Effects on Ultrastructure, Composition and Specific Surface Area of the Gills of Odontesthes bonariensis Under Subchronic Glyphosate-Based Herbicide Exposure.

Gills represent one of the major sites of gas exchange of fish, consequently they are in continuous close contact with the aquatic environment and its pollutants. In the present study the effects on gills of pejerrey fish, Odontesthes bonariensis, under glyphosate-based herbicide subchronic exposure were analyzed. Adult animals were exposed to sublethal concentrations of a glyphosate-based commercial formulation (1 and 10 PMG mg L-1, PMG: glyphosate active ingredient) for 15 days, while control group was maintained in rearing water. Ultrastructural changes in gills were observed by scanning electron microscopy (SEM). The composition of the surface epithelium and specific surface area were determined by energy dispersive spectroscopy (EDS) and N2 (g) adsorption-desorption isotherms, respectively. The herbicide exposure induced severe alterations in gill ultrastructure, as shown in the SEM micrographs. Accordingly, an increase in surface area of the gills of exposed animals was determined. These results support that gills parameters of freshwater fish are sensitive morphological biomarkers for glyphosate exposure.

First molecular data for Lernaea cyprinacea (Copepoda: Cyclopoida) infesting Odontesthes bonariensis, a commercially important freshwater fish in Argentina / Primeiros dados moleculares para Lernaea cyprinacea (Copepoda: Cyclopoida) infestando Odontesthes bonariensis, um peixe de água doce comercialmente importante na Argentina

Abstract Parasitic copepods of the family Lernaeidae are often found infesting freshwater fishes worldwide. They cause lernaeosis, a disease that can lead to serious pathogenic effects on their fish hosts. The most common lernaeid is the Lernaea cyprinacea, which has been widely introduced through importation of tropical fishes, e.g. cyprinids. In South America, it is one of the most common parasites both in wild and in farmed fish in the central region of Argentina. The silverside Odontesthes bonariensis is the most important fish of the sport fisheries of Argentina and one of the fish most affected by lernaeosis. Six specimens of copepods were collected from 30 specimens of O. bonariensis collected in a Pampean shallow lake (33°25'28"S 62°53'56"W) of Córdoba (Argentina). The 28S rRNA gene of L. cyprinacea was amplified by means of PCR to obtain the 28S rDNA sequence. The sequence obtained of this parasite from Argentina showed high genetic similarity with those from various geographical origins. The present study provided molecular characterization of L. cyprinacea in South America for the first time.

Resumo Os copépodos parasitos da família Lernaeidae são frequentemente encontrados infestando peixes de água doce em todo o mundo, causando a lernaeose, uma doença que pode levar a graves efeitos patogênicos em seus hospedeiros. O lerneídeo mais comum é a Lernaea cyprinacea, que tem sido amplamente introduzida por meio da importação de peixes tropicais, tais como ciprinídeos. Na América do Sul, é um dos parasitos mais comuns em peixes selvagens, bem como em peixes de cultivo na região central argentina. Odontesthes bonariensis é um dos peixes mais importantes para a pesca esportiva na Argentina e um dos mais afetados pela lerneose. Um total de seis espécimes desses copépodes foram coletados de espécimes de 30 O. bonariensis capturados em um lago de pouca profundidade nos Pampas (33°25'28"S 62°53'56"W) em Córdoba (Argentina). O gene 28S rRNA de L. cyprinacea foi amplificado por PCR para obter a sequência do 28S rDNA. A sequência obtida desse parasito da Argentina mostrou alta similaridade genética com aquelas de outras origens geográficas. O presente estudo forneceu, pela primeira vez, uma caracterização molecular de L. cyprinacea na América do Sul.

Pituitary-thyroid axis development during the larval-juvenile transition in the pejerrey Odontesthes bonariensis.

