The Interactive Effects of the Anti-Sea Lice Pesticide Azamethiphos and Temperature on Oxidative Damage and Antioxidant Responses in the Oyster Ostrea chilensis.

Azamethiphos is used in the salmon industry to treat sea lice and is subsequently discharged into the sea, which may affect non-target species (NTS). A rise in seawater temperature could enhance the sensitivity of NTS. Thus, in the present investigation, the combined effects of azamethiphos (0 µg L-1, 15 µg L-1 and 100 µg L-1) and temperature (12 °C and 15 °C) was assessed over time (7 days) in the gonads and gills of the oyster Ostrea chilensis, assessing its oxidative damage (lipid peroxidation and protein carbonyls) and total antioxidant capacity. Our results indicated that in gonads and gills, lipid peroxidation levels increased over time during exposure to both pesticide concentrations. Protein carbonyl levels in gills increased significantly in all experimental treatments; however, in gonads, only pesticide concentration and exposure time effected a significant increase in protein damage. In both, gill and gonad temperature did not influence oxidative damage levels. Total antioxidant capacity in gonads was influenced only by temperature treatment, whereas in the gills, neither temperature nor azamethiphos concentration influenced defensive responses. In conclusion, our results indicated the time of pesticide exposure (both concentrations) had a greater influence than temperature on the cellular damage in this oyster.

Transient species driving ecosystem multifunctionality: Insights from competitive interactions between rocky intertidal mussels.

Anthropogenic biodiversity loss poses a significant threat to ecosystem functioning worldwide. Numerically dominant and locally rare (i.e., transient) species are key components of biodiversity, but their contribution to multiple ecosystem functions (i.e., multifunctionality) has been seldomly assessed in marine ecosystems. To fill this gap, here we analyze the effects of a dominant and a transient species on ecosystem multifunctionality. In an observational study conducted along ca. 200 km of the southeastern Pacific coast, the purple mussel Perumytilus purpuratus numerically dominated the mid-intertidal and the dwarf mussel Semimytilus patagonicus exhibited low abundances but higher recruitment rates. In laboratory experiments, the relative abundances of both species were manipulated to simulate the replacement of P. purpuratus by S. patagonicus and five proxies for ecosystem functions-rates of clearance, oxygen consumption, total biodeposit, organic biodeposit, and excretion-were analyzed. This replacement had a positive, linear, and significant effect on the combined ecosystem functions, particularly oxygen consumption and excretion rates. Accordingly, S. patagonicus could well drive ecosystem functioning given favorable environmental conditions for its recovery from rarity. Our study highlights therefore the key role of transient species for ecosystem performance. Improving our understanding of these dynamics is crucial for effective ecosystem conservation, especially in the current scenario of biological extinctions and invasions.

Cognitive improvement following endovascular embolization in patients with intracranial dural arteriovenous fistula: The Neuropsychology in dural ArterIal Fistula (NAIF) Study.

BACKGROUND: Cognitive improvement after endovascular embolization of an intracranial dural arteriovenous fistula (dAVF) remains unexplored. We aim to investigate cognitive changes following endovascular embolization of dAVFs. METHODS: Neuropsychology in dural ArterIal Fistula (NAIF) was a prospective multicentric study including patients with an angiographic diagnosis of dAVF who underwent endovascular embolization over the course of 4 years. A complete neuropsychological evaluation comprising five cognitive domains (attention and executive functions, memory, language, praxis, gnosis) was performed at baseline and 3 months follow-up. Mean Z scores for cognitive tests were compared pre- and post-treatment using paired sample t-tests, where higher Z scores indicate better cognition. Effect sizes were computed as Cohen's d. RESULTS: A total of 32 patients (mean age 61.1±15.4 years, 10 (31.3%) females) were included. Patients exhibited improved performance in attention and executive functions: executive functions-attention (+0.282, P=0.009, d=0.29), executive functions-fluencies (+0.283, P=0.029, d=0.4), and executive functions-processing speed (+0.471, P=0.039, d=0.41). There was an increase in memory: verbal learning and verbal delayed recall scores (+0.513, P<0.001, d=0.55, and +0.385, P=0.001, d=0.41, respectively), while verbal recognition parameters (+0.839, P=0.086, d=0.37) and visual memory (delayed recall) (+0.430, P=0.060, d=0.35) displayed trends toward improved performance. Regarding language, there was significant overall improvement (+0.300, P=0.014, d=0.24), but neither praxis nor gnosis changed significantly. These cognitive outcomes were independent of the severity (measured as Cognard classification), and no patient experienced cognitive worsening. CONCLUSION: This study suggests that endovascular embolization confers cognitive benefits on dAVF patients undergoing endovascular embolization and may be beneficial even for patients with a low risk of hemorrhage.

