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1

Proctocaecum blairi sp. nov. [Digenea, Cryptogonimidae] from the freshwater crocodile, Crocodylus johnstoni, in Northern Territory, Australia

100%
Tkach V. V., Snyder S. D.
Acta Parasitologica
|
2010
|
tom 55
|
nr 3
240-244
Proctocaecum blairi sp. nov. is described from specimens found in the intestine of an Australian freshwater crocodile, Crocodylus johnstoni, from Northern Territory, Australia. The most important diagnostic features of the new species are the body proportions and size, the position of the pharynx (relative length of the prepharynx and oesophagus), the relative length and position of the vitelline fields, and the number, shape and size of the circumoral spines. The new species is morphologically most similar to Proctocaecum atae, P. elongatum, P. crocodili, P. gairhei and Acanthostomum slusarskii. It differs from all of these species in having a much longer prepharynx, and differs from both P. atae and P. crocodili in having a much longer body and posteriorly situated vitelline fields. Proctocaecum blairi sp. nov. differs from P. elongatum in having a shorter body, a greater forebody to hindbody ratio, a much smaller ventral sucker, and a higher number of circumoral spines (23 vs 21 in P. elongatum). The new species differs from P. gairhei in possessing a much larger body length:width ratio and an ovary separated from the anterior testis by a seminal receptacle. Acanthostomum slusarskii lacks a gonotyl and has fewer circumoral spines than the new species. Proctocaecum blairi sp. nov. is the third species of Proctocaecum and the fourth cryptogonimid species known from crocodiles in Australia.
2

Description and phylogenetic relationships of Pojmanskatrema balcanica n. gen., n. sp. (Digenea: Dicrocoeliidae) from the Eurasian water shrew Neomys fodiens (Mammalia: Soricidae) in Bulgaria

100%
Hildebrand J., Tkach V. V.
Acta Parasitologica
|
2019
|
tom 64
|
nr 2
3
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Molecular systematic study of Neascus-type metacercariae (Diginea, Diplostomidae) in gynogenetic and sexual fish across a complex landscape

100%
Tkach V. V., Schlosser L. M.
Wiadomości Parazytologiczne. Suplement
|
2004
|
tom 50
4

Two new species of Hymenolepis (Cestoda: Hymenolepididae) from Spalacidae and Muridae (Rodentia) from Eastern Palearctic

100%
Makarikov A. A., Tkach V. V.
Acta Parasitologica
|
2013
|
tom 58
|
nr 1
Previously unrecognized species of the genus Hymenolepis are described based on specimens from spalacid and murid (Murinae) rodents. Hymenolepis rymzhanovi sp. nov. from the Siberian zokor, Myospalax myospalax (Laxmann), from East Kazakhstan, and H. apodemi sp. nov. from Eurasian field mice, Apodemus peninsulae (Thomas), A. uralensis (Pallas) and A. agrarius (Pallas), from the south of Russian Far East, western Siberia and south-eastern Kazakhstan are characterized. The new species differ from other species of the genus by the morphology of the scolex, the relative position and length of the cirrus-sac and the relative position and arrangement of the testes. Differential criteria of species of Hymenolepis (sensu stricto) are also discussed.
5

Alloglossidium fonti sp. nov. (Digenea, Macroderoididae) from black bullheads in Minnesota with molecular differentiation from congeners and resurrection of Alloglossidium kenti

100%
Tkach V. V., Mills A. M.
Acta Parasitologica
|
2011
|
tom 56
|
nr 2
Alloglossidium fonti sp. nov. is described based on specimens from black bullheads (Ameiurus melas) collected from several localities in northwestern Minnesota. The new species is morphologically closest to A. corti and A. geminum. These two species were also found in the same region as A. fonti sp. nov. and sometimes in the same individual fish. Examination of numerous genetically marked specimens has demonstrated that the most reliable distinguishing feature among the three species is the position of anterior margin of the vitelline fields. In the new species they are situated at the level of anterior margin of ventral sucker while in A. corti it is at the level of intestinal bifurcation or even further anteriorly, and in A. geminum it is at the level of posterior margin of ventral sucker or further posteriorly. The new species has a relatively smaller cirrus sac than A. geminum. Despite rather minor, albeit stable morphological differences, the molecular data strongly supported the status of A. fonti sp. nov. as a new species. Moreover, molecular data and morphological examination of new material suggested that A. kenti, earlier synonymized with A. corti, is a valid species that is resurrected here. Comparison of 2420 base long sequences of nuclear rDNA (partial 18S, complete ITS region, and partial 28S) obtained from multiple specimens of all 4 species collected in Minnesota, North Dakota, Nebraska and Mississippi, showed essentially no intraspecific variability (except for 1 base difference in the ITS2 region of A. fonti sp. nov.), but has demonstrated pronounced interspecific differences. The new species was not found in the four examined catfish species from the Red River of the North (on the border between North Dakota and Minnesota) and neighbouring North Dakota.
6
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Fine structure of the infective eggs of the dilepidid cestode Hepatocestus hepaticus [Baer, 1932], a parasite of shrew