The morphological development of the thyroid gland of pejerrey Odontesthes bonariensis during larval-juvenile transition was studied and related to whole-body concentrations of thyroxine (T4 ) and tri-iodothyronine (T3 ). A complementary (c)DNA fragment of the thyroid-stimulating hormone ß-subunit (tshb) was sequenced and transcript levels quantified during this period. Follicles with eosinophilic and T4 -immunoreactive colloids were detected at hatching together with tshb transcript levels and whole-body concentrations of T4 and T3 hormones. Thyroid follicles were located in the subpharyngeal region associated with the ventral aorta below the hyoid bone. Follicle structure switched from the rounded form at hatching to oval in juveniles. Significant increase of follicle number per larva, mean colloidal area and total colloidal area was observed throughout development with maximum values at the end of the larval-juvenile transition. A significant decrease of tshb expression together with a significant increase in T4 and T3 whole-body concentrations was observed prior to achieving the juvenile phenotype. These results are in accordance with a negative feedback regulation of tshb expression by thyroid hormones and a possible association between thyroid hormone levels and the acceleration of metabolic processes necessary to complete metamorphosis.

Evaluation of the Health Status of the Silverside (Odontesthes bonariensis) at a RAMSAR Site in South America.

The objective of this work was to evaluate the health status of an economic and ecologically important fish species from Mar Chiquita Lake, a RAMSAR site located in Cordoba, Argentina, relative to the levels of selected persistent organic pollutants (POPs) in lake water and fish tissues. Odontesthes bonariensis was used as a model species, and its health was estimated by means of histological indices in gills and liver. Sampling was performed according to rainy and dry seasons (i.e. dry, rainy and post-rainy). Gill and liver histopathology were evaluated by semi-quantitative indices and morphometric analysis. Although epithelial lifting in gills and lipid degeneration in liver were frequently registered, they are considered as reversible if environmental conditions improve. During rainy and post-rainy seasons fish presented significantly higher scores of liver and total indices. These higher index scores were correlated with increased levels of POPs in gill and liver tissue. Therefore, preventive measures are needed to mitigate the entry of these compounds into the lake.

Effects of estradiol and ethinylestradiol on sperm quality, fertilization, and embryo-larval survival of pejerrey fish (Odontesthes bonariensis).

17ß-Estradiol (E2) and synthetic 17α-Ethinylestradiol (EE2) are estrogenic compounds present in surface waters as a consequence of municipal sewage discharges. The aim of this study was to evaluate the effects of E2, EE2 and its mixtures on different reproductive parameters and embryo-larval survival in pejerrey fish (Odontesthes bonariensis). In order to analyze the effect of these compounds on sperm quality, fertilization%, embryo-larval survival (%), and the point of no return (PNR), different assays were performed using concentrations 175, 350, 700 and 1400 ng/L of E2; 22.5, 45, 90 and 180 ng/L of EE2 and mixtures M1 (175 E2+22.5 EE2, ng/L), M2 (350 E2+45 EE2, ng/L), M3 (700 E2+90 EE2, ng/L) and M4 (1400 E2+180 EE2 ng/L). No significant differences in motility parameters were observed between E2 and EE2 treatments and the control group. However, a significant decrease in motility% was recorded for all mixtures tested compared with the control samples. For fertilization%, only sperm activated with M4 showed a significant decrease compared with the control group. In the case of embryo survival, there was only a significant decrease in the highest concentration of EE2 compared with the control group. For the mixtures, M3 is the one that had the most adverse effect on embryo survival. In larval survival, there was a significant decrease in concentration 175 and 700 ng/L of E2 compared with the control group. In EE2 treatments, the ones with a significant reduction in larval survival were concentration 45 and 90 ng/L. And for the mixture treatments, M1, M3 and M4 had a significantly lower larval survival than the control group. In comparison to other treatments, M1 demonstrated a significant difference in PNR when compared with the control group. The results obtained demonstrated that the exposure to mixtures of E2 and EE2 affected fish sperm motility, fertilization% and, embryo and larval survival even at relevant environmental concentrations highlighting the necessity of considering the effects of pollutants mixtures in ecotoxicological studies.

Subcellular energy balance of Odontesthes bonariensis exposed to a glyphosate-based herbicide.

Water pollution by agrochemicals is currently one of the most critical problems for the conservation of aquatic ecosystems. Glyphosate [N-(phosphonomethyl) glycine); PMG] is the main broad-spectrum post emergence herbicide used for the control of a wide range of pests in soybean crops. Adenylate energy charge (AEC) reflects the energy balance of the cells, a measure of the energy available from the adenylate pool: adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP). Background adenylates, phosphagens and the AEC index of two year old Odontesthes bonariensis were determined in some tissues by HPLC, and the impact on subcellular energy balance of sublethal glyphosate-based herbicide exposure was analyzed. The doses used were 0 (control tank), 1 or 10mg PMGL(-1), trials were carried out during 15 days. AEC values in brain, liver and muscle from control fish were 0.37 ± 0.02, 0.49 ± 0.05 and 0.56 ± 0.03, respectively (means ± SEM). While brain ATP concentrations were undetectable (hence low values of AEC), the muscle tissue showed the highest concentrations of the more energetic molecules: 0.18 µmole ATP g(-1) and 8 µmole phosphocreatine g(-1) (PCrg(-1)). In the brain, no significant changes were detected in exposed fish compared to controls. Instead, in both the liver and muscle of animals exposed to the highest concentration of the herbicide, significant changes in the AEC (reduction of 26% and 15%, p<0.05) with respect to the control group were determined. Chronic exposure (15 days) of Odontesthes bonariensis to 1 and 10mgL(-1) of formulated glyphosate did not affect brain AEC. However, the highest concentration of the herbicide produced a significant decrease in liver and muscle AEC manifesting adverse sublethal effects on the energy metabolism. These results suggest the usefulness of AEC as a biomarker of fish glyphosate exposure.

Surface ultrastructure of the gills of Odontesthes bonariensis (Valenciennes, 1835)(Teleostei: Atheriniformes) from a temperate shallow lake / Estudio ultraestructural de las branquias de Odontesthes bonariensis (Valenciennes, 1835) (Teleostei: Atheriniformes) de un lago somero templado

We studied the gill epithelium of juveniles of Odontesthes bonariensis using scanning electron microscopy with a particular interest in the relationship between cell morphology and the different functional aspects of gills. The specimens used were collected in Laguna de los Padres, Buenos Aires Province, Argentina. The gill filaments or primary lamellae are arranged in two rows along the convex outer face of the gill arch forming the anterior and posterior hemibranchiae. On its concave inner face, each arch supports two rows of gill rakers forming the pharyngeal region wall. The primary lamellae are lined by a stratified epithelium made up of polygonal cells with well-defined outlines and cell membrane microfolds. Several mucous and chloride cells were observed in the primary lamellae. The epithelial cells of the secondary lamellae have ill-defined outlines and few microfolds. Both the arches and gill rakers are covered by a stratified epithelium of polygonal cells, among which mucous cells and taste corpuscles are abundant. The ultrastructural analysis of gills of O. bonariensis contributes to the advancement of knowledge of the organ histophysiology and of future histopathological studies.

Se estudió el epitelio branquial de juveniles de Odontesthes bonariensis utilizando microscopía electrónica de barrido con un interés particular en la relación entre la morfología celular y los distintos aspectos funcionales de las branquias. Los ejemplares utilizados fueron colectados en la Laguna de los Padres, Provincia de Buenos Aires, Argentina. Los filamentos branquiales o laminillas primarias están dispuestos en dos filas a lo largo de la cara exterior convexa del arco branquial formando las hemibranquias anterior y posterior. En su cara interior cóncava, cada arco sostiene dos hileras de branquiespinas que forman la pared de la región faríngea. Las laminillas primarias están revestidas por un epitelio estratificado constituido por células poligonales con contornos bien definidos y micropliegues de la membrana celular. Se observaron numerosas células clorhídricas y mucosas en las laminillas primarias. Las células epiteliales de las laminillas secundarias tienen contornos poco definidos y escasos micropliegues. Tanto los arcos como las branquiespinas están cubiertos por un epitelio estratificado de células poligonales, entre las cuales hay abundantes células mucosas y corpúsculos gustativos. El análisis ultraestructural de las branquias de O. bonariensis proporciona información para avanzar en el conocimiento de la histofisiología del órgano y para realizar futuros estudios histopatológicos.

Multimatrix measurement of persistent organic pollutants in Mar Chiquita, a continental saline shallow lake.

RAMSAR sites are determined by specific characteristics of the environment in terms of ecological productivity as well services for human development, but they are also one of the most threatened ecosystems. Thus, the objective of this work was to evaluate the dynamic of Persistent Organic Pollutants (POPs) in different biotic and abiotic matrixes of the RAMSAR site (wetlands with international importance), Mar Chiquita Lake. Sampling was performed according to land use (agricultural, urban, and industrial) at two stations: Laguna del Plata and Campo Mare. POPs were analyzed in superficial water (Sw), suspended particulate material (SPM), bottom sediment (Bs) and fish tissues (Odontesthes bonariensis). Organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were analyzed by GC-ECD. HCHs, Endosulfans, DDTs, PCBs and PBDEs were found in all matrixes at both stations. The high persistence and transport processes are responsible for the occurrence of HCHs, DDTs and PCBs in Bs, SPM and fish tissues, even many years after their prohibition. PBDEs showed lower levels according to the scarcity of punctual sources in the area. Endosulfan showed variable amounts in agreement with application periods since this pesticide was used until a few years ago in this area. Finally, PCB levels overpassed the acceptable daily intake for human consumption being a risk for human health Thus, the present report confirms the occurrence of POPs in Mar Chiquita lake, alerting on the contribution of agricultural and urban pollutants in a RAMSAR site. Current results also raise concerns on biomagnification processes through the food web.

Seasonal changes in the somatic indices of the freshwater silverside, Odontesthes bonariensis (Teleostei, Atheriniformes) from a Neotropical shallow lake (Argentina) / Mudanças sazonais nos índices somáticos do Odontesthes bonariensis (Teleostei, Atheriniformes) em uma lagoa da região Neotropical (Argentina)

The study object was an Odontesthes bonariensis (Valenciennes, 1835) population of a characteristically shallow lake from the pampasic region. Over one year, zooplankton and fish samples were collected monthly. As a function of time and gender, several indices were investigated (relative weight, mesentery fat index, gonadosomatic index, hepatosomatic index and somatic index) and were related to zooplanktonic community dynamics, the main energy food source for this species. The results indicate that the seasonal information contained in the weight compartments is most important in mesentery fat, gonads and liver. The zooplankton availability modulates reserves (fat) behaviour and physiologic activity (liver), determining spawn intensity. Thus, in spring spawns, with higher zooplankton availability, mature individuals of the population, males and females, transfer energy from the food to the gonads. In autumn spawns, they use the fat reserves for gonad ripening.

O objeto do estudo foi a população Odontesthes bonariensis (Valenciennes, 1835) de uma lagoa característica da região dos pampas argentinos. Durante um ano, recolheram-se mostras mensais da comunidade zooplanctônica e da população de peixe-rei. Pesquisaram-se vários índices (peso relativo e os índices de gordura mesentérica, gônado-somático, hepato-somático e somático) em função do tempo e do sexo, relacionando-os com a dinâmica de comunidade de zooplâncton, a principal fonte de energia para esta espécie. Os resultados indicam que a informação sazonal contida nos compartimentos de peso é muito importante na gordura mesentérica, nas gônadas e no fígado. A disponibilidade do zooplâncton modula as reservas (gordura), o comportamento e a atividade fisiológica (fígado), determinando a intensidade da desova. Assim, na desova de primavera, com disponibilidade mais elevada do zooplâncton, a maioria dos indivíduos maduros da população, machos e fêmeas, transferem energia do alimento às gônadas. No outono os peixes usariam principalmente as reservas de gordura para a maduração gonadal.

Seasonal variation of parasitism in pejerrey Odontesthes bonariensis (Atheriniformes, Atherinopsidae) from La Viña reservoir (Córdoba, Argentina) / Variação sazonal do parasitismo em Peixe-rei Odontesthes bonariensis (Atheriniformes, Atherinopsidae) no reservatório La Viña, Córdoba, Argentina

The pejerrey Odontesthes bonariensis is the most important freshwater fish of Argentina central region. The present study was conducted to describe the seasonal variation of parasitism in O. bonariensis from La Viña reservoir (31º 17'S, 65º 01'W), located in the province of Córdoba, Argentina. Between years 1999 and 2002, 573 fishes were caught, and their parasite infection and relative weight (Wr) were assesed. Three parasites were found, Lernaea cyprinacea (Crustacea), Contracaecum spp. larvae (Nematoda) and Cangatiella macdonaghi (Cestoda). Overall, Contracaecum spp. prevalence and intensity were very low. Lernaea cyprinacea and Cangatiella macdonaghi prevalences increased during summer and spring (P < 0.01), respectively. Lernaea cyprinacea infection showed also seasonal differences in intensity (P < 0.05), as well as C. macdonaghi regarding parasites density (P < 0.01). Cangatiella macdonaghi average parasites density was 32.0 (±22.5) cestodes per cm³ of digestive content. No association between parasitism and fish relative weight was found. Besides the seasonality variations observed, the parasite burden found did not compromise fish body condition.

O peixe rei Odontesthes bonariensis é um peixe de água doce de grande importância na região central da Argentina. O objetivo deste trabalho foi descrever a sazonalidade do parasitismo de O. bonariensis no reservatrio La Viña (31º 17'S, 65º 01'W), província de Córdoba, Argentina. Durante os anos 1999 e 2002 foram capturados 573 peixes. Nestes se fez à avaliação da condição corporal usando como parâmetro o peso relativo e identificaram-se os seguintes parasitos: Lernaea cyprinacea (Crustacea), Contracaecum spp. (Nematoda) e Cangatiella macdonaghi (Cestoda). As prevalências e intensidades de Contracaecum spp. foram muito baixas. Houve diferenças nas prevalências de L. cyprinacea e C. macdonaghi na época do ano (P < 0,01), sendo maiores no verão e na primavera, respectivamente. Houve diferenças estacionais na intensidade de L. cyprinacea (P < 0,05) e na densidade de C. macdonaghi (P < 0,01), neste ultimo alcançou-se um valor máximo nas amostras de 32,0 (±22,5) parasitos por cm³ de conteúdo digestivo. Não houve associação entre o parasitismo e o peso relativo dos peixes. Embora haja certa sazonalidade, as diferentes cargas parasitárias encontradas nâo prejudicam a saúde de O. bonariensis enquanto sua condição corporal.

The significance of cortisol on acclimation to salinity in pejerrey Odontesthes bonariensis

The role of cortisol on the osmoregulation of pejerrey Odontesthes bonariensis at different salinities was investigated in adult fish injected with 0.7mg hydrocortisone per 100g body weight of fish, and transferred to 0, 5 and 20ppt of NaCl. Blood cortisol was 566ng/ml at the beginning of the experiment (0h) but surged to 1250ng/ml within 3h in cortisol-injected fish. Cortisol levels were influenced not only by treatment but also by time, being higher at 3h compared to 24h. Salinity level, time of exposure and their interaction, but not cortisol treatment, significantly affected plasma osmolality and the concentration of ions Cl- and Na+. This study showed that exogenous cortisol does not seem to play a significant role on the regulation of plasma osmolality and concentration of individual ions in pejerrey

Investigou-se a participação do cortisol na osmoregulação de peixe-rei Odontesthes bonariensis, em diferentes salinidades, em peixes adultos injetados com 0,7mg hidrocortisona por 100g de peso corporal, e transferidos para 0, 5 e 20ppt de NaCl. No inicio do experimento (0h), o cortisol encontrado no plasma foi de 566ng/ml, aumentando para 1250ng/ml em 3h em peixes injetados com cortisol. A concentração de cortisol foi influenciada não somente pelo tratamento, mas também pelo tempo, sendo maior 3h após a inoculação, comparada à 24h. A salinidade, o tempo de exposição e a interação desses dois fatores, mas não o tratamento com o cortisol, afetaram significativamente a osmolaridade e a concentração dos íons Cl- e Na+ do plasma. Este estudo mostrou que, o cortisol exógeno não influi significativamente na regulação da osmolaridade e da concentração de íons Na+ e Cl- no plasma em peixe-rei