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Monogeneans are parasitic flatworms that may be a threat for finfish aquaculture. In this study, the anthelmintic activity of two terpenes, geraniol and β-citronellol, was tested in vitro against ancyrocephalin and diplectanid monogeneans. Experiments were performed in both water and a culture medium. We observed that monogeneans in culture medium may be more tolerant to treatments compared with bioassays performed only in water. Concentrations of 300 mg/L of both compounds were required to kill 100% of monogeneans at 1 h postexposure. The toxicity of β-citronellol to fish was not evaluated. However, geraniol at 300 mg/L and 150 mg/L killed juvenile Nile Tilapia Oreochromis niloticus and White Snook Centropomus viridis, respectively, after a few minutes. Therefore, the present work suggests that other alternatives should be studied for use against monogeneans in aquaculture.

Seriola rivoliana cultivated in Mexico are infected by Neobenedenia sp. (Monogenea: Capsalidae), resulting in dermal ulceration and subsequent bacterial invasion that can cause fish death. This study assesses the effects of temperature over hatching success, oncomiracidia longevity, and infection success. The experimental design consisted of culturing the parasite at temperatures ranging between 16 and 32 °C. The oncomiracidia infection success, time to sexual maturity, and size at sexual maturity of Neobenedenia sp. were examined only at three temperatures (20 °C, 24 °C, and 30 °C). Experiments were conducted under controlled conditions in the laboratory. The oncomiracidia development was found to be faster at warmer temperatures (4-5 days between 24 and 30 °C) than in colder treatments (7-11 days between 18 and 20 °C). Hatching success and oncomiracidia longevity were higher at 24 °C and 26 °C. At 20 °C, 24 °C, and 30 °C, infection success was greater than 90%. Additionally, the laid eggs were observed at 9, 12, and 15 days at 30 °C, 24 °C, and 30 °C, respectively. The results of this study will allow for improving the temporal schedule of applications of treatments against Neobenedenia sp. by the function of temperatures. In conclusion, it is recommended to treat fish more frequently if the temperature in cultures is higher than 24 °C, because Neobenedenia sp. development is faster. As an alternative, the fish could be moved to deeper and cooler waters.

Terpenes are naturally produced compounds with a broad range of biological activities. Currently, there is limited information regarding the anthelminthic effect of terpenes against monogenean parasites of fish. The aim of this work was to evaluate the in vitro efficacy of two terpenes [α-terpinene and (+)-limonene oxide] against ancyrocephalid monogeneans found on farmed Nile tilapia (Oreochromis niloticus). (+)-Limonene oxide was more effective in killing these parasites than α-terpinene, with 86 and 90% mortality at concentrations of 36 and 55.4 mg/L, respectively, with a 5-h treatment. The estimated 5-h EC(50) of (+)-limonene oxide was 4.8 mg/L. Even though this compound has the potential to be used as an anthelmintic compound in finfish aquaculture, before in vivo experiments are performed, additional studies are needed to find a more effective concentration, as well as to evaluate other terpenic compounds.

The mechanisms of action of silver nanoparticles (AgNPs) in monogenean parasites of the genus Cichlidogyrus were investigated through a microarray hybridization approach using genomic information from the nematode Caenorhabditis elegans. The effects of two concentrations of AgNPs were explored, low (6 &micro, g/L Ag) and high (36 &micro, g/L Ag). Microarray analysis revealed that both concentrations of AgNPs activated similar biological processes, although by different mechanisms. Expression profiles included genes involved in detoxification, neurotoxicity, modulation of cell signaling, reproduction, embryonic development, and tegument organization as the main biological processes dysregulated by AgNPs. Two important processes (DNA damage and cell death) were mostly activated in parasites exposed to the lower concentration of AgNPs. To our knowledge, this is the first study providing information on the sub-cellular and molecular effects of exposure to AgNPs in metazoan parasites of fish.

The occurrence of parasitic infections in Nile tilapia (Oreochromis niloticus (Linnaeus, 1758)) cultured in Sinaloa, Mexico were investigated. Fish samples were obtained from different fish farms over the last 11 yr. In total, 433 fish were examined and 13 parasite species (8 protozoans and 5 monogeneans) were found. Trichodina spp., Cichlidogyrus spp., and Gyrodactylus spp. were the most-common parasites and occurred in most years, reaching prevalences of 81, 60, and 48%, respectively. Trichodina spp. and Cichlidogyrus spp. were the only species to be found in 5 fish farms in the same year, which occurred in 2008. These results suggest that parasite infections in farmed tilapia have likely become permanently established in Sinaloa, probably because of the poor water quality and incorrect management practices. We argue that better educational programs are needed to correctly comply with biosecurity measures to prevent and control fish diseases.

Diclidophoridae and Capsalidae are families of monogenean parasites that include some of the most pathogenic species for cultured finfish. In this study, the efficacy of praziquantel (PZQ) and a combination anthelmintic (PZQ, ivermectin, pyrantel pamoate and fenbendazole) commercialized under the name of Adecto® (Adler Pharma) were evaluated in vitro against adults and eggs of the diclidophorid Tagia ecuadori and the capsalid Neobenedenia melleni. Freshwater and formalin immersions were also evaluated against T. ecuadori for comparative purposes. In addition, the efficacy in vivo of Adecto® as a bath treatment to eliminate mixed infections as well as the median lethal concentration (LC50) of this drug in juvenile, healthy bullseye puffer fish (Sphoeroides annulatus) were determined. Triglycerides, hemoglobin, total protein and glucose levels were measured in three groups of fish: uninfected, infected and infected/treated with Adecto®. At the doses tested, PZQ did not have a concentration-dependent effect. Thus, 2.5 mg/L PZQ was 100% effective against adults of T. ecuadori after 20 h, and 3 mg/L killed 87% of N. melleni after 12 h. Adecto® had a concentration-dependent effect. The concentration required to kill all parasites in the minimum time was 20 mg/L Adecto® (12 h for T. ecuadori, and 16 h for N. melleni). Neither PZQ nor Adecto® were effective at inhibiting egg hatching. Adults of T. ecuadori were highly tolerant to freshwater; mortality was

