Holdfast Organ Research Articles

Variability and phenotypic diversity of the Diplostomum Petromyzifluviatilis Diesing, 1850 trematodes, parasites of lampreys (Lampetrinae, Petromyzontidae)

Variability and phenotypic diversity of Diplostomum petromyzifluviatilis metacercariae from two lamprey species, the river lamprey Lampetra fluviatilis (Baltic Sea basin) and the Pacific lamprey Lethenteron camtschaticum (Arctic Ocean basin), were studied. It was found that metacercariae from both hosts are similar as in the number of variations in body shape, oral and ventral suckers, and pharynx, so in the frequency of occurrence. Differences in population diversity by variations in the shape of the Holdfast organ were found. It was shown that gostal forms possess the similar range of variability of plastic characters, but has different distribution of frequency classes of the variation curve. We hypothesized that the change in the distribution and character of variation in the size of metacercariae from the Arctic lamprey is one of the population mechanisms of species adaptation to the northern limit of its range.

Ferramentas de identificação do Diplostomum spathaceum Rudolphi, 1819 (Diplostomida: Diplostomidae), um trematódeo parasita da gaivota de arenque (Larus argentatus)

ABSTRACT Specimens of the genus Diplostomum von Nordmann, 1832 (Trematoda, Diplostomidae) were collected from the intestine of the herring gull, Larus argentatus (Laridae), from El-Manzala Lake (Port Said City, Egypt). This parasite species was morphometrically, morphologically, and molecularly studied using the internal transcribed spacer (ITS1-5.8S-ITS2) gene region. The presence of a trematode species of Diplostomum spathaceum Rudolphi, 1819 (Diplostomidae) was observed in 70 % of the examined gull species. This species has generic features of the genus Diplostomum. Distinct criteria that discriminated this species from congeners were the division for body parts, the egg-shaped forebody with a smaller length than the hind body, the ventral sucker being smaller in size than the oral one, the position of the ventral sucker being near to the holdfast, vitellaria was compact and rarely extend anteriorly to the holdfast organ, and smaller egg size. Partial ITS1-5.8S-ITS2 sequences from diplosomite recovered in this study showed that they grouped with members of the genus Diplostomum and formed a monophyletic group supporting the morphological description. Findings obtained from molecular analysis are consistent with data from morphological classification where the parasite recorded was morphologically similar to Diplostomum spathaceum with a first record in Egyptian gulls.

Lophoura Kölliker in Gegenbaur, Kölliker & Müller, 1853 species (Copepoda: Siphonostomatoida: Sphyriidae) off South Africa with a key to all valid species.

Lophoura Kölliker in Gegenbaur, Kölliker & Müller, 1853 is one of the eight genera of Sphyriidae which currently consists of 19 accepted species. Lophoura species are mesoparasites of various teleosts occurring worldwide. Post metamorphic females are highly transformed with longitudinally elongated cephalothoraces and elongated necks bearing holdfast organs anteriorly. The shape and structure of the holdfast organ is mostly the main character used for the identification of species. Additionally, the structure of the posterior processes attached laterally to the perianal swelling on the posterior margin of the trunk is also used to distinguish different species. The posterior processes consist of a central porous peduncle with stalks of varying shapes and sizes. The morphology of Lophoura males bear resemblance to that of lernaeopodid males. Re-descriptions of the habitus of the post metamorphic females of L. tetraloba Ho & Kim I.H., 1989, L. cf. edwardsi Kölliker, 1853, L. caparti (Nuńes-Ruivo, 1962) and L. cornuta (Wilson C.B., 1919), including notes on the immature females of L. tetraloba and L. cf. edwardsi, are provided. Additionally, information regarding the structure and position of some of the appendages of L. tetraloba, L. cf. edwardsi and L. caparti is provided. Furthermore, the study provides the first illustrated descriptions of the male of L. tetraloba. A description is also done of an incomplete unidentied Lophoura species which differs from other accepted species. A morphological identification key to post metamorphic females of all accepted Lophoura species is provided, as well as new host and geographical records of Lophoura species.

