Light and electron microscopy were used to study the ultrastructure
of the
cement apparatus, namely cement glands and
cement ducts of mature specimens of the acanthocephalan parasite
Pomphorhynchus laevis Müller, 1776, recovered from
the digestive tracts of fish Leuciscus cephalus Risso, 1826.
In addition, the cement glands of immature P. laevis found
within the body cavity of the fish Alburnus alburnus alborella
De Filippi, 1844 were examined. In a mature male of P. laevis
the 6 cement glands are rounded to oval in shape and each of them has an
outer cytoplasmic layer containing nuclei and
surrounding a space for storage of the cement material within the gland.
The nuclei have an irregular outline and the
cytoplasm of the cells contains round, membrane-bound secretory granules
approximately 1 μm in diameter. Nuclei
surrounded by secretory granules were present inside the gland lumen. Within
the gland ducts of mature males, granules
were present within the wall thickness and, inside the luminal area,
mitochondria were encountered. In contrast, within
the cement glands of immature P. laevis there were no secretory
granules and the chromatin of the nuclei appeared
condensed. The nature of the secretory product of the cement glands was
investigated with histological and electrophoretic
methods. A protein with molecular weight of 23 kDa was recorded as a major
component of cement.