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The International Satellite Symposium on the "Reproductive and
Developmental Biology of Parasitic Platyhelminths" was held in Olsztyn on
10 September 1998, during the 18th Jubilee Meeting of the Polish
Parasitological Society (PPS), commemorating the 50th Anniversary of its
foundation.
My aim as organizer of this Symposium, on behalf of the Institute
of Parasitology, Polish Academy of Sciences, was to invite the original
contributions as well as pertinent but unavoidably selective reviews of
recent advances in our understanding of the reproduction and development
of parasitic Platyhelminthes. It is hoped that the original contributions
and review papers presented at this Symposium supply not only the
background of critically evaluated past work on these groups of parasites
but also provide an indication of the directions in which research in this
field is progressing at the moment. Some of the contributions presented
there highlighted surprising gaps in our knowledge; if their publication
here can stimulate further research to fill these voids, the main function
of this Symposium would be partially realized. Due to a long Polish
tradition in this field of research, we would like also to organize
similar meetings in the future, at more or less regular intervals. The
next occasion will be the 8th European Multicolloquium of Parasitology,
which will take place in Poznan, Poland, between 10th and 14th September
2000.
The Polish school of parasitology (C. Janicki, L. W. Wisniewski,
J.S. Ruszkowski, W. Michajlow, K. Rybicka, L. Jarecka) has a long tradition
in this field of research and always significantly contributed towards its
development and current progress.
The topic of the Symposium was a broad one and included papers on
the spermatogenesis, vitellogenesis, fertilization, embryonic development
and larval stages of all groups of parasitic platyhelminths studied by
means of different methods and techniques including light and electron
microscopy, cytochemistry, biochemistry and immuno-cytochemistry.
The first speaker, Professor David W. Halton, presented results of
his fascinating studies on the role of the neuroactive substances in
reproduction and development in Platyhelminthes. Using antisera to
endogenous flatworm FMRFamide-related peptides (FaRPs) and to biogenic
amine, 5-hydroxytryptamine (5-HT), comparison has been made, through
confocal imaging, of the immunostaining of ootype innervation in
trematodes. He showed that the neuropeptic substances may have a
hormonal-like influence on reproductive development in flatworms, as well
as serving to regulate motility of the ootype wall and associated ducts,
essential for oviposition. The second paper on the functional morphology
and ultrastructure of the eggs, uterus and paruterine capsules of
Distoichometra bufonis (Cestoidea, Nematotaeniidae) was presented
by Professor David Bruce Conn. His original results expanded the basis for
comparing eggs and associated reproductive structures that occur among the
more common cestodes of terrestrial hosts. Three other papers presented on
the ultrastructure of cestode eggs were on comparative ultrastructure of
some cyclophyllidean eggs (Chomicz and Walski), and the original results
on infective eggs of dilepidid Hepatocestus hepaticus (Swiderski
and Tkach), as well as original results on egg morphogenesis and
ultrastructure in the hymenolepidid cestode, Staphylocystoides
stefanskii (Tkach and Swiderski).
Professor Willi E. R. Xylander concluded his paper on larval
biology of Gyrocotylidea and Amphilinidea and the evolution of Cestoda
with a statement that the extremely high egg production in these parasites
compensates offspring loss by lower rates of host finding due to a passive
mode of infection.
The results of Professors L. Jarecka, M. D. B. Burt, and B.
MacKinnon on the tegument ultrastructure of the larval forms of some
Pseudophyllidea, Haplobothridea, and Cyclophyllidea may provide further
evidence in support of Janicki's Cercomer Theory.
Two papers were presented on the ultrastructure and cytochemistry
of Mehlis' gland and egg-shell formation in Schistosoma haematobium
and
Schistosoma japonicum (Moczon and Swiderski, and Swiderski, Moczon
and
Eklu-Natey). In both schistosome species, the glycoprotein expelled from
the Mehlis' gland forms a relatively thick "cocoon" around the
ovum-vitellocytes complex and apparently induces degranulation of
vitelline cells (expulsion of "shell-globules" = polyphenolated
proteins).
Two review papers were presented on the comparative ultrastructure
of fertilization in parasitic Platyhelminthes (Swiderski and Conn) and on
the comparative ultrastructure of vitellocytes and vitellogenesis in
cestodes (Swiderski and Xylander). The ultrastructural studies on
fertilization in parasitic flatworms are rare: two on cestodes, three on
digeneans and two on monogeneans. Their results indicate that the gamete
fusion in species with uniflagellate and biflagellate sperm is essentially
similar. This homogeneity in flatworm fertilization patterns contrasts
sharply with the great variety in their sperm ultrastructure. The second
review on vitellogenesis, in particular a comparison of interrelationships
which exist between types of vitellocytes, vitellogenesis, types of
embryonic development, ovoviviparity and life cycles indicated parallelism
and analogies in adaptation to the parasitic way of life in different
groups of cestodes.