Parasites in Imported Edible Fish and a Systematic Review of the Pathophysiology of Infection and the Potential Threat to Australian Native Aquatic Species

Previous research has shown that certain types of edible fish imported into Australia are infected with Euclinostomum/Isoparorchis digenetic trematodes. In the present study, imported Channa fish were examined for parasites which were then morphologically identified to the lowest taxonomic unit possible. Here we provide the first Australian report of Pallisentis sp. Van Cleave, 1928 (Prevalence (P) 35.9%) of family Quadrigyridae; Genarchopsis sp. Ozaki, 1925 (P. 16.5%), family Derogenidae and Senga sp. Dollfus, 1934 (P. 4.8%) in edible imported Channa fish (n = 103). Pallisentis sp. and Senga sp. have invasive hold fast organs which cause significant mechanical damage to fish intestinal structures and Euclinostomum/Isoparorchis cause severe pathology and loss of marketability in infected fish. These exotic parasites, if introduced into Australia, have the potential to negatively impact the health, fecundity, resilience and marketability of native and commercial fish species. Biosecurity is a constant ontogenesis of novel hypothesis based on current scientific discoveries. To further increase understanding of how parasitism impacts fish health, a systematic literature review was conducted and the pathophysiology of infection described. Potential exposure pathways and parasite host associations in Australia are discussed.

Alaria alata (Digenea: Diplostomidae) from Korean Raccoon Dog, Nyctereutes procyonoides koreensis, in Korea.

We report a species of diplostomid fluke recovered from 3 carcasses of wild Korean raccoon dog, Nyctereutes procyonoides koreensis, in Korea. A total of 107 diplostomid flukes were recovered from the small intestines of Korean raccoon dogs, which were obtained from the Gangwon Wildlife Medical Rescue Center. Worms fixed with 10% neutral formalin were subjected to microscopic observation and those fixed in 70% ethanol were used for molecular genomic analysis. The worm was divided into 2 separate parts, forebody and hindbody, with a total length of 3,020-4,090 (3,855) µm and a width of 1,210-1,770 (1,562) µm. The boat-shaped forebody has a pair of characteristic tentacular appendage, 2 suckers, holdfast organ, and vitelline follicles. The oval to cylindrical hindbody has reproductive organs. The ovary was round or elliptical and located in the anterior of the testes. Two large testes were slightly segmented and tandemly arranged, occupying almost half of hindbody. The short uterus contained a relatively small number of unembryonated eggs sized 130-140×85-96 µm. The partial sequence of 18S rRNA of this fluke was consistent with Alaria alata. Based on the morphological and molecular characteristics, the diplostomid flukes recovered from the small intestine of Korean raccoon dogs were identified as A. alata (Digenea: Diplostomidae).

Metacercariae in the brain of Erythrinus cf. erythrinus (Characiformes: Erythrinidae) from Iguazú National Park (Argentina): do they belong to Dolichorchis lacombeensis (Digenea, Diplostomidae)?

In Argentina, the family Diplostomidae is composed of eight genera: Austrodiplostomum Szidat & Nani; Diplostomum von Nordmann; Dolichorchis Dubois; Hysteromorpha Lutz; Neodiplostomum Railliet; Posthodiplostomum Dubois; Sphincterodiplostomum Dubois; and Tylodelphys Diesing. During a parasitological survey of fishes from the Iguazú National Park we detected diplostomid metacercariae in the brain of Erythrinus cf. erythrinus. Fish were caught using crab traps, transported alive to the field laboratory, cold-anaesthetized and euthanized by cervical dissection. Some metacercariae were heat-killed in water and fixed in 10% formalin and others were preserved in alcohol 96% for DNA extraction. They were sequenced for the partial segment of the 28S rDNA, internal transcribed spacer (ITS) rDNA and cytochrome c oxidase subunit I (COI) mtDNA genes. Phylogenetic reconstruction was carried out using Bayesian inference and the proportion (p) of absolute nucleotide sites (p-distance) was obtained. In the 28S rDNA tree, the metacercaria sequenced grouped as Dolichorchis sp. The COI mtDNA p-distance between the metacercariae with Dolichorchis lacombeensis was 0.01. There is a small number of ITS sequences for the Diplostomidae family deposited in the GenBank. The oral sucker, ventral sucker, holdfast organ and the distance between oral and ventral suckers are larger in the adult compared with the metacercariae. Additionally, hind-body length and width are larger in the adult due to the development of the genital complex. Further studies using an integrative approach will help confirm the affiliation of other species to the genus Dolichorchis.

