No description available.

Aim: This series of studies assessed the influence that digenean parasites exert on a host population beyond the initial cost of infection. It aimed to address the discrepancy between the exclusion of parasites from most ecological studies, and their functional importance within the wider free-living community. It also assessed methodologies that utilise the diversity of the parasite community as well as the phenotypic effects of parasitism, as potential tools for ecology and palaeoecology. Results: From 2004-2007, in excess of 53,000 snails were dissected during the course of these studies. Making it one of the most detailed parasitological studies undertaken on a single host parasite interaction in this field. Community studies - Parasite diversity was found to be influenced by local scale abiotic, as well as large scale environmental patterns. Parasite diversity correlates with the distribution of definitive avian hosts, which in turn correlates with intertidal benthic communities. These correlations provide an effective methodology for monitoring ecosystem health. Behavioural studies - A critical assessment of parasite mediated behavioural change revealed the indirect cost of gigantism in the host population to be a side effect, and that differences in behaviours were often a result of size rather than infection. Growth/Morphometric studies - Gigantism was revealed as both infection and environment driven. Finally, morphometric analysis revealed conchiometric markers that provide tools for reconstructing past environments and infection prevalence. Main conclusions: The functional importance of digenean parasitism within the intermediate host snail Hydrobia ulvae, extends far beyond the individual. Digeneans directly and indirectly manipulate the host population, in turn affecting wider community structure. Environmental, abiotic and biotic factors can leave observable imprints on the infected and uninfected host population. Such markers can provide tools and methodologies for furthering our understanding of both extinct and extant host-parasite populations.

This study was designed to provide the foundation for future work on the ecology and evolution of Necturus-parasite systems by providing vital parasite survey information for the aquatic salamander Necturus alabamensis. During this study 115 N. alabamensis were collected from north Florida. Hosts yielded the cestode Proteocephalus loennbergi, monogeneans from the genus Sphyranura, digeneans from the genus Gorgoderina, and what appears to be several nematode species. Nematodes, digeneans, and cestodes were abundant while monogeneans were rare. Monogenean and cestode parasites were categorized as specialists (parasites specific to one species or the species of a single genus), and digenean and nematode parasites were categorized as generalists (infecting numerous, possibly distantly related hosts). Statistical analysis did not indicate a parasite load difference between sites for digeneans and cestodes but did indicate a difference for nematodes. Helminth populations appear to be overdispersed (the majority of the parasites are found in only a few hosts). This study provides insight into some aspects of the ecological relationships of N. alabamensis and its helminths. However, parasite surveys of the other members of Necturus are necessary for the evaluation of evolutionary relationships within this system.

No description available.

Orientador: Reinaldo José da Silva / Resumo: Este estudo primeiramente investigou e descreveu a diversidade de parasitas metazoários associados a 26 espécies de anuros em uma região de transição entre Mata Atlântica e Cerrado no noroeste paulista, Brasil. Em seguida, procuramos analisar os padrões de agregação e distribuição das populações parasitárias nas diferentes espécies de hospedeiros bem como a estrutura e composição da comunidade componente. Também foram reportados novos registros de ocorrência em anuros do Brasil e considerações taxonômicas para algumas espécies de helmintos. As 26 espécies de anuros apresentaram um total de 40 taxa de parasitas metazoários: Aplectana hylambatis, Aplectana membranosa, Brevimulticaecum sp. (larva), Cosmocerca cf. chilensis, Cosmocerca parva, Cosmocerca podicipinus, Cosmocercidae gen. sp., Falcaustra mascula, Ochoterenella digiticauda, Ochoterenella sp., Oswaldocruzia mazzai, Oxyascaris caudacutus, Oxyascaris sp., Parapharyngodon cf. alvarengai, Physaloptera sp. (larva), Raillietnema minor, Raillietnema sp., Rhabdias sp.1, Rhabdias sp.2, Rhabdias sp.3, Schrankiana formosula, Spiroxys sp. (larva) (Nematoda), Centrorhynchidae gen. sp. (cisto), Cistacanto não identificado (Acanthocephala), Cylindrotaenia americana (Cestoda), Brachycoelium salamandrae, Bursotrema sp. (metacercária), Catadiscus marinholutzi, Catadiscus propinquus, Catadiscus sp., Clinostomum sp., Gorgoderina diaster, Gorgoderina sp., Heterodiplostomum sp. (metacercária), Lophosicyadiplostomum sp. (metacercária), metac... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In the present study, we firstly investigated and described the diversity of metazoan parasites associated with 26 anuran species from a transitional area between Mata Atlântica and Cerrado in Northwest of São Paulo State, Brazil. Thereafter, we searched for aggregation and distribution patterns of parasite populations from different host species as well as the structure and composition of component communities. Also, we reported new records of occurrence in Brazilian anurans and taxonomic considerations for some parasite species. The 26 anuran species presented a total of 40 metazoan parasite taxa: Aplectana hylambatis, Aplectana membranosa, Brevimulticaecum sp. (larvae), Cosmocerca cf. chilensis, Cosmocerca parva, Cosmocerca podicipinus, Cosmocercidae gen. sp., Falcaustra mascula, Ochoterenella digiticauda, Ochoterenella sp., Oswaldocruzia mazzai, Oxyascaris caudacutus, Oxyascaris sp., Parapharyngodon cf. alvarengai, Physaloptera sp. (larvae), Raillietnema minor, Raillietnema sp., Rhabdias sp.1, Rhabdias sp.2, Rhabdias sp.3, Schrankiana formosula, Spiroxys sp. (larvae) (Nematoda), Centrorhynchidae gen. sp. (cyst), Unidentified cystacanth (Acanthocephala), Cylindrotaenia americana (Cestoda), Brachycoelium salamandrae, Bursotrema sp. (metacercariae), Catadiscus marinholutzi, Catadiscus propinquus, Catadiscus sp., Clinostomum sp., Gorgoderina diaster, Gorgoderina sp., Heterodiplostomum sp. (metacercariae), Lophosicyadiplostomum sp. (metacercariae), Unidentified metacercariae, ... (Complete abstract click electronic access below) / Doutor

No description available.

six species of gyliauchenids are reported in this study, five in the genus Gyliauchen and one in Apharyngogyliauchen. G. pomacentri n.sp. is described from a single specimen recovered from one of one Pomacentrus philippinus, G. parapapillatus n.sp. is described from 42 specimens in one of one Siganus virgatus. Gyliauchen zancli n.sp. is described from a single specimen in one of one Zanclus cornutus. Gyliauchen nahaensis Ozaki, 1937 is redescribed from 189 specimens in one of two siganus punctatus and establishes a new locality record, and in one of one zanclas cornutus, a new host record. Gyliauchen sp. is described from two specimens of two of four Siganus spinus.

Orientador: Reinaldo José da Silva / Resumo: Nos últimos anos, os parasitas foram reconhecidos como importantes componentes dabiodiversidade global, dado os importantes papéis desempenhados por esses organismosem ecossistemas naturais. Embora o conhecimento sobre a diversidade de parasitas tenhaaumentado nas últimas décadas, o número de espécies de parasitas de peixes no Brasil érelativamente baixo quando comparado com a biodiversidade das espécies hospedeiras.Desta forma, o presente trabalho teve como objetivo realizar um levantamento dabiodiversidade dos parasitas de peixes procedentes de quatro locais em uma área sob ainfluência de Pequenas Centrais Hidrelétricas (PCHs) no rio Sapucaí-Mirim, Estado de SãoPaulo, Brasil, bem como avaliar a estrutura das comunidades de metazoários parasitas depeixes Characiformes e de quatro espécies do gênero Leporinus. Durante o período demarço de 2012 a julho de 2013, foram coletados 462 espécimes pertencentes a 16 espéciesde peixes das ordens Characiformes, Siluriformes, Gymnotiformes e Perciformes.Observou-se que 86,58% dos espécimes estavam parasitados por pelo menos um taxon demetazoário parasita. Os parasitas encontrados pertenciam a oito diferentes grupos(Myxozoa, Monogenea, Digenea, Cestoda, Nematoda, Acantocephala, Arthopoda eAnnelida), sendo coletado um total de 6.830 parasitas. Noventa e sete taxa de parasitasforam encontrados, sendo que a classe Monogenea foi o grupo que apresentou o maiornúmero de espécies, seguido do filo Nematoda e da s... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Recently, parasites have been recognized as important components of global biodiversitybecause the important roles played by these organisms in natural ecosystems. Althoughknowledge about the diversity of parasites has increased in recent decades, the number ofparasite species of fishes in Brazil is relatively low compared to the biodiversity of hostspecies. Thus, this study aimed to survey the biodiversity of fish parasites from foursampling sites in an area under the influence of Small Hydroelectric Power Plants in theSapucaí-Mirim River, São Paulo State, Brazil, as well as to evaluate the structure ofmetazoan parasite communities of Characiformes and four species of Leporinus sp. FromMarch 2012 to July 2013, 462 fish specimens of 16 species of Characiformes,Siluriformes, Perciformes, and Gymnotiformes were collected. It was observed that86.58% of fish specimens were parasitized by at least one metazoan parasite taxon. Theparasites found belonged to eight different groups (Myxozoa, Monogenea, Digenea,Cestoda, Nematoda, Acantocephala, Arthopoda and Annelida) and a total of 6,830parasites were collected and analyzed. Ninety-seven parasite taxa were found, andMonogenea was the group that had the highest number of species, followed by Nematodaand Digenea. The parasite communities of Characiformes showed mainly differencesamong the host species, although belonging to the same order or family. The sampling site,condition factor and the host body ... (Complete abstract click electronic access below) / Doutor

La présente Thèse représente une importante contribution à la connaissance de l’ultrastructure de la spermiogenèse et du spermatozoïde des Digènes. Nous présentons des nouvelles données spermatologiques concernant huit espèces appartenant à sept familles et superfamilles de Digènes. Ils s’agissent de Brachycoelium salamandrae (Gorgoderoidea : Brachycoeliidae), Diplodiscus subclavatus (Paramphistomoidea : Diplodiscidae), Elstia stossichianum et Wardula capitellata (Microscaphidioidea : Mesometridae), Euryhelmis squamula (Opisthorchioidea : Heterophyidae), Mediogonimus jourdanei (Microphalloidea : Prosthogonimidae), Robphildollfusium fractum (Lepocreadioidea : Gyliauchenidae), et Rubenstrema exasperatum (Plagiorchioidea : Omphalometridae). Les résultats obtenus sur la spermiogenèse et/ou le spermatozoïde sont comparés avec le reste de Digènes. De plus, nous discutons de l’importance de certains caractères ultrastructuraux pour une meilleure compréhension des relations phylogénétiques chez les Digènes. La spermiogenèse chez les Digènes est assez homogène. Cependant, il y a certains aspects comme la variabilité du nombre de bandes du corps intercentriolaire et l’angle de rotation flagellaire qui méritent une attention particulière. Concernant le spermatozoïde, nous avons proposé, après une analyse précise des données spermatologiques disponibles, sept modèles de spermatozoïde chez les Digènes. Les caractères du spermatozoïde les plus utiles pour l’établissement de ces modèles sont : (a) le type d’axonème/es (patron 9+‘1’ des Trepaxonemata, 9+‘1’ spécial et 9+0), (b) l’extrémité antérieure du spermatozoïde (avec un ou deux axonèmes), (c) la présence/absence de l’association « expansion latérale+ornementations externes+microtubules corticaux » ou « ornementations externes+microtubules corticaux », (d) la présence ou l’absence d’ornementations externes et leur localisation sur le spermatozoïde, (e) le patron des microtubules corticaux parallèles, absents ou disposés en un ou deux champs, et (f) le caractère terminal dans l’extrémité postérieure du spermatozoïde (noyau, axonème ou microtubules corticaux). D’autres caractères comme les corps épineux ou les boutons cytoplasmiques ornementés peuvent avoir une importance particulière pour certains taxons. La récente description des corps épineux suppose une reconsidération de certaines études anciennes où ces structures peuvent être mal interprétés ou considérés comme des artéfacts. Les boutons cytoplasmiques ornementes sont un nouveau caractère trouvé chez les Mesometridae (E. stossichianum et W. capitellata). Les spermatozoïdes des espèces étudiées dans cette thèse appartiennent aux modèles 1, 2 ou 3. Le modèle 1, caractérisé par la présence de l’association « expansion latérale+ornementations externes+microtubules corticaux », est présent chez Diplodiscus subclavatus, Elstia stossichianum et Wardula capitellata. De plus, la plupart des Echinostomatoidea, Paramphistomoidea et Pronocephaloidea présentent ce modèle. Le modèle 2 est caractérisé par l’association « ornementations externes+microtubules corticaux » et par une extrémité postérieure du spermatozoïde contenant le noyau. Il est présent chez Brachycoelium salamandrae, Robphildollfusium fractum et Rubenstrema exasperatum. Finalement, Euryhelmis squamula et Mediogonimus jourdanei présentent un spermatozoïde du modèle 3 comme chez certains Opisthorchioidea et certaines familles telles que les Allocreadiidae, Deropristidae, Lepocreadiidae et Troglotrematidae. Le modèle 3 diffère du modèle 2 par l’extrémité postérieure contenant un axonème. Le modèle 4 est similaire aux modèles 2 et 3, mais l’extrémité postérieure contient seulement des microtubules corticaux. Il est présent chez les Opecoelidae et Opistholebetidae. Le modèle 5 exhibe un seul champ (ventral) de microtubules corticaux et ne présente pas l’association « ornementations externes+microtubules corticaux ». Il est observé chez les Faustulidae, Hemiuridae et les Lecithasteridae. Le modèle 6 est observé chez les schistosomes. Ils présentent un spermatozoïde aberrant, non filiforme, avec un seul axonème du type 9+‘1’ spécial. Finalement, le modèle 7, caractérisé par la présence d’axonèmes du type 9+0 et par l’absence de microtubules corticaux, est établit seulement pour Didymozoon sp. / The present Thesis represents a contribution to the knowledge about the ultrastructure of spermiogenesis and of the mature spermatozoon of digeneans. We present for the first time spermatological data concerning eight species belonging to seven families and superfamilies: Brachycoelium salamandrae (Gorgoderoidea: Brachycoeliidae), Diplodiscus subclavatus (Paramphistomoidea: Diplodiscidae), Elstia stossichianum and Wardula capitellata (Microscaphidioidea: Mesometridae), Euryhelmis squamula (Opisthorchioidea: Heterophyidae), Mediogonimus jourdanei (Microphalloidea: Prosthogonimidae), Robphildollphusium fractum (Lepocreadioidea: Gyliauchenidae), and Rubenstrema exasperatum (Plagiorchioidea: Omphalometridae). A global analysis of the spermatological characteristics of these species and those already described in the Digenea, allow us to establish seven sperm models within digeneans. The importance of several ultrastructural characteristics, combined with the proposed models are discussed in order to contribute to a better understanding of digenean phylogenetic relationships.

Dissertação(mestrado)-Universidade Federal do Rio Grande, Programa de Pós-Graduação em Aqüicultura, Instituto de Oceanografia, 2010. / Submitted by Cristiane Silva (cristiane_gomides@hotmail.com) on 2012-07-27T17:53:57Z No. of bitstreams: 1 dissertao de eduardo em pdf.pdf: 149902 bytes, checksum: 3c4a46e26293690177aa2d20d50a32ae (MD5) / Approved for entry into archive by Bruna Vieira(bruninha_vieira@ibest.com.br) on 2012-07-27T18:31:32Z (GMT) No. of bitstreams: 1 dissertao de eduardo em pdf.pdf: 149902 bytes, checksum: 3c4a46e26293690177aa2d20d50a32ae (MD5) / Made available in DSpace on 2012-07-27T18:31:32Z (GMT). No. of bitstreams: 1 dissertao de eduardo em pdf.pdf: 149902 bytes, checksum: 3c4a46e26293690177aa2d20d50a32ae (MD5) Previous issue date: 2010 / Considerando a importância da tainha Mugil platanus Günther, 1880 como fonte de alimento e alternativa de emprego para comunidades locais, este estudo objetiva estabelecer a fauna parasitária e a forma de utilização de M. platanus pelos parasitos, definir a toxicidade do formol e a concentração eficaz para erradicar ou mesmo minimizar a parasitose e, por último, verificar quais as lesões causadas pelo formol e/ou pelos parasitos em juvenis da tainha M. platanus. Quarenta juvenis de tainha M. platanus com peso 1 ± 0,26g e comprimento 4,1 ± 0,4cm foram coletados em arroio na Praia do Cassino, no município de Rio Grande - RS - Brasil. Os hospedeiros foram necropsiados e os ectoparasitos foram fixados em formol 5 %, corados, clarificados e posteriormente montados em lâminas permanentes com bálsamo do Canadá para identificação. Outros foram montados em meio de Grey-Wess para verificação de estruturas esclerotizadas. Os endoparasitos foram fixados em AFA e