Black Rockfish (Sebastes melonops) caught with X-Cell tumor.
Observation by Nikki Whittern:
A black rockfish was caught and pulled from the water near the backside of Hog Island. When pulling it out of the water, it was quickly noticed that the fish had a creme colored growth along its gill cover, growing outward from around the gills. The same abnormality was spotted where the pelvic fin meets the underside of the fish. Other abnormal symptoms included bulging eyes, and a small white particle located on the gills. I have researched moderately about what the growth may be, and I'm under the impression that it could possibly be a fungus growing on the gills in addition to an infection. In the image provided you can see a small white particle located in the gills, (circled) resembling a 'cottony' growth leading me to believe that it is a fungus growth. In regard to the creme colored membrane I am unsure of what it is. I am curious as to what these growths are, and what caused these symptoms.
Ted Meyers State Fish Pathologist writes:
The abnormal growth in the rockfish images below is consistent with what has been known in the literature as an X-cell tumor. The mass is actually comprised of xenomas or enlarged host cells containing a parasite recently characterized as an alveolate protozoan. More information can be found in the publication "X-Cells Are Globally Distributed, Genetically Divergent Fish Parasites Related to Perkinsids and Dinoflagellates"
These masses are usually bilateral and most common in Pacific cod, rockfish and flatfish, generally associated with pseudobranchs and gill filaments. X-cells pose no known human health concern.
Comments from LEO Editors:
Protozoa are single-cell eukaryotes. These are organisms that are made of a single cell whose nucleus is enclosed in a membrane (as oppose to prokaryotes like bacteria whose components are enclosed together in the cell membrane). Protozoa are responsible for several diseases seen in Alaskan fish species. Some fishers may already be familiar with some of these diseases, such as Ichthyophonus and Henneguya. For more information on protozoan fish disease, see the Alaska Department of Fish and Game Common Diseases of Wild and Cultured Fishes in Alaska. Erica Lujan
