Ichthyophthirius multifiliis

Name

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

Classification

Species of Ciliophora, phylum Alveolata.

Life Cycle

Figs. 1– 3 (page 635).

Figure 1

Life cycle of Ichthyophthirius multifiliis parasitizing many species of freshwater fish. 1 Swarmer 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 contractile vacuole) are formed. 9...