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Free keywords:
Schistocephalus solidus; in vitro; procercoid; plerocercoid; tegumental layer; defence; trade-off
Abstract:
With the present study, a culture system for successive life-cycle stages of the tapeworm Schistocephalus
solidus was developed and this report documents for the first time, cultivation of the procercoid stage of S.
solidus from eggs. Additionally we have transformed procercoids dissected from experimentally infected
copepods and cultured procercoids into the early plerocercoid stage in vitro. Observations in the culture
suggest that the coracidia can interact with their external environment and need no host specific stimuli,
except for the components in the culture medium, for activation and hatching from the embryophore.
Increasing the culture medium pH from 7.3 to 8.0 improved escape rates and frequencies of hook contractions,
suggesting that the oncosphere may recognize and respond to environmental conditions along the
host intestine. Procercoids in the culture did not stop growing indicating that conditions within the copepod
may be important to limit growth and to induce transformation to plerocercoids. When procercoids
are dissected from copepods and transferred to the culture, the outer tegument layers and cercomer
starts to loosen. Comparison of the lectin staining of the loosened outer tegument layers and cercomer
in procercoids dissected from copepods confirms that transitions of both, the oncosphere to procercoid
and procercoid to plerocercoids, has taken place in the in vitro cultures.
