Acta Parasitologica, Vol. 52, No. 4, 2007,
325–334.
DOI: 10.2478/s11686-007-0054-8
Larisa G. Poddubnaya (1)*, Tomáš Scholz (2, 3), Céline Levron (2), Roman Kuchta (2, 3) and David I. Gibson (4)
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Frontal glands in the pseudoscolex of Paraechinophallus japonicus (Yamaguti, 1934) (Cestoda, Bothriocephalidea, Echinophallidae)
(1) Institute of Biology for Inland Waters, Russian Academy of Sciences, 152742, Borok, Yaroslavl Province, Russia; (2) Institute of Parasitology, Biology Centre of the Czech Academy of Sciences and (3) Faculty of Science, University of South Bohemia, Branišovská 31, 370 05 České Budĕjovice, Czech Republic; (4) Department of Zoology, Natural History Museum, Cromwell Road, London SW7 5BD, UK
*Corresponding author:
poddubny@ibiw.yaroslavl.ru
ABSTRACT
The glands in the pseudoscolex of the echinophallid cestode Paraechinophallus japonicus (Bothriocephalidea), a parasite of the bathypelagic fish Psenopsis anomala
(Perciformes, Centrolophidae), were studied using scanning and transmission electron microscopy. Two types of glands, with different morphological types of secretory granules
and mechanisms for discharging their glandular secretion, were observed. Both types of gland cell bodies are localized in the parenchyma of the pseudoscolex.
The syncytial glands of type I are characterized by the production of small (all ~0.25 µm in diameter), rounded, dense secretory granules which pass though thin
projections into the distal tegumental layer of the pseudoscolex. This type of gland has a unique method of discharging its secretory granules, which we call tumulogenesis.
The elimination of the secretory products is realized by an encroachment of the basement membrane and underlying tegumental muscles into the surface region of the distal cytoplasm of the tegument,
resulting in the formation of a 'glandular stalk' above which develops a superficial glandular tumulus. In the region of the glandular material of the tumulus, the basement membrane of the stalk forms
a dilation, and the appearance of a membrane-bound area serves to separate the tumulus from the distal cytoplasm of the tegument. Unicellular glands of type II are characterized by large granules (0.4–0.9 µm in diameter),
the presence of peripheral microtubules in the terminal region of their ducts and an eccrine mechanism for the discharge of their secretory granules. Acomparative analysis of the distribution and morphology of the types of scolex
glands among members of the different families of the 'Pseudophyllidea' (currently believed to represent two distinct orders, Bothriocephalidea and Diphyllobothriidea) is presented.
KEY WORDS:
Cestoda, Paraechinophallus japonicus, pseudoscolex, frontal glands, tumulogenesis, TEM, SEM