Genomic resources for Platyhelminthes of the class Monogenea are scarce, despite the diversity of these parasites, some species of which are highly pathogenic to their fish hosts. This work aimed to generate de novo-assembled transcriptomes of two monogenean species, Scutogyrus longicornis (Dactylogyridae) and Rhabdosynochus viridisi (Diplectanidae), providing a protocol for cDNA library preparation with low input samples used in single cell transcriptomics. This allowed us to work with sub-microgram amounts of total RNA with success. These transcriptomes consist of 25,696 and 47,187 putative proteins, respectively, which were further annotated according to the Swiss-Prot, Pfam, GO, KEGG, and COG databases. The completeness values of these transcriptomes evaluated with BUSCO against Metazoa databases were 54.1% and 73%, respectively, which is in the range of other monogenean species. Among the annotations, a large number of terms related to G-protein-coupled receptors (GPCRs) were found. We identified 109 GPCR-like sequences in R. viridisi, and 102 in S. longicornis, including family members specific for Platyhelminthes. Rhodopsin was the largest family according to GRAFS classification. Two putative melatonin receptors found in S. longicornis represent the first record of this group of proteins in parasitic Platyhelminthes. Forty GPCRs of R. viridisi and 32 of S. longicornis that were absent in Vertebrata might be potential drug targets. The present study provides the first publicly available transcriptomes for monogeneans of the subclass Monopisthocotylea, which can serve as useful genomic datasets for functional genomic research of this important group of parasites.Assemblage de novo du transcriptome et identification des récepteurs couplés aux protéines G (RCPG) chez deux espèces de Monogènes parasites de poissons.Les ressources génomiques pour les Plathelminthes de la classe Monogenea sont rares, malgré la diversité de ces parasites dont certaines espèces sont hautement pathogènes pour leurs hôtes poissons. Ce travail visait à générer des transcriptomes assemblés de novo pour deux espèces de monogènes, Scutogyrus longicornis (Dactylogyridae) et Rhabdosynochus viridisi (Diplectanidae), fournissant un protocole pour la préparation de la bibliothèque d’ADNc avec des échantillons à faible apport utilisés en transcriptomique unicellulaire, ce qui a permis de travailler avec des quantités inférieures au microgramme d’ARN total avec succès. Ces transcriptomes se composent de 25 696 et 47 187 protéines putatives, respectivement, qui ont ensuite été annotées selon les bases de données Swiss-Prot, Pfam, GO, KEGG et COG. L’exhaustivité de ces transcriptomes évaluée avec BUSCO par rapport aux bases de données des Métazoaires était respectivement de 54,1 % et 73 %, ce qui est dans la gamme des autres espèces de monogènes. Parmi les annotations, un grand nombre de termes liés aux récepteurs couplés aux protéines G (RCPG) ont été trouvés. Nous avons identifié 109 séquences de type RCPG chez R. viridisi et 102 chez S. longicornis, y compris des membres de la famille spécifiques de Platyhelminthes. La rhodopsine était la plus grande famille selon la classification GRAFS. Deux récepteurs putatifs de la mélatonine trouvés chez S. longicornis représentent le premier signalement de ce groupe de protéines chez les Plathelminthes parasites. Quarante RCPG de R. viridisi et 32 de S. longicornis, qui sont absents chez les Vertébrés, pourraient être des cibles médicamenteuses potentielles. La présente sont fournit les premiers transcriptomes accessibles au public pour les monogènes de la sous-classe Monopisthocotylea, qui peuvent servir d’ensembles de données génomiques utiles pour la recherche génomique fonctionnelle de cet important groupe de parasites.

The in vitro and in vivo antihelmintic activity of cobalt(II), copper(II) and zinc(II) coordination compounds of tinidazole (tnz) were investigated in cultivated spotted rose snapper, infested with dactylogyrid monogeneans. The tinidazole coordination compounds [Co(tnz)2Cl2], [Co(tnz)2Br2], [Cu(tnz)2Cl2], [Cu(tnz)2Br2], [Zn(tnz)2Cl2] and [Zn(tnz)2Br2] were synthesized and spectroscopically characterized. Their molecular structures were determined by their single crystal X-ray diffraction. The metal ions presented distorted tetrahedral geometries, with an intramolecular bifurcated lone pair S O ⋯ π, from the sulfone group with the imidazolic ring, which contributed to the stability of the compounds in solid state and in solution. Adults of dactylogyrids were exposed in vitro to tinidazole and its coordination compounds. The effective median concentrations of copper(II) coordination compounds were lower than those of cobalt(II) and zinc(II), tnz showed no activity. In vivo oral intubation tests were carried out with [Cu(tnz)2Br2], [Zn(tnz)2Br2] and tnz on snappers infected with dactylogyrids, where the copper(II) compound showed better activity. The absorption and distribution assessment for the [Cu(tnz)2Br2], showed that copper concentrations in liver were significantly higher than in blood and gills, indicating bioaccumulation in this organ. In vivo baths of [Cu(tnz)2Br2] at 25 mg/L showed an effective (95% at 8 h) antihelmintic effect, while [Zn(tnz)2Br2] had low antihelmintic efficacy. This study indicates that [Cu(tnz)2Br2] has an effective antihelmintic activity towards dactylogyrids monogeneans affecting cultivated spotted red snapper.

Summary The helminth communities of L. guttatus from Mazatlan Bay (MB) and Banderas Bay (BB), on the Pacific coast of Mexico, were studied during two consecutive years. A total of 536 fish were collected and 19 parasite taxa registered (six digeneans, two cestodes, nine nematodes, and two monogeneans). Infection levels of common helminth species (Helicometrina nimia, Siphodera vinaledwardsii, Tetraphyllidea gen. sp., Pseudoterranova sp., Ancyrocephalidae gen. sp. and Microcotyloides incisa) as well as the infracommunity indices varied significantly between MB and BB, and among dry and rainy seasons; however, no clear seasonal patterns were observed. Pseudoterranova larvae appeared frequently in MB, possibly because of the presence of the California sea lion in this locality. Similarity analysis did not show a clear separation of parasite species composition between both localities, which suggest that fish samples came from a single population of L. guttatus.

Severe infections of the spotted rose snapperLutjanus guttatusresulting from dactylogyrid monogeneans present a risk to aquaculture. Currently, the diagnosis of this infection requires the morphological identification and manual quantification of parasites. Based on the characterization of the 28S rRNA gene of dactylogyrid species present inL. guttatus, specific primers were designed for real-time polymerase chain reaction (qPCR) using EvaGreen® chemistry. The standard curve method estimated the number of dactylogyrids accurately. A total of 85 gill samples from cage-cultured fish infected with dactylogyrids were analysed. The estimated number of dactylogyrids using this molecular method was very similar to the manual count that was performed initially. The standardized qPCR approach will be helpful as a complementary method for the early routine monitoring of dactylogyrid infections and for epidemiological studies in which a high number of fish must be studied.