In addition to the few invited review papers, numerous authors
presented original result of their recent or current research in this
field in the poster session. The Symposium involved 30 participants from 8
countries of Europe, and from the USA, Canada and Senegal. The abstracts
of all accepted contributions were published in the special number of
Wiadomosci Parazytologiczne, vol. 44, no. 3, 1998, which was
distributed
to all participants at the Meeting in Olsztyn.
The publication of the selected, complete papers presented at this
Symposium was in the hands of Editor in Chief of Acta
Parasitologica. The
style and format of the Symposium contribution correspond to those of this
journal. Our original idea was to publish full versions of all selected,
invited papers presented at the Symposium, in one issue of Acta
Parasitologica. Due to various reasons and to our sincere regret, this
was
not possible and thus only 6 papers appear as review or original,
reviewed papers in this issue. As some authors were already committed to
publish somewhere else or they were not ready to meet the rather short
deadline, their contributions will follow as regular, reviewed papers
published in forthcoming issues of Acta Parasitologica.
I would like to take this opportunity to express my sincere thanks
to Professor David W. Halton, Queen's University of Belfast, U.K. and
Professor D. Bruce Conn, Berry College, Georgia, U.S.A., for their
chairmanships of the Symposium.
My gratitude is also due to Professor Katarzyna Niewiadomska, the
President of the PPS for her suggestion to schedule our Symposium as a
"satellite meeting" in the framework of the 18th Jubilee Meeting of the
PPS as well as for her assistance and advice in all stages of its
organization.
Scientific Programme of the International Satellite Symposium:
Ultrastructure of oncospheral envelopes at the final stage of infective
egg formation in some species of Cyclophyllidea - Lidia Chomicz
and Michal Walski (Warsaw, Poland)
Functional morphology and ultrastructure of the eggs, uterus and
paruterine capsules of Distoichometra bufonis (Platyhelminthes:
Cestoidea: Nematotaeniidae) - David Bruce Conn (Mount Berry,
U.S.A.)
Neuroactive substances in reproduction and development in
platyhelminths - David W. Halton, Aaron G. Maule and Chris Shaw
(Belfast,
U.K.)
Tetraphyllidean cercoid ultrastructure: Janicki's "Cercomer Theory"
revisited - Lena Jarecka, Michael D. B. Burt and Barbara M.
MacKinnon (New Brunswick, Canada)
Cell compound of parenchyma and extracellular matrices of Triaenophorus
nodulosus (Cestoda) in ontogenesis - Janetta V. Korneva
(Borok, Russia)
Striated rootlets in spermatids of Anoplocephaloides dentata
(Anoplocephalidae) and Dipylidium caninum (Dipylidiidae): a new
finding in the Cyclophyllidea - Jordi Miquel, Cheikh Tidiane Ba
and Bernard Marchand (Barcelona, Spain; Dakar, Senegal and
Banyuls-sur-Mer, France)
Schistosoma japonicum: the chemical nature of the secretion
produced by
the Mehlis' gland - Tadeusz Moczon and Zdzislaw Swiderski (Warsaw,
Poland)
The fine structure of uterine, prostatic and Mehlis' glands of
Caryophyllidea and Cyathocephalata - Larisa G. Poddubnaya (Borok,
Russia)
Implication of Phyllobothrium lactuca (Cestoda, Tetraphyllidea,
Phyllobothriidae) spermiogenesis on phylogenesis within the
Tetraphyllidea - Aminata Sene, Cheikh Tidiane Ba, Jordi Miquel and
Bernard Marchand (Dakar, Senegal; Barcelona, Spain and
Banyuls-sur-Mer, France)
Comparative ultrastructure of fertilization in parasitic
Platyhelminthes - Zdzislaw Swiderski and David Bruce Conn (Warsaw,
Poland and Mount Berry, U.S.A.)
The ultrastructure and cytochemistry of Mehlis' gland and egg-shell
formation in Schistosoma haematobium - Zdzislaw Swiderski,
Tadeusz Moczon and D. T. Eklu-Natey (Warsaw, Poland and Geneva,
Switzerland)
Fine structure of the infective eggs of the dilepidid cestode
Hepatocestus hepaticus (Baer, 1932), a parasite of shrews -
Zdzislaw Swiderski and Vasyl Tkach (Warsaw, Poland and Kiev,
Ukraine)
Types of vitellocytes and vitellogenesis in the Cestoda in relation to
different types of embryonic development, ovoviviparity and life
cycles - Zdzislaw Swiderski and Willi E. R. Xylander (Warsaw,
Poland and Gorlitz, Germany)
A study of egg assembly in the monogenean (plathyhelminth) fish skin
parasite, Entobdella soleae, using a fast preservation technique
and transmission electron microscopy - Tracy Tappenden and Graham
Kearn (Norwich, U.K.)
Late stages of egg morphogenesis and ultrastructure of infective eggs in
the cestode Staphylocystoides stefanskii (Cyclophyllidea,
Hymenolepididae) - Vasyl Tkach and Zdzislaw Swiderski (Kiev,
Ukraine and Warsaw, Poland)
Larval biology of Gyrocotylidea and Amphilinidea and the evolution of
Cestoda - Willi E. R. Xylander (Gorlitz, Germany)