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During parasitological surveys of marine fishes and zooplankton in localities of the Northwestern Pacific coast of Mexico, 28 Gafftopsail pompano (Trachinotus rhodopus Gill) and 50 mysid crustaceans (Metamysidopsis frankfiersi Hendrickx & Hernández-Payán) we identified to be infected with adults and cystacanths, respectively of an acanthocephalan morphologically corresponding to the genus Rhadinorhynchus Lühe, 1911. DNA sequences of the small (SSU) and large (LSU) subunits of ribosomal DNA, and cytochrome c oxidase subunit 1 (cox 1) from mitochondrial DNA were obtained. Phylogenetic analyses revealed that the newly sequenced individuals in a clade with Rhadinorhynchus sp. from carangids in other localities of the Pacific coast of Mexico; together, all these individuals formed an independent lineage that is recognized herein as a new species, Rhadinorhynchus trachinoti n. sp. The new species is morphologically distinguished from the other 38 congeners by having a long and cylindrical proboscis armed with 12 longitudinal rows bearing 16-18 hooks each. The ecological information gathered from the parasites, together with genetic evidence, confirms that the Gafftopsail pompano is the definitive host of R. trachinoti n. sp., while mysid crustaceans serve as the intermediate host. Current records also indicate that R. trachinoti n. sp. is distributed along the Pacific coast of Mexico, from Mazatlán, Sinaloa in the north to Puerto Angel, Oaxaca in the south. This distribution aligns with the Mexican Coastal Current, which extends from the Gulf of Tehuantepec in Oaxaca to the entrance of the Gulf of California and southern Baja California., Competing Interests: Declarations. Conflict of interest: No conflict of interest exists among the authors Ethical approval: The sampling in this work complies with the current laws and animal ethics regulations of México. Consent to participate: All the listed authors have made significant contributions to the study and agreed to participate. Consent for publication: All authors have read and agreed to the published version of the manuscript., (© 2024. The Author(s).)

The success of Procamallanus (Spirocamallanus) inopinatus infection in fish involves a complexity of variables. This study aims to evaluate the relationship between abundance of P. (S.) inopinatus with biometric and somatic parameters, sex, relative condition factor (Kn) and hosts diet, as well as to evaluate length relationship of the parasites and the hosts. The fishes were collected by the mesh method and data, length, weight, sex, gonad and liver weight, Gonadosomatic index (GSI) and hepatosomatic index (HSI), Kn and stomach content were recorded. Twenty-seven specimens of P. (S.) inopinatus were collected in the intestine from Serrasalmus rhombeus and 52 from Leporinus friderici. In general, the prevalence, mean intensity and mean abundance of infection was higher in L. friderici. The total abundance was explained by the variables GSI, HSI total length, gonad and liver weight. Fish relative condition factor (kn) and sex were not influenced by the infection, being that the parasite infection did not impair the body condition of the hosts. There is no relationship between host length and parasite length in any of the evaluated fish species. On average, S. rhombeus parasites are 0.69 cm larger than L. friderici parasites.

The gray snapper Lutjanus griseus is a commercially important fish species along its distribution range in the western Atlantic Ocean. However, despite its importance, there is still little knowledge about its parasitic fauna for the Mexican coasts of the Gulf of Mexico. The aims of this research were to generate a list of the parasitic fauna present in juvenile gray snapper L. griseus from a coastal lagoon located in southeastern Mexico, to evaluate the infection levels of parasites and to determine the relationship between the abundance of parasites and the fish size and condition factor. Samples of L. griseus (12 - 29.2 mm) were obtained in two periods of the year (dry and rainy seasons) to examine the intra-annual variability of its parasitic fauna. A total of 17 parasite species were recorded belonging to six taxonomic groups (Myxozoa, Monogenea, Digenea, Cestoda, Nematoda and Acanthocephala). The highest levels of infection (abundance, prevalence and intensity of infection) were found for the monogeneans Euryhaliotrema griseus and Euryhaliotrema fastigatum . There were no significant correlations between the total abundance of parasites and the fish condition and size (total length) in not any of the two seasons studied, suggesting that the body size and the biological condition index of the host did not directly influence the abundance of parasites in early life stages of L. griseus . Moreover, the species of parasites found that could be zoonotic for humans through the consumption of raw or inadequately cooked fish were the nematodes Contracaecum sp. type 1, Contracaecum sp. type 2, Cucullanus pargi and Pseudoterranova sp. The presence of the monogeneans E. griseus and E. fastigatum was also highlighted because these ectoparasite species are known to cause harm to fish under culture systems. All the parasite species found in this study, except nematodes, were new records of geographic distribution., Competing Interests: Conflict of Interest Authors declare no conflict of interest., (© 2022 M. A. Rodríguez-Santiago, L. Ramos-Colorado, L. García-Magaña, M. I. Grano-Maldonado, J. Iannacone, A. Vázquez-Caballero, published by Sciendo.)