Impact of Balloon Guide Catheters in Elderly Patients Treated with Mechanical Thrombectomy: Insights from the ROSSETTI Registry.

BACKGROUND AND PURPOSE: Several nonrandomized studies have demonstrated the effectiveness of balloon guide catheters in treating patients with anterior circulation large-vessel occlusion. However, their impact on the elderly populations has been underreported. We aimed to analyze the effect of balloon guide catheters in a cohort of elderly patients (80 years of age or older) with anterior circulation large-vessel occlusion. MATERIALS AND METHODS: Consecutive patients from June 2019 to June 2022 were collected from the ROSSETTI Registry. Demographic and clinical data, angiographic endovascular technique, and clinical outcome were compared between balloon guide catheter and non-balloon guide catheter groups. We studied the association between balloon guide catheters and the rate of complete recanalization after a single first-pass effect modified TICI 2c-3, as well as their association with functional independence at 3 months. RESULTS: A total of 808 patients were included during this period, 465 (57.5%) of whom were treated with balloon guide catheters. Patients treated with balloon guide catheters were older, had more neurologic severity at admission and lower baseline ASPECTS, and were less likely to receive IV fibrinolytics. No differences were observed in terms of the modified first-pass effect between groups (45.8 versus 39.9%, P = .096). In the multivariable regression analysis, balloon guide catheter use was not independently associated with a modified first-pass effect or the final modified TICI 2c-3, or with functional independence at 3 months. CONCLUSIONS: In our study, balloon guide catheter use during endovascular treatment of anterior circulation large-vessel occlusion in elderly patients did not predict the first-pass effect, near-complete final recanalization, or functional independence at 3 months. Further studies, including randomized clinical trials, are needed to confirm these results.

Understanding the Symbiotic Relationship between the Sea Urchin Loxechinus albus (Molina, 1782) and the Pea Crab Pinnaxodes chilensis (H. Milne Edwards, 1837): a Potential Parasitism.

The echinoderm Loxechinus albus has a symbiotic relationship with the pinnotherid crustacean Pinnaxodes chilensis. Females of the crustacean develop in the terminal section of the sea urchin's digestive system, remaining there for life. This relationship has been suggested as commensalism. However, a potential negative impact on gonadal development and on the morphology of the sea urchin's digestive system suggest that it is instead parasitic. To study if there is a negative impact of the crustacean symbiont on the host, specimens of L. albus of all sizes were collected from a rocky shore in southern Chile. The gonadal and somatic tissues of sea urchins that were and were not harboring the pinnotherid were weighed and compared. Our results show that the presence of the pinnotherid was related to sea urchin gonads of lower biomass, decreased gonadosomatic index levels, and alterations in the morphology of the terminal portion of the host digestive system. The lower gonadal biomass suggests a negative impact on gamete production as well as a diversion of energy due to changes of the digestive system tissues and the potential consumption of algal food by the resident crustacean. These results suggest that the prolonged relationship between these two species is one of parasitism rather than one of commensalism.

Specific plasticity of the anemone Anthopleura hermaphroditica to intertidal and subtidal environmental conditions of the Quempillén estuary.

The cellular capacity of marine organisms to address rapid fluctuations in environmental conditions is decisive, especially when their bathymetric distribution encompasses intertidal and subtidal zones of estuarine systems. To understand how the bathymetric distribution determines the oxidative damage and antioxidant response of the estuarine anemone Anthopleura hermaphroditica, individuals were collected from upper intertidal and shallow subtidal zones of Quempillén River estuary (Chile), and their response analysed in a fully orthogonal, multifactorial laboratory experiment. The organisms were exposed to the effects of temperature (10°C and 30°C), salinity (10 ppt and 30 ppt) and radiation (PAR, > 400-700 nm; PAR+UV-A, > 320-700 nm; PAR+UV-A+UV-B, > 280-700 nm), and their levels of lipid peroxidation, protein carbonyl and total antioxidant capacity were determined. The results indicated that the intertidal individuals of A. hermaphroditica presented higher levels of tolerance to the stressful ranges of temperature, salinity, and radiation than individuals from the subtidal zone, which was evident from their lower levels of oxidative damage to lipids and proteins. These results were consistent with increased levels of total antioxidant capacity observed in subtidal organisms. Thus intertidal individuals could have greater plasticity to environmental variations than subtidal individuals. Future studies are needed to understand the mechanisms underlying stress adaptation in individuals from this estuarine anemone subjected to different environmental stressors during their life cycles.