Ciliate ectoparasites are one of the most important groups of pathogens in fish culture, and the traditional treatments are sometimes harmful to the fish and the environment. Thus, the search for novel compounds that are effective at low concentrations and safe for fish are necessary to optimise treatments in aquaculture. The antiprotozoal capacity of silver nanoparticles (AgNPs) against the ciliate Tetrahymena has been documented; however, their toxicity may vary with the synthesis methodology and nanoparticle size. The objectives of this study were a) to evaluate the acute toxicity in vitro of two AgNPs (Argovit™ and UTSA) on Tetrahymena sp., a biological model for ciliated ectoparasites of fish and b) to test the safety of lethal and higher doses of UTSA AgNPs for ciliates on the fish C. estor. Light microscopy and scanning electron microscopy (SEM) were used to determine whether AgNPs affected the structure of the cell surface of Tetrahymena. The mortality, histopathological alterations and metagenomics of the fish were used to determine the major effects of UTSA AgNPs. In Tetrahymena, the median lethal concentration (LC50) for Argovit™ was 2501 ± 1717 ng/L at 15 min and 796 ± 510 ng/L at 60 min, while the LC50 for UTSA AgNPs was 4 ± 2 and 1 ± 0.6 ng/L at 15 min and 60 min, respectively. A concentration of 3300 ng/L Argovit™ and 10.6 ng/L UTSA AgNPs for 15 and 60 min, respectively, was 100% effective against Tetrahymena. After 60 min of exposure to 0.25 and 0.50 ng/L UTSA AgNPs, the number of cilia significantly reduced, there were small holes on the cell surface, and the cellular membrane was ruptured. In fish exposed to lethal (10.6 ng/L) and higher (31.8 and 95.4 ng/L) doses of UTSA, the AgNPs did not affect fish survival after 96 h, and there were no signs of histopathological damage or gut microbial changes. This study is the first report on microscopic and ultrastructural changes in Tetrahymena after exposure to significantly low concentrations of UTSA AgNPs with antiprotozoal efficacy without evidence of harmful effects on fish. These results provide the basis for further studies of both pet aquarium and commercial fish that may validate these findings at a larger experimental scale, taking into account AgNPs bioaccumulation, safety for human consumption and environmental impact.

The effective formalin therapeutic concentration (ETC) against Cichlidogyrus spp. infecting tilapia was obtained. Also, the stress and immune response to formalin baths in O. niloticus were achieved. A static bioassay with four concentrations (0.5, 1.0, 1.5, 2.0 mL L -1 ) of formaldehyde (37% dilution) in water, and one control without this substance was performed. Results evidenced that 1.5 mL L -1 of formalin for 40 min was the ETC to eradicate monogeneans without manifesting macroscopic damage to fishes. Thirty tilapias underexposure with ETC of formalin (FORM Group) were evaluated for stress, utilizing cortisol and glucose determination, and immune response (lysozyme activity and differential counting of organic defense cells). Other 30 tilapias without cichlidogyriasis and with no exposure to formalin were the Control Group. Evaluation times were: three hour pre-treatment (T0), and one hour, three days and three months post-treatment (T1, T2, and T3, respectively). A peak of cortisol (~326 ng mL -1 ) was observed in tilapias of FORM Group at T1 with significant differences with the control group ( P ˂ 0.05). Similarly, glucose concentration reached significant values (~119 mg dL -1 ) at one hour after the conclusion of treatment ( P ˂ 0.05). Those values returned to the basal limit at the last time of the study. The lysozyme activity and white blood cells in differential counting showed no significant differences in the same conditions ( P > 0.05). Results confirmed total control of cichlidogyriasis with the ETC of formalin obtained and an evident resistance of tilapia to treatment as stabilization of its physiological stress response was achieved.

Los copépodos parásitos de la familia Caligidae, comúnmente llamados "piojos de mar", son descritos como uno de los problemas más serios que afectan a la industria del salmón en la etapa de engorda en el mar a nivel mundial, causando lesiones en la piel, crecimiento lento y mortalidad. Gran parte de los conocimientos biológicos y ecológicos de estos organismos se han obtenido a partir de especies de aguas frías o templadas. En México, el conocimiento de este grupo de parásitos se ha limitado a registros esporádicos de especies nuevas o ya conocidas, pero poco se sabe sobre su biología y ecología. La diversidad de calígidos en peces silvestres puede ser alta en las costas mexicanas, por lo que no debería descartarse su potencial riesgo sanitario en áreas de interés para la piscicultura marina. En este artículo se resume el conocimiento actual sobre el ciclo de vida, localización de hospedero, ecología, efecto en la salud de los peces y métodos de control de calígidos. Mejorar el conocimiento de este grupo de parásitos facilitaría no sólo posibles estrategias de prevención y control de enfermedades de los peces, sino también el manejo y conservación de recursos naturales, ya que las granjas de peces pueden producir parásitos que impacten las poblaciones naturales de peces. Parasitic copepods of the family Caligidae, the so-called sea lice, may be deleterious to marine or brackish finfish aquaculture. To date, biological and ecological studies of sea lice have been mostly restricted to species from cold or temperate regions. In Mexico there are some records of sea lice species on marine fishes; however, the research regarding their biology and ecology has been scarce. It is possible that a high biodiversity of sea lice is distributed in coastal waters of Mexico; therefore, their significance as pathogenic parasites should increase. The purpose of this review is to outline the current knowledge of the life cycle, host location, ecology, effect on fish health, and control strategies of sea lice in order to establish supportive basis for natural resource management and control of parasites and diseases of marine fish cultured in Mexico.

The Caligidae, also known as sea lice, is a family of parasitic copepods of fish that consists of 31 genera and more than 450 species, some of which have been deleterious to cultured fish. The goal of this paper was to structure a list of sea lice species known from the Neotropical region based on information from published records. A total of 115 sea lice species found on 217 fish species were listed, including 58 species of Caligus and 22 of Lepeophtheirus. It seems that the inventory of this group of parasites is far from complete. Considering the promotion of finfish sea-cage aquaculture throughout the coastal areas of Latin America, a better understanding of the sea lice biodiversity will support systematic work on parasitic copepods in the Neotropics and will provide fundamental information that could impact fish disease control and prevention strategies.