Prevalence and Histopathological Studies on Intestinal Cestode Parasite of Avian Host Gallus Domesticus (L) From Nashik Region, Maharashtra State, India

Abstract: The lowest infection is recorded in rainy season and highest in summer season, may be due to life cycle stages and intermediate host availability increases in winter and became adult in definitive host in summer. No nematode and trematode parasite were considered and identified during the study period. Cysts were found deep in submucosa, although touches to serosa. The non-penetrative type of worms is Cotugnia sp. and Thaparea sp.; while the penetrative type of worm is Raillietina sp. and Paruterina sp. Free gravid segments mostly found in the posterior region of intestine while mature segments are freely suspended from scoleces in the lumen of intestine, only scoleces are attached, either superficially (non-penetrative type) or deep in submucosa (Penetrative type). Keywords: Cestode, histopathology, prevalence, hold-fast organs, Penetrative scolex

DESCRIPTION AND PHYLOGENETIC POSITION OF A NEW SPECIES OF HERPETODIPLOSTOMUM FROM PHRYNOPS GEOFFROANUS IN BRAZIL AND A REEVALUATION OF CHELONIODIPLOSTOMUM.

As presently recognized, Herpetodiplostomum is a small genus of proterodiplostomid digeneans parasitic in crocodilians. Most members of Cheloniodiplostomum, a genus of proterodiplostomids that parasitize chelonians, were originally placed within Herpetodiplostomum. The 2 genera were distinguished based on the presence/absence of papillae on the holdfast organ and anterior extent of vitellarium. Our study of Herpetodiplostomum and Cheloniodiplostomum revealed a lack of consistent morphological differences between the genera. Therefore, we consider Cheloniodiplostomum to be a junior synonym of Herpetodiplostomum. Recent molecular phylogenetic studies included a number of proterodiplostomid taxa; however, DNA sequence data are not available for any Herpetodiplostomum or Cheloniodiplostomum species. Herein, we describe a new Herpetodiplostomum species from Geoffroy's side-necked turtle Phrynops geoffroanus from Mato Grosso State, Brazil. The new species can be distinguished from other Herpetodiplostomum species based on the distribution of vitellarium, level of development of holdfast papillae, and ratio of prosoma:opisthosoma width, among other characters. We provide the first molecular phylogeny of the Proterodiplostomidae that includes a Herpetodiplostomum species. The limited geographic distribution of Herpetodiplostomum spp. within the geographic ranges of caimans suggests a secondary host switching event from crocodilians to chelonian definitive hosts in the evolution of Herpetodiplostomum.

Ultrastructure of the Anisakid nematode, Raphidascaroides sp (Nematoda: Anisakidae) from the freshwater fish Rhinogobius ocellatus (Fowler, 1937) with attendant histopathological alterations in Lekki Lagoon, Lagos, Nigeria

The objective of this study is to report the parasitic infections in the gobiid fish with histopathogical changes and the SEM description of the recovered parasites for possible unreported morphological details and for the purpose of control measures in the fish species. Fishes were procured, dissected and examined parasitologically. The nematode, Raphidascaroides sp was the only recovered parasite from the intestine of the gobiid fish. Fixation of the parasites was done in 2.5% glutaldehyde and were post fixed in 1% Osmium tetraoxide, sputter coated and examined with the Scanning Electron Microscope. The infected tissues were also fixed in Bouins fluid.The overall prevalence of infections was 70.7%. Male specimens of the fish species were more susceptible to infections (71.4%) than the female specimens (66.6.) The Raphidascaroides sp. ultrastructure revealed three lips with dentigerous ridges.The two ventrolateral lips measures 68.6 and 69.7 µm while the third lip has a length of 55.1 µm with corresponding breadth of 66.0 µm, 40.5 µm and 59.3 µm respectively. The histopathological alterations in the fish species revealed goblet cell hyperplasia and moderate lymphocytic infiltration of the lamina propria.The dominant and only parasite recovered from the fish host is Raphidascaroides sp, an anisakid nematode whose pathological consequences is mild owing to lack of holdfast organs in nematodes. The ultrastructural description of the parasites is the first report in Nigeria. There is a conclusion that there may be similar food and feeding habits of the fish, Rhinogobius ocellatus with Gymnarchus niloticus with a report of the same parasites in its intestinal mucosa.

