Candy-Corn Nudibranch and Finger Copepod
Janolus fuscus and Ismaila belciki
Friday Harbor Marine Laboratories, University of Washington
San Juan Island, Washington
Archival Pigment Print
I studied this photograph for some time before realizing that I was looking at more than one animal: the nudibranch, facing the camera, and two parasitic copepods embedded in its head. The copepods themselves are buried inside the host, but their emergent, white egg masses give them away. If you’re familiar with copepods as tiny crustaceans swimming in the plankton, it may come as a surprise to learn that many species are parasitic on other animals. The white finger copepod, commonly found on this species of nudibranch, feeds on the blood of its host. While it doesn’t generally kill the nudibranch, it does appear to lower its fecundity: Parasitized animals lay fewer eggs than unparasitized ones do.