100%
Swiderski Z., Tkach V. V.
Wiadomości Parazytologiczne
|
1998
|
tom 44
|
nr 3
7

Notocotylus fosteri sp.nov. [Trematoda, Notocotylidae] from the rice rat, Oryzomys palustris in Florida

100%
Kinsella J. M., Tkach V. V.
Acta Parasitologica
|
2005
|
tom 50
|
nr 3
Notocotylus fosteri sp. nov. (Trematoda, Notocotylidae) is described from the caecum of the rice rat, Oryzomys palustris, from a salt marsh on Waccasassa Bay, Florida, U.S.A. The new species differs from previously described Notocotylus species principally in the extreme prebifurcal position of the genital pore, which overlies the posterior margin of the oral sucker, but also by the number of ventral papillae (10-13/row), and the length of the metraterm relative to the cirrus sac (89%). This is only the second species of this genus found in North American mammals.
8
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Late stages of egg morphogenesis and ultrastructure of infective eggs in the cestode Staphylocystoides stefanskii [Cyclophyllidea, Hymenolepididae]

100%
Tkach V. V., Swiderski Z.
Wiadomości Parazytologiczne
|
1998
|
tom 44
|
nr 3
9

Choanocotyle platti sp.nov. from the Northern long-necked turtle, Chelodina rugosa [Pleurodira, Chelidae] in Australia

100%
Tkach V. V., Snyder S. D.
Acta Parasitologica
|
2007
|
tom 52
|
nr 4
Choanocotyle platti sp. nov. (Digenea, Choanocotylidae) is described from the northern long-necked turtle, Chelodina rugosa (Pleurodira, Chelidae) from the Daly and Mary Rivers, Northern Territory, Australia. This is the fifth known member of Choanocotyle. Choanocotyle platti sp. nov. differs from Choanocotyle nematoides Jue Sue et Platt, 1998 and Choanocotyle hobbsi Platt et Tkach, 2003 by smaller body length, larger oral sucker, relatively greater distance between tests, and prepharynx with an infolded posterior region. In addition the new species does not have the looped cirrus sac characteristic of Choanocotyle nematoides. Comparison of sequences of 18S, ITS (ITS1, 5.8S, ITS2) and partial 28S regions of nuclear rDNA among all 3 species strongly supports the status of Choanocotyle platti sp. nov. as a new species.
10

Late stages of egg maturation in the cestode Pseudhymenolepis redonica Joyeux et Baer, 1935 [Cyclophyllidea, Hymenolepididae], a parasite of shrews