Phylogenetic position of Sphincterodiplostomum Dubois, 1936 (Digenea: Diplostomoidea) with description of a second species from Pantanal, Brazil.

Sphincterodiplostomum is a monotypic genus of diplostomid digeneans that parasitize fish-eating birds in the neotropics. The type species Sphincterodiplostomum musculosum has a unique, dorsal, tubular invagination in the opisthosoma with a muscular sphincter. Whereas larvae of S. musculosum are relatively commonly reported in Neotropical fish helminth surveys, adult specimens from birds are rarely collected. Prior to our study, no DNA sequence data for S. musculosum were available. Our molecular and morphological study of mature and immature adult Sphincterodiplostomum specimens from three species of birds and one species of crocodilian revealed the presence of at least two species of Sphincterodiplostomum in the neotropics. We provide the first molecular phylogeny of the Diplostomoidea that includes Sphincterodiplostomum. In addition, this is the first record of S. musculosum from caimans, along with the first record of fully mature adult S. musculosum from green kingfisher Chloroceryle americana. The new species of Sphincterodiplostomum (Sphincterodiplostomum joaopinhoi n. sp.) can be morphologically distinguished from S. musculosum based on the anterior extent of vitelline follicles, narrower prosoma, substantially smaller holdfast organ and structure of tegumental spines. Our data revealed 0.7% interspecific divergence in 28S and 10.6-11.7% divergence in cox1 sequences between the two Sphincterodiplostomum species.

Morphological and Molecular Characterization of Apharyngostrigea pipientis Faust, 1918 (Trematoda: Diplostomidea) from Ardeacinerea jouyi, Egretta intermedia and Nycticorax nycticorax in Korea

An intestinal strigeiid trematode, Apharyngostrigea pipientis, was detected from Ardea cinerea jouyi, Egretta intermedia and Nycticorax nycticorax between July, 2006 and June, 2020 in Daejeon metropolitan city and Kangwondo, Republic of Korea. It was observed with a light and scanning electron microscope (SEM), and molecularly analyzed with 18S rRNA genes. The infection rate of the strigeiid trematode was 25.9% (7/27). The body is cylindrical in whole mount, greatly elongated in outline and shows a strong dorsal curvature. The overall measurements are: length 4.1-4.8 ㎜; fore-body 1.00-1.20 ㎜ by 0.8-0.9 ㎜; hind-body 3.2-3.6 ㎜ by 0.43-0.46 ㎜. The body is covered by a relatively thick cuticle, devoid of spines. The oral sucker leads into a short esophagus that is devoid of a muscular pharynx. The holdfast organ is enormously developed. The vitelline follicles distributed dorsal wall of fore-body and hind-body. This strigeiid trematode especially differs from other species of genus Apharyngostrigea in morphology. Although these A. pipientis are several morphological distinctions from Apharyngostrigea cornu, the partial sequence of 18S rRNA showed the sequence homology of A. pipientis (99.9%) and A. cornu (99.8%), and this result revealed their conspecific relationship between A. cornu and A. pipientis. This is the first report of A. pipientis in the Republic of Korea.

First Description of the Metacercaria of Nematostrigea serpens serpens (Nitzsch, 1819) (Trematoda, Strigeidae) and Phylogenetic Affiliation of Nematostrigea vietnamiensis Zhokhov & Mishina, 2011.

