1,721,141 research outputs found
Study of cement apparatus, cement production and transportation in adult male Neoechinorhynchus rutili (Acanthocephala, Eoacanthocephala)
No full textInvestigation with light and electron microscopy has been made of the cement apparatus of mature male Neoechinorhynchus rutili parasite of Gasterosteus aculeatus. N. rutili possesses a single compact mass of glandular tissue (cement gland) with eight giant nuclei. The nucleus is lobed shape and has a conspicuous nucleolus with granular appearance. The cytoplasm of the gland contains prominent rough endoplasmic reticulum, mitochondria and electron dense secretory granules. A short duct connects the gland with a single separate cement reservoir. The duct appears to lack a lumen and is seen as an electron dense compact structure. Many microtubules of approximately 150 nm in outer diameter are located through the cytoplasm of the duct. It is proposed that in N. rutili the microtubules are responsible for the transport of cement granules from the gland to the reservoir. The cement reservoir appears as a compact organ filled with granules measuring at least 0.5 m in diameter
Histopathology in Leuciscus cephalus (Pisces: Cyprinidae) resulting from infection with Pomphorhynchus laevis (Acanthocephala)
No full textThe histopathology present in Leuciscus cephalus Risso 1826 from the River Po, naturally infected with the acanthocephalan Pomphorhynchus laevis Müller 1776, was studied and described. The parasite was only found within the host's digestive tract, and a density of 10 P. laevis per square centimeter was common. On histological examination it was noticed that both male and female parasites penetrated deeply through all the layers of the host digestive tract by means of their slender neck, bulb and proboscis; thus the bulb and proboscis become encapsulated beneath the serosa and mesentery. As a result, the presence of a capsule was noticed on the external surface of the host digestive tract. P. laevis caused local damage to the intestinal wall, and the parasite elicited an intense host reaction. The response of L. cephalus at the attachment site of the acanthocephalan was hyperplasia of host connective tissue, with cellular infiltration. In a few hosts, the presence of a fibrous nodule on..
Cypria replans (Crustacea: Ostracoda) as an intermediate host of Neoechinorhynchus rutili (Acanthocephala: Eoacanthocephala) in Italy
No full textA total of 2,568 specimens of 3 species of ostracod, namely Herpetocypris sp., Ilyocypris sp., and Cypria reptans Brohnstein, 1928, was collected between November 1994 and April 1995 from the Ceresina Canal, a tributary of the River Brenta (northern Italy), and examined for larval helminths. Larvae of Neoechinorhynchus rutili Müller, 1780 were found in the hemocoel of C. reptans. The prevalence of infection ranged from 8.57 to 14.51%. Most larvae were in the cystacanth stage (a new geographical record for this cystacanth). Not more than 3 larvae were encountered in a single host. Among 48 aquatic alder fly larvae of Sialis lutaria collected over 6 mo, together with the crustacean, no infected larvae were encountered. Specimens of Gasterosteus aculeatus (Pisces: Gasterosteiformis) collected with the arthropods from the same site were found to be parasitized with adult N. rutili. Fish stomach content analysis showed ostracods to be a major food item of three-spined sticklebacks in the study area during much of the year
Occurrence of Pomphorhynchus laevis Müller 1776 (Acanthocephala) in Silurus glanis (L.) from the River Po
No full textThe sheatfish, Silurus glanis (L.), from the terminal part of River Po was examined for the presence of helminth parasites. Of 182 S. glanis specimens, 95 (52.2%) were infected with the acanthocephalan Pomphorhynchus laevis. Mid-gut followed by fore-gut appeared to be the most infected portions of host alimentary canal. In 45 sheatfish of total length < or = 40 cm, specimens of P. laevis were found encapsulated in mesenteric and peritoneal tissues. A comparison between light and electron microscopy on features and stages of testis development in both encapsulated male P. laevis and intestinal male parasites showed that the encysted acanthocephalans were immature; mature spermatozoa were rarely found within the testis of worms from the alimentary canal. Among extraintestinal P. laevis specimens, the presumable eversion of parasite praesoma was observed and described. The results of the present survey suggest that small-size individuals of S. glanis could be used as paratenic host by P. ..