We describe for the first time the transmission route employed by the parasitic larvae of the freshwater mussel Anodontites trapesialis (Lamarck, 1819) during cohabitation on the guppy Poecilia reticulata Peter, 1859. The freshwater mussel and fish-host were employed as a model system to investigate the infection and parasite establishment. Laboratory experiments included video recording and histopathological analysis of the infection. In vivo video observations demonstrated that lasidium larvae could be transmitted to guppies during direct contact. A series of histology samples and photography suggest that this larva attaches and colonizes possibly on-site on the outer surface of the fish, causing cellular inflammation in the epidermis layer with cellular hyperplasia in the zone of parasite attachment. An evident hyaline layer, cellular hypertrophy, and a large number of undifferentiated proliferating cells were observed. Hemorrhagic tissue and swelling were observed in the epidermis and dermic zone. The total number of larvae per male and female guppy was 525 ± 86 and 494 ± 167, respectively. No parasitic preference was detected for male versus female parasitized fish., (© 2022 M. I. Grano-Maldonado, I. B. Madureira, N. S. S. Trigueiro, N. V. Gonçalves, T. L. Rocha, published by Sciendo.)

This study analyzed the parasitism by Clinostomum sp. metacercariae of the neotropical fish Cichlasoma paranaense (Kullander 1983) and environmental variables' influence on their host-parasite relationship in Central Brazil. Fish were collected in five impoundments (I) from three towns: Itauçú (n = 2), Inhumas (n = 1), and Goiânia (n = 2), Goiás State, Brazil. Ninety-five fish were analyzed, weighted and length measured. Afterward, the presence of metacercariae in the gills, muscles, fins, and body cavities was investigated. The metacercariae were fixed in AFA solution, kept in 70% alcohol, and stained with carmine. The infection prevalence revealed that 0.64, 0.56 and 0.91% of fish was infected. The abundance was 4.14, 3.22 and 5.88, with a mean intensity of 6.44, 5.80 and 6.42 per impoundment (I 13, I 15 and I 16), respectively. The frequency of metacercariae was higher in fish collected in Goiânia. High frequency of parasites was observed in the gills, muscles, and fins. The limnological variables did not present direct interference in the parasitism. The fish' standard length influenced the number of metacercariae positively but did not differ to the relative condition coefficient.

The aim of this study was to characterize potential fungal species affecting mangrove species in Mexico. The phytopathogens were identified based on morphological and molecular characteristics using internal transcribed spacer (ITS1/ITS4) primers then sequenced and compared with the other related sequences in GenBank (NCBI). Three fungal species were identified as Colletotrichum queenslandicum (Weir and Johnst, 2012) from black mangrove (Avicennia germinans); Colletotrichum ti (Weir and Johnst, 2012) from white mangrove (Laguncularia racemosa) and buttonwood mangrove (Conocarpus erectus); Fusarium equiseti (Corda) from red mangrove (Rhizophora mangle). In addition, C. ti and F. equiseti were identified from mango Mangifera indica L. sampled close by the mangrove area. This study provides first evidence of anthracnose on four mangrove species caused by Colletotrichum and Fusarium species in the "Términos" coastal lagoon in Campeche State southern Mexico. This is the first time that C. queenslandicum and C. ti are reported in Mexico. F. equiseti has not been reported affecting M. indica and R. mangle until the present work. Little is known regarding fungal diseases affecting mangroves in Mexico. These ecosystems are protected by Mexican laws and may be threatened by these pathogenic fungus. This is the first report of the effect of Trichoderma harzianum TRICHO-SIN as an effective biological control against of Colletotrichum and Fusarium species.