"Specimens of wild populations of the spotted rose snapper,Lutjanus guttatus(Steindacher) were studied for monogenean parasites in 2 localitiesalong the Mexican Pacific coast (Mazatlán, Sinaloa and Chamela Bay, Jalisco). Five species of dactylogyrids were found on the gills of their hosts:Haliotrematoides guttati(García-Vargas, Fajer-Ávila, & Lamothe-Argumedo, 2008),H. plectridiumKristky and Mendoza-Franco inKritsky,Tingbao, & Yuan, 2009,H. spinatusKristky and Mendoza-Franco inKritsky et al. (2009),Euryhaliotrema perezponceiGarcía-Vargas, Fajer-Ávila & Lamothe-Argumedo, 2008 andE. mehen(Soler-Jiménez, García-Gasca, & Fajer-Avila, 2012). Freshly collected specimens providedan opportunity to study and compare specimens from different localities in further detail and few morphological characters were added to thedescription of each species. Additionally, a fragment of 856 bp of the 28S ribosomal RNA (D1–D3) was obtained for all the sampled monogeneans,and a phylogenetic analysis along with all available sequences of dactylogyrids was conducted to establish the systematic position of the specieswithin the Ancyrocephalinae. Our results suggest that species ofHaliotremamight be included inHaliotrematoidesgenus. In addition, the geneticdivergence data suggest thatH.guttatiandH.spinatusmay represent a species complex; however, this asseveration needs additional data.All Rights Reserved © 2015 Universidad Nacional Autónoma de México, Instituto de Biología. This is an open access item distributed under theCreative Commons CC License BY-NC-ND 4.0."

Finfish mariculture is typically threatened by parasite and disease outbreaks. Therefore, it is important to identify parasite species of potential risk for this activity. Snappers are valuable food fish worldwide. In the Eastern Pacific, spotted rose snapper (Lutjanus guttatus [Steindachner, 1869]) is a firm candidate for sea-cage aquaculture. In the current study, the parasitism of caged L. guttatus by dactylogyrids was evaluated for the first time during a complete farming period. Twenty five thousand juvenile fish produced at the Research Center for Food and Development (CIAD, Mazatlan Unit) were reared in a sentinel sea-cage from February to November 2012 in Mazatlan Bay, Mexico. A fish sample (n = 15) was obtained every month. Dactylogyrids from the left second gill arch were identified and quantified. A total of 18,704 dactylogyrids distributed in three species, Euryhaliotrema perezponcei Garcia-Vargas, Fajer-Avila and Lamothe-Argumedo, 2008, E. mehen (Soler-Jimenez, Garcia-Gasca and Fajer-Avila, 2012), and Haliotrematoides guttati Garcia-Vargas, Fajer-Avila and Lamothe-Argumedo, 2008 (Monogenea: Dactylogyridae) was found, which were able to infect caged L. guttatus since the first month of the farming period. Prevalence of these parasite species was 100% all the time, except for initial low values for E. mehen and H. guttati. The mean intensity of infection of each dactylogyrid species varied significantly between sampling months. Euryhaliotrema perezponcei was the most abundant parasite, reaching the highest mean intensity in May, June and July (154.3, 296.9 and 176.6 parasites/host, respectively). No clear seasonality of infection was observed; however, the influence of the water temperature on the observed infection levels is discussed. There was no mortality, change on behavior or pathological signs. However, given the rapid infection and proliferation of dactylogyrids, particularly E. perezponcei on L. guttaus reared in a sentinel sea-cage, outbreak of these parasites could be expected when this fish species is cultured on a large scale.

Based on light and scanning electron microscopical studies, three new gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) are described from marine fishes of the genus Lutjanus Bloch (Perciformes: Lutjanidae) in the northern Gulf of Mexico: P. longispicula sp. n. from the ovary of the northern red snapper L. campechanus (Poey) (type host) and silk snapper L. vivanus (Cuvier); P. latispicula sp. n. from the ovary and rarely testes of the grey snapper L. griseus (Linnaeus); and P. synagridis sp. n. (only males available) from the ovary of the lane snapper Lutjanus synagris (Linnaeus). These species are mainly characterised by the lengths of spicules (378-690 µm, 135-144 µm and 186-219 µm, respectively) and spicule shapes, structure of the distal portion of the gubernaculum and the structure of the male caudal end. These are the first valid, nominal species of gonad-infecting philometrids reported from fishes of the family Lutjanidae in the western Atlantic region.

ATP-Binding Cassette (ABC) transporters are proteins that actively mediate the transport of a wide variety of molecules, including drugs. Thus, in parasitology, ABC transporters have gained attention as potential targets for therapeutic drugs. Among the parasitic Platyhelminthes, ABC transporters have been identified and classified in a few species of Trematoda and Cestoda but not in Monogenea. Monogeneans are mainly ectoparasites of marine and freshwater fish, although they can also be found on other aquatic organisms. Severe epizootics caused by monogeneans have been reported around the world, mainly in confined and/or overcrowded fish. The purpose of this study was to identify the ABC transporters in four species of monogeneans (Gyrodactylus salaris, Protopolystoma xenopodis, Eudiplozoon nipponicum and Neobenedenia melleni) for which genomic resources are publicly available. For comparative purposes, ABC transporters were also identified in endoparasitic (Schistosoma mansoni and Echinococcus granulosus) and free-living (Macrostomun lignano and Schmidtea mediterranea) platyhelminths. Thirty-two putative ABC transporters were identified in the genome of G. salaris, 40 in the genome of P. xenopodis, 46 in the transcriptome of E. nipponicum and 9 in a rather limited ESTs set available for N. melleni. Of the eight ABC subfamilies (A-H) known in metazoans, subfamily H was the only one not found in any monogenean species. In contrast, ABCC was the best represented subfamily. Phylogenetic analyses showed a few cases of one-to-one orthologous relationships, which agree with results from other metazoan species. We found some monogenean ABC members related to subfamilies B, C and G involved in drug resistance in humans. This information may be useful for future functional studies on ABC transporters in monogeneans.

Euryhaliotrematoides mehen n. sp. (Monogenea: Dactylogyridae) is described based on specimens collected from the gills of the spotted rose snapper Lutjanus guttatus (Steindachner) off Mazatlan, Sinaloa, on the northwestern coast of Mexico. The synapomorphy of this genus is the presence of a funnel-shaped base of the male copulatory organ. This new species differs from all other species of the genus by possessing a male copulatory organ with a base with a thickened margin and a membranous accessory piece resembling a scarf and covering about 60% of its distal region. PCR products of the 28S rRNA (831 bp) and 18S rRNA (662 bp) genes were sequenced and submitted to GenBank (accession numbers HQ615997 and JF938069, respectively). BLASTn searches revealed no 100% identical hits with the previously registered monogenean sequences.

