Acta Parasitologica, Vol. 51, No. 4, 2006, 255-263 Larisa G. Poddubnaya(1)*, David I. Gibson(2), Zdzislaw Swiderski(3,4) and Peter D. Olson(2) - Vitellocyte ultrastructure in the cestode Didymobothrium
rudolphii (Monticelli, 1890): possible evidence for the recognition of divergent taxa within the Spathebothriidea
(1)Institute of Biology for Inland Waters, RAS, 152742, Borok, Yaroslavl Region, Russia; (2)Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK; (3)W. Stefanski Institute of Parasitology, Polish Academy of Sciences, 51/55 Twarda Street, 00-818 Warsaw, Poland; (4)Department of General Biology and Parasitology, Warsaw Medical University, 5 Chalubinskiego Street, 02-004 Warsaw, Poland
*Corresponding author: poddubny@ibiw.yaroslavl.ru
ABSTRACT
In the spathebothriidean tapeworm Didymobothrium rudolphii (Monticelli, 1890) the fine structure of the vitellocytes at different stages of their development within the vitelline follicles, vitelline ducts and uterus was studied for the first time using
transmission electron microscopy. The vitellocyte inclusions of D. rudolphii are: shell globule clusters containing tightly packed shell globules associated with a matrix of moderate electron density, glycogen granules, large electron-lucent lipid droplets (up to 3 um in diameter), and, occasionally, a lipid droplet may occur in the nucleus of the vitellocytes. The diameter of the clusters ranges from 0.4 to 2.5 um, the number of shell globules in the clusters varies from 8 to 45, and the size of the globules ranges
from 0.12 to 0.25 um and they are of approximately homogeneous sizes within a cluster. Most vitellocyte lipid droplets have a heterogeneous configuration with a 'cavity' inside them when they are within vitelline ducts and intrauterine eggs. Vitellocytes of the eggs contain dark concentric bodies and lipid droplets. The interstitial tissue has a syncytial structure. The morphological parameters of the diameter and shape of shell globule clusters, arrangement of shell globules in clusters, number and diameter of globules within clusters, types of lipid droplets and presence of dark concentric bodies are compared with those of two other spathebothriidean genera, Cyathocephalus and Diplocotyle. The comparative data demonstrate that vitelline material morphology has unique features in three spathenothriidean genera and may be used as evidence for the recognition of separate
taxa.
KEY WORDS: Didymobothrium rudolphii, Spathebothriidea, Cestoda, vitellocytes, ultrastructure