I enjoyed taking this vermilion star close-up (Mediaster aequalis) photo last week while diving near Victoria. It’s interesting how sea stars circulate seawater through their bodies as a way of providing nutrients to the animal, and assisting with locomotion. The ocean water enters and leaves the sea star in a controlled manner through a round disc called a madreporite or sieve plate. The madreporite has grooves and small pores through it and is located on the top surface of the sea star. It can be seen here in the upper right of this photograph.
Sunlight contains all the visible light we see (red, orange, yellow, green, blue, violet) and appears white, but when sunlight penetrates into the ocean red light is the first to be absorbed with increased depth. The result is that what appears bright red to me (when illuminated by my dive light), appears blackish to other underwater creatures in natural light at that depth, and so it’s interesting that this bright sea star tends to disappear into the reef. The vermilion star can grow to 8 inches (20 cm) across, and has a range from northern Alaska to northern Mexico.