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<br />248
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<br />TRANS, AM, MICROSC, SOC,
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<br />parasitic flatworms and, apparently, the number present is related to the size
<br />of the cilium (Lyons, 1969), If the cilium is very long, many collars will be
<br />present and the rootlet system will be well-developed. No doubt, such collars
<br />serve to support the cilium. Septate desmosomes are evident in the sensilla
<br />of the cestodes described earlier, as well as in B, acheilognathi, and serve
<br />to attach the bulb to the tegument.
<br />The tegument of B, acheilognathi is composed of an outer syncytial layer
<br />with underlaying perikarya; such an arrangement is typical of all cestode
<br />species examined to date. Small mitochondria are abundant in the lower one-
<br />half of the syncytial layer, whereas large mitochondria are prominent in the
<br />cytons, The functional significance of this size difference is not known. Also
<br />prominent within the syncytium are membrane-bound vesicles which prob-
<br />ably are pinocytotic (pinosomes). Although it has been long speculated that
<br />the cestode tegument could take up macromolecules by pinocytosis, such a
<br />phenomenon has been demonstrated only recently. Hopkins et al. (1978)
<br />showed that pinocytosis occurs in the tegument of the plerocercoid of Schis-
<br />tocephalus solidus and Threadgold & Hopkins (1981) reported the same phe-
<br />nomenon in the tegument of adult S. solidus and Ligula intestinalis. The
<br />pinosomes described by these investigators are remarkably similar in size
<br />and shape to the vesicles seen within the syncytium of B. acheilognathi; it
<br />seems reasonable to assume that these vesicles are involved in the same
<br />process.
<br />Muscle bundles occur within the perinuclear region and just below the
<br />basal membrane in B. acheilognathi. These muscles are comparable in mor-
<br />phology to those described from other cestode species (Hess, 1980; Lumsden
<br />& Byam, 1967), The cytons of B. acheilognathi contain a prominent nucleus,
<br />actively secreting Golgi bodies, ribosome-rich endoplasmic reticulum vesi-
<br />cles, glycogen granules, and large mitochondria, The condition of the Golgi
<br />apparatus and endoplasmic reticulum indicates a cell that is synthesizing
<br />protein actively. The fate of this protein, however, is not known, Tedesco &
<br />Coggins (1980) indicated that the inclusions found within tumuli are synthe-
<br />sized within the cytons. Another possibility is that some of these vesicles may
<br />contain enzymes, or may contribute to the glycocalyx which covers the ex-
<br />ternal plasma membrane (Smyth, 1969).
<br />
<br />LITERA TURE CITED
<br />
<br />ANDERSEN, K. 1975, Comparison of surface topography of three species of Diphyllobothrium
<br />(Cestoda: Pseudophyllidea) by scanning electron microscopy, Int, ]. Parasitol" 5: 293-
<br />300,
<br />1979, Variation in scolex morphology within and between some species of the genus Pro-
<br />teocephalus Weinland (Cestoda: Proteocephala) with reference to strobilar morphology,
<br />Zool, Scr" 8: 241-248,
<br />ARME, C, & THREADGOLD, L. 1976, A unique tegumentary cell type and unicellular glands
<br />associated with the scolex of Eubothrium eras sum (Cestoda: Pseudophyllidea), Rice Univ,
<br />Stud" 62: 21-34,
<br />BERGER, J, & METTRICK, D, F, 1971. Microtrichial polymorphism among hymenolepid tape-
<br />worms as seen by scanning electron microscopy, Trans, Am, Microsc, Soc" 90: 393-403,
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