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Cetaceans are recognized as bioindicators of pollution in oceans. These marine mammals are final trophic chain consumers and easily accumulate pollutants. For example, metals are abundant in oceans and commonly found in the cetacean tissues. Metallothioneins (MTs) are small non-enzyme proteins involved in metal cell regulation and are essential in many cellular processes (cell proliferation, redox balance, etc.). Thus, the MT levels and the concentrations of metals in cetacean tissue are positively correlated. Four types of metallothioneins (MT1, 2, 3, and 4) are found in mammals, which may have a distinct expression in tissues. Surprisingly, only a few genes or mRNA-encoding metallothioneins are characterized in cetaceans; molecular studies are focused on MT quantification, using biochemical methods. Thus, we characterized, in transcriptomic and genomic data, more than 200 complete sequences of metallothioneins (mt1, 2, 3, and 4) in cetacean species to study their structural variability and to propose to the scientific research community Mt genes dataset to develop in future molecular approaches which will study the four types of metallothioneins in diversified organs (brain, gonad, intestine, kidney, stomach, etc.).

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Bioaccumulation of Hg and Cd from food is a complex ecological process that has been oversimplified in the past. Common dolphins (Delphinus delphis) provide a powerful model to biomonitor metal concentrations in marine environments worldwide. We combined proportions-based nutritional geometry with metal analysis, stomach content analysis and the proximate composition of prey, to yield novel insights into the accumulation of Hg and Cd. Our analysis showed an age-related accumulation trend for Cd and Hg in kidney and liver, with highest concentrations found at 18 years of age. When viewed through the lens of nutritional ecology, Argentine anchovy (58.1 Mass %) and South American long-finned squid (22.7 Mass %), provided most of the dietary intake of protein (P) and lipids (L) (P:L ratio = 2.6:1.0) and also represented the main source for Cd and Hg levels accumulated in their bodies. This study presents unprecedented evidence on metal accumulation in relation to age and nutritional intake in a marine predator.

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In this study, we investigated the metal handling capacity of non-tolerant and tolerant populations of Palaemon argentinus to cadmium (Cd), through evaluating of the main mechanisms of metal detoxification, metallothioneins (MT) and metal-rich granules (MRG), to probe that the presence of MRG in the second population is responsible of that condition. The tolerant population were exposed to 3.06 and 12.26 µg Cd·L-1, while the non-tolerant shrimp were exposed to 3.06 µg Cd·L-1. Each experiment involved the exposure during 3, 7, 10 and 15 days and, the depuration during 7, 14, 21 and 28 days, for which shrimp were transferred to clean water. The range values of MT concentrations for non-tolerant shrimp were: 12.24-23.91 µg g (w.w), while for tolerant shrimp were: 8.75-16.85 µg g (w.w); MRG levels were: 0.12-0.57 µg g (w.w) and 0.3-2.1 µg g (w.w), respectively. The results showed different strategies for Cd detoxification: the induction of MT was the main pathway in the non-tolerant population, while the formation of Cd-MRG was the main mechanism for tolerant shrimp. These differences could be related to the environmental history and the health status of each populations.

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The objective of this study was to analyze the toxicological responses of the estuarine polychaete Laeonereis acuta after acute (96h), subchronic (7 days) and chronic (14 days) exposure to cadmium (Cd). Concentrations of metallothioneins (MT), lipid peroxidation (LPO), total Cd and metal-rich granules (MRG) were evaluated. Seasonal variations of MT and LPO levels in the wild were also measured. Polychaetes were obtained in the Quequén estuary located southeast of Buenos Aires Province, Argentina. For the acute toxicity assay, individuals were exposed to 10; 30, 65; 310; 600; 1300; 2000; 4300; 8100; 16300µgCdL-1, which included levels of environmental relevance and median lethal concentrations (LC50) for related species of polychaete. Based on 96h LC50 values, polychaetes were exposed to sublethal doses of Cd. The concentrations for both subchronic and chronic assays were: 10; 30; 65; 310; 600; 1300; 2000; 4300µgCdL-1. The 96h LC50 value was 8234.9µgL-1, which was within the values reported for other species of polychaete, indicating a high tolerance to Cd. MT induction was not observed for any time exposure. In additoin, LPO levels showed no differences with respect to control levels, which indicated an absence of oxidative damage caused by Cd. However, the total Cd and MRG-Cd concentrations in L. acuta in all tested treatments showed significant differences with respect to control levels. L. acuta were able to accumulate Cd in their tissues in the form of granules which are the main mechanism of Cd detoxification.

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The Commerson's dolphin is the most common endemic odontocete of subantarctic waters of Tierra del Fuego, Argentina incidentally caught in fishing nets. The species is classified as "Data Deficient" by the IUCN. Metallothioneins (MTs) are considered as suitable biomarkers for health and environmental monitoring. The aims of the study were to assess MT concentrations in the liver and kidney of bycaught specimens. Moreover, correlations with Zn, Se, Cd, Ag and Hg, and the molar ratios of MT:metals were estimated to evaluate if there is an indication of their respective protective role against metal toxicity in tissues. Hepatic and renal MT concentrations were similar, ranging from 11.6 to 29.1nmol·g(-1) WW, and Kidney/Liver ratios ranging from 0.73 to 1.93 corresponded to normal ranges. Results suggest that MTs are related to physiological ranges for the species. This information constitutes the first MT report on Commerson's dolphins and possibly considered as baseline for species' conservation.

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Chronic oiling affects seabirds, with short (individual survival) and long-term (dynamics of population) effects. Magellanic penguin is the most affected species in Argentina. The aim was to evaluate the use of blood biochemical-molecular biomarkers (MT and TBARs) to assess health status of Magellanic penguin exposed to chronic environmental oiling, in addition with routine hematological analyses (differential WBC count and PCV). Oiled specimens presented significant higher RBC metallothionein and TBARs concentrations than those from shelter; while routine hematological parameters were within normal levels for penguins and did not show any difference between both groups. These results demonstrated the higher sensibility of both biomarkers, evidencing effects on health status by chronic oiling; furthermore, they are the first report in blood metallothionein and oxidative stress in S. magellanicus. These studies will be useful for a better assessment of the health condition in rehabilitation centers (short term); and, as early warning signals in natural colonies (long term).(AU)

El empetrolamiento crónico afecta a las aves marinas, con efectos a corto (supervivencia del individuo) y largo plazo (dinámica de la población). El ping³ino de Magallanes es la especie más afectada en Argentina. El objetivo fue evaluar el uso de biomarcadores bioquímicos-moleculares (MT y TBARS) en sangre para evaluar el estado de salud del ping³ino de Magallanes expuesto a empetrolamiento crónico ambiental, además de los análisis hematológicos de rutina (recuento diferencial de leucocitos y hematocrito). Los ejemplares empetrolados presentaron concentraciones significativamente mayores de metalotioneínas en fracción celular y peroxidación lipídica que aquellos de albergue; por el contrario, los parámetros hematológicos de rutina estuvieron dentro de los niveles normales para los ping³inos y no mostraron ninguna diferencia entre los grupos. Estos resultados demuestran la mayor sensibilidad de los dos biomarcadores, evidenciando efectos del empetrolamiento crónico sobre el estado de salud; además, este es el primer reporte de concentraciones de metalotioneínas en sangre y el estrés oxidativo en S. magellanicus. Estos estudios son de utilidad para una mejor evaluación del estado de salud en los centros de rehabilitación (corto plazo); y, como señales de alerta temprana en las colonias naturales (largo plazo).(AU)

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Chronic oiling affects seabirds, with short (individual survival) and long-term (dynamics of population) effects. Magellanic penguin is the most affected species in Argentina. The aim was to evaluate the use of blood biochemical-molecular biomarkers (MT and TBARs) to assess health status of Magellanic penguin exposed to chronic environmental oiling, in addition with routine hematological analyses (differential WBC count and PCV). Oiled specimens presented significant higher RBC metallothionein and TBARs concentrations than those from shelter; while routine hematological parameters were within normal levels for penguins and did not show any difference between both groups. These results demonstrated the higher sensibility of both biomarkers, evidencing effects on health status by chronic oiling; furthermore, they are the first report in blood metallothionein and oxidative stress in S. magellanicus. These studies will be useful for a better assessment of the health condition in rehabilitation centers (short term); and, as early warning signals in natural colonies (long term).

El empetrolamiento crónico afecta a las aves marinas, con efectos a corto (supervivencia del individuo) y largo plazo (dinámica de la población). El pingüino de Magallanes es la especie más afectada en Argentina. El objetivo fue evaluar el uso de biomarcadores bioquímicos-moleculares (MT y TBARS) en sangre para evaluar el estado de salud del pingüino de Magallanes expuesto a empetrolamiento crónico ambiental, además de los análisis hematológicos de rutina (recuento diferencial de leucocitos y hematocrito). Los ejemplares empetrolados presentaron concentraciones significativamente mayores de metalotioneínas en fracción celular y peroxidación lipídica que aquellos de albergue; por el contrario, los parámetros hematológicos de rutina estuvieron dentro de los niveles normales para los pingüinos y no mostraron ninguna diferencia entre los grupos. Estos resultados demuestran la mayor sensibilidad de los dos biomarcadores, evidenciando efectos del empetrolamiento crónico sobre el estado de salud; además, este es el primer reporte de concentraciones de metalotioneínas en sangre y el estrés oxidativo en S. magellanicus. Estos estudios son de utilidad para una mejor evaluación del estado de salud en los centros de rehabilitación (corto plazo); y, como señales de alerta temprana en las colonias naturales (largo plazo).

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In the present study, the acute toxicity of cadmium (Cd) in white shrimp (Palaemonetes argentinus) from a metal polluted lagoon (Los Padres, LP) and from unpolluted lagoon (Nahuel Ruca, NR) was evaluated. Both population, were exposed to 3.06, 12.26, 30.66, 61.32, 306 and 613.2 µg Cd · L(-1) for 96-h. The sublethal effects of Cd were examined by two cellular biomarkers: metallothionein (MT) and lipid peroxidation (LPO). The seasonal variations of biomarkers in both lagoons were also evaluated. P. argentinus demonstrated a high sensitivity to Cd, with values of 96-h LC50 lower and close to those of highly sensitive species; therefore, can be proposed as a good indicator species. The LC(50) values of shrimp from LP (24-h: 269.8, 48-h: 67.45, 72-h: 30.66, 96-h: 24.50 µg Cd · L(-1)) were higher than those from NR (24-h: 153.3, 48-h: 32.65, 72-h: 18.40, 96-h: 12.26 µg Cd · L(-1)), indicating a higher tolerance to Cd, and it was related to their origin. Differential responses in terms of MT induction and LPO between populations were also detected. In NR shrimps, the MT synthesis was induced very fast (24-h) and even at the minimum concentration tested (3.06 µg Cd · L(-1)), while no increases were observed in LPO levels. In contrast, the MT and LPO levels in LP shrimps were not increased relative to control, although they were more tolerant to Cd than those of NR; suggesting the presence of another mechanism involved in the detoxification of Cd. The differences in both sensitivity and biochemical responses to Cd may be related with their environmental histories.

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Plastic debris (PD) ingestion was examined in 106 Franciscana dolphins (Pontoporia blainvillei) incidentally captured in artisanal fisheries of the northern coast of Argentina. Twenty-eight percent of the dolphins presented PD in their stomach, but no ulcerations or obstructions were recorded in the digestive tracts. PD ingestion was more frequent in estuarine (34.6%) than in marine (19.2%) environments, but the type of debris was similar. Packaging debris (cellophane, bags, and bands) was found in 64.3% of the dolphins, with a lesser proportion (35.7%) ingesting fishery gear fragments (monofilament lines, ropes, and nets) or of unknown sources (25.0%). PD ingestion correlated with ontogenetic changes in feeding regimes, reaching maximum values in recently weaned dolphins. Because a simultaneous increase in gillnet entanglement and the bioaccumulation of heavy metals take place at this stage, the first months after trophic independence should be considered as a key phase for the conservation of Franciscana dolphin stocks in northern Argentina.

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