The genus Nematostrigea comprises trematodes parasitising in fish-eating birds of Europe, Africa, and North America. Their life cycle is unknown. To provide the first description of metacercariae of Nematostrigea serpens serpens, a nominative subspecies of the type species of Nematostrigea, and to record metacercaria of Nematostrigea vietnamiensis, with molecular data. Encysted metacercariae of N. serpens serpens and N. vietnamiensis were collected from fish in Russia and Vietnam, respectively, and were processed, identified, and documented using standard morphological techniques. The 28S rRNA gene of metacercariae of both species and the cox1 gene of metacercariae an earlier studied adult of N. serpens serpens were sequenced and used for phylogenetic analysis. Metacercaria of N. serpens serpens have a spatulate body with a foliate forebody and a short hindbody, two long lateral rectilinear pseudosuckers, and the holdfast organ with bifurcated anterior and entire posterior external lobes. The analysis of the cox1and 28S rRNA gene sequences unequivocally showed the conspecificity of metacercariae and adult stage of N. serpens serpens. Based on the 28S rRNA gene sequence-based phylogenetic analysis, the genus Nematostrigea is a sister taxon to the group of strigeid genera Cotylurus + Ichthyocotylurus. Morphological and phylogenetic data demonstrated that N. vietnamiensis does not belong to the genus Nematostrigea and is possibly be affiliated with the crassiphialine trematodes. This is the first record of metacercariae of N. serpens serpens. N. vietnamiensis, renamed Prodiplostomulum vietnamiense comb. nov., must be moved to the crassiphialine 'Prodiplostomulum'-type metacercariae group.

First report of Diplostomidae metacercariae (Trematoda: Digenea) in African catfish Clarias gariepinus (Siluriformes: Clariidae) in Brazil.

Clarias gariepinus is a fish from North of South Africa and was later introduced in several countries, including Brazil. The present study aimed to describe the first report of Diplostomidae metacercariae in C. gariepinus in Brazil. For this, 30 C. gariepinus were captured in a lake in the city of Campos dos Goytacazes, RJ, Brazil. Fishes were euthanized using freezing and necropsied for collection of parasites. The organs were dissected and analyzed for the presence of parasites that were processed for light and scanning electron microscopy. Trematodes were stained with Semichon's Carmine and Gomori's Trichrome, observed and schematized under a light microscope with image analysis software. A total of 190 trematodes were collected from the gills, suprabranchial organs, heart, stomach, intestinal mesentery, liver and body cavity of the fish. The parasites had a foliaceous body divided by a discrete constriction, without genital primordia, and a holdfast organ present at the posterior region, typical of metacercariae of the family Diplostomidae. It was classified as the 'Diplostomulum' morphotype, based on the morphology of the reserve bladder structure. This is the first report of the metacercariae of Diplostomidae parasitizing C. gariepinus in the Americas. This fish acts as an intermediate or paratenic host of this digenean in Brazil.

Morphological and molecular characterization of six Indian Tetracotyle type metacercariae (Digenea: Strigeidae Railliet, 1919), using ribosomal and mitochondrial DNA

Strigeids have a cup-shaped fore body, containing a holdfast organ with two lobes and hind body. The species diversity of strigeids remains incomplete, especially in the Indian sub-continent. Here, we described six Tetracotyle type metacercariae (T. muscularis, T. fausti, T. lucknowensis, T. xenentodoni, T. mathuraensis and T. glossogobii) from five fresh water fish, collected at Lucknow (India). Next, we characterized these metacercariae using ribosomal (18S, 28S, ITS2) and mitochondrial DNA (COI) to determine their systematic and phylogenetic position. Molecular identification using inter-specific variation range for all four molecular markers revealed 1.9–4.9% (18S); 3.3–8.8% (28S); 6.8–12.9% (ITS2), and 3.5–9.4% (COI) among six Tetracotyle type metacercariae. In phylogenetic analysis, constructed by neighbour-joining (NJ) and maximum likelihood (ML) methods, T. fausti, T. glossogobii, T. xenentodoni, T. lucknowensis and T. mathuraenis nested as sister groups with the member of strigeids for all four markers used; T. muscularis, however, formed a basal clade. Furthermore, phylogenetic placement states the monophyly of the Tetracotyle type of metacercariae in all the markers (18S, 28S, COI), except ITS2.