The present study investigated the effect of β-1,3/1,6-glucan on growth, haematology, innate immunity and resistance against dactylogyrids on the spotted rose snapper (Lutjanus guttatus). Fish were fed during 5 weeks with commercial diet (control group) and same diet supplemented with three levels of β-glucans (0·05%, 0·1% and 0·5%/kg feed). The results showed that at concentrations of 0·05% and 0·1%, fish growth was enhanced, and in weeks 2 and 4, an increase in cellular responses such as percentage of monocytes, neutrophils, respiratory burst activity and nitric oxide activity was observed. In diet with 0·5%β-glucans, changes were registered at the end of the experiment. At week 2, 0·05%β-glucans showed the best response to most of the analysed parameters. In a second trial, diet with 0·05%β-glucans was chosen to prove its effect on the resistance of infected fish with monogeneans. The results showed that fish reduce significantly the number of dactylogyrids, and parameters such as WBC, percentage of lymphocytes, neutrophils and eosinophils were increased. In addition, WBC and percentage of thrombocytes increased in the control (+). The β-glucans have the potential to be use in diet formulations of the spotted rose snapper and to limit the adverse effects of dactylogyrids.

The present study is the first description of the egg morphology, embryonic development, and time required for hatching, and longevity of the oncomiracidium of Heterobothrium ecuadori (Meserve, 1938) Sproston, 1946. Experiments found that hatching time fluctuated between 7 and 10 days with a mean of 7.5 ± 1 days at 23 ± 1° C and 35 ‰. Eggs were provided with a polar filamentous appendage. The body of the oncomiracidium was flattened dorso-ventrally, 156 ± 9 μm long and 65 ± 8 μm wide. A full description of the egg development and morphology of the oncomiracidium is provided. The longevity of the oncomiracidia was 4–7 days at 21 ± 1°C, with a mean survival time of 121.8h. The ability to rear diclidophorids like H. ecuadori and to record precise information on their development provides valuable data for further studies.

A new nematode species, Philometra floridensis sp. n. (Philometridae), is described from male and female specimens found in the ovary of red drum, Sciaenops ocellatus (Linnaeus) (Sciaenidae, Perciformes), from the Gulf of Mexico off Treasure Island, Florida, USA. Based on light and scanning electron microscopy examination, the new species differs from most other gonad-infecting Philometra spp. in having a smooth gubernaculum with a distinct dorsal tooth on the distal tip. The new species is most similar to P. carolinensis Moravec, de Buron & Roumillat, 2006, but differs in length and shape of spicules. It can be distinguished from P. carolinensis and other species with unknown males, by the markedly greater body length of gravid females (up to about 100 cm). Philometra floridensis is the third valid gonad-infecting species of Philometra reported from sciaenids.

Concurrent infections provoked by the sea lice Lepeophtheirus simplex and the monogenean Neobenedenia sp. on bullseye puffer fish Sphoeroides annulatus, reared in tanks, have been related to skin pathology and mortality. Freshwater treatment is widely used to treat two parasite groups, but the results differ depending on the parasite species, life stage and exposure time. The present study describes the effectiveness of freshwater treatments to remove both parasites. Sea lice nauplii and free swimming copepodids, reared in the laboratory, were exposed to freshwater treatments for periods from 30 s to 16 min. Fish experimentally infected with sea lice or monogeneans were exposed to freshwater for 15 to 90 min and 10 to 60 min, respectively. All sea lice nauplii and copepodids were killed by freshwater dips at 2.5 and 14 min, respectively. For pre-adult and adult sea lice, 30 and 60 min of freshwater exposure significantly reduced up to 95 and 99% respectively. However, most freshwater exposures did not reduce chalimus stages more than 10%. Immature and adult populations of monogeneans showed a significant reduction of 95% at 20 min of exposure. These results indicate that, if used properly, freshwater baths constitute an efficient alternative to control these mixed ectoparasite infections on bullseye puffer fish reared in tanks.

Aim: To characterize and identify vibrios present in wild and cultured juvenile snappers (Lutjanus guttatus) in northwestern Mexico. Methods and Results: Spotted rose snapper juveniles were collected at four localities in northwestern Mexico. Bacteria were isolated from external lesions, kidney, liver, and spleen from cultured and wild caught organisms. In total, 280 isolates were obtained and fingerprinted with rep-PCR (GTG5). Nearly 93·2% of the strains belonged to the Vibrionaceae family. Species and genera identified were Photobacterium damselae subsp. damselae (76 strains), Photobacterium leiognathi (13), Vibrio sp. (24), Vibrio alginolyticus (12), Vibrio campbellii (19), Vibrio fortis (9), Vibrio harveyi (49), Vibrio ichthyoenteri (4), Vibrio mediterranei (4), Vibrio parahaemolyticus (1), Vibrio ponticus (2), Vibrio rotiferianus (22), and four potential new species. Conclusions: A wide diversity of vibrios was found in the external lesions and internal organs of both wild and cultured spotted rose snapper juveniles. In total, 12 species of vibrios and four potential new species were identified. Significance and Impact of the Study: This is the first study on the vibrios present in the spotted rose snapper and therefore might serve as a basis for future studies and diagnosis.

Ancyrocephaline monogeneans such as Haliotrema sp. and Euryhaliotrema sp. are common parasites infecting gills on the red snapper, Lutjanus guttatus , an important potential fish species for aquaculture in Mexico. The effectiveness of different treatments against these monogeneans using in vitro and in vivo assessments on the viability of eggs and adults was evaluated. Eggs from both monogenean species were in vitro exposed to sodium hypochlorite, drying, formalin, and freshwater for 3 h, and returned to seawater to determine post-treatment hatching. Adults of both parasites were also in vitro exposed to formalin, freshwater, and caprylic acid for periods ranging from 10 to 60 min using seawater as control. In vivo tests were carried out with freshwater, formalin, and praziquantel (active ingredient of Drontal™ Plus and Vermiplex™ Plus) on snappers infected with both parasites. After 3 h exposure, egg hatching was completely suppressed at 120 mg l − 1 of available chlorine, while drying, formalin (83 mg l − 1 ) and freshwater showed eggs viabilities of 10, 23, and 10% respectively. In vitro freshwater exposure significantly reduced the mean intensity of ancyrocephaline adults (99% at 30 min), followed by formalin at 51 mg l − 1 (72% at 60 min) and caprylic acid at 334 mg l − 1 (5% at 30 min). In vivo freshwater baths for 30 min removed 100% of ancyrocephalines, although this method was stressful for the fish, while formalin (60 min at 51 mg l − 1 ), Drontal™ Plus (12-h at 4.5 mg l − 1 ) and Vermiplex™ Plus (24-h at 3.5–4.5 mg l − 1 ) removed 72, 100 and 100% respectively. This study indicates that praziquantel, freshwater, and formalin baths were effective against ancyrocephaline adults from red snapper, and sodium hypochlorite would be useful to prevent horizontal infection with eggs on fish-rearing facilities.

