Isaurus tuberculatus is a variable, tough-bodied zoanthid that is usually found singly or in small clusters. The photos show some of the variations in color and texture. We see these most often in lagoon Halimeda patches on sand at depths of about 8 to 20m or so.
Like some of the other anemones and corals, some individuals of Isaurus tuberculatus appear bright orange at depths deeper than orange light penetrates from the surface. This generally happens because certain proteins in the tissue of the animal absorb light at shorter wavelengths that penetrate to this depth and re-emits it in the longer wavelength orange. The first photo below shows how the zoanthid looks in natural light; the second shot was taken with artificial light, which overpowers and washes out the orange light being emitted, making the zoanthid look brown.
Created 1 August 2018