Covering behaviour in the sea urchin Pseudechinus magellanicus (Temnopleuridae) in central Patagonia, Argentina

Abstract

ABSTRACT The sea urchin Pseudechinus magellancus exhibits a covering behaviour through which it captures different items from the environment and arranges them on its aboral surface with the assistance of podia. The items mainly used include detached algae and inorganic items available in the substrate. Spatial (between sites) and vertical (along a coastal depth gradient from intertidal tidepools to upper circalittoral zones) variability was found in the composition of covering items, indicating that coverage is strongly influenced by the availability of the utilised items. Inorganic biogenic items (eg shell remnants) were prevalent in the lower intertidal, while detached algae predominate in subtidal environments. A positive selection of larger items from those available in the environment was found at least in the intertidal tidepools. The species exhibited an equal degree of coverage between juveniles and adults, and also a higher proportion of individuals with high coverage in the intertidal zone compared to the subtidal zone. The degree of coverage between sites with dissimilar sediment input was similar. The covering behaviour in P. magellanicus may not be a response to a single factor but rather an advantageous trait with multiple functions that could have been selected simultaneously.