The anthelmintic activity of 1,10-phenanthroline, a metalloenzyme inhibitor

Paramphistomosis is a chronic, debilitating parasitic disease of livestock prevalent in the tropical and sub-tropical countries. Globally there is a heavy reliance on anthelmintics but concerns over drug resistance encourage the search for new leads. Metalloproteinases play a significant role in the biology and life cycle of parasitic helminths. The efficacy of metalloproteinase inhibitor, 1,10-Phenanthroline (1,10-phe) which is commonly used as a specific enzyme inhibitor in biochemical assays, was tested in vitro on Gigantocotyle explanatum tegument as a marker of anthelmintic action. The scanning electron microscopy revealed that the tegumental surface exhibited considerable changes in the worms treated with the metalloenzyme inhibitor, 1,10-phe. The untreated control worms appeared normal showing smooth tegumental surface with abundant dome shaped papillae in the anterior to mid region, while their density was less around the acetabulum which serves as a hold-fast organ helping the worms to remain attached in biliary passage. The 1,10-phe produced significant tegumental damage when the liver amphistomes were in vitro exposed to this compound at 12.5 µM concentration. The surface changes appeared in the form of edematous ridges with prominent furrows and erosion of the dome shaped papillae with rosette shaped deep lesions as a result of which deep parenchymatous tissues were exposed. The collapse of sensory bulbs as well as sloughing of tegument, particularly in the anterior-mid region was observed. The nature of damage could be comparable to various anthelmintics used in previous studies. To the best of our knowledge this is the first report of direct exposure of amphistome worms to zinc metallo-enzyme inhibitor, however, further in vivo studies are required to ascertain the anthelmintic efficacy of 1,10-phe.

Central European Strigeidae Railliet, 1919 (Trematoda: Strigeidida): Molecular and comparative morphological analysis suggests the reclassification of Parastrigea robusta Szidat, 1928 into Strigea Abildgaard, 1790

Strigeidae Railliet, 1919 are digenean parasites of birds and mammals that are characteristic by their cup-shaped forebody and bilobed holdfast organ. Despite that the family is taxonomically unsettled, particularly due to a very limited number of visible autapomorphic identification features, molecular phylogenetics have never been applied to analyze the relationships among European members of Strigeidae except for the genus Ichthyocotylurus. Here, we analyze the Strigeidae found during the examination of Czech birds performed from 1962 to 2017, and we provide comparative measurements and host spectra, including prevalence and intensity; we also provide and analyze sequences of four DNA loci of 12 of the Strigeidae species. We suggest the reclassification of Parastrigea robusta Szidat, 1928 as Strigea robusta (Szidat, 1928) Heneberg and Sitko, 2018 comb. n. The genera Strigea Abildgaard, 1790 and Parastrigea Szidat, 1928 appear paraphyletic, and morphological diagnostic features of genera within Strigeini Dubois, 1936 are invalid. The mute swan Cygnus olor hosts two Cotylurus spp., Cotylurus syrius Dubois, 1934 and a second species with molecular identification features shared in part with Cotylurus cornutus (Rudolphi, 1808) and Cotylurus gallinulae Lutz, 1928. New host records are provided for seven species. Analyses of non-European genera of the Strigeidae are needed to provide an updated key to Strigeini.

Strigeid parasites of Circus buffoni from Argentina, with the description of a new species of Parastrigea Szidat, 1928.

Studying the Helminthological Collection of Museo de La Plata (MLP-He), several specimens of digeneans, recovered parasitizing a long-winged harrier, Circus buffoni (Accipitridae) from Buenos Aires Argentina, were analysed. The morphological and morphometric analysis of these specimens revealed the presence of two strigeid species, one of them new for science. Parastrigea buffoni n. sp. is characterised by a forebody differentiated in a retractile cephalic region with a large opening and a balloon-shaped collar region or collerette, suckers located in cephalic region, holdfast organ with well development dorsal and ventral lips that can emerge through opening, a claviform hindbody, a large copulatory bursa with muscular ring (Ringnapf) and a genital cone well delimited, crossed by a sinuous hermaphroditic duct with internal rugae. The euryxenous parasite, Strigea falconis brasiliana, is briefly described, parasitizing a new host. This is the first record of helminths parasitizing long-winged harrier.

First record of a rare transversotrematid cercaria larva (Trematoda: Digenea) from Rajasthan, India: focus on seasonal occurrence and host-specificity of diverse cercariae.

