Helminth fauna of Scomberomorus sierra (Actinopterygii: Scombridae) in southeastern Gulf of California, Mexico

Summary From January to May 2015, a sample of 50 individuals of the Pacific sierra Scomberomorus sierra Jordan and Starks, 1895 captured off Mazatlán (southeastern Gulf of California, Mexico) were reviewed for helminths. A total of 6, 255 parasitic worms belonging to 11 species (9 in adult stage and 2 larvae) were obtained. Trematoda was the best represented group with 6 species of Didymozoidae Monticelli, 1888 and 1 of Bucephalidae Poche, 1907. In addition, 2 monogenean species and 2 of Nematoda were collected. In this study, the first molecular sequences for didymozoid species in Mexico were generated, and for Glomeritrema sp. at worldwide level. The most prevalent species were Didymocylindrus sp. (92 %) and Didymocystis scomberomori (MacCallum & MacCallum, 1916) (88 %), whereas the monogenean Thoracocotyle crocea MacCallum, 1913 reached the highest value of mean intensity (75.2). The coincidence between the helminthological composition established in our study and that reported for the same scombrid in 4 localities from the Mexican South Pacific (sharing 10 species) suggests that this group of species persistently parasitize S. sierra throughout its distribution along the Mexican Pacific coast; furthermore, due to the richness of didymozoids and the affinity of Thoracocotylidae species for S. sierra, both groups can be considered typical parasites of this fi sh.

New record of monogeneans (Platyhelminthes: Monogenea) infecting some marine fishes from the Peruvian coastal zone

A parasitological survey searching monogeneans infesting marine fish was carried out during June 2018 and January 2020 from the coastal zone of Puerto Pizarro, Tumbes (northern Peru) and from the coastal zone of Chorrillos, Lima (central Peru). The gills, skin, nasal cavities, or branchial gill-cover of seven species were sampled. Ten monogenean species assigned to six families and nine genera were identified. The monogeneans Callorhynchocotyle callorhynchi (Manter, 1955); Capsala biparasiticum (Goto, 1894) Price, 1938; Euryhaliotrema sagmatum Kritsky & Boeger, 2002; Listrocephalos kearni Bullard, Payne &Braswell, 2004; Magniexcipula lamothei Bravo-Hollis, 1981; Nasicola klawei (Stunkard, 1962) Yamaguti, 1968; and Pseudorhabdosynochus anulus Violante-Gonzalez & Rojas-Herrera, 2011 are registered for the first time in Peru. While Capsala gregalis (Wagner & Carter, 1967) Chisholm & Whittington, 2007; Heterocotyle margaritae Chero, Cruces, Sáez, Santos & Luque, 2020; and Monocotyle luquei Chero, Cruces, Iannacone, Sanchez, Minaya, Sáez & Alvariño, 2016 have been previously registered in Peruvian waters, however, the region of Tumbes (northern Peru) represent a new locality record for these species.

Parasitic flatworms infecting thorny skate, Amblyraja radiata: infection by the monogeneans Acanthocotyle verrilli and Rajonchocotyle emarginata in Svalbard

Parasite diversity above the Arctic circle remains understudied even for commercially valuable host taxa. Thorny skate, Amblyraja radiata, is a common bycatch species with a growing commercial value. Its natural range covers both sides of the North Atlantic including the Arctic zone. Svalbard is a Norwegian archipelago located on the northwest corner of the Barents Shelf which sustains a spectacular species diversity. So far, several monogenean species have been reported infecting thorny skate across the Atlantic Ocean. In the present study, we intend to fill in the knowledge gap on monogenean parasites infecting thorny skate in the northern part of its range and thus indirectly assess the connectivity between the thorny skate populations off the Svalbard coast and from previously studied locations. 46 monogenean individuals were recovered from 11 specimens of thorny skate. Following morphological and molecular assessment, two species of monogeneans, Acanthocotyle verrilli and Rajonchocotyle emarginata, were identified. The results serve as the northernmost record for both parasite genera and the first record of monogenean species off Svalbard. Detailed morphometric evaluation revealed a relatively high level of morphological variation in A. verrilli compared to its congeners. Phylogenetic reconstruction placed A. verrilli in a well-supported clade with A. imo. Our study also suggests high diagnostic significance of sclerotised structures in the identification of Rajonchocotyle. Even though the occurrence of two directly transmitted parasite species supports the previously suggested long-distance migration of A. radiata, future studies employing highly variable genetic markers are needed to assess the ongoing and historical migration patterns.HighlightsFirst record of monogenean species in SvalbardNorthernmost record for representatives of Acanthocotylidae and HexabothriidaeTransatlantic occurrence of parasites supports connectivity of thorny skate populations

An updated list of monogenoidea from marine fishes of Vietnam

In this paper, we updated the list of monogenean species from marine fishes of Vietnam. Taxonomic position of monogenean species were arranged according to the current classification system. A total of 220 monogenean species from 152 marine fish species were listed. Distribution, hosts and references of each species were given. In addition, amendations of taxonomic status of taxa were also updated.

Responses of monogenean species to variations in abiotic parameters in tilapiculture

Fish farming is becoming an increasingly popular agricultural activity, and water quality in these environments is a major concern. Fish parasites, such as monogeneans, respond to changes in abiotic conditions, either with an increase or decrease in population. This study aimed to identify gill monogeneans and analyse their relationships with abiotic factors during the ontogenetic development of Nile tilapia over the fish culture cycle in Mato Grosso do Sul, Brazil. Fish were sampled monthly for eight months, and a total of 200 fish were collected. The physical and chemical water parameters were measured and correlated with the abundance of each monogenean species. Over the fish culture cycle, the physical and chemical parameters fluctuated, and the water quality decreased. The parasites found included Cichlidogyrus tilapiae, Cichlidogyrus thurstonae, Cichlidogyrus sclerosus, Cichlidogyrus halli and Scutogyrus longicornis. The abundances of all species showed significant differences during ontogenetic development (body size) and C. tilapiae, C. sclerosus, C. thurstonae and S. longicornis were correlated with changes in abiotic conditions. However, C. halli was not significantly correlated with any of the evaluated physical or chemical parameters. Understanding how different monogenean species respond to changes in the physical and chemical parameters of water during a production cycle can prevent peaks in abundance and subsequent sanitary problems.

