ABSTRACT This study analyzes the spatial and temporal variability of phytoplankton biomass and taxonomic composition in the surface waters of Todos Santos Bay, a semi-enclosed bay within the upwelling zone of the Baja California peninsula (México). Two methodological approaches (microscopy and chemotaxonomy [CHEMTAX]) were used to describe the variability of some genera and species (observed under the microscope) and the importance of those groups that cannot be observed microscopically. Phytoplankton biomarker pigments were measured with high-resolution liquid chromatography and used as input to run the CHEMTAX software to determine the contribution of the main phytoplankton groups to chlorophyll-a (Chl-a). The microscopic analyses showed that diatoms and dinoflagellates comprised 65 and 33% of the total cells, respectively. Dinoflagellates were most abundant in the inner bay and during cold months; the most frequent and abundant genera were Tripos, Protoperidinium, and Prorocentrum. Among diatoms, the most frequent genera were Cylindrotheca, Guinardia, Navicula, Pseudo-nitzschia, and Chaetoceros. CHEMTAX indicated that, together with diatoms, the flagellates prymnesiophytes and chlorophytes contributed a median of 80% to Chl-a, with chlorophytes as the most important group (29.9%). The high contribution of these flagellates suggests that they are represented by small-sized cells not visible by the light microscopy used. However, CHEMTAX largely underestimated the contribution of dinoflagellates (due to the presence of many mixotrophic species). Hence, our results emphasize the importance of using both techniques for a more detailed evaluation of the taxonomic composition of phytoplankton in this and other coastal regions.

Abstract This study aimed to search parasites in 333 ornamental fish from five Brazilian states (Ceará, Minas Gerais, São Paulo, Paraná and Santa Catarina). Fish were sent from eight farms located in the municipalities of Fortaleza, Patrocínio do Muriaé, São Francisco do Glória, Cascavel, Timbó, Iguape, Jacareí and Mairinque. All fish received anesthesia earlier to euthanasia procedures. After the search for parasites, it was verified that 70.6% (235/333) of fishes were infected by at least one type of parasite, being 12 types of parasites identified: monogeneans, digenean metacercariae, cestodes, nematodes, Lernaea cyprinacea, trichodinids, Piscinoodinium pillulare, Ichthyophthirius multifiliis, diplomonad flagellates, Ichthyobodo sp., Chilodonella sp., and Tetrahymena sp. The proportion of infected fishes among the farms is compared through statistical tests, besides, animal handling adopted in each farm is also discussed. The importance of ensuring fish health in order to make the ornamental freshwater fish industry economically viable and reduce losses in production is highlighted. 33 Ceará, Ceará (Ceará Gerais Paulo Catarina. Catarina . Catarina) Fortaleza Muriaé Glória Cascavel Timbó Iguape Mairinque procedures 706 70 6 70.6 235/333 235333 235 (235/333 parasite 1 identified monogeneans metacercariae cestodes nematodes cyprinacea trichodinids pillulare multifiliis flagellates sp tests besides discussed highlighted 3 7 70. 235/33 23533 23 (235/33 235/3 2353 2 (235/3 235/ (235/ (235 (23 (2 (

Resumo O objetivo deste estudo foi pesquisar parasitas presentes em 333 peixes ornamentais de cinco estados brasileiros (Ceará, Minas Gerais, São Paulo, Paraná e Santa Catarina). Os peixes eram oriundos de oito pisciculturas localizadas nos municípios de Fortaleza, Patrocínio do Muriaé, São Francisco do Glória, Cascavel, Timbó, Iguape, Jacareí e Mairinque. Todos os peixes foram anestesiados e eutanasiados para a pesquisa de parasitas. Após análise microscópica, foi verificado que 70.6% (235/333) dos peixes estavam infectados por ao menos uma espécie de parasita, sendo identificados 12 tipos: monogenoides, metacercárias, cestoides, nematoides, Lernaea cyprinacea, tricodinídeos, Piscinoodinium pillulare, Ichthyophthirius multifiliis, flagelados diplomonados, Ichthyobodo sp., Chilodonella sp., e Tetrahymena sp. A proporção de peixes infectados entre cada piscicultura é comparada através de testes estatísticos, além disso, o manejo adotado pelas diferentes pisciculturas também é discutido. A importância de assegurar a sanidade de peixes ornamentais, de forma a tornar a atividade economicamente viável e reduzir perdas na produção é enfatizada. 33 Ceará, Ceará (Ceará Gerais Paulo Catarina. Catarina . Catarina) Fortaleza Muriaé Glória Cascavel Timbó Iguape Mairinque microscópica 706 70 6 70.6 235/333 235333 235 (235/333 parasita 1 tipos monogenoides metacercárias cestoides nematoides cyprinacea tricodinídeos pillulare multifiliis diplomonados sp estatísticos disso discutido enfatizada 3 7 70. 235/33 23533 23 (235/33 235/3 2353 2 (235/3 235/ (235/ (235 (23 (2 (

Abstract In vitro excystation of cysts of microscopically identified Chilomastix mesnili and Retortamonas sp. isolated from Japanese macaques and Retortamonas sp. isolated from small Indian mongooses could be induced using an established protocol for Giardia intestinalis and subsequently by culturing with H2S-rich Robinson’s medium supplemented with Desulfovibrio desulfuricans. Excystation usually began 2 h after incubation in Robinson’s medium. DNA was isolated from excysted flagellates after 4 h of incubation or from cultured excysted flagellates. Phylogenetic analysis based on their 18S rRNA genes revealed that two isolates of C. mesnili from Japanese macaques belonged to the same cluster as a C. mesnili isolate from humans, whereas a mammalian Retortamonas sp. isolate from a small Indian mongoose belonged to the same cluster as that of an amphibian Retortamonas spp. isolate from a ‘poison arrow frog’ [sequence identity to AF439347 (94.9%)]. These results suggest that the sequence homology of the 18S rRNA gene of the two C. mesnili isolates from Japanese macaques was similar to that of humans, in addition to the morphological similarity, and Retortamonas sp. infection of the amphibian type in the small Indian mongoose highlighted the possibility of the effect of host feeding habitats. sp H2Srich HSrich H2S rich H S Robinsons Robinson s desulfuricans C humans spp poison frog AF AF43934 94.9%. 949 94.9% . 94 9 (94.9%)] similarity habitats Srich HS AF4393 94.9 (94.9%) AF439 94. (94.9% AF43 (94.9 AF4 (94. (94 (9 (

Resumo Excistação in vitro de cistos de Chilomastix mesnili e Retortamonas sp. identificados microscopicamente, isolados de macacos japoneses e Retortamonas sp. isolados de um pequeno mangusto indiano podem ser induzidos usando um protocolo estabelecido para Giardia intestinalis e, subsequentemente por cultura com meio de Robinson rico em H2S suplementado com Desulfovibrio desulfuricans. A excistação geralmente começou 2 h após a incubação em meio de Robinson. O DNA foi isolado de flagelados excistados após 4 h de incubação ou de flagelados excistados cultivados. A análise filogenética baseada em seus genes 18S rRNA revelou que dois isolados de C. mesnili de macacos japoneses pertenciam ao mesmo grupo que um isolado de C. mesnili de um humano, enquanto um isolado de Retortamonas sp. de um mamífero, o pequeno mangusto indiano, pertencia ao mesmo agrupamento do isolado de Retortamonas spp. do anfíbio, ’sapo ponta-de-flecha’ [identidade sequencial para AF439347 (94,9%)]. Esses resultados sugeriram que a homologia sequencial do gene 18S rRNA dos dois isolados de C. mesnili de macacos japoneses era semelhante a de um humano, além da semelhança morfológica, e a infecção de Retortamonas sp. do tipo anfíbio ao pequeno mangusto indiano destacou a possibilidade de ser afetado pelo habitat alimentar de seu hospedeiro. sp microscopicamente HS H S desulfuricans cultivados C humano mamífero spp sapo pontadeflecha ponta flecha ponta-de-flecha identidade AF AF43934 94,9%. 949 94,9% . 94 9 (94,9%)] morfológica hospedeiro AF4393 94,9 (94,9%) AF439 94, (94,9% AF43 (94,9 AF4 (94, (94 (9 (

ABSTRACT Background: Here, Leishmania presence in sand flies from Três Lagoas, Mato Grosso do Sul, Brazil, after visceral leishmaniasis (VL) was investigated. Methods: In April 2022, two light traps were deployed within and around the residence for two days post-VL case report. Results: A total of 120 Lutzomyia longipalpis were collected. Suprapyloric flagellates were found in a female sand fly with eggs and residual blood during midgut dissection. Sequencing of ITS1 and cytb fragments confirmed Leishmania infantum DNA and identified Homo sapiens as the blood source, respectively. Conclusions: This study emphasizes the importance of monitoring sand flies in VL endemic areas. Background Here Lagoas Sul Brazil (VL investigated Methods 2022 postVL post report Results 12 collected dissection ITS source respectively Conclusions areas 202 1 20 2

Abstract Chaco province is included in Argentinean ecoregions with human tegumentary leishmaniasis case records. During 2012-2014 in Pampa del Indio town an ecoepidemiological study was carried out including phlebotomine dynamics and its natural infection with Leishmania demonstrated by sand flies dissection, polymerase chain reaction and sequencing. The species recorded were: Migonemyia migonei (72.79%), Nyssomyia neivai (23.6%), Evandromyia cortelezzii (0.94%), Evandromyia sallesi (0.39%), Cortelezzii complex (1.61%), Evandromyia aldafalcaoae (0.05%), Psathyromyia bigeniculata (0.02%), Brumptomyia brumpti (0.6%) and Corumbaensis complex (0.01%). A total of 380 females sand flies (Cortelezzii complex, Mg. migonei and Ny. neivai) from peridomicile and extradomicile were individually dissected and no flagellates were observed in the intestinal tract. Later, these females were arranged in 38 pools for molecular analyses and Leishmania braziliensis DNA was amplified in 3 pools with a minimum infection rate of the total females of 0.8%, while specific rates were 0.5% for the Cortelezzii complex and 1.5% for Mg. migonei. In conclusion, our results would strengthen the hypothesis that, in the study area, these species are candidates to be incriminated as vectors, while further studies will be required to fulfill the criteria to characterize both species as proven vectors of Le. braziliensis.

ABSTRACT OBJECTIVE To perform an entomological survey, evaluating the circulation of Leishmania spp. in sand flies captured from the new foci of visceral leishmaniasis (VL) in the coastal region of São Paulo state. METHODS Sand flies were captured from November 2016 to September 2018 using light traps of the Centers for Disease Control (CDC), in the neighborhood where VL cases were reported. Leishmania spp. circulation was evaluated by gut dissection and molecular analysis of the females captured. RESULTS Nyssomyia intermedia was the more frequent species (90,7%) within the 1,203 sand flies captured. We found no flagellates in dissected females, but two pools containing females of Ny. intermedia presented DNA of L. infantum. CONCLUSION Our results suggest that Ny. intermedia might be involved in the establishment of this new VL focus in Sao Paulo. However, before incriminating this species as a L. infantum vector, further studies should investigate other vectorial capacity parameters, including competence, survival, and feeding habits.

ABSTRACT OBJECTIVE To perform an entomological survey, evaluating the circulation of Leishmania spp. in sand flies captured from the new foci of visceral leishmaniasis (VL) in the coastal region of São Paulo state. METHODS Sand flies were captured from November 2016 to September 2018 using light traps of the Centers for Disease Control (CDC), in the neighborhood where VL cases were reported. Leishmania spp. circulation was evaluated by gut dissection and molecular analysis of the females captured. RESULTS Nyssomyia intermedia was the more frequent species (90,7%) within the 1,203 sand flies captured. We found no flagellates in dissected females, but two pools containing females of Ny. intermedia presented DNA of L. infantum. CONCLUSION Our results suggest that Ny. intermedia might be involved in the establishment of this new VL focus in Sao Paulo. However, before incriminating this species as a L. infantum vector, further studies should investigate other vectorial capacity parameters, including competence, survival, and feeding habits.

Abstract INTRODUCTION Visceral leishmaniasis (VL) transmission has been associated with two different populations of the Lutzomyia longipalpis complex in São Paulo state. METHODS In a recent focus of VL, we captured and dissected sand flies and investigated Leishmania infantum infection by parasitological, PCR, and sequencing analysis. RESULTS Flagellates were observed in 2 of 47 (4.2%) cembrene-1 Lu. longipalpis females. The sequences obtained matched those of Le. infantum. CONCLUSIONS We found that the transmission of Le. infantum by cembrene-1 females may occur at a high rate in this focus of VL and presented new data on the vector capacity of this population.

Resumo Em sua superfície externa, muitas plantas podem acumular água da chuva formando fitotelmata, ou seja, micro-habitat aquáticos colonizados por diversos organismos, entre eles, os flagelados protistas. Fez-se um inventário de flagelados heterotróficos associados ao fitotelmata da bromélia Aechmea distichantha Lem., encontrada em paredões rochosos em um trecho da bacia do alto rio Paraná. As bromélias foram retiradas manualmente de paredão rochoso e, em laboratório, a água foi retirada dos tanques de cada planta, e foram montadas culturas dos organismos em placas de Petri. Os flagelados heterotróficos foram, então, observados in vivo sob microscópio óptico Olympus BX51, com sistema de contraste de interferência diferencial (DIC) acoplado. Dezesseis espécies flagelados heterotróficos foram registradas, desenhadas e descritas, sendo uma espécie pertencente ao Domínio Amorpha e 15 espécies ao Domínio Diaphoretiches. Os grupos mais especiosos foram Euglenida e Kinetoplastea. A diversidade relativamente reduzida de flagelados heterotróficos, quando comparada ao plâncton de lagos e reservatórios, pode estar relacionada ao fato de os fitotelmata serem habitats limitados, com condições ambientais extremas, selecionando, assim, organismos tolerantes a esses ambientes.

Abstract Many plants may accumulate rainwater, forming phytotelmata, aquatic microhabitats inhabited by various organisms. The aim of this study was to conduct an inventory of heterotrophic flagellates associated with phytotelmata of the bromeliad Aechmea distichantha Lem., found in rocky cliffs on the Upper Paraná River. The bromeliads were removed manually from the rocky wall, the water was removed and cultures of organisms of each plant were mounted in Petri dishes. Sixteen species of heterotrophic flagellate were recorded, drawn and described, among them one species belonging to the Amorpha Domain and 15 species to the Diaphoretiches Domain. The groups with most species were Euglenida and Kinetoplastea. The low diversity of heterotrophic flagellates recorded in this study, compared to the plankton of lakes and reservoirs, is probably related to the fact that phytotelmata are habitats with extreme environmental conditions, thus selecting organisms tolerant to these environments.

Resumen Objetivo: Evaluar la eficacia de la asociación cloruro de isometamidium+clorhidrato de oxitetraciclina (Isopan® Laboratorio Reveex de Venezuela) en el control de infecciones por Tripanosoma vivax y Anaplasma marginale en bovinos. Materiales y métodos: Doce bovinos de aproximadamente un año de edad fueron asignados al azar, a dos grupos de seis animales cada uno. Un grupo fue inoculado por vía venosa con 10 mL de sangre con una parasitemia de 3,5% de Ana- plasma marginale en extendido sanguíneo coloreado; el segundo grupo se inoculó, por la misma vía, con cinco mL de sangre de una cepa de campo de Trypanosoma vivax con una parasitemia de tres flagelados por campo en un frotis sanguíneo delgado coloreado. En todas las terneras, la temperatura rectal, el hematocrito y la parasitemia fueron registrados con frecuencia diaria o inter-diaria hasta los días 49 posinoculación y 27 postratamiento en el caso de A. marginale y hasta los días 11 posinoculación y 21 postratamiento en el caso de T. vivax. Resultados: La asociación oxitetraciclina-isometamidium fue 100% eficaz contra Trypanosoma vivax desde un día después de su aplicación y por el término de 29 días experimentales. La asociación tuvo una eficacia promedio contra Anaplasma marginale de 75,59% aunque cuatro de las terneras requirieron un segundo tratamiento contra Anaplasma entre los días 10 y 27 después del tratamiento. Conclusiones: La asociación oxitetraciclina - isometamidium mostró una eficacia de 100% contra Trypanosoma vivax y de 75,59% en promedio, contra Anaplasma marginale, aunque no previno un nuevo episodio de anaplasmosis entre los días 10 y 27 después del tratamiento.

Abstract Objective: To evaluate the efficacy of the association Isometamidium Chloride + Oxytetracycline Hydrochloride (Isopan® Reveex Laboratories, Venezuela) on the control of infections by Trypanosoma vivax and Anaplasma marginale in bovine. Materials and methods: Twelve one-year old heifers were randomly assigned to two groups of six animals each. Heifers on one group were each inoculated intravenously with 10 mL of blood showing a 3.5% parasitemia with Anaplasma marginale on stained blood smears. Heifers in the other group were inoculated intravenously with five mL of blood containing a field strain of T. vivax with a parasitemia of 3 flagellates per microscopic field in a stained blood smear. In all heifers, rectal temperature, haematocrit and parasitemia were monitored daily or every other day until days 49 post inoculation and 27 post treatment in the case of A. marginale and 11 post inoculation and 21 post treatment in the case of T. vivax. Results: The association oxitetracicline-isometamidium was 100% efficacious against T. vivax from day one after administration and until the 21th experimental day. The association showed an average efficacy of 75.59% against A. marginale, though four heifers required a second treatment against Anaplasma between days 10 and 27 after treatment. Conclusions: The association Oxitetracicline - isometamidium showed a 100% efficacy against T. vivax and an average of 75.59% efficacy against A. marginale but did not prevent a second anaplasmosis episode between days 10 and 27 following the first treatment.

Resumo Objetivo: Avaliar a eficácia da associação cloreto de isometamidio + cloridrato de oxitetraciclina (Isopan® Laboratorio Reveex de Venezuela) no controle de infecções por Trypanosoma vivax e Anaplasma marginale em bovinos. Materiais e métodos: Doze bovinos de aproximadamente 1 ano de idade foram distribuídos aleatoria- mente em dois grupos de 6 animais cada. Um grupo foi inoculado por via venosa com 10 mL de sangue com parasitemia de Anaplasma marginale de 3,5% em esfregaço de sangue corado; o segundo grupo foi inoculado, pela mesma via, com cinco mL de sangue de uma cepa de Trypanosoma vivax com parasitemia de três flagelados por campo em esfregaço de cor fina. Em todos os bezerros, temperatura retal, hematócrito e parasitemia foram registrados diariamente ou inter-diariamente até os dias 49 pós-inoculação e 27 pós-tratamento no caso de A. marginale e até os dias 11 pós-inoculação e 21 pós-tratamento no caso de A. de T. vivax. Resultados: A associação oxitetraciclina-isometamídio foi 100% eficaz contra o Trypanosoma vivax um dia após sua aplicação e pelo prazo de 29 dias experimentais. A associação teve uma eficácia média contra o Anaplasma marginale de 75,59%, embora quatro dos bezerros precisassem de um segundo tratamento contra o Anaplasma entre os dias 10 e 27 após o tratamento. Conclusões: A associação oxitetraciclina-isometamídio mostrou eficácia de 100% contra Trypanosoma vivax e 75,59% em média contra Anaplasma marginale, embora não tenha prevenido novo episódio de anaplasmose entre os dias 10 e 27 após o tratamento.

Resumen La clasificación basada en rasgos y grupos funcionales establecidos en la morfología del fitoplancton posibilitó una aproximación factible y objetiva en la evaluación de seis sistemas de diferente tipo, origen, morfología y condición limnológica pertenecientes a las regiones amazónica, andina y caribe de Colombia. Se estableció específicamente la relación entre las variables continuas y categóricas del fitoplancton (volumen, superficie, dimensión lineal máxima, presencia de aerótopos, mucílago, flagelo y exoesqueleto de sílice) con los parámetros limnológicos de transparencia, profundidad máxima, temperatura y concentración de iones inorgánicos. Se seleccionaron entre dos y ocho estaciones durante tres o cuatro periodos climáticos en series anuales entre el 2005 y el 2007 tomando las muestras en la zona limnética. Los taxones identificados se clasificaron en uno u otro grupo funcional basado en la morfología (GFBM) según las dimensiones morfológicas y la presencia de rasgos especializados de cada taxón. Entre los resultados más relevantes se destacó el grupo V (flagelados unicelulares de tamaño medio a grande) en ambientes poco profundos y turbios, con excepción de la llanura del Bajo Sinú en el Caribe, donde dominaba el grupo VII (colonias mucilaginosas con los lípidos y aerótopos). En los lagos profundos y de gran transparencia en montañas sobresalieron los grupos IV (tamaño medio y ausencia de rasgos especializados) y VII. Los grupos propuestos en la clasificación permitieron exponer los patrones funcionales del ensamblaje del fitoplancton y explicar significativamente su variación en respuesta a las características de los sistemas.

Abstract The classification based on phytoplankton traits and functional groups allowed a feasible and objective approach in the evaluation of six tropical systems of different types, origin, morphology, and limnological condition in the Amazon, Andean, and Caribbean regions of Colombia. Specifically, this work established the relationship between continuous and categorical variables of phytoplankton (volume, surface area, maximum linear dimension, presence of aerotopes, mucilage, flagellum, and silica exoskeleton) and limnological parameters such as transparency, maximum depth, temperature, and inorganic ions concentration. We selected two to eight stations during three or four climatic periods in annual series between 2005 and 2007 taking samples in the limnetic area. The identified taxa were classified into morphology-based functional groups (MBFG) according to the morphological dimensions and the presence of specialized traits of each taxon. Group V (unicellular o colonial flagellates of medium to large size) predominated in shallow and turbid environments, except for the Caribbean Bajo Sinu plains where group VII (large mucilaginous colonies) dominated. In the deep and highly transparent mountain lakes, groups IV (organisms of medium size lacking specialized traits) and VII predominated. The groups proposed classification exposed the functional patterns of the phytoplankton assembly and significantly explained its variation in response to the characteristics of the systems.

ABSTRACT Fish-killing algal species are responsible for important global economic losses to the finfish industry. Chile is the world’s second-largest salmon exporter, and fish-killing algal blooms have widely impacted its production in the last decades. The lack of standardized analytical methods to quantify and characterize the so-called “ichthyotoxins” has hindered our understanding of the underlying ichthyotoxic modes of action. The novel application of a highly sensitive and reproducible fish RTgill-W1 cell line-based assay has allowed significant progress in the field. In this study, the ichthyotoxic potency of the main microalgae species, which has been reported in fish-killing events in the historical Chilean monitoring programs, was assessed. The dinoflagellate Karenia selliformis was the most ichthyotoxic species against the RTgill-W1 (cell viability down to 8%), representing the major threat for the local salmon industry. In comparison, the raphidophyte Heterosigma akashiwo and the dinoflagellate Prorocentrum micans were the least toxic (gill cell viability down to 81 and 89%, respectively). Importantly, ichthyotoxic flagellates were more toxic to fish gill cells upon rupture. These results have important implications for the mitigation and management of algal blooms by the salmon industry.

Abstract INTRODUCTION: Trypanosomes can infect humans and animals. This is the first record of the occurrence of Trypanosoma evansi in Rondônia. METHODS: Blood samples were collected from 7 dogs and 22 humans. Furthermore, triatomines and tabanids were collected. RESULTS: It was observed that 42.8% of the dogs tested positive for T. evansi and 14.3% presented mixed infection; 15% of the triatomines tested positive for flagellates identified as T. cruzi TCI (3 specimens), T. cruzi TCI, and T. rangeli (1 specimen), and one with T. cruzi TCV. Two tabanids were infected with T. theileri. CONCLUSIONS: These findings may benefit vector control strategies.

ABSTRACT Intensive growth of aquatic macrophytes interferes with water quality and ecosystem dynamics worldwide. Although mechanically removing macrophytes is the most commonly used method for their eradication, it can also cause undesirable disturbances in aquatic reservoir communities. We performed laboratory incubations of phytoplankton sampled before and after macrophytes were mechanically removed from the Piraquara II reservoir, South Brazil. We analyzed changes in growth and composition of the main phytoplankton groups with respect to nutrient shifting. Prior to removing the macrophytes, the phytoplankton community was dominated by low cell abundances of diatoms and flagellates. In contrast, growth rates of cyanobacteria (mainly Cylindrospermopsis raciborskii, Pseudanabaena sp., and Geitlerinema sp.) and of colonial chlorophytes were favored after macrophyte removal, while the abundances of diatoms and flagellates decreased. Our results suggest that removing macrophytes causes dramatic changes in phytoplankton composition and biomass and selects for toxigenic species of cyanobacteria. These changes were probably associated with the disturbance caused by removing the macrophytes, which immediately created new environmental conditions prone to species competition. These findings indicate that the use of mechanical techniques to manage macrophytes should be carefully considered, along with monitoring of harmful species and changes of limnological parameters.

ABSTRACT Periphyton has a strong relationship with aquatic macrophytes, which are key components of spatial heterogeneity in the littoral zone. We evaluated the relationship between the community structure of periphytic algae on Utricularia foliosa and macrophyte richness and coverage and limnological variables in a shallow reservoir. Water sampling for physical, chemical and biological analyses was performed at sites with contrasting macrophyte coverage and richness in each of the four main seasons of the year. Periphytic algae were evaluated for density and species composition. High densities of diatoms and filamentous cyanobacteria in the periphyton were observed at sites with high macrophyte coverage and richness, while high abundances of flagellates of Chrysophyceae and Chlorophyceae were found at sites with low macrophyte richness. Light and nutrient availability were determining factors of the temporal variability of the periphytic algae community. We concluded that the interaction between seasonality and spatial heterogeneity (macrophyte community structure and limnological variables), explained the variability in species composition and algal density of the periphyton. Therefore, seasonality and spatial heterogeneity acted as determining factors for periphyton structure on a free-floating macrophyte with high structural complexity.