Three lined Nudibranch

Three-lined Nudibranch30″x37″

Three-lined Nudibranch
Flabellina trilineata


Friday Harbor Marine Laboratories, University of Washington
San Juan Island, Washington

Archival Pigment Print

Curling its body and bristling the appendages (cerata) on its back, this nudibranch strikes a defensive pose. At the tip of each appendage is a brown sac filled with stinging cells. When disturbed, the animal discharges the cells via tiny pores. Remarkably, the stinging cells are not produced by the nudibranch itself: It appropriates them from its prey, tiny colonial animals called hydroids, which are related to sea anemones and jellyfish. After a meal, the stinging cells are transferred from the stomach to the sacs at the ceratal tips via red-colored fingers of the digestive system, plainly visible in the photograph. The cells are stored in the sacs for the nudibranch’s own defense.