The relationship between parasites and environmental stress were studied in two tropical coastal lagoons of Northwest Mexico: Urias estuary (highly polluted) and Teacapan estuary (slightly polluted). Metazoan parasites were examined in 292 white mullet (Mugil curema) specimens collected bimonthly during a year from both systems. Haliotrema mugilinus, Metamicrocotyla macracantha, Ergasilus sp., Caligus sp., Holobomolochus sp., and Lernaeopodidae were found in gills, while Contracaecum sp. larvae III was found liver, hepatic portal vein and kidneys. Ecological indices were influenced by the slightly higher number of parasitic species in Urias compared to Teacapan, as well as the clear dominance of two species: Ergasilus sp. and Contracaecum sp. in both systems. In fact, Ergasilus sp. showed considerably higher abundance in Urias, possibly indicating that its success was a result of adverse conditions affecting the host, while Contracaecum sp showed higher abundances in Teacapan, suggesting that the environmental conditions occurring in Urias could have produced negative impacts on the nematode's infective potential.

Gregarines from Nematopsis genus are a common intestinal parasite infection in the white shrimp, Litopenaeus vannamei, that is cultured on the Pacific coast of Mexico. Slow growth and mortalities of white shrimp have been associated with gregarine infections. Control of gregarine infections in Mexican shrimp farms with antibiotics by empirical methods is becoming increasingly important. However, no effective chemotherapeutic control has been demonstrated. The objective of the present study was to evaluate the effectiveness of oral administration of sodium monensin, Elancoban™ and sulfachloropyrazine, Avimix-ST™ in removing Nematopsis gametocysts from the intestine of naturally infested cultured white shrimp (L. vannamei). Four experiments were carried out where different concentrations of antibiotics were administered to naturally infested shrimp through medicated feed for 5 consecutive days. The experimental system consisted of glass aquaria containing 8–10 shrimp. Concentrations of antibiotic varied from 2 to 8 g kg−1 for Elancoban™ and from 1.5 to 7 g kg−1 for Avimix-ST™. After 5 days of treatment, both products significantly reduced the mean intensity of Nematopsis gametocysts when compared to the control. Elancoban™ treatment reduced Nematopsis gametocysts by 92% and 94% at 5.5 and 6 g kg−1, respectively, and Avimix-ST™ reduced the numbers of gametocysts by 85% and 83% at 2.5 and 3.5 g kg−1, respectively. No mortalities were recorded for these treatments. The study demonstrates the effectiveness of Elancoban™ and Avimix-ST™ used in medicated feed as a gregarinostats in the control of Nematopsis gametocysts in the white shrimp L. vannamei.

First attempts at culturing Sphoeroides annulatus (bullseye puffer fish) resulted in recurrent parasitic infestations caused by the monogenea Heterobothrium ecuadori and the dinoflagellate Amyloodinium ocellatum, both of which are associated to mortality events in other cultured species. However, little information exists on the therapeutic levels to prevent and control such infections. The objective of the present study was to evaluate the safety of formalin to bullseye puffer fish and determine the efficacy of formalin to control parasitic infestations. The formalin median lethal concentration (LC50) for the bullseye puffer fish ranged from 1095 mg l−1 at 30 min and 972 mg l−1 at 60 min to 79 mg l−1 at 72 h. The formalin in vitro effective median concentration (EC50) against H. ecuadori was 225 mg l−1 at 30 min and 87 mg l−1 at 60 min. The resulting therapeutic index was 5 at 30 min and 11 at 60 min. Formalin was further tested in vivo against A. ocellatum. In comparison to the controls, 51 mg l−1 of formalin significantly reduced the number of parasites on the skin (97%) and gills (68%) of fish after 1 h of exposure, while 4 mg l−1 significantly reduced the numbers on the skin (66%) and gills (84%) after 7 h. The differences in toxicity between the bullseye puffer fish and specific parasites indicated that formalin was efficacious in the control of parasitic epizootics in the bullseye puffer fish culture.

Farming of finfish in sea cages is gaining popularity worldwide. These systems are a suitable environment for the emergence, establishment and transmission of parasites or pathogens, such as sea lice (Copepoda: Caligidae), known to cause serious diseases and economic losses in finfish aquaculture worldwide. In coastal waters of Jaramijó, Ecuador, there are plans to culture spotted rose snapper (Lutjanus guttatus) and longfin yellowtail (Seriola rivoliana); however, the information about the occurrence of sea lice on fish from this country is scarce. To address this problem, a parasitological survey of economically important fish caught by artisanal fishermen was conducted between June 2013 and May 2014. A total of 608 fish belonging to 66 species were examined. Sea lice were found on 23 fish species. The diversity of these parasites consisted of 22 species of Caligus and 5 species of Lepeophtheirus. Most sea lice species (66%) occurred in a single fish species only, with low infection levels. The most frequently encountered species were Caligus asperimanus Pearse, 1951, Caligus mutabilis Wilson, 1905 and Caligus rufimaculatus Wilson, 1905. Taxonomic remarks are presented for some of the species recorded during this survey. All but two sea lice records are new to Ecuador, considerably expanding the geographical range of some species.