During the survey of freshwater snail hosts and their digenean larval trematode parasites, a rare cercaria larva belonging to family Transversotrematidae and subclass Digenea (Trematoda) was recovered from the snail species Melanoides striatella tuberculata inhabiting perennial Som river of Udaipur district, Rajasthan, India. More than 28% mature specimens of these snails were found to be infected with transversotrematid cercaria larvae in the spring season. Body of this cercaria is large, bowl-shaped, biocellate, spinose, transparent and laterally extended having two pigmented eye spots, two hold fast organs extended from the junction of body and tail, large tail with two foliated furcal rami, and cyclocoel intestinal caeca. As far as the authors are aware, this is the first record of a transversotrematid larva from Rajasthan, India. Simultaneously, other forms of cercariae viz., amphistome, echinostome, monostome, gymnocephalous, furcocercous and xiphidiocercous cercariae were also recovered from fifteen species of pulmonate and operculate snails including Lymnaea acuminata f. patula, L. acuminata f. chlamys, L. acuminata f. typica, L. acuminata f. rufescens, L. luteola f. australis, L. luteola f. typica, L. luteola f. impura, Planorbis (Indoplanorbis) exustus, and Anisus (Gyraulus) convexiusculus, Faunus ater, Melania (Plotia) scabra, Thiara (Tarebia) lineata, Melanoides striatella tuberculata, Vivipara bengalensis race gigantica and V. bengalensis race mandiensis. The seasonal occurrence and host-specificity of diverse trematode cercaria larvae are also discussed besides the first record of a rare transversotrematid cercaria larva from Rajasthan, India.

Studies on hold-fast organs of piscean cestode parasites from Maharashtra State, India

Present study deals with hold-fast organs of some Piscean tapeworms collected from Maharashtra State India. Hold-fast organs of tapeworms are important for attachment and adhesion. These organs of attachment are in the form of muscular suckers, rostellum, spines, hooks, tentacles etc. The work on hold-fast organs of Piscean tapeworms is very essential for research in taxonomy and histopathology. Hence, the present study was undertaken on the role and status of diversity of holdfast organs with special reference to histopathology of Piscean tapeworms collected from Maharashtra State, India. Tapeworms were collected and studied from certain fishes and localities.

Tegumental ultrastructure of adult Quinqueserialis quinqueserialis (Trematoda: Notocotylidae): an intestinal parasite of muskrat (Ondatra zibethicus).

Ten adult Quinqueserialis quinqueserialis specimens were removed from the intestine of a naturally infected muskrat, and scanning electron microscopy was used to study the morphological characteristics of the trematodes. The mature trematode, which was easy to recognize by the monostome holdfast organ, with no anterior cone, measured 2200-2500μm in length by 900-1050μm in width. The body was elongated and tapering at the anterior end, but the posterior end was rounded, and in some specimens was slightly truncated. The mouth opening lay at the anterior end and was surrounded by the oral sucker, which was round, small to medium in size, and subterminal. The tegument of the rim and inside of the oral sucker was smooth and had two types of papillae, domed and rosette papillae. Around the oral sucker, tegument was covered with sharp, pointed spines. The common genital pore was located on the median line of the body, posterior to the oral sucker. The cirrus had smooth tegument at the base and was armed with numerous conical spines throughout its length. The ventral surface was concave and provided with five distinct longitudinal rows of ventral papillae, which extended from the anterior to the posterior end of the body. Each row consisted of 15 to 20 papillae, making 81 to 88 papillae in all. These papillae were variable in size. In most specimens, the papillae were simple knob-like structures, but in some cases, they appeared to be bi- or trifurcate. The tegument at the base of each ventral papilla showed minute spiny pattern, but it was smooth or folded on top and had small rosette and ciliated papillae. Tegument at the edges of the worm was smooth in the mid-parts, spiny on lateral parts, and included rosette papillae. The dorsal surface of the worm was smooth and slightly convex, and the tegument was provided with two large domed papillae in one third of the anterior end of the dorsal part, few thick spines in the mid-part, and excretory pore at the level just posterior to the end. No spines or papillae were seen around the excretory pore.