100%
Tkach V. V., Swiderski Z.
Acta Parasitologica
|
1997
|
tom 42
|
nr 2
Ultrastructural characteristics of developing eggs in the late preoncospheral and oncospheral stage and that of the uterine capsules in the hymenolepidid cestode, Pseudhymenolepis redonica Joyeux et Baer, 1935, are described. The uterus in this species breaks down very early into uniovular capsules. The uterine wall consisted of a syncytial flat uterine epithelium separated from the medullary parenchyma by a thin extracellular basal matrix. The uterine epithelium contained elongated nuclei with prominent nucleoli in the juxtalumenal cytoplasm. Its apical plasma membrane was folded into long microlamellae. The differentiating and mature oncosphere were surrounded by three envelopes: (1) an outer envelope, still containing the nuclei in the preoncospheral stage; (2) an inner envelope consisting of three layers - an extraembryophoral cytoplasmic layer, a thin and discontinuous embryophore, and intraembryophoral cytoplasmic layer; (3) a thin oncospheral membrane, closely surrounding the oncosphere. The relative thickness of the extraembryophoral and intraembryophoral layers of the inner envelope was changing during egg maturation. The numerous small mitochondria which were initially present only in the intraembryophoral layer, were concentrated later in the extraembryophoral layer and in many cases were observed in the embryophoral pores. The above data may suggest that these cytoplasmic organelles are pushed through the embryophoral pores as a result of the pressure of the developing oncosphere. The oncosphere surface was covered by the cytoplasmic oncospheral tegument, basal lamina and a layer of subtegumental somatic muscles. Several cell types were distinguished in the differentiating and mature oncospheres, namely: the germinative cells; somatic cells (= myocytons of somatic and hook muscles); the bi-lobed penetration gland with its secretory granules; the “neurosecretory” cells with their characteristic dense-cored membrane-bound vesicles. Each oncosphere had three pairs of embryonic hooks: one median, one dorso-lateral and one ventro-lateral pair. The degenerating hook-forming cells or oncoblasts remained visible around the hook handles. The details of the ultrastructure of the uterine capsules, oncospheral envelopes and different cell types of differentiating and mature oncospheres of P. redonica are discussed in comparison with literature data on other hymenolepidids, parasites of mammals and birds.
11

Drepanidotaenia czaplinskii sp.n. [Cyclophyllidea, Hymenolepididae] a new cestode from Netta rufina [Pall.] [Anseriformes, Anatidae]

100%
Kornyushin V. V., Tkach V. V.
Acta Parasitologica
|
1995
|
tom 40
|
nr 3
New species Drepanidotaenia czaplinskii sp. n. from Netta rufina (Pall.) (Anatidae) is described and figured. The new species differs from the type species of the genus, D. lanceolata, by longer rostellar hooks (0.055-0.060 in D. czaplinskii vs. 0.030-0.037 in D. lanceolata) and a relatively shorter hook blade, in cirrus size and shape, in cirrus sac size and length of vagina. The narrow interpretation of generic diagnosis of Drepanidotaenia (Spassky and Spasskaya 1954) is supported and only two valid species (D. lanceolata, D. czaplinskii) are recognized in this genus.
12

Electron microscopical studies on the cellular organisation of the oncospheres of the hymenolepidid cestode, Staphylocystoides stefanskii [Zarnowski, 1954]

100%
Swiderski Z., Tkach V. V.
Acta Parasitologica
|
1999
|
tom 44
|
nr 1
The cellular organisation of the oncospheres of S. stefanskii has been examined by means of light and transmission electron microscopy. The reconstruction of hexacanth larvae was based on serial semithin sections and its results have been correlated with partial reconstruction from ultrathin sections. The surface of the oncospheres was covered by a thin layer of oncospheral tegument. Five major cell types have been distinguished in mature oncospheres of S. stefanskii: (1) about 10 germinative cells, situated in the posterior pole of the oncosphere; (2) about 36 somatic cells (= myocytons of somatic and hook muscles); (3) a bi-nucleate medullary centre representing a perikaryon of oncospheral tegument; (4) a bi-nucleate, U-shaped penetration gland and (5) two nerve cells containing characteristic dense-core vesicles. The total number of cells in mature oncospheres was thus about 50, while the number of nuclei was about 52. The hook-muscle system of oncospheres, composed of peripheral and hook muscles, is similar to that described in other cyclophyllideans. The oncospheral hooks were formed in specialised hook-forming cells or oncoblasts. The oncoblasts are retained in mature oncospheres only as a thin layer of anucleated cytoplasm around the hook handle region, which seems to be a common feature for the mammalian hymenolepidids. The data on the oncospheral cell types and their number are in agreement with formerly proposed hypothesis (Swiderski 1972, 1983), assuming that the progressive reduction in number of oncospheral cells is one of the characteristic features in cestode evolution.
13

Differentiation and ultrastructure of the oncospheral envelopes in the hymenolepidid cestode Staphylocystoides stefanskii [Zarnowski, 1954]