Methods for quantifying eggs and oviposition rate of Dawestrema cycloancistrium (Monogenea: Dactylogyridae), monogenean parasite of Arapaima gigas (Teleostei: Osteoglossidae)

Dawestrema cycloancistrium is the main ectoparasite causing mortality in fingerlings of pirarucu (Arapaima gigas) in Amazonian aquaculture. Very little is known about the D. cycloancistrium reproductive index and appropriate methods of collecting eggs for investigation. This study aimed to determine the oviposition rate of D. cycloancistrium. To achieve this aim, two egg quantification methods were tested: the estimative method (ME) and the total counting method (MT). Compared with the MT, the ME overestimated the number of eggs counted, which were 2943.5 ± 2840.6 and 1041.5 ± 533 eggs, and the oviposition rate, which was 80.1 ± 58.7 and 31.4 ± 16.4 eggs/parasite/day, for ME and MT, respectively. These results show that for studies quantifying D. cycloancistrium eggs, the total eggs in the sample must be counted, as the estimates made using subsamples are not representative. Using the MT, the oviposition rate for D. cycloancistrium was determined to be 31.4 ± 16.4 eggs per adult parasite per day. The present study demonstrates the egg production capacity of a monogenean species parasite of A. gigas, providing basic biological data for D. cycloancistrium.

Monogenean parasites of sardines in Lake Tanganyika: diversity, origin and intraspecific variability

Whereas Lake Tanganyika’s littoral and benthic zones are famous for their diverse fish communities, its pelagic zone is dominated by few species, of which two representatives of Clupeidae (Limnothrissa miodon and Stolothrissa tanganicae) take a pivotal role. We investigated the monogenean fauna infecting these freshwater clupeids to explore the link between parasite morphology and host species identity, or seasonal and geographical origin, which may reveal host population structure. Furthermore, we conducted phylogenetic analyses to test whether these parasitic flatworms mirror their host species’ marine origin. Based on 406 parasite specimens infecting 385 host specimens, two monogenean species of Kapentagyrus Kmentová, Gelnar and Vanhove, gen. nov. were morphologically identified and placed in the phylogeny of Dactylogyridae using three molecular markers. One of the species, Kapentagyrus limnotrissae comb. nov., is host-specific to L. miodon while its congener, which is new to science and described as Kapentagyrus tanganicanus Kmentová, Gelnar and Vanhove, sp. nov., is infecting both clupeid species. Morphometrics of the parasites’ hard parts showed intra-specific variability, related to host species identity and seasonality in K. tanganicanus. Significant intra-specific differences in haptor morphometrics between the northern and southern end of Lake Tanganyika were found, and support the potential use of monogeneans as tags for host population structure. Based on phylogenetic inference, we suggest a freshwater origin of the currently known monogenean species infecting clupeids in Africa, with the two species from Lake Tanganyika representing a quite distinct lineage.

Morphological and molecular (28S rRNA) data of monogeneans (Platyhelminthes) infecting the gill lamellae of marine fishes in the Campeche Bank, southwest Gulf of Mexico

During the examination of 913 fish specimens belonging to four families in the Campeche Bank (Gulf of Mexico), 23 gill ectoparasitic monogenean species were found, which belong to three families: Dactylogyridae, Microcotylidae and Diclidophoridae. The speciesEuryhaliotremaamydrum,E.carbuncularium,E.dunlapae,E.fajeravilae,E.fastigatum,E.longibaculum,E.paracanthi,E.tubocirrus,Haliotrematoidescornigerum,H.gracilihamus,H.heteracantha,H.longihamus,H.magnigastrohamus,H.striatohamus,Hamatopedunculariabagre,Neotetraonchusbravohollisae, andN.felis(all Dactylogyridae) were found on the hostsLutjanussynagris,L.griseus,Ariopsisfelis,Bagremarinus,Archosargusrhomboidalis, andHaemulonplumieri. Additionally,Microcotylearchosargi,Microcotylesp., andMicrocotyloidesincisa(all Microcotylidae) were found onL.griseusandA.rhomboidalis; finally,Choricotylesp. 1,Choricotylesp. 2, andChoricotylesp. 3 (all Diclidophoridae) were found onH.plumieri. The prevalence, abundance, mean intensity of infection, and supplementary taxonomic revisions for all monogeneans found are provided. Partial sequences of the 28S rRNA gene were also obtained for monogeneans of ariid, sparid, and haemulid host fishes to explore their systematic position within the Monogenea. New locality and host records for some previously described species ofEuryhaliotrema,Hamatopeduncularia,Microcotyle, andChoricotylefrom lutjanid, ariid, sparid, and haemulid hosts were reported. The present study adds evidence supporting the interoceanic occurrence of the same monogenean species (on lutjanids) on the west-east Atlantic and Pacific Oceans (= amphiamerican species). As previously suggested, there are at least, two possibilities to explain that parasite distribution: differentiation of morphological features in these monogeneans have resulted in only slight to insignificant morphological changes developing over the extended period of 3.2 mya (when the Isthmus of Panama was closing) and/or speciation is only evident at molecular level.