VAR (ECU, CU) of whelk gliding along kelp holdfast, its "leg" grasping rootlets as rest of its body inches forward. Shot of mollusk passing keyhole limpet on its way down to ocean floor (limpet has cap-shaped exterior shell, similar to a clam; 3 to 6 cm in size, is a marine gastropod; whelk is of similar size). (43080)