EFFECTS OF ANATOMY AND ENVIRONMENT ON THE RELATIVE PRESERVABILITY OF ASTEROIDS - A BIOMECHANICAL COMPARISON

Echinoderms are relatively fragile and highly variable in terms of pos t-mortem durability. Different styles or rates of decay among differen t species of asteroids are likely to depend upon the amount and arrang ement of soft tissues which link the ossicles within the body wall. Th is study examines the mechanical behavior of the aboral integument of Solaster stimpsoni and Pisaster ochraceus after intervals of decay as an indicator of their relative preservability and post-mortem strength . Tissue samples were allowed to decay at 14-degrees-C in running seaw ater or buried in fine wet sediment. The maximum force required to bre ak samples of Solaster decreases significantly over a period of nine d ays, at which time complete decay of the body wall occurs. Pisaster sa mples tend to stretch without breaking. These differences in mechanica l behavior are attributed to different skeletal anatomies: Solaster ha s a sheet-like body wall containing fiat, platelike ossicles, while Pi saster has a much thicker integument with many overlapping broad and e longated ossicles. There is no difference in decay behavior between bu ried and surface samples of Solaster, suggesting that a relatively ano xic environment does not in itself retard the breakdown of soft tissue s. Although the mechanical behavior of asteroid integument after inter vals of decay seems to correlate with species-specific skeletal organi zation, differences in preservability between species ultimately depen d not only on inherent anatomical differences but on the interaction o f anatomy and environment.