniform size and there were only two types present (tables and 'C' shapes). Ossicles are often used to differentiate between species. Figure 2: Two different ossicle types found ventrally on S. horrens Figure 3: Ossicles found ventrally on S. horrens Figure 4: Ossicles found dorsally on S. horrens (table type) Tube feet are one of the most important features of any Echinoderms, as they function in respiration, waste removal and locomotion (Ruppert et al., 2004). They have been modified dorsally on S. horrens to wart-like structures and modified to buccal feet (tentacles) for feeding (Ruppert et al., 2004). Figure 5: Ventral tube feet Figure 6: Ventral tube feet and Buccal podia (tentacles) Figure 7: Tube feet modified to wart-like structures on dorsal side of S. horrens