The interactive effect of anti-sea lice pesticide azamethiphos and temperature on the physiological performance of the filter-feeding bivalve Ostrea chilensis: A non-target species.

The pesticide azamethiphos used by the salmon industry to treat sea lice, is applied as a bath and subsequently discharged into the sea. The effects of azamethiphos concentration (0, 15 and 100 µg L-1) on the physiology of the Chilean oyster (Ostrea chilensis) at two temperatures (12 and 15 °C) was examined. In all azamethiphos treatments, oysters kept at 15 °C had clearance rates (CR) higher than oysters kept at 12 °C. The oxygen consumption rate (OCR) increased at higher temperatures, except with 100 µg L-1 of azamethiphos, where no changes were observed. Sixty days after the exposure, survival rates of 91 and 79% (15 and 100 µg L-1, respectively), were observed compared to the controls, a situation independent of the experimental temperature. The interaction between temperature and pesticide has detrimental effects on the physiological performance and survival of O. chilensis, and these effects should also be assessed for other non-target species.

Effects of Ultraviolet Radiation on Sediment Burial Parameters and Photo-Oxidative Response of the Intertidal Anemone Anthopleura hermaphroditica.

Anthopleura hermaphroditica is an intertidal anemone that lives semi-buried in soft sediments of estuaries and releases its brooded embryos directly to the benthos, being exposed to potentially detrimental ultraviolet radiation (UVR) levels. In this study, we investigated how experimental radiation (PAR: photosynthetically active radiation; UVA: ultraviolet A radiation; and UVB: ultraviolet B radiation) influences burrowing (time, depth and speed) in adults and juveniles when they were exposed to PAR (P, 400-700 nm), PAR + UVA (PA, 315-700 nm) and PAR + UVA + UVB (PAB, 280-700 nm) experimental treatments. The role of sediment as a physical shield was also assessed by exposing anemones to these radiation treatments with and without sediment, after which lipid peroxidation, protein carbonyls and total antioxidant capacity were quantified. Our results indicate that PAB can induce a faster burial response compared to those anemones exposed only to P. PAB increased oxidative damage, especially in juveniles where oxidative damage levels were several times higher than in adults. Sediment offers protection to adults against P, PA and PAB, as significant differences in their total antioxidant capacity were observed compared to those anemones without sediment. Conversely, the presence or absence of sediment did not influence total antioxidant capacity in juveniles, which may reflect that those anemones have sufficient antioxidant defenses to minimize photooxidative damage due to their reduced tolerance to experimental radiation. Burrowing behavior is a key survival skill for juveniles after they have been released after brooding.

Non-consumptive effects of a predatory snail (Acanthina monodon) on a dominant habitat-forming mussel species (Perumytilus purpuratus).

Predators can influence prey through direct consumption as well as through non-consumptive effects (NCEs). NCEs usually occur mediated by behavioral changes in the prey upon detection of predator cues. Such changes may involve reduction of feeding with a variety of physiological consequences. We evaluated NCEs from an intertidal predatory snail (Acanthina monodon) on a dominant habitat-forming mussel species (Perumytilus purpuratus) from the southeastern Pacific coast. We tested whether A. monodon exerts negative NCEs on clearance rate, oxygen consumption rate, biodeposit production, and between-valve gap size in P. purpuratus. We found that waterborne predator cues triggered a decrease in these variables except biodeposit production. However, the organic content of the biodeposits increased in the presence of predator cues. The snail's physical contact with the mussels strengthened the negative NCEs on between-valve gap size. Since P. purpuratus is a dominant filter-feeder and foundation species in rocky intertidal habitats, predator NCEs on this species might indirectly influence ecosystem-level processes and community structure.

Addition of intracranial aspiration to balloon guide catheter does not improve outcomes in large vessel occlusion anterior circulation stent retriever based thrombectomy for acute stroke.

