Artifactual and natural variation of Oochoristica javaensis: Statistical evaluation of in situ fixation
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Lack of knowledge of the extent of natural morphological variation can undermine proper taxonomic decisions. Confounding this problem is artifactual variation that arises from improper fixation techniques. For the morphologically based taxonomy of the cestode genus Oochoristica, little information exists on the plasticity of important taxonomic characters. In addition, paratypes of several species of Oochoristica are highly contracted and contorted. These paratypes were recovered from preserved hosts; thus, the tapeworms were killed and fixed inside the host (in situ fixation). Experiments demonstrated that in situ fixation of Oochoristica javaensis results in highly contracted specimens, and statistical comparisons between relaxed and in situ-fixed tapeworms revealed significant differences for proglottid measurements. Natural variation for the paratypes recovered from preserved hosts is likely misrepresented by the artificial variation induced by in situ fixation. Lastly, data from natural infections suggested that proglottid characters of O. javaensis are plastic and may be subject to crowding effects.
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Criscione, C. D., & Font, W. F.
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