100%
Tkach V. V., Swiderski Z.
Acta Parasitologica
|
1998
|
tom 43
|
nr 4
Ultrastructure of the oncospheral envelopes in developing and fully formed eggs of the hymenolepidid cestode, Staphylocystoides stefanskii (Zarnowski, 1954), is described. The uterus in this species is saccular, with deep infoldings of the uterine wall which form pocket-like structures. The uterine wall is composed by a flat syncytial uterine epithelium containing elongated nuclei with prominent nucleoli. The differentiating and mature oncospheres are surrounded by three envelopes: (1) an outer envelope; (2) an inner envelope consisting of three layers - an extraembryophoral cytoplasmic layer, a dense and relatively thick embryophore, and an intraembryophoral cytoplasmic layer; (3) a thin oncospheral membrane, surrounding the oncosphere. The outer envelope usually contains 2 nuclei in the preoncospheral stage, however, no nuclei were observed in this layer in the fully formed eggs. The inner envelope shows in sectioned material 1-2 nuclei in its intraembryophoral layer. The extraembryophoral layer of the inner envelope increases in thickness during the egg maturation. The embryophore was initially discontinuous, formed by the blocks of the electron-dense substance, and situated directly under the outer limiting membrane of the inner envelope. Later the neighbouring blocks fuse together and finally produce a continuous dense layer of embryophore. The embryophore remains slightly vacuolised for some time and finally forms a thick homogeneously electron-dense layer. The oncospheral membrane appears striated on the high-power micrographs. The ultrastructure of oncospheral envelopes in S. stefanskii is compared with those in other mammalian hymenolepidids.
14

Ultrastructure of embryonic development of Inermicapsifer madagascariensis [Cestoda, Anoplocephalidae] with emphasis on the cellular organisation of the infective eggs

100%
Swiderski Z., Tkach V. V.
Acta Parasitologica
|
2002
|
tom 47
|
nr 2
The cellular organisation of the infective eggs of I. madagascariensis has been reconstructed at light (LM) and electron microscopy (EM) level from serial semithin (LM) and ultrathin sections (EM). The oncospheres are surrounded by parenchymatic capsules. The total number of oncospheral cells' is about 44 (50 nuclei). Among them, five major cell types have been distinguished. These consisted of: (1) a six-nucleate, U-shaped penetration gland; (2) a bi-nucleate medullary centre (= sunken perikaryon of oncospheral tegument); (3) two nerve cells of neurosecretory type; (4) about 30 somatic cells (= myocytons of hook and somatic musculature); and (5) about 12 germinative cells (two groups of 6 cells), localised in the posterior pole of the hexacanth. The functional ultrastructure of hook-muscle system and penetration gland and their role in host tissue penetration are discussed.
15

Ultrastructural studies on the cellular organisation of the oncospheres of the nematotaeniid cestode, Nematotaenia dispar [Goeze, 1782]

100%
Swiderski Z., Tkach V. V.
Acta Parasitologica
|
1997
|
tom 42
|
nr 3
A complete reconstruction of the constituents of the mature egg of N. dispar has been attempted at the light microscope level based on serial semithin sections, and results have been correlated with partial reconstruction from ultrathin sections. The outer coat of the oncosphere consists of an anucleate cytoplasmic layer of tegument, a basal lamina, and two layers of peripheral, somatic musculature. The oncospheral hooks and their associated muscle system, situated in the anterior pole of the larvae, together with penetration gland secretion appear to play an important role in host tissue penetration. The bases of each lateral hook pair are joined by a common zone of “connective” material whereas the medial hook bases are embedded in individual cups of this material. Five major types of oncospheral cells have been distinguished. These consisted of: (1) a bi-nucleate medullary centre (= subtegumental cell); (2) a bi-nucleate, U-shaped penetration gland; (3) two nerve cells of neurosecretory type; (4) about 34 somatic cells (= cell bodies of somatic and hook muscles); and (5) about 12 germinative cells, arranged in two groups of six cells, situated in the posterior pole of the hexacanth. The position of oncospheral structures remains fixed in relation to one another but at the same time is somewhat arbitrary due to the high plasticity of the hexacanth during movements.
16

Rhabdias mcguirei sp. nov. (Nematoda, Rhabdiasidae) from the flying lizard, Draco spilopterus (Squamata, Agamidae) of the Northern Philippines

81%
Tkach V. V., Kuzmin Y., Brown R. M.
Acta Parasitologica
|
2011
|
tom 56
|
nr 4
Rhabdias mcguirei sp. nov., is described on the basis of specimens found in the lungs of northern Philippine flying lizards, Draco spilopterus (Reptilia, Agamidae) collected in Aurora province, Luzon Island, Philippines. It is characterized by a rounded oral opening, a buccal capsule consisting of anterior and posterior parts, and the shape of the cuticular inflation in the anterior part of the body: the cuticle is less inflated in the anterior-most part, with the inflation gradually thickening up to the level of the oesophageal-intestinal junction. The new species is differentiated from the 11 most closely related species of Rhabdias previously known from lizards.
17

Alloglossidium demshini sp. nov. (Digenea: Macroderoididae) from leeches in Minnesota

81%
Tkach V. V., Greiman S. E., Steffes K. R.
Acta Parasitologica
|
2013
|
tom 58
|
nr 4
Alloglossidium demshini sp. nov. is described based on specimens from leeches Haemopis grandis collected in northwestern Minnesota. The new species is morphologically closest to Alloglossidium schmidti. The two species can be readily differentiated based on several morphological characters. The cirrus sac in A. schmidti is almost entirely situated anterior to the ventral sucker while in A. demshini sp. nov. it is situated dorsal to the ventral sucker and its proximal end almost reaches the posterior end of ventral sucker or extends posterior to it. The new species has a prepharynx that is substantially longer than the esophagus while in A. schmidti the situation is the opposite. The two species also differ in the position of the ovary and the position of the testes and vitelline fields in relation to the ends of the ceca. Hirudineatrema oschmarini described from leeches in Eastern Palaearctic and Alloglossidium richardsoni described in North America demonstrate great morphological similarity. Nevertheless, Hirudineatrema cannot be synonymized with Alloglossidium at this point because of several peculiar morphological features of H. oschmarini such as a V-shaped excretory bladder and the apparent presence of a true seminal receptacle in the latter species. These features need to be re-evaluated before any taxonomic decision can be made.
18
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Content available

Some new insights into relations within superfamily Dicrocoeliidae (Digenea) based on molecular data

81%
Hildebrand J., Laskowski Z., Tkach V. V.
Annals of Parasitology
|
2016
|
tom 62
|
nr Suppl.
19

The systematic position and structure of the genus Leyogonimus Ginetsinskaya, 1948 (Platyhelminthes: Digenea) with comments on the taxonomy of the superfamily Microphalloidea Ward, 1901

81%
Kanarek G., Zalesny G., Sitko J., Tkach V. V.
Acta Parasitologica
|
2017
|
tom 62
|
nr 3
20

New genetic lineages, host associations and circulation pathways of Neorickettsia endosymbionts of digeneans

81%
Tkach V. V., Schroeder J. A., Greiman S. E., Vaughan J. A.
Acta Parasitologica
|
2012
|
tom 57
|
nr 3
Neorickettsia is a genus of intracellular bacteria endosymbiotic in digeneans that may also invade cells of vertebrates and are known to cause diseases of wildlife and humans. Herein, we report results of screening for Neorickettsia of an extensive collection of DNA extracts from adult and larval digeneans obtained from various vertebrates and mollusks in the United States. Seven isolates of Neorickettsia were detected by PCR and sequenced targeting a 527 bp long region of 16S rRNA. Sequence comparison and phylogenetic analysis demonstrated that four isolates matched published sequences of Neorickettsia risticii. Three other isolates, provisionally named “catfish agents 1 and 2” (obtained from Megalogonia ictaluri and Phyllodistomum lacustri, both parasitic in catfishes) and Neorickettsia sp. (obtained from cercariae of Diplostomum sp.), differed from previously known genotypes of Neorickettsia and are likely candidates for new species. All 7 isolates of Neorickettsia were obtained from digenean species and genera that were not previously reported as hosts of these bacteria. Members of four digenean families (Dicrocoeliidae, Heronimidae, Macroderoididae and Gorgoderidae) are reported as hosts of Neorickettsia for the first time. Our study reveals several new pathways of Neorickettsia circulation in nature. We have found for the first time a Neorickettsia from a digenean (dicrocoeliid Conspicuum icteridorum) with an entirely terrestrial life cycle. We found N. risticii in digeneans (Alloglossidium corti and Heronimus mollis) with entirely aquatic life cycles. Previously, this Neorickettsia species was known only from digeneans with aquatic/terrestrial life cycles. Our results suggest that our current knowledge of the diversity, host associations and circulation of neorickettsiae is far from satisfactory.
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