corados em carmim de Semichon, clarificados e posteriormente montados em lâminas permanentes com bálsamo do Canadá para identificação. Foram identificados Ligophorus cf. uruguayense (Monogenoidea: Ancyrocephalidae) e Solostamenides cf. platyorchis (Monogenoidea: Microcotylidae) nas brânquias. Foram reportados Digenea e Nematoda nos intestinos. A prevalência (P %) de L. cf. uruguayense foi 100 %, a intensidade de infestação (II) variou entre 2 e 110, a intensidade média de infestação (IMI) foi 23,4 e a abundância média (AX) foi 23,4. A prevalência (P %) de S. cf. platyorchis foi 10 %, a intensidade de infestação (II) variou entre 1 e 3, a intensidade média de infestação (IMI) foi 1,5 e a abundância média (AX) foi 0,15. A prevalência (P %) de Digenea foi 92,5 %, a intensidade de infecção (II) variou entre 1 e 40, a intensidade média de infecção (IMI) foi 2,67 e a abundância média (AX) foi 2,47. A prevalência (P %) de Nematoda foi 6,7 %, a intensidade de infecção (II) foi 1, a intensidade média de infecção (IMI) foi 1 e a abundância média (AX) foi 0,07. Os elevados índices de infestação por Monogenoidea e de infecção por Digenea apontam o potencial dano que estes parasitos podem representar nos cultivos. Para analisar a toxicidade do formol para M. platanus e a eficácia deste quimioterápico no controle de parasitos, foram realizados quatro experimentos. Os juvenis foram mantidos em béqueres de 1 L, densidade 8 peixes/ béquer, temperatura da água 21 °C, fotoperíodo 12 h, salinidade da água 5, aeração suave e constante e mantidos em jejum e em observação para análise da sobrevivência. Para determinar a toxicidade do formol aos juvenis foi realizado um teste de toxicidade aguda 96 h, em que os tratamentos foram um controle (sem adição de formol na água) mais 5 concentrações: T1 (5), T2 (8), T3 (15), T4 (30) e T5 (50) mg/L de formol em triplicata. Para verificar a eficácia no controle parasitário foi administrado um banho profilático de 1 h de formol, em que os tratamentos foram um controle (sem adição de formol na água) mais 5 concentrações: T1 (25), T2 (50), T3 (100), T4 (150) e T5 (200) mg/L de formol na água em triplicata. No teste letal de toxicidade aguda, não houve diferença significativa (P > 0,05) entre as réplicas e a temperatura (°C), salinidade, pH, O2 dissolvido na água (mg/L), amônia total (mg/L) e a concentração letal mediana a 50 % (CL50) em 96 h foi estimada em 20,77 mg/L de formol. No banho profilático com formalina durante 1 h, todos os tratamentos foram eficientes eliminando 100 % dos parasitos, exceto no tratamento com 25 mg/L, em que foram identificados L. cf. uruguayense em 13,33 % dos peixes. Houve 100 % de sobrevivência dos hospedeiros em todos os tratamentos, exceto na concentração 200 mg/L em que a sobrevivência foi 87,5 %. Banhos com 25 mg/L de formol durante 1 h são indicados para o controle de S. cf. platyorchis e 50 mg/L para o controle de L. cf. uruguayense, por possuir menor concentração de formol e alta sobrevivência dos peixes. Porém, nenhuma das concentrações testadas é eficiente no controle de endoparasitos. Por último, para determinar as lesões causadas nas brânquias de formol e/ou pelos Monogenoidea, três peixes de cada tratamento, provindos do banho profilático com formol para o controle de parasitoses foram encaminhados para análise histológica. Foi observado que o aumento da concentração de formol causou lesões mais graves nas brânquias. Foi observada hiperplasia leve nos animais mantidos como controle, desprendimento do epitélio respiratório no T2, hiperplasia moderada no T3, aumento da atividade opercular no T4 e necrose, natação errática e mortalidade no T5. Os resultados histopatológicos deste estudo mostram que banhos de 50 mg/L de formol durante 1 hora podem ser aplicados em juvenis de M. platanus para o controle de Monogenoidea, pois nesta concentração, as lesões histológicas causadas nos hospedeiros são leves e a sobrevivência dos juvenis é alta. / Considering the importance of mullet Mugil platanus Günther, 1880 as a food source and alternative employment for local communities, this study aims to establish the parasitic fauna and how M. platanus use by the parasites to define the toxicity of formaldehyde and the effective concentration to minimize or even eradicate the parasites and, lastly, to evaluate the damages caused by formaldehyde and/or parasites in the juvenile mullet M. platanus. Forty juvenile mullet M. platanus weighing 1 ± 0.26 g and length 4.1 ± 0.4 cm were collected in the stream at Cassino Beach, in Rio Grande - RS - Brazil. The hosts were necropsied and the parasites were fixed in 5 % formaldehyde, stained, clarified and subsequently mounted on permanent slides with Canada balsam for identification. Others parasites specimens were mounted in the middle of Gray-Wess to check sclerotic structures. The endoparasites were fixed in AFA and stained with carmine Semichon, clarified and subsequently mounted on permanent slides with Canada balsam for identification. It was identified Ligophorus cf. uruguayense (Ancyrocephalidae) and Solostamenides cf. platyorchis (Microcotylidae) in the gills. It was reported Digenea and Nematoda in the intestines. The prevalence (P %) of L. cf. uruguayense was 100 %, the intensity of infestation (II) ranged between 2 and 110, the average intensity of infestation (IMI) was 23.4 and average abundance (AX) was 23.4. The prevalence (P %) of S. cf. platyorchis was 10 %, the intensity of infestation (II) ranged between 1 and 3, the average intensity of infestation (IMI) was 1.5 and mean abundance (AX) was 0.15. The prevalence (P %) of Digenea was 92.5 %, the intensity of infection (II) ranged between 1 and 40, the average intensity of infection (IMI) was 2.67 and the average abundance (AX) was 2.47. The prevalence (P %) of Nematoda was 6.7 %, the intensity of infection (II) was 1, the mean intensity of infection (IMI) was 1 and mean abundance (AX) was 0.07. High levels of infestation Monogenoidea and infection Digenea point to the potential damage that these bodies may represent the cultures. To analyze the toxicity of formalin to M. platanus and efficacy of chemotherapy in the control of parasites, four experiments were conducted. Juveniles were kept in beakers of 1 liter, density 8 fish/beaker, water temperature 21 °C, 12 h photoperiod, water salinity 5, smooth and constant aeration and maintained at fasting and under observation for survival analysis. To determine the toxicity of formaldehyde was carried out acute toxicity test, in which the treatments were a control (no added formaldehyde in water) and 5 more concentrations: T1 (5), T2 (8), T3 (15), T4 (30) and T5 (50) mg/L of formaldehyde in triplicate. To verify the effectiveness of formaldehyde on parasite control was given a bath of 1 h of the substance in which the treatments were a control (no added formaldehyde in water) and 5 more concentrations of formaldehyde: T1 (25), T2 (50) , T3 (100), T4 (150) and T5 (200) mg/L of formaldehyde in water in triplicate. In the test lethal acute toxicity, no significant difference (P > 0.05) between treatment and temperature (°C), salinity, pH, dissolved O2 in water (mg/L), total ammonia (mg/L) and lethal concentration to 50 % of the sample (LC50) at 96 h was estimated to be 20.77 mg/L of formaldehyde. In the final bath of formaldehyde for 1 h, all treatments were efficient by eliminating 100 % of parasites, except for treatment with 25 mg/L, which were identified L. cf. uruguayense in 13.33 % of the fish. There was 100 % survival of the hosts in all treatments, except at the concentration 200 mg/L in which survival was 87.5 %. Baths with 25 mg/L formaldehyde for 1 h are indicated for the control of S. cf. platyorchis and 50 mg/L for the control of L. cf. uruguayense, because it has lower concentration of formaldehyde and high survival of fish. However, none of the concentrations tested is effective against endoparasites. Finally, to determine the damage caused by formaldehyde in the gills and/or the Monogenoidea, three fish per treatment, coming the final bath of formaldehyde to control parasitosis were sent for histological analysis. It was observed that increasing the concentration of formaldehyde caused more severe lesions in the gills. Mild hyperplasia was observed in animals kept as control, detachment of the respiratory epithelium in T2, moderate hyperplasia in T3, increased opercular activity in T4 and necrosis, erratic swimming and mortality in T5. Histopathological results of this study show that bath of formaldehyde at a concentration of 50 mg/L for 1 hour can be applied to juveniles of M. platanus to control Monogenoidea, because in this concentration, histological lesions caused in the host are lightweight and survival of juveniles is high.