Summary
Ultrastructural observations of the lappets of the adult and metacercarial stage of Diplostomum phoxini Faust, 1918, indicate that the tegument is specialised in this region, possesses finger-like processes and receives the ducts of secretory glands. The glands are unicellular with the nucleated portion lying in the fore-body and possess long necks, supported by microtubules, which discharge at the surface of the tegument. Two types of gland cell are present: type A which produces large secretion bodies with homogeneous contents and type B producing egg-shaped bodies with a core of lightly staining material and dense apical and peripheral regions. The extrusion pattern is holocrine and in the ‘mature’ gland cell the cytoplasm becomes completely replaced by secretion. The lappets and both types of gland cell are fully formed at the ‘mature’ metacercarial stage.
Zusammenfassung
Ultrastrukturelle Untersuchungen an den Hautzotten adulter Würmer wie von Metacercarien bei Diplostomum phoxini Faust, 1918, lassen erkennen, daß das Integument dieser Region eine spezielle Struktur aufweist. Es besitzt fingerförmige Fortsätze und nimmt die Ausführgänge von Sekretionsdrüsen auf. Die einzelligen Drüsen liegen mit ihrem kernhaltigen Anteil im vorderen Teil des Körpers. Ihre langen Ausführgänge werden von Mikrotubuli begleitet, die sich zur Oberfläche des Integuments hin verlieren. Es lassen sich zwei Arten von Drüsenzellen unterscheiden: Typ A produziert große homogene Sekrettropfen; Typ B erzeugt eiförmige Körperchen mit stark lichtbrechendem Inhalt, deren Spitze und Peripherie aus dichterem Material bestehen. Der Sekretionsmodus ist der einer holokrinen Drüse; in den „reifen“ Drüsenzellen wird das gesamte Cytoplasma durch Sekrete ersetzt. Sowohl die Hautzotten als auch die beiden Drüsenzelltypen sind bereits bei „reifen“ Metacercarienstadien vollständig ausgebildet.
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Erasmus, D.A. Studies on the host-parasite interface of strigeoid trematodes. Z. F. Parasitenkunde 32, 48–58 (1969). https://doi.org/10.1007/BF00259961
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DOI: https://doi.org/10.1007/BF00259961