Responses of Squalius cephalus intestinal mucous cells to Pomphorhynchus laevis
No full textIntestinal mucous cell numbers and their glycoconjugate composition were investigated by histochemical methods in uninfected chub, Squalius cephalus, and in conspecifics naturally parasitised with the acanthocephalan Pomphorhynchus laevis. A sub-population of 42 chub from the River Tiber (Perugia, Italy) were sampled and screened for ecto and endoparasites. No parasites were found in gills and in other visceral organs of chub and P. laevis appeared to be the only enteric worm encountered. In all infected chub (twenty-eight out of 42) this acanthocephalan was encountered mainly in the mid-gut. In situ, an excessive yellowish mucus or catarrh was observed around each acanthocephalan. Hyperplasia and hypertrophy of the mucous cells were only evident near the site of P. laevis attachment where the total number of mucous cells and the number of those containing acidic, particularly non-sulphated mucins, or mixed glycoconjugates were significantly higher. In intestinal regions of infected fish far away from the point of parasite attachment, there were no statistical differences in the density of mucous cells in comparison to uninfected fish. Interestingly, in parasitised chub, the length of intestinal folds were significantly larger close to the sites at which P. laevis attach when compared to the length of the intestinal folds located further away from the acanthocephalans and/or in uninfected intestines. The effect of P. laevis on intestinal mucous cells of S. cephalus was compared to other parasite-host systems and the role of enhanced mucus production in parasitized intestines was discussed
Fish parasites (special issue)
No full textFish (Elasmobranchia and Actinopterygii) inhabit the majority of aquatic habitats globally. They are crucial for human nutrition but they may be negatively affected by parasitic protists and metazoan parasites. Fish parasites are also an extraordinary group of animals because of their ecological and evolutionary importance and unique adaptations to parasitism. They also play a key role in ecosystem functioning. In the present special issue, 13 review and research articles on major groups of fish parasites are provided to document the current advancement in our understanding of different aspects of their biology, ecology and associations with their fish hosts. The existing gaps in our knowledge of these peculiar animals are mapped and future trends in their research outlined
A morphological and ultrastructural study of Telosentis exiguus (Acanthocephala, Palaeacanthocephala)
No full textScanning electron microscope observations on Telosentis exiguus (Acanthocephala), an endoparasite of Atherina boyeri (Osteichthyes, Atherinidae), provided more detailed and precise data on surface structures of taxonomic relevance. Trasmission electron microscope observations on the integument revealed the presence of numerous channels which penetrate the integumental syncytium and, through branching, increase (up to 61 times) the absorptive surface area. Bundles of filaments and an electrondense cytoplasmic matrix in the outermost region provide a cytoskeletal support. © 1990 Taylor & Francis Group, LLC
Acanthocephalan infections in Atherina boyeri (Pisces: Atherinidae) from Tirso
No full textInfections by the acanthocephalan Telosentis exiguus (Von Linstow, 1901) and another unknown acanthocephalan were studied in the sand smelt Atherina boyeri (Risso, 1810) from the Tirso River mouth in Sardinia. Only a few specimens of T. exiguus (1 male and 2 cystacanths) were found in the host digestive tract; some larvae of an unidentified acanthocephalan encysted in the liver of A. boyeri were also found and are described
Cyathocephalus truncatus (Cestoda: Spathebothridea) in its intermediate host Echinogammarus stammeri (Amphipoda) from the River Brenta, northern Italy
No full textA study was carried out on the occurrence of the tapeworm Cyathocephalus truncatus (Pallas, 1781) (Cestoda: Spathebothridea) in its intermediate host, the amphipod Echinogammarus stammeri, in the River Brenta. A total of 18,860 E. stammeri was examined from July 1990 to June 1994; only 25 of them (prevalence 0.13%) were infected with tapeworm larvae (intensity of infection 1 larva/host). Co-occurrence of C. truncatus larvae with the larva of the acanthocephalan Pomphorhynchus laevis (Müller, 1776) was recorded in 15 amphipods. Tapeworms were localized in the anterior portion of each amphipod's hemocoel, in intimate contact with E. stammeri internal organs such as the alimentary canal, and frequently induced its displacement. No differences in integumental pigmentation were noticed between infected and non-infected amphipods, and some infected E. stammeri females were ovigerous
- …
