Thysanozoon nigropapillosum, the yellow-spotted flatworm, is a species of marine
flatworm in the family
Pseudocerotidae. The species is native to the tropical Indo-Pacific region, where it lives in shallow reef habitats. Flatworms are
hermaphrodites, each being able to act as either male or female. As a donor of sperm, it can grip the margin of the recipient's body, using its two penises in a chopstick-like manner, and deposit sperm on the surface of the skin of the recipient, even while it is actively swimming.
This picture shows a yellow-spotted flatworm photographed in Manta Ray Bay, on the island of
Yap in the Federated States of Micronesia. The flatworm is seen swimming to the right at a depth of 12 metres (40 ft) by undulating the margins of its body. The pseudotentacles at the front have simple eyes and sensory receptors to enable the flatworm to find
tunicates on which it feeds.Photograph credit:
Betty Wills