Lepeophtheirus simplex Ho, Gómez et Fajer-Avila, 2001 is a parasite of Sphoeroides annulatus (Jenyns), an economically important fish species, with potential for aquaculture, in northwestern Mexico. The goal of this study was to describe the developmental stages under experimental conditions and seasonal fecundity of this parasite on wild fish. There are two naupliar, one copepodid, two chalimus and two pre-adult stages preceding the adult of L. simplex. The results support previous findings, which point out that the life cycle of the caligid copepods includes only six post-naupliar stages. The generation time from egg extrusion to adult for L. simplex was approximately 10 days at 22 °C. The body length of the ovigerous females ranged between 2.2 and 4.1 mm, and its fecundity between 12 and 36 eggs per string. Fecundity was negatively correlated with the egg size and positively correlated with the egg string length. Our data did not reveal significant differences in fecundity among sampling months, but ovigerous females were significantly larger in March (when water temperature was 22 °C) than in June and July (when water temperature was 30 °C). To some extent, our fecundity results contrast with those found in species of sea lice from higher latitudes. Undoubtedly, biological information on different species of sea lice from different environmental conditions will enhance our understanding of their infection strategies and will be valuable, given the increasing interest in marine fish farming in Mexico.

A histopathological survey of wild and cultured shrimp from the Gulf of Mexico was carried out to determine the prevalence and severity of infectious diseases and parasites, affecting four species of penaeid shrimp (Litopenaeus setiferus, Farfantepenaeus aztecus, F. duorarum, and L. vannamei). Around 60 shrimp were obtained from each of 10 sampling stations during different months in 1999 and 2000. One station was a shrimp culture farm from Tamaulipas State, and nine were wild stations from Tamaulipas (five), Veracruz (one), and Campeche (three) States. Thirty shrimp from each station were used for histological analysis. The remaining shrimp were frozen and kept at −20 C to carry out PCR techniques to determine the presence of white spot syndrome virus (WSSV). Some in situ hybridization analyses were applied to ascertain cases of WSS viral disease. Fresh analysis was carried out in shrimp from only one station for parasite identification. The histopathological survey performed on 688 shrimp showed no evidence of viral diseases. Two shrimp from one station were histologically diagnosed as having presumptive WSSV. Tissues from the same shrimp were processed for in situ hybridization and another 20 samples from the same station were processed to run PCR techniques. In each case, the results were negative. The same PCR procedure was applied to the rest of the frozen samples and none of them showed the presence of the WSSV. No important bacterial infections were observed in any of the wild or cultured shrimp analyzed. Fresh analysis demonstrated the presence of the cestode Prochristianella hispida and the gregarines Cephalolobus penaeus and Nematopsis penaeus. Histological analysis showed that the abundance of P. hispida varied from 7 to 90%, and G1 to G4 grades of severity were observed, with G1 being the most common. Gregarines were commonly observed in the histological slides, with a prevalence varying from 3 to 56% and G1 severity in most cases. Haplosporidan infection was observed in one sample of F. duorarum, which is the first report of this parasite in this host. Two invasive epibionts, the filamentous bacteria Leucothrix sp. and the ciliate Ascophrys sp., were found in four sampled stations. The study showed that in ten stations sampled from 1999 to 2000 in the Gulf of Mexico, shrimp populations had no serious infectious diseases.

The parasitic nematode Philometra floridensis infects the ovary of its only host, the economically important fish species Sciaenops ocellatus, but the factors influencing host suscepti- bility and potential pathogenic effects are unknown. Here we report new information on these topics from evaluations of infected and uninfected hosts collected from the northeastern Gulf of Mexico. Fish length and age were evaluated vis-a-vis nematode prevalence to check for ontoge- netic differences in host susceptibility. To evaluate health and reproductive consequences of infection, we looked for effects in Fulton's condition factor (K) and batch fecundity estimates (BF), and we evaluated ovarian tissue histologically to check for oocyte atresia and other host re - sponses. We observed localized pathological changes in fish ovarian tissue associated with female nematodes, including leucocytic exudates, granulomatous inflammation, and Langhans-type multinucleated giant cells; the hosts, however, appeared to maintain high fecundity and actually exhibited, on average, better health index scores and higher relative fecundity than did unin- fected fish. These differences are likely explained by the parasite's tendency to disproportionately infect the largest, actively spawning fish and by the localization of pathogenic changes, which could have masked effects that otherwise would have been reflected in mass-based health indica- tors. Although we did not detect negative effects on measures of overall health or reproductive output, further research is needed to better elucidate the relationship between these parasites and other factors affecting host reproductive potential, such as egg quality.

The mechanism of the cyclization of meso-(1-hydroxy-2-propenyl)octaethylporphyrin to octaethylbenzochlorin is proposed. Chlorin intermediates were isolated, characterized and then converted to octaethylbenzochlorin. A rhodinobenzochlorin was isolated on demetallation of Ni coprobenzochlorin with methane sulfonic acid and its structure was confirmed by X-ray crystallography.

The crystal structure of a pyridine-ligated, high-spin Ni(II) complex of 2,3,7,8,12,13,17,18-octabromo-5,15-bis(isopropyl)-10,20-bis(isopropylidenyl) porphyrin, 2, is reported and compared to the unligated, low-spin Ni(II) complex, 1, previously reported. The results demonstrate that conversion to high-spin Ni(II) in nonplanar, sterically encumbered porphyrins induces a significant core expansion about the Ni while nonplanarity is still retained. The expansion of the core parameters (Ni−N, Ct-Cα, Ct-Cmeso) and the Ni−Naxial distances are characteristic of the dx2-y2 and dz2 orbital occupancies in high-spin Ni(II) porphyrins and document the structural consequences of the spin conversion in severely nonplanar Ni(II) porphyrins. The stereochemical results are particularly relevant to ligation effects in nonplanar Ni biomolecules and synthetic porphyrins increasingly used as biomimetic models of conformational effects in chromophores and prosthetic groups in vivo, and to the remarkably wide range of lifetime...

The crystal structures of four different conformers of the sterically encumbered porphyrins ZnDPP, H2DPP, and NiDPP are reported (DPP = 2,3,5,7,8,10,12,13,15,17,18,20-dodecaphenylporphyrin). In com...

Synthetic porphyrin−quinone complexes are commonly used to mimic electron transport in photosynthetic reaction centers and to probe the effects of energetics, distances, and relative orientations on rates of electron transfer between donor−acceptor couples. The structures of two such models have been determined by X-ray diffraction. The redox pairs consist of a zinc porphyrin covalently linked to benzoquinone in cis and trans configurations via a cyclohexanediyl bridge. The crystallographic studies were undertaken to provide a structural foundation for the extensive body of experimental and theoretical results that exists for these compounds in both the ground and photoinduced charge-separated states. The results validate conclusions reached from theoretical calculations, EPR and two-dimensional NMR results for these states.