The emerging growth of nanotechnology has attracted great attention due to its application in the parasite and intermediate host control. However, the knowledge concerning the mechanism of action (MoA) and toxicity of nanomaterials (NMs) to snails remain unclear. In this context, the present study revised the historical use of snails as experimental models in nanotoxicological studies and summarized the MoA and toxicity of NMs in aquatic and land snails. The data concerning the bioaccumulation, reproductive and transgenerational toxicity, embryotoxicity, genotoxicity and potential molluscicidal activity of NMs were revised. Furthermore, the data about the experimental conditions, such as exposure time, concentrations, cell and tissue-specific responses, snail species and nanoparticle types are discussed. Revised data showed that the toxic effects of NMs were reported for 21 snail species with medical, veterinary and ecological importance. The NM toxicity to snails is dependent on the physical and chemical properties of NMs, as well as their environmental transformation and experimental design. The NM bioaccumulation on snails was related to several toxic effects, such as reactive oxygen species (ROS) production, oxidative stress, following by oxidative damage to DNA, lipids and proteins. The NM metabolism in snails remains unknown. Results showed the potential use of NMs in the snail control program. Also, significant research gaps and recommendations for future researches are indicated. The present study confirms that snails are suitable invertebrate model system to assess the nanotoxicity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The aim of this investigation was to identify the parasites present in the largely understudied pleasure oyster Crassostrea corteziensis in Sinaloa state in the northwestern Mexican Pacific coast. Inspection of twenty-eight oysters collected on "Ceuta" lagoon revealed the presence of the digenean Stephanostomum sp . (Digenea: Acanthocolpidae) cysts. Metacercariae were found encapsulated and embedded in the digestive gland and mantle tissue of oysters. The prevalence of infection revealed that 84.6 % were infected, the abundance was 13.62, with a mean intensity of 16.09 per host. The members of this genus are characterized by a double crown of spines in the cephalic region surrounding the buccal opening of the worm. Significantly, we report the first incidence of the digenean Stephanostomum sp of the family Acanthocolpidae parasitizing Crassostrea corteziensis . Further we report that this bivalve is now considered a new intermediate host, and the northwestern Mexican Pacific coast is a new geographical distribution area for this digenean. The findings contribute to our understanding of the biology, biodiversity and host preference of these parasites, with implications for health risks posed by human consumption of the pleasure oyster., Competing Interests: Conflicts of Interest Authors have no potential conflict of interest pertaining to this submission to Helminthologia., (© 2019 M. I. Grano-Maldonado, F. Rubalcava-Ramirez, A. Rodriguez-Santiago, F. Garcia-Vargas, A. Medina-Jasso, M. Nieves-Soto, published by Sciendo.)

This study aims to describe the ultrastructure of coiled musculature fibers component of Gyrodactylus gasterostei and its role in this parasite transmission. The present work employs transmission electron microscopy to analyze G. gasterostei musculature, revealing the presence of myosin and actin bands in the underlying epithelium, typical arrangement of the skeletal muscle. This study unravels for the first time the existence of a coil muscle component in which it seems to be responsible for the remarkable flexibility of the musculature of Gyrodactylus and the efficiency of its transmission method to reach a nearby fish host. The elasticity of the musculature described in this study may be comparable with the other specialized elastic musculature within the animal kingdom (i.e., lizards tongue). The clarification of the basic biology of these monogenean parasites and its musculature biochemical systems hold the promise of possible novel muscle targets for a new generation of antiparasitic drugs., Competing Interests: There are no conflicts of interest.

This study examines the distribution and depletion of stored lipids in Gyrodactylus gasterostei Gläser, 1974, migrating off its three-spine stickleback host Gasterosteus aculeatus L., with the prospect that it might prove informative for interpreting the biology of other gyrodactylids species more generally. Nonfeeding life cycle stages, such as the dispersal stages of parasites, are dependent for survival upon finite energy reserves gathered during feeding phases. Thus, those individuals with more limited reserves will die sooner and consequently have less time available to find a new host once detached. At this stage, the principal energy reserves in gyrodactylids are stored as large lipid droplets. Confocal laser scanning microscopy has been used to investigate the distribution of lipid droplets in Gyrodactylus , which have migrated off their fish host, testing the hypothesis that these droplets function as a proxy for the nutritional state. This study demonstrated that the lipid droplets were particularly associated with the gut and that there is a significant variability in the volume of stored lipid carried out by each individual. Transmission electron microscopy showed that gyrodactylids carry lipid droplets at all stages of their life cycle, including at release from the birth pore. It is likely that transferring worms requires stored energy reserves to survive in the event of failure to establish contact with a new host. These reserves could allow the parasite to survive without a host for several days., Competing Interests: There are no conflicts of interest.

