Tilapia Topic: Skin Microscopy

Examine skin and select an area that appears abnormal. Cut a small piece of the skin and place it into a drop of saline on a clean glass slide. Cover with a slip cover, and additional saline if needed.

Compare your sample with the following Disease Vectors:

Amyloodinium sp 0.03 to 0.05 mm spherical to pear shaped and attached by a short stalk. blackish in color and vacuolated (e.g. full of tiny spherical bubbles) under transmitted light

Caligus sp. a parasitic copepod 2 to 3 mm in length (visable to the naked eye)

Epistylis sp., a stalked colonial protozoan. 0.05 mm cup or tulip shaped. attached by branching stalks to the skin. cilia around the rim of the open (apical) end of the "bell. May contract to a ball-shape or detach from stalks and swim away. colonies are large enough to be visible with the naked eye as soft, fluffy growths protruding from sores on the skin.

Ichthyobodo sp. (Costia), a flagellated ectoparasite. VERY small, about 0.007 mm or the size of a red blood cell. It may be found attached to gill or skin cells by its narrow end or moving in a jerky circular motion in the wet-mount fluid near the tissue

Saprolegnia spp. fungi at 100X to 400X appears as a branching tangle of root-like filaments (e.g. the hyphae). The filaments are clear and about 0.005 mm in diameter.

Myxobacteria long (0.003-0.01 mm) thin (0.0005 mm) rod shaped bacteria often seen in clumps or "stacks" which move by flexing or gliding.

Ichthyophthirius multifiliis ("Ich", marine: Cryptocaryon irritans), a protozoan ectoparasite. can vary in size from 0.02 mm to nearly 1 mm depending on the age of the parasite The cilia along the perimeter of the organism beats and slowly propels the protozoan forward. Under transmitted light in wet-mount preparations, Ich appears brownish in color.

Monogenetic Trematodes parasitic flatworms. May be small (0.3 to 0.4 mm) or large (2to 3 mm) . Hooks on one end may be attached to the host fish. If still alive, will flex rapidly or contract slowly.

Scyphidia sp. a free-living protozoan. stumpy (~0.04 mm in height), cylindrical shaped with a ring of cilia around the apical end and an expanded sucker shaped basal end in contact with the skin of the fish. when detached from the fish change to a fast moving saucer shape.

Tricodina sp., a protozoan ectoparasites ~0.04 mm circular saucer shaped and very fast moving when alive. rimmed by cilia and on the bottom side. peculiar denticular rings with teeth that point inward.