Morphological features of the testis of freshwater blood flukes of the genus Sanguinicola Plehn, 1905, with consideration of the testicular patterns in the Aporocotylidae

This is the first detailed study assessing the morphological features of the testis and testicular sperm of members of the freshwater blood flukes Sanguinicola sp. from Leuciscus idus (Cyprinidae) and for S. volgensis from Pelecus cultratus (Cyprinidae), and the marine blood fluke Aporocotyle simplex from Hippoglossoides platessoides (Pleuronectidae). The present study reports a unique feature in the distribution of germinal cellular components in freshwater Sanguinicola sp., showing the presence of the individual spermatocytes or their clusters in the testicular lobes, and the gathering of spermatid rosettes and spermatozoa within middle testicular lumen, which extends along the entire length of the testis. In contrast, each testis of marine A. simplex contains the usual mixed distribution of germ cells at various stages of development. The first TEM data on spermatozoon character of studied species has shown, unusual for digenean sperm structure, the absence of cortical microtubules in sperm principal region. Moreover, a variation in axoneme patterns is revealed in the studied aporocotylids, belonging to the different aporocotylid lineages a 9 + 0 axonemal type observed for freshwater teleost-infective species, Sanguinicola sp. and S. volgensis, and a 9 + ‘1’ axonemal type revealed in spermatozoa of marine teleost-infective species A. simplex. The results discussed with the published data on the digenean sperm structure and the testicular patterns in the Aporocotylidae likely represent additional characteristics supporting the divergent evolutionary lineages of freshwater and marine aporocotylids. We anticipate future morphological studies of the sperm structure in aporocotylids of three lineages for an understanding of their phylogenetic relationships

Diversity and Phylogenetic Relationships of European Species of \u3ci\u3eCrepidostomum\u3c/i\u3e Braun, 1900 (Trematoda: Allocreadiidae) Based on rDNA, with Special Reference to \u3ci\u3eCrepidostomum oschmarini\u3c/i\u3e Zhokhov & Pugacheva, 1998

Background Within the genus Crepidostomum Braun, 1900, identification of species and taxonomic decisions made only on the basis of adult morphology have resulted in great problems associated with evaluating actual diversity and validity of species. Life cycle data, while equal in importance to adult characters, are scarce, controversial or incomplete for most Crepidostomum spp. In this study, rDNA sequences generated from adult and larval Crepidostomum spp. and some other allocreadiid species were analyzed to reveal the diversity and phylogenetic relationships of the species and their host range. Detailed morphological description based on light microscopy, SEM tegumental surface topography and genetic data are provided for the poorly known trematode C. oschmarini Zhokhov & Pugacheva, 1998 found in the intestine of two teleost fish species, Barbatula barbatula (L.) and Cottus gobio L. Results We characterized 27 isolates of adult and larval parasites. Based on newly obtained 28S and ITS1-5.8S-ITS2 rDNA sequences, new intermediate and final hosts were ascertained, and life cycles clarified for some allocreadiids. New knowledge on the diversity and phylogenetic relationships of European Crepidostomum spp. was gained. The validity of C. oschmarini was verified based on comparative sequence analysis. Ophthalmoxiphidiocercariae of C. oschmarini were recorded in sphaeriid bivalves Pisidium (Euglesa) casertanum (Poli). Additionally, morphological differences between gravid specimens of C. oschmarini and other related species were observed. Conclusions Species of the Allocreadiidae parasitizing fishes in Europe are distributed among two monophyletic genera, Allocreadium and Bunodera, and two paraphyletic Crepidostomum clades. A complex of Crepidostomum metoecus (syn. C. nemachilus), C. oschmarini and Crepidostomum sp. 2 clustered in one clade, and a complex of C. farionis, Crepidostomum sp. 1 and, probably, C. wikgreni in the other. Molecular data indicated that C. oschmarini and Crepidostomum sp. 2 presumably have a wide geographical distribution in Europe. The new data provided evidence that Crepidostomum is a more diverse genus than can be judged from morphological data and host switching in this genus may occur independently of fish-host phylogen

Ultrastructural evidence for completion of the entire miracidial maturation in intrauterine eggs of the digenean Brandesia turgida (Brandes, 1888) (Plagiorchiida: Pleurogenidae)

Results of this TEM study provide ultrastructural evidence that miracidial morphogenesis is fully completed within the intrauterine eggs situated in the most posterior uterine regions of the pleurogenid trematode Brandesia turgida (Brandes, 1888). The ultrastructural characteristic of different larval organelles and cell types of these eggshell-enclosed, but fully formed, cilated miracidia is described. The body wall of the pyriform mature miracidium of B. turgida is composed of ciliated epidermis and underlying peripheral body musculature. Two miracidial flame cells of the protonephridial excretory system are localized in the central region of the ciliated larvae. Three types of miracidial glands were observed: a single apical gland, two lateral glands, and several small vesiculated glands; each gland type contains characteristic, but different types of secretory granules. The anterior end of each miracidium consists of an apical papilla on which are situated the exits of the three main larval glands: an exit of a single apical gland as well as the individual exits of two lateral glands. The exits of vesiculated glands, containing characteristic spherical membrane-bound and highly electron-dense granules, evidently different from the two other types of secretory granules of apical and lateral glands, were not identified. Germinative cells, grouped together in a sac-like germinative follicle, are situated in the medioposterior part of the larva, the germatophore. The germinative cells contain numerous electron-dense heterochromatin islands arranged in the form of a network or chain-like pattern and distributed mainly in the karyoplasm adjacent to the nuclear membrane. The thin layer of granular cytoplasm is rich in free ribosomes and contains a few small mitochondria. Both nuclear and cytoplasmic features if these cells indicate their great developmental potential for further growth and multiplication in postembryonic stages of the life cycle. In the mature eggs, the areas of focal cytoplasmic degradation were frequently observed and may be involved in the autolysis of some embryonic structures. Obtained results are compared with available literature data on the functional ultrastructure of the miracidia of other digeneans

Ultrastructural evidence for completion of the entire miracidial maturation in intrauterine eggs of the digenean Brandesia turgida (Brandes, 1888) (Plagiorchiida: Pleurogenidae)

Results of this TEM study provide ultrastructural evidence that miracidial morphogenesis is fully completed within the intrauterine eggs situated in the most posterior uterine regions of the pleurogenid trematode Brandesia turgida (Brandes, 1888). The ultrastructural characteristic of different larval organelles and cell types of these eggshell-enclosed, but fully formed, cilated miracidia is described. The body wall of the pyriform mature miracidium of B. turgida is composed of ciliated epidermis and underlying peripheral body musculature. Two miracidial flame cells of the protonephridial excretory system are localized in the central region of the ciliated larvae. Three types of miracidial glands were observed: a single apical gland, two lateral glands, and several small vesiculated glands; each gland type contains characteristic, but different types of secretory granules. The anterior end of each miracidium consists of an apical papilla on which are situated the exits of the three main larval glands: an exit of a single apical gland as well as the individual exits of two lateral glands. The exits of vesiculated glands, containing characteristic spherical membrane-bound and highly electron-dense granules, evidently different from the two other types of secretory granules of apical and lateral glands, were not identified. Germinative cells, grouped together in a sac-like germinative follicle, are situated in the medioposterior part of the larva, the germatophore. The germinative cells contain numerous electron-dense heterochromatin islands arranged in the form of a network or chain-like pattern and distributed mainly in the karyoplasm adjacent to the nuclear membrane. The thin layer of granular cytoplasm is rich in free ribosomes and contains a few small mitochondria. Both nuclear and cytoplasmic features if these cells indicate their great developmental potential for further growth and multiplication in postembryonic stages of the life cycle. In the mature eggs, the areas of focal cytoplasmic degradation were frequently observed and may be involved in the autolysis of some embryonic structures. Obtained results are compared with available literature data on the functional ultrastructure of the miracidia of other digeneans

Ultrastructure of the intrauterine eggs of Didymobothrium rudolphii (Monticelli, 1890) (Cestoda, Spathebothriidea, Acrobothriidae) and its phylogenetic implications

DOI: 10.2478/s11686-010-0037-zThe intrauterine polylecithal eggs of the spathebothriidean cestode Didymobothrium rudolphii (Monticelli, 1890) were examined by means of transmission electron microscopy (TEM). Each unembryonated egg is composed of a fertilised oocyte or ovum and several vitelline cells, all surrounded by a newly formed shell. The lumen of the proximal uterus is packed with unutilised vitelline material and eggs at different stages of shell formation. In the proximal region of the uterus, the fertilised oocytes, initially surrounded by dense, discontinuous islands of eggshell material and containing long axonemes of spermatozoa in their cytoplasm, were frequently observed. Sperm axonemes also remain in the oocyte cytoplasm of eggs surrounded by a thick electron-dense shell until the sperm nucleus is transformed into a male pronucleus. Despite the fact that the two-pronuclei stage and cell divisions within the eggs of D. rudolphii were never observed, individual eggs containing several blastomeres of different sizes were seen in the middle and distal regions of the uterus. This provides indirect evidence that at least a few initial cleavage divisions must take place in the intrauterine eggs and direct evidence that the early embryonic development of D. rudolphii starts in utero. The several vitellocytes present in each egg contain nutritive reserves for the developing embryos; these are composed mainly of numerous lipid droplets and a moderate amount of glycogen. In the eggs containing early embryos composed of several blastomeres, the cytoplasm of the degenerating vitellocytes exhibits the presence of so-called 'foci of cytoplasmic degradation', which appear to be involved in the autolytic process of the vitellocyte cell components and inclusions, such as a high accumulation of lipids and glycogen. This progressive degeneration of the vitellocytes, considered as an example of programmed cell death or apoptosis, likely contributes towards the resorption of nutritive reserves by the developing embryo. Some of the results of this study are commented upon in relation to the affiliation of the spathebothriideans with other lower cestode groups

Trophic diversification and parasitic invasion as ecological niche modulators for gut microbiota of whitefish

Introduction: The impact of parasites on gut microbiota of the host is well documented, but the role of the relationship between the parasite and the host in the formation of the microbiota is poorly understood. This study has focused on the influence that trophic behavior and resulting parasitism has on the structure of the microbiome. Methods: Using 16S amplicon sequencing and newly developed methodological approaches, we characterize the gut microbiota of the sympatric pair of whitefish Coregonus lavaretus complex and the associated microbiota of cestodes parasitizing their intestine. The essence of the proposed approaches is, firstly, to use the method of successive washes of the microbiota from the cestode’s surfaces to analyze the degree of bacterial association to the tegument of the parasite. Secondly, to use a method combining the sampling of intestinal content and mucosa with the washout procedure from the mucosa to understand the real structure of the fish gut microbiota. Results and discussion: Our results demonstrate that additional microbial community in the intestine are formed by the parasitic helminths that caused the restructuring of the microbiota in infected fish compared to those uninfected. Using the desorption method in Ringer’s solution, we have demonstrated that Proteocephalus sp. cestodes possess their own microbial community which is put together from “surface” bacteria, and bacteria which are weakly and strongly associated with the tegument, bacteria obtained after treatment of the tegument with detergent, and bacteria obtained after removal of the tegument from the cestodes.info:eu-repo/semantics/publishedVersio

Trophic diversification and parasitic invasion as ecological niche modulators for gut microbiota of whitefish

Introduction: The impact of parasites on gut microbiota of the host is well documented, but the role of the relationship between the parasite and the host in the formation of the microbiota is poorly understood. This study has focused on the influence that trophic behavior and resulting parasitism has on the structure of the microbiome. Methods: Using 16S amplicon sequencing and newly developed methodological approaches, we characterize the gut microbiota of the sympatric pair of whitefish Coregonus lavaretus complex and the associated microbiota of cestodes parasitizing their intestine. The essence of the proposed approaches is, firstly, to use the method of successive washes of the microbiota from the cestode’s surfaces to analyze the degree of bacterial association to the tegument of the parasite. Secondly, to use a method combining the sampling of intestinal content and mucosa with the washout procedure from the mucosa to understand the real structure of the fish gut microbiota. Results and discussion: Our results demonstrate that additional microbial community in the intestine are formed by the parasitic helminths that caused the restructuring of the microbiota in infected fish compared to those uninfected. Using the desorption method in Ringer’s solution, we have demonstrated that Proteocephalus sp. cestodes possess their own microbial community which is put together from “surface” bacteria, and bacteria which are weakly and strongly associated with the tegument, bacteria obtained after treatment of the tegument with detergent, and bacteria obtained after removal of the tegument from the cestodes

Comparative analysis of the cytoarchitecture of the excretory bladder of adult Digenea (Platyhelminthes) with consideration of the presence of mineralized excretory corpuscles in marine and freshwater adult worms

The ultrastructural differences are shown between the cytoarchitecture of the excretory bladder and excretory inclusions in four digenean species, two azygiids, the marine Otodistomum cestoides and the freshwater Azygia lucii, the marine derogenid Derogenes varicus and the freshwater allocreadiid Acrolichanus auriculatus. The unusual cytoarchitecture of the bladder epithelium of the azygiid digeneans, consisting along its entire length of two alternating, morphologically different zones, tegumental and cellular excretory epithelial zones, connected by septate junctions, has recorded for the first time for the Digenea and, in general, for the Neodermata. It, possible, suggests the participation of the tegumental distal cytoplasmic layer in the formation of their excretory bladder epithelium. Like most digeneans, the excretory bladder of A. auriculatus and D. varicus has a syncytial epithelial lining. Based on available literature and our own results, we can confirm the presence of the excretory corpuscles in adult marine digeneans and their absence from freshwater species, regardless of the digenean localization in their host. The present study shown that in marine digeneans, the excretory corpuscles are associated with specialized excretory cells or excretory syncytial epithelium. Ultrastructural data were obtained on the possible growth of the excretory bladder epithelium due to the migration of undifferentiated cells into the epithelial lining in studied marine species. We may assume that the bladder epithelium of marine adult digeneans specializes, in addition to the excretory function, in osmoregulatory function

Spermiogenesis and spermatozoon ultrastructure in basal polyopisthocotylean monogeneans, Hexabothriidae and Chimaericolidae, and their significance for the phylogeny of the Monogenea

Sperm ultrastructure provides morphological characters useful for understanding phylogeny; no study was available for two basal branches of the Polyopisthocotylea, the Chimaericolidea and Diclybothriidea. We describe here spermiogenesis and sperm in Chimaericola leptogaster (Chimaericolidae) and Rajonchocotyle emarginata (Hexabothriidae), and sperm in Callorhynchocotyle callorhynchi (Hexabothriidae). Spermiogenesis in C. leptogaster and R. emarginata shows the usual pattern of most Polyopisthocotylea with typical zones of differentiation and proximo-distal fusion of the flagella. In all three species, the structure of the spermatozoon is biflagellate, with two incorporated trepaxonematan 9 + “1” axonemes and a posterior nucleus. However, unexpected structures were also seen. An alleged synapomorphy of the Polyopisthocotylea is the presence of a continuous row of longitudinal microtubules in the nuclear region. The sperm of C. leptogaster has a posterior part with a single axoneme, and the part with the nucleus is devoid of the continuous row of microtubules. The spermatozoon of R. emarginata has an anterior region with membrane ornamentation, and posterior lateral microtubules are absent. The spermatozoon of C. callorhynchi has transverse sections with only dorsal and ventral microtubules, and its posterior part shows flat sections containing a single axoneme and the nucleus. These findings have important implications for phylogeny and for the definition of synapomorphies in the Neodermata. We point out a series of discrepancies between actual data and interpretation of character states in the matrix of a phylogeny of the Monogenea. Our main conclusion is that the synapomorphy “lateral microtubules in the principal region of the spermatozoon” does not define the Polyopisthocotylea but is restricted to the Mazocraeidea

Aporocotyle simplex

<i>3.2. The anterior esophagus of A. simplex</i> <p>The long unbranched esophagus leads directly from the muscular anterior foregut (Fig. 1D, G and 2A). The esophageal epithelial lining is a prolongation of the anterior foregut epithelium with sunken cell bodies (Fig. 2C). The epithelial syncytial lining of the short anterior esophageal portion projects its cytoplasm into the lumen, possessing luminal irregular, broad and angular cytoplasmic protrusions variable in shape and size (Fig. 2B, C, E). Due to these cytoplasmic protrusions, the esophageal cytoplasmic lining varies in thickness from 0.2 to 6.5 μm and contains a number of electron-dense bodies, which are similar to those that fill the body syncytial tegumental cytoplasm and anterior foregut epithelium (Fig. 2B, C, E). Besides tegumental dense bodies, numerous rounded vesicles (about 0.2–0.3 μm in diameter), with moderately dense content or empty-looking, fill the cytoplasmic matrix (Fig. 2B, C, E). These vesicles may liberate their contents into the esophageal lumen (Fig. 2B, C, E). An extensive system of regularly arranged tubular structures is present in the moderately dense cytoplasm of the esophageal lining (Fig. 2E). The luminal surface of the epithelial lining is smooth, the basal plasma membrane is surrounded by a thin electron-dense basal lamina and a thick layer of extracellular matrix, below which are thick bands of circular and longitudinal myofibrils (Fig. 2B and C). Sunken cell body processes connect to the epithelial lining and open into the epithelial cytoplasm (Fig. 2C). The distal portion of these processes contains numerous longitudinally oriented microtubules and electron-dense bodies in their cytoplasmic matrix (Fig. 2C). Electron-dense membranous whorls may be present within the anterior foregut as well as within the anterior esophageal lumen (Fig. 2B).</p>Published as part of <i>Poddubnaya, Larisa G., Hemmingsen, Willy & MacKenzie, Ken, 2023, Digestive system of the marine blood fluke, Aporocotyle simplex (Odhner, 1900) (Digenea: Aporocotylidae) with consideration of the digenean digestive morphology, pp. 11-22 in Zoologischer Anzeiger 305</i> on page 12, DOI: 10.1016/j.jcz.2023.05.003, <a href="http://zenodo.org/record/10376067">http://zenodo.org/record/10376067</a&gt