BACKGROUND: Balloon guide catheter (BGC) in stent retriever based thrombectomy (BGC+SR) for patients with large vessel occlusion strokes (LVOS) improves outcomes. It is conceivable that the addition of a large bore distal access catheter (DAC) to BGC+SR leads to higher efficacy. We aimed to investigate whether the combined BGC+DAC+SR approach improves angiographic and clinical outcomes compared with BGC+SR alone for thrombectomy in anterior circulation LVOS. METHODS: Consecutive patients with anterior circulation LVOS from June 2019 to November 2020 were recruited from the ROSSETTI registry. Demographic, clinical, angiographic, and outcome data were compared between patients treated with BGC+SR alone versus BGC+DAC+SR. The primary outcome was first pass effect (FPE) rate, defined as near complete/complete revascularization (modified Thrombolysis in Cerebral Infarction (mTICI) 2c-3) after single device pass. RESULTS: We included 401 patients (BGC+SR alone, 273 (66.6%) patients). Patients treated with BGC+SR alone were older (median age 79 (IQR 68-85) vs 73.5 (65-82) years; p=0.033) and had shorter procedural times (puncture to revascularization 24 (14-46) vs 37 (24.5-63.5) min, p<0.001) than the BGC+DAC+SR group. Both approaches had a similar FPE rate (52% in BGC+SR alone vs 46.9% in BGC+DAC+SR, p=0.337). Although the BGC+SR alone group showed higher rates for final successful reperfusion (mTICI ≥2b (86.8% vs 74.2%, p=0.002) and excellent reperfusion, mTICI ≥2 c (76.2% vs 55.5%, p<0.001)), there were no significant differences in 24 hour National Institutes of Health Stroke Scale score or rates of good functional outcome (modified Rankin Scale score of 0-2) at 3 months across these techniques. CONCLUSIONS: Our data showed that addition of distal intracranial aspiration catheters to BGC+SR based thrombectomy in patients with acute anterior circulation LVO did not provide higher rates of FPE or improved clinical outcomes.

Balloon guide catheter improvements in thrombectomy outcomes persist despite advances in intracranial aspiration technology.

BACKGROUND: First-pass effect (FPE) has been established as a key metric for technical success and strongly correlates with better clinical outcomes. Most data supporting improved outcomes with the use of a balloon guide catheter (BGC) predate the advent of last-generation large-bore intracranial aspiration catheters. We aim to evaluate the impact of BGC in FPE and clinical outcomes in a large cohort of patients treated with contemporary technology. METHODS: Patients were recruited from the prospectively ongoing ROSSETTI registry. This registry includes all consecutive patients with anterior circulation large-vessel occlusion (LVO) from 10 comprehensive stroke centers in Spain. Demographic, clinical, angiographic, and clinical outcome data were compared between BGC and non-BGC groups. FPE was defined as the achievement of mTICI2c-3 after a single device pass. RESULTS: 426 patients were included out of which 271 (63.62%) used BCG. BGC-treated patients had higher FPE rate (45.8% vs 27.7%; P<0.001), higher final mTICI ≥2 c recanalization rate (76.8% vs 50.3%, respectively; P<0.001), shorter procedural time [median (IQR), 30 (19-58) vs 43 (33-71) min; P<0.001], higher NIHSS difference from admission to 24 hours [median (IQR), 8 (2-12) vs 3 (0-10); P=0.001], and lower mortality rate (17.6% vs 29.8%, P=0.026) compared with non-BGC patients. BGC use was an independent predictor of FPE (OR 2.197, 95% CI 1.436 to 3.361; P<0.001), and excellent clinical outcome at 3 months (OR 0.34, 95% CI 0.17 to 0.68; P=0.002). CONCLUSIONS: Our results support the benefit of BGC use on angiographic and clinical outcomes in anterior circulation LVO ischemic stroke remain significant even when considering recent improvements in intracranial aspiration technology.

Community-wide consequences of nonconsumptive predator effects on a foundation species.

