Ichthyophthirius multifiliis

Name

Greek: ichthys = Fisch, phtheiros = louse; Latin: multus = much, filia = daughter.

Classification

Species of Ciliophora, phylum Alveolata.

Life Cycle

Figures 1, 2, 3, and 4

Ichthyophthirius multifiliis, Fig. 1

Life cycle of Ichthyophthirius multifiliis parasitizing many species of freshwater fish. 1Swarmer penetrates the skin of a fish and becomes encysted (EN) by host tissues. 2 The encysted swarmer grows to be a trophozoite, reaching a diameter of up to 1 mm; the skin then presents with a large grayish pustule at these places. 3 Upon rupture of the pustules, the trophozoites, which have numerous contractile vacuoles, are liberated and swim about feebly. Upon coming to rest on the bottom of the pond, the trophozoite secretes a thick-walled gelatinous cyst wall about itself. 4–8 Within an hour of encystation, the mother trophozoite starts reproduction by simple transverse division, this being repeated until up to 1,024 30–50 μm-long, pear-shaped swarmers (with a single...