The spatial distribution and coexistence of monogenean dactylogyrids was assessed on the gills of 63 specimens of wild spotted rose snapper, Lutjanus guttatus (Steindachner), caught in the Mazatlan Bay, Sinaloa, Mexico. Five species are reported: Euryhaliotrema perezponcei Garcia-Vargas, Fajer-Avila et Lamothe-Argumedo, 2008, Euryhaliotrematoides sp., Haliotrematoides spinatus Kritsky et Mendoza-Franco, 2009, H. plectridium Kritsky et Mendoza-Franco, 2009, and H. guttati Garcia-Vargas, Fajer-Avila et Lamothe-Argumedo, 2008. All except E. perezponcei and H. guttati represent new geographical records for the Pacific coast. The most prevalent dactylogyrid species was E. perezponcei (100%), H. plectridium and H. spinatus had >80% prevalence, and H. guttati and Euryhaliotrematoides sp. had the lowest prevalence. The mean abundance of H. plectridium and E. perezponcei was close to 60 parasites/fish, whereas Euryhaliotrematoides sp. and H. guttati had the lowest abundance. The dactylogyrid species exhibited a tendency for attachment to gill arch 2: 25% attachment occurring on gill arch 1, 30% on 2, 27% on 3 and 18% on 4, and showed a significant preference for the central sector of the gill (42%). Haliotrematoides plectridium had a preference for attachment to gill arches 2 and 3 and the central sector. Haliotrematoides spinatus tended to settle on the gill arches 2 and 3 and had a preference for the central sector. Euryhaliotrema perezponcei tended to settle on the gill arches 1 and 2 and the anterior gill sector. Euryhaliotrematoides sp. and H. guttati did not show a preference for any gill arch or sector. The intraspecific aggregation was stronger than the interspecific aggregation, indicating that all the dactylogyrid species on spotted rose snapper were aggregated, and there was no evidence of competition among the species.

El copepodo condracantido Pseudochondracanthus diceraus es un parasito frecuente en las branquias del botete diana silvestre, Sphoeroides annulatus en Sinaloa, Mexico. El presente estudio constituye la primera descripcion de algunos parametros sanguineos y la histologia branquial de S. annulatus infestados por hembras adultas de P. diceraus. Se aclimataron sesenta y dos peces silvestres en tanques experimentales por 15 dias y a los 16 y 21 dias se tomaron muestras para la realizacion de los analisis. Se observo un 100% de prevalencia y una intensidad media de 7,16 (1-17) parasitos por pez. P. diceraus prefirio los sectores anteriores y posteriores de cada arco branquial. Los porcentajes de leucocitos fueron significativamente menores en peces con las mas altas intensidades de infestacion. La respuesta branquial del hospedero fue mas pronunciada cerca del sitio de fijacion del parasito y estuvo caracterizada por hiperplasia y fusion de las lamelas secundarias, hiperplasia condrocitica de las lamelas primarias, atrofia del epitelio lamelar e incremento del numero de celulas mucosas. Los danos en el tejido branquial del botete diana son causados por las antenas grandes y robustas modificadas en forma de grapa que emplea el parasito para fijarse al pez. Esto indica que altas prevalencia e intensidades de infestacion por P. diceraus representan un riesgo de salud potencial para el cultivo de esta especie de pez.

The present study investigated the effect of β-1,3/1,6-glucan on growth, haematology, innate immunity and resistance against dactylogyrids on the spotted rose snapper (Lutjanus guttatus). Fish were fed during 5 weeks with commercial diet (control group) and same diet supplemented with three levels of β-glucans (0·05%, 0·1% and 0·5%/kg feed). The results showed that at concentrations of 0·05% and 0·1%, fish growth was enhanced, and in weeks 2 and 4, an increase in cellular responses such as percentage of monocytes, neutrophils, respiratory burst activity and nitric oxide activity was observed. In diet with 0·5%β-glucans, changes were registered at the end of the experiment. At week 2, 0·05%β-glucans showed the best response to most of the analysed parameters. In a second trial, diet with 0·05%β-glucans was chosen to prove its effect on the resistance of infected fish with monogeneans. The results showed that fish reduce significantly the number of dactylogyrids, and parameters such as WBC, percentage of lymphocytes, neutrophils and eosinophils were increased. In addition, WBC and percentage of thrombocytes increased in the control (+). The β-glucans have the potential to be use in diet formulations of the spotted rose snapper and to limit the adverse effects of dactylogyrids.

The aim of the present study was to obtain a basic knowledge of the hematology in order to determine changes in blood parameters of the spotted rose snapper Lutjanus guttatus. The morphological features of blood cells were described according to the observations made by light microscopy of Wright-Giemsa-stained blood films. The reference intervals and the mean value were determined for each hematological parameter evaluated in healthy fish and data were compared to those of naturally infected, with dactylogyrid monogeneans fish. Infected fish showed a prevalence of 100% and a mean intensity of 246.6 parasites per fish. Mean values of HCT, WBC, thrombocytes percentage and eosinophils percentage were significantly higher (P

Examination of the gill lamellae of 3 species of Centropomus spp. (Centropomidae) from 9 localities around the southern coast of Florida revealed 3 species of Rhabdosynochus (Monogenoidea, Diplectanidae). The common snook, Centropomus undecimalis, was infected with Rhabdosynochus rhabdosynochus (30 of 37 infected; prevalence 81%), Rhabdosynochus hargisi (9 of 37; 24%), and Rhabdosynochus hudsoni (20 of 37; 46%); the fat snook, Centropomus parallelus, with R. rhabdosynochus (12 of 22; 55%) and R. hudsoni (8 of 22; 36%) (new host records for both); and the tarpon snook, Centropomus pectinatus, with R. hudsoni (3 of 4; 75%) (new host record). Snooks infected with R. rhabdosynochus were collected only from tidal waters of salinity ≤10.4 ppt, where the parasite dominated the monogenoidean community. Rhabdosynochus hargisi and R. hudsoni showed greater salinity tolerance; the former dominated where salinity was ≥28.8 ppt. Thus, salinity appears to be a determinate factor in partitioning the monogenoidean community, while water depth and temperature and host population (as defined by collection locality) did not appear to affect occurrence of Rhabdosynochus spp. on snooks in Florida. With the exception of Tampa Bay for R. hargisi , each locality represented a new geographic record for the respective diplectanid. The type species, R. rhabdosynochus, is redescribed based on specimens collected from its type host, C. undecimalis.