Acta Parasitologica, Vol. 51, No. 1, 2006, 51-58 Mohammed H. Ibraheem(1)* and John S. Mackiewicz(2) - Scolex development, morphology and mode of attachment of
Wenyonia virilis Woodland, 1923 (Cestoidea, Caryophyllidea)
(1)Department of Zoology, Faculty of Science, Minia University, El-Minia 61519, Egypt; (2)Department of Biological Sciences,
State University of New York, Albany, NY 12222, U.S.A.
*Corresponding author: mohamhas@hotmail.com
ABSTRACT
Development and morphology of the scolex and mode of attachment of Wenyonia virilis Woodland, 1923, a caryophyllaeid cestode
from the silurid Nile fish Synodontis schall (Bloch et Schneider, 1801), were studied by means of light and scanning electron
microscopy (SEM). Scolex and genital primordia changes through four stages of juvenile development are described.
Longitudinal ridges do not appear on the scolex until the cestode has well defined genital primordia. This is in stark contrast
to other caryophyllidean genera in which the basic morphology of the adult scolex becomes evident at the procercoid stage in
the oligochaete intermediate host. The scolex of the adult has 13 to 19 prominent longitudinal ridges and deep furrows that come
together at the apex to form an apical ring, a protrusible terminal introvert within the apical ring that forms a deep apical pouch
when fully retracted, and a central group of Faserzellen. The scolex of W. virilis appears similar to the rugomonobothriate scolex
of another African caryophyllid, Monobothrioides chalmersius (Woodland, 1924). Comparisons are made with other caryophyllideans
having a scolex with a terminal structure: Monobothrium Diesing, 1863, Djombangia Bovien, 1926 and Caryoaustralus
Mackiewicz et Blair, 1980. The terminal introvert may be responsible for attachment in early juvenile stages, but may be supplemented
by the longitudinal ridges and furrows later in development. Host tissue appears to be drawn into these furrows that
function as weak organs of attachment. We could not determine how the introvert of adult worms functions in attachment. At
the site of attachment, the mucosa showed necrosis and degeneration and the submucosa exhibited vacuolization and infiltration
with lymphocytes and leucocytes.
KEY WORDS: Caryophyllidea, Wenyonia virilis, scolex attachment, scolex morphology, terminal introvert, SEM