This study examines the transmission strategies employed by parasites in order to colonize new hosts. Three-spined sticklebacks, Gasterosteus aculeatus L., were challenged with Gyrodactylus gasterostei Gläser, 1974 in a chamber and the colonization of new hosts was observed. Live-video recording indicates that gyrodactylid transmission possibly maximizes the chances of contact with an alternatively feeding response from dead parasitized hosts to predatory stickleback. It is proposed that host scavenge feeding may comprise an additional route for gyrodactylid transmission, although its relative importance with respect to other recognized routes remains uncertain. Although it was clearly demonstrated that G. gasterostei can reside in the mouth of its host, the study revealed that scavenging-feeding upon dead parasitized hosts did not contribute significantly to the level of infection in 3 h and parasite transmission observed on the feeding fish. A series of experimental exposures and scanning electron microscope images suggest that once ingested, the parasites can attach to the lining of the buccal cavity and then migrate to their preferred colonization site on the outer surface of the fish. In addition to the direct contact infection pathway normally associated with many. This study highlights that diagnosticians should be aware of the fact that the oral cavity may act as temporary transmission location for gyrodactylid fauna., (© 2014 Wiley Periodicals, Inc.)

The aim of this study, therefore, was to investigate the ultrastructure of gyrodactylid sensilla and to ascertain how these may be employed in the colonisation of new hosts using the Gyrodactylus gasterostei Gläser, 1974--Gasterosteus aculeatus L. model. As Gyrodactylus has no specific transmission stage in its life-cycle, movement between hosts must be achieved by strategies employed by the adult. This study suggests that certain sensilla, presented for the first time in Gyrodactylus gasterostei, may serve as chemoreceptors and mechanoreceptors and possible photoreceptors. The results of this study provide photographic data using scanning electron microscope (SEM) and transmission electron microscopy (TEM) concerning the sensory structures that are found on the tegument and in the sub-tegumental zone of G. gasterostei that infect 3-spine sticklebacks (Gasterosteus aculeatus L.). For this reason, it is vital to understand the factors underlying transmission to a new host, and a detailed, ultrastructural examination of the sensory structures that are used may improve current understanding of the receptors that Gyrodactylus species employ to interpret both their host and ambient environments. Such information may assist in the interpretation of transmission behaviors, particularly their responses to chemical or physical cues which gyrodactylids employ in host location during the transmission process., (© 2014 Wiley Periodicals, Inc.)

Background: The high transmission potential of species belonging to the monogenean parasite genus Gyrodactylus, coupled with their high fecundity, allows them to rapidly colonise new hosts and to increase in number. One gyrodactylid, Gyrodactylus salaris Malmberg, 1957, has been responsible for devastation of Altantic salmon (Salmo salar L.) populations in a number of Norwegian rivers. Current methods of eradicating G. salaris from river systems centre around the use of non-specific biocides, such as rotenone and aluminium sulphate.Although transmission routes in gyrodactylids have been studied extensively, the behaviour of individual parasites has received little attention. Specimens of Gyrodactylus gasterostei Gläser, 1974 and G. arcuatus Bychowsky, 1933, were collected from the skin of their host, the three-spined stickleback (Gasterosteus aculeatus L.), and permitted to attach to the substrate. The movements of individual parasites were recorded and analysed., Results: The behaviour patterns of the two species were similar and parasites were more active in red light and darkness than in white light. Four octopaminergic compounds were tested and all four inhibited the movements of parasites. Treatment ultimately led to death at low concentrations (0.2 μM), although prolonged exposure was necessary in some instances., Conclusions: Octopaminergic compounds may affect the parasite's ability to locate and remain on its host and these or related compounds might provide alternative or supplementary treatments for the control of G. salaris infections. With more research there is potential for use of octopaminergic compounds, which have minimal effects on the host or its environment, as parasite-specific treatments against G. salaris infections.

The association of Gyrodactylus anguillae Ergens, 1960 with the glass eel stage of Anguilla anguilla (L.) (total body length 61.4 ± 4.9 mm; range 55-70) is reported from the north-western Mediterranean coast of Spain for the first time. A sample of 12,600 glass eels, caught by professional fishermen operating in the mouth of the rivers Fluvià, La Muga and Ter (north-east Spain), was subject to mortalities of ∼ 1.75% of stock/day following transfer to a research facility. Subsequent losses over a 31-day period amounted to 56% of the initial stocked biomass. Although the moderate burdens of G. anguillae/host (20.2 ± 6; range 11-32) were the primary reason for a subsequent treatment, a simultaneous infection with Trichodina jadranica Raabe, 1958, Trichodina anguillae Wu, 1961 and Ichthyophthirius multifiliis Fouquet, 1876, makes it impossible to attribute the high mortality of glass eels in this case to a single pathogen. A histopathological examination of the gills of moribund fish showed them to be swollen, hyperplastic and necrotic. This study also redescribes G. anguillae, providing for the first time a full 27 character morphometric description of the attachment hooks, and importantly, a photographic record of the armature of the haptor and the male copulatory organ., (Copyright © 2011 Elsevier B.V. All rights reserved.)