Predators can exert nonconsumptive effects (NCEs) on prey, which often take place through prey behavioural adjustments to minimise predation risk. As NCEs are widespread in nature, interest is growing to determine whether NCEs on a prey species can indirectly influence several other species simultaneously, thus leading to changes in community structure. In this study, we investigate whether a predator can exert NCEs on a foundation species and indirectly affect community structure. Through laboratory experiments, we first tested whether the predatory marine snail Acanthina monodon exerts negative NCEs on larviphagy (consumption of pelagic larvae) and phytoplankton filtration rates of the mussel Perumytilus purpuratus, an intertidal foundation species. These hypotheses stem from the notion that mussels may decrease feeding activities in the presence of predator cues to limit detection by predators. Afterwards, a field experiment tested whether the presence of A. monodon near mussel beds leads to higher colonisation rates of invertebrates that reproduce through pelagic larvae (expected under a lower larviphagy in P. purpuratus) and to a lower algal biomass on P. purpuratus shells (expected under a lower metabolite excretion in the mussels), thereby changing the community structure of the species typically found in P. purpuratus beds. The laboratory experiments revealed that waterborne cues from A. monodon limit the larviphagy and filtration rates of P. purpuratus. In turn, the field experiment showed that A. monodon cues led to greater abundances of barnacles and bivalves and a lower algal biomass in P. purpuratus beds, thus altering community structure. Overall, this study shows that a predator can indirectly affect community structure through NCEs on an invertebrate foundation species. As invertebrate foundation species are ubiquitous worldwide, understanding predator NCEs on these organisms could help to better understand community regulation in systems structured by such species.

Impact of short-term elevated temperature stress on winter-acclimated individuals of the marine gastropod Crepidula fornicata.

The intertidal zone is an especially stressful thermal habitat, typically exposing residents to air temperatures for up to 6 h at a time, twice daily. Tolerance to elevated temperatures has been particularly well-studied for a variety of intertidal species, especially with regard to upper thermal limits during summers. However, in recent years, as climates have been changing around the world, temperate zone intertidal organisms have sometimes been exposed to periods of unusually high air temperatures during the winter. The present study sought to examine the impact of elevated temperatures on survival and clearance rates of winter-acclimated intertidal individuals of the sedentary marine suspension-feeding gastropod Crepidula fornicata. Individuals were collected intertidally from Nahant, Massachusetts from late January to early April each year for 5 years, maintained in the laboratory at the acclimation temperature of 6 °C, and exposed in the laboratory for 3 h to temperatures as high as 37 °C in seawater either once or twice, 24 h apart. Although mean clearance rates were substantially reduced for at least the next 12-24 h after individuals were returned to the 6 °C control condition following exposures to elevated temperatures as low as 21-26 °C, we saw little mortality even following two 3 h exposures to 35 °C, or single exposures to 37 °C. Mortality was substantial, however, in one experiment following a double exposure to 37 °C. Smaller individuals (~5-12 mm in shell length) were somewhat more sensitive to the thermal stress than adults were. Intertidal members of C. fornicata in Massachusetts seem well-prepared to deal with the increasing range of winter air temperatures associated with the global climate confusion predicted for future years. Additional studies will be required to understand the physiological and biochemical mechanisms used by winter-acclimated individuals of this species to tolerate such periodic substantial temperature increases of 29-31 °C.

Plastic response of the oyster Ostrea chilensis to temperature and pCO2 within the present natural range of variability.

Estuaries are characterized by high fluctuation of their environmental conditions. Environmental parameters measured show that the seawater properties of the Quempillén estuary (i.e. temperature, salinity, pCO2, pH and ΩCaCO3) were highly fluctuating and related with season and tide. We test the effects of increasing temperature and pCO2 in the seawater on the physiological energetics of the bivalve Ostrea chilensis. Juvenile oysters were exposed to an orthogonal combination of three temperatures (10, 15, and 20°C) and two pCO2 levels (~400 and ~1000 µatm) for a period of 60 days to evaluate the temporal effect (i.e. 10, 20, 30, 60 days) on the physiological rates of the oysters. Results indicated a significant effect of temperature and time of exposure on the clearance rate, while pCO2 and the interaction between pCO2 and the other factors studied did not show significant effects. Significant effects of temperature and time of exposure were also observed on the absorption rate, but not the pCO2 nor its interaction with other factors studied. Oxygen consumption was significantly affected by pCO2, temperature and time. Scope for growth was only significantly affected by time; despite this, the highest values were observed for individuals subject to to 20°C and to ~1000 µatm pCO2. In this study, Ostrea chilensis showed high phenotypic plasticity to respond to the high levels of temperature and pCO2 experienced in its habitat as no negative physiological effects were observed. Thus, the highly variable conditions of this organism's environment could select for individuals that are more resistant to future scenarios of climate change, mainly to warming and acidification.

The filter-feeding bivalