The terminology of larval cestodes or metacestodes
The terminology of larval cestodes or metacestodes
The terminology of larval cestodes or metacestodes
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21Figure 4. Schematic representations <strong>of</strong> six f<strong>or</strong>ms <strong>of</strong> <strong>larval</strong> <strong>cestodes</strong>. A. Procercoid; B, Plerocercoid; C, Merocercoid (redrawn from Dollfus,1942); D, Plerocercus (redrawn from Dollfus, 1942); E, Cysticercoid (redrawn from Gabrion, 1981); F, Cysticercus (redrawn from Gabrion,1981).the development <strong>of</strong> too few <strong>cestodes</strong> has been studiedin detail to date to allow general usage <strong>of</strong> thesecharacters.<strong>The</strong> preceding arguments theref<strong>or</strong>e justify the use<strong>of</strong> only two primary characters f<strong>or</strong> the current classification<strong>of</strong> <strong>larval</strong> <strong>cestodes</strong>: (1) presence <strong>of</strong> a primarylacuna; (2) scolex developing externally <strong>or</strong> retracted/inverted.Secondary characters <strong>of</strong> potential butcurrently limited in application are (1) presence <strong>of</strong> acercomer and (2) presence <strong>of</strong> a bladder, as these eithermay not be determinable (1) <strong>or</strong> may be homoplasious(2).Using the primary characters identified above, sixputative life-cycles are possible. Since no life-cyclesare known in which a primary lacuna develops butthe scolex is not withdrawn <strong>or</strong> invaginated (Freeman,
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