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Simple Summary: Leptophallus nigrovenosus is a trematode parasite found in snakes that requires feeding on amphibians to acquire the parasite. Firstly, this study investigated, in detail, the sensory receptors on the cercariae of these parasites, shedding light on the adaptations that allow them to find their host species. Secondly, the metacercariae of Salamandra salamandra were studied using histology to examine inflammatory responses in the eyes and potential eye damage. This study involved collecting snails (Planorbius metidjensis) and observing the emergence of cercariae. Salamander larvae were then exposed to these cercariae, and the larvae were later examined for the presence of metacercariae. Notably, this study is the first to report the presence of L. nigrovenosus in the snail P. metidjensis, a previously unrecorded host. These findings revealed that members of the genus Salamandra can serve as secondary intermediate hosts for L. nigrovenosus. Such infections in amphibians can lead to various eye issues, including cloudiness, inflammation, and tissue damage, ultimately affecting their survival. This research highlights the need for further investigation into trematode infections in amphibian eyes, which would provide valuable insights into their prevalence, transmission dynamics, and impact on host populations. (1) Background: Leptophallus nigrovenosus, an esophageal parasite that primarily affects water snakes of the genus Natrix, has a known life cycle that involves snail and amphibian hosts. However, the biological aspects, chaetotaxic patterns, and pathogeny of this parasite in its hosts have not been fully elucidated. (2) Methods: Snails (Planorbarius metidjensis) were collected in Spain and examined for cercaria emergence. The larvae were used to experimentally infect Salamandra salamandra, and metacercariae were isolated. Their chaetotaxy was studied using microscopy and scanning electron microscopy. The eye histology was also examined. (3) Results: The cercariae displayed distinctive morphological characteristics. The results of this study revealed three types of ciliated sensory papillae on the cercarial teguments, suggesting an adaptation for host detection and orientation. The metacercariae isolated from subcutaneous tissues showed oval bodies covered in spines. The chaetotaxy patterns matched those of Leptophallinae species. This is the first report of the presence of L. nigrovenosus in the snail P. metidjensis. Additionally, this study detected metacercariae in the eyes of S. salamandra, emphasizing the need for further research on trematode infections in amphibian eyes. (4) Conclusions: Members of the genus Salamandra can serve as secondary intermediate hosts for L. nigrovenosus, and the presence of metacercariae in amphibian eyes may have implications for the survival and habitat management of these amphibians. Understanding this parasite's prevalence, transmission dynamics, and impacts on host populations is crucial for conservation strategies. [ABSTRACT FROM AUTHOR]

Highlights • Sperm characters are described for Glypthelmins staffordi. • Present work constitutes the first study in the family Glypthelminthidae. • Great similitudes have been observed between the spermatozoon of G. staffordi and those of other plagiorchioideans. Abstract The present study describes the ultrastructural organization of the mature spermatozoon of the digenean Glypthelmins staffordi (Glypthelminthidae) by means of transmission electron microscopy. Live digeneans were collected from the Chinese edible frog (Hoplobatrachus rugulosus) in Udon Thani Province (Thailand). The ultrastructural study reveals that the mature spermatozoon of G. staffordi is a filiform cell, which is tapered at both extremities. It exhibits the Bakhoum et al.'s type IV of spermatozoon of digeneans characterized by the 9+'1' axonemes of trepaxonematan Platyhelminthes, the presence of the association "external ornamentation-cortical microtubules", the external ornamentation located in the posterior part of the anterior region, the arrangement of parallel cortical microtubules in two bundles and with its maximum number located in the anterior part of the sperm cell, and the presence of two mitochondria. Other characteristics are the presence of spine-like bodies, a posterior extremity containing only the nucleus, and the presence of a large amount of glycogen granules. Results of the present study are particularly compared with the existing data in other families of the Plagiorchioidea, namely the Brachycoeliidae, the Haematoloechidae, the Omphalometridae and the Plagiorchiidae. [ABSTRACT FROM AUTHOR]

The prevalence of Opisthorchis viverrini, a fish-borne zoonotic trematode that can provoke cholangiocarcinoma, is high in the Northeast Thailand. The aim of this study was to determine the prevalence of O. viverrini metacercariae in the cyprinid fish and determine its association of O. viverrini infection among the consumers who regularly buy fish in the markets. A cross-sectional study was conducted in nine provinces covering 20 districts of Thailand, and we examined 778 cyprinoid fish specimens belonging to five species purchased from local markets. Pepsin-HCl digestion method was used to recover O. viverrini metacercariae from fish. In all districts surveyed, O. viverrini metacercariae-positive fish were found with the infection rates ranging from 3.9 to 21.1%. All five fish species studied were positive for O. viverrini metacercariae: Henicorhynchus siamensis (13.7%), Cyclocheilichtys spp. (12.7%), Hampala spp. (8.1%), Systomus spp. (6.9%) and Barbonymus goniatus (5.0%). An average prevalence of O. viverrini infection was 7.1% in the fish consumers surveyed in the markets. The source of fish was determined and our results showed that parasitized fish are sold in markets up to 100 km away from the point of capture, which contributes to the dispersion and maintenance of this helminthiasis. Our results point to the transmission of liver flukes via markets, in spite of many active programs of health education, elimination, prevention and control aimed to reduce O. viverrini infection and subsequent cholangiocarcinoma in the endemic areas of Thailand. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Ultrastructural characters of spermiogenesis and the mature spermatozoon of Brachycoelium salamandrae are described by means of transmission electron microscopy. Spermiogenesis begins with the formation of a differentiation zone containing a nucleus, several mitochondria, and two centrioles associated with striated rootlets and with an intercentriolar body between them. The two centrioles originate two free flagella that grow orthogonally to the median cytoplasmic process before fusing with it. The final stage of spermiogenesis is characterized by a constriction of the ring of arched membranes and the liberation of the young spermatozoon. In this final stage a pear shaped electron-dense material appears at the level of centrioles. Spermatozoon of B. salamandrae exhibits two axonemes of different length with the 9+‘1’ trepaxonematan pattern, a nucleus, two mitochondria, two bundles of parallel cortical microtubules and granules of glycogen. Additionally, the spermatozoon of B. salamandrae shows external ornamentations of the plasma membrane and spinelike bodies. The most relevant spermatozoon characters of B. salamandrae are discussed and compared with those of other species belonging to the superfamily Gorgoderoidea. [Copyright &y& Elsevier]