Patiria miniata (Bat Stars)

These are "bipinnarian" larvae of the bat star Patiria miniata. They look a lot like the sea cucumber "auricularia" larvae from the last post, but you can tell the difference between starfish and sea cucumber larvae by looking at the ciliated band on the oral hood, which in starfish is separate from the ciliated band that outlines the larval body. These larvae have been eating red algae, which stained their stomachs pink. If you look closely, you may see to thin sacks on the sides of the larval gut. These are the larval "coeloms"--pouches of mesoderm that line the body walls of many complex animals. One of the larval coeloms will ultimately contribute to the water vascular system of the adult starfish.

Here's what the adults look like: