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Abstract Introduction: The endoparasite Dendrogaster argentinensis infects the intertidal brooder sea star Anasterias antarctica. This sea-star species is in the highest trophic level in the Beagle Channel. Objective: To study the effects of parasitism by D. argentinensis on the fitness and reproduction of A. antarctica. Methods: Adults from the brooder sea-star were collected from the rocky intertidal of Ensenada Zaratiegui bay (54°51' S & 68°29' W), Argentina. Eight seasonal samplings were performed (four seasons in two years) in the upper and low intertidal. During dissection, parasites were removed, and all organs were extracted and weighed separately. Results: Dendrogaster argentinensis prevalence was the highest for the region (20.4 %). Parasitized individuals were more frequent in the low intertidal in all seasons, with a higher difference in summer, where it is likely that the higher temperatures and strong winds could make the upper intertidal more challenging for a parasitized individual. Five parasitized individuals were castrated. Generally, the gonadal (GI) and somatic (pyloric caeca, PCI; stomach, SI; body wall, WI) indexes were lower in parasitized than non-parasitized individuals. Conclusions: Parasitism by D. argentinensis negatively affects A. antarctica condition. It affects reproduction because it reduces the GI, and can also produce castration. The parasite competes for the sea-stars' energetic resources, also decreasing the individual's capacity for feeding (reduced stomach) and growth (reduced body wall).

Resumen Introducción: El endoparásito Dendrogaster argentinensis infecta a la estrella de mar Anasterias antarctica, especie que se encuentra en el nivel trófico más alto del Canal Beagle. Objetivo: Estudiar los efectos del parasitismo de D. argentinensis en la condición fisiológica y reproducción de A. antarctica. Métodos: Adultos de la estrella de mar incubadora fueron recogidos del intermareal rocoso de la bahía Ensenada Zaratiegui (54°51' S & 68°29' W). Se realizaron ocho muestreos estacionales (cuatro temporadas en dos años) en el intermareal superior y bajo. Durante la disección, se removieron los parásitos, y todos los órganos, los cuales fueron pesados por separado. Resultados: La prevalencia de D. argentinensis fue la más alta de la región (20.4 %). Los individuos parasitados fueron más frecuentes en el intermareal bajo en todas las estaciones, siendo la mayor diferencia en verano, donde es probable que las temperaturas más altas y los fuertes vientos puedan hacer que el intermareal superior sea más desafiante para un individuo parasitado. Se observaron cinco individuos parasitados que estaban castrados. Generalmente, los índices gonadales (GI) y somáticos (ciego pilórico, estómago, y pared del cuerpo) fueron menores en los individuos parasitados que no parasitados. Conclusiones: El parasitismo de D. argentinensis afecta negativamente la condición fisiológica de A. antarctica. Afecta a la reproducción en términos de bajo GI y puede causar castración. El parásito compite por los recursos energéticos de las estrellas de mar, disminuyendo también la capacidad del individuo para alimentarse (reducción del estómago) y crecer (reducción de la pared del cuerpo).

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Pinnatoxins (PnTXs) produced by the cosmopolitan dinoflagellate Vulcanodinium rugosum are highly potent cyclic imines that represent a risk for seafood consumers, artisanal fisheries, and the local aquaculture industry. Among the eight known PnTXs, pinnatoxin-G (PnTX-G) is the most frequent toxin analog detected in shellfish. Despite PnTX-G is still not internationally regulated, the French Agency for Food, Environmental and Occupational Health and Safety established that a risk for human consumers may exist when the accumulation of PnTX-G in shellfish exceeds 23 µg kg-1. This study reports the first detection of these fast-acting lipophilic toxins in localized shellfish banks (Mytilus chilensis) from the Chilean coast. Among 32 sentinel sampling stations monthly monitored for phytotoxins detection and quantification between 2021 and 2022 along the southern Chilean coast (from 36°25' S to 54°57'S), PnTx-G was only detected in shellfish from the southernmost region of Magallanes in concentrations that ranged between 15 and 100 µg kg-1, highlighting the binational (Chile/Argentina) Beagle Channel as a 'hotspot'. As Chile is one of the major mussel producers worldwide, this result raises concern about the potential adverse effect of PnTXs for human health and point to the need of governmental actions for an enhanced monitoring of these emerging toxins. To date, the production of PnTXs has not yet been associated with any microalgae species in Chilean waters.

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Osmoregulatory findings on crabs from high Neotropical latitudes are entirely lacking. Seeking to identify the consequences of evolution at low temperature, we examined hyperosmotic/hypo-osmotic and ionic regulation and gill ion transporter gene expression in two sub-Antarctic Eubrachyura from the Beagle Channel, Tierra del Fuego. Despite sharing the same osmotic niche, Acanthocyclus albatrossis tolerates a wider salinity range (2-65‰ S) than Halicarcinus planatus (5-60‰ S); their respective lower and upper critical salinities are 4‰ and 12‰ S, and 63‰ and 50‰ S. Acanthocyclus albatrossis is a weak hyperosmotic regulator, while H. planatus hyperosmoconforms; isosmotic points are 1380 and ∼1340 mOsm kg-1 H2O, respectively. Both crabs hyper/hypo-regulate [Cl-] well with iso-chloride points at 452 and 316 mmol l-1 Cl-, respectively. [Na+] is hyper-regulated at all salinities. mRNA expression of gill Na+/K+-ATPase is salinity sensitive in A. albatrossis, increasing ∼1.9-fold at 5‰ compared with 30‰ S, decreasing at 40-60‰ S. Expression in H. planatus is very low salinity sensitive, increasing ∼4.7-fold over 30‰ S, but decreasing at 50‰ S. V-ATPase expression decreases in A. albatrossis at low and high salinities as in H. planatus. Na+/K+/2Cl- symporter expression in A. albatrossis increases 2.6-fold at 5‰ S, but decreases at 60‰ S versus 30‰ S. Chloride uptake may be mediated by increased Na+/K+/2Cl- expression but Cl- secretion is independent of symporter expression. These unrelated eubrachyurans exhibit similar systemic osmoregulatory characteristics and are better adapted to dilute media; however, the expression of genes underlying ion uptake and secretion shows marked interspecific divergence. Cold clime crabs may limit osmoregulatory energy expenditure by hyper/hypo-regulating hemolymph [Cl-] alone, apportioning resources for other energy-demanding processes.

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The purpose of this paper is to investigate the trace metal content in edible biomonitors (i.e., mollusks) in the Beagle Channel (southern Patagonia) and to assess the human health risks associated with their consumption. Rationale: The monitoring breakdown structure (MBS) conceptual model was applied to four sampling campaigns (2005 → 2012) that collected 729 samples of Mytilus chilensis and Nacella magellanica. The composition of trace elements (Cd, Cr, Cu, Ni, Pb and Zn) in the mollusks was determined using graphite furnace (GFAAS) or flame atomic absorption spectrometry (FAAS). We compared the mean obtained values with the maximum levels (MLs) of each element established by international organizations. Then, based on semi-structured interviews, we calculated the estimated daily intake (EDI) of local residents and compared it with safety reference doses, i.e., the provisional tolerable daily intake (PTDI), provisional maximum tolerable daily intake (PMTDI), and tolerable daily intake (TDI), as well as the benchmark dose level lower confidence limit for Pb (BMDL01, a reference point (RP)/point of departure (POD). Moreover, to obtain information about the potential health risks of ingesting heavy metals (HMs) through mollusk consumption, we evaluated the target hazard quotient (THQ) and the hazard index (HI). Findings: For Cd and Pb, 65% and 40% of bivalves exceeded the MLs established by the Mercado Común del Sur (Mercosur), respectively. Except for Cd in N. magellanica (i.e., 1.20 µg/kg/bw/day), EDI values were clearly lower than the safety reference doses. For Cr, Cu, Ni, Pb and Zn, mussels were safe for consumption and did not raise concerns for public health. Likewise, THQ values were well below one for most of the studied metals, indicating that the exposed human population is assumed to be safe. Occasional high consumers of mollusks from the most contaminated sites may be at some health risk. Originality: The food production system and the environment are complex systems; this is crucial to understand when we consider ecosystems as a food source (i.e., marine ecosystems). Here we consider edible biomonitors, that are organisms that can have a dual function. They are food, and at the same time, if properly calibrated, they can act as indicators of environmental quality. This study is the first to investigate relevant essential and non-essential trace metal content in two edible mollusks from the Beagle Channel in a long-term survey (2005 → 2012). The information variety was high; approximately thirteen thousand determinations were conducted to support the risk assessment for mollusk consumption. Other aspects connected with the health risks and the uncertainty factors related to the presence of essential and non-essential minerals in edible mollusks as well as the use of the MBS are also discussed.

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The Beagle Channel is a remote subantarctic environment where mussel aquaculture initiatives have existed since the early 1990s. Here we analyze phytoplankton biomass and composition, and the occurrence of harmful microalgae species and their toxins at three sites during the period 2015-2016. The occurrence of potentially harmful algae was observed throughout the study period, including toxigenic dinoflagellates such as Alexandrium catenella (Group I of the A. tamarense complex), A. ostenfeldii, Dinophysis acuminata, Gonyaulax spinifera, Azadinium sp., and the diatoms Pseudo-nitzschia australis and P. fraudulenta. Toxic dinoflagellates were detected in low densities whereas a Pseudo-nitzschia bloom was observed in late February. Isolates of A. catenella and P. delicatissima sensu stricto were phylogenetically characterized. The toxin profile of A. catenella was dominated by GTX4, while P. delicatissima sensu stricto showed no production of the neurotoxin domoic acid in culture conditions. The results provide base-line information for the management of harmful algal blooms in this little explored subantarctic area.

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Gammaridea and Corophiidea amphipod species from the Beagle Channel and the Straits of Magellan were listed for the first time; their faunas were compared on the basis of bibliographic information and material collected in one locality at Beagle Channel (Isla Becasses). The species Schraderia serraticauda and Heterophoxus trichosus (collected at Isla Becasses) were cited for the first time for the Magellan region; Schraderia is the first generic record for this region. A total of 127 species were reported for the Beagle Channel and the Straits of Magellan. Sixty-two species were shared between both passages (71.3 % similarity). The amphipod species represented 34 families and 83 genera. The similarity at genus level was 86.4 %, whereas 23 of the 34 families were present in both areas. For all species, 86 had bathymetric ranges above 100 m and only 12 species ranged below 200 m depth. In the Beagle Channel, only one species had a depth record greater than 150 m, whereas in the Straits of Magellan, 15 had such a record. The Beagle Channel and the Straits of Magellan contain 57.5 % of the species, 71 % of the genera and 77.3 % of the families of Gammaridea and Corophiidea from the entire Magellan region.

Se confeccionó el primer listado de anfípodos Gammaridea y Corophiidea del Canal Beagle y del Estrecho de Magallanes, y se compararon, en forma preliminar, sus faunas con base en información bibliográfica y material recolectado en una localidad del Canal Beagle (Isla Becasses). Las especies Heterophoxus trichosus y Schraderia serraticauda (recolectadas en Isla Becasses) son citadas por primera vez para la región magallánica; Schraderia representa el primer registro genérico para dicha región. Un total de 127 especies fueron registradas para el Canal Beagle y el Estrecho de Magallanes, compartiendo entre ambos 62 especies, lo que representa una similitud del 71.3 %. El total de las especies pertenece a 34 familias y 83 géneros. La similitud a nivel genérico fue del 86.4 %, mientras que 23 familias estuvieron presentes en ambos pasajes. Del total de especies, 86 presentaron rangos de profundidad menores a los 100 m y sólo 12 especies superaron los 200 m. Sólo una especie tuvo un registro superior a los 150 m de profundidad en el Canal Beagle, mientras que 15 superaron dicha profundidad en el Estrecho de Magallanes. En el Canal Beagle y el Estrecho de Magallanes se registró el 57.5 % de las especies, 71 % de los géneros y 77.3 % de las familias conocidas para la región magallánica.

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