Analysis of sediments carried by a tropical intertidal sea cucumber in relation to background substrates

On the Pacific coast of Costa Rica,the sea cucumber Holothuria cf. kefersteini is typically found covered by natural sediments acquired in the rocky intertidal zone.  We examined the composition and diversity of substrate on individuals captured at San Miguel Biological Station, Costa Rica.  Sampling was done at low tide from June- July 2012.  Sediment materials were removed from the back of each sea cucumber and separated to three equal areas of the animal: head, middle, and rear.  

            At the time of capture, all sea cucumbers were entirely covered by adhered sediments.  H. cf. kefersteini at this location carried sand, shell fragments, pebbles, and other small items, with individual variation.  

            Background sediment composition was assessed photographically and by sampling in the field for comparison with the sediments borne by the sea cucumbers.

            Experimental manipulations showed sea cucumbers in laboratory aquaria (1) tended to shed small amounts of their sediment loads, and (2) did not actively or passively pick up sediments from the bottom of the tank whether sediments were natural (sand, pebbles) or artificial (flattened aluminum foil balls).

            Experimental manipulations of sea cucumbers in the field indicated that (1) when buried in substrate, sea cucumbers do not pick up sediments actively or passively, but (2) if sediments are sprinkled on the animal’s back, some adhesion, takes place.  These data suggest sea cucumbers rely on wave action between high and low tides to deposit the substrates on their backs.  Once sediment is deposited,sea cucumbers can attach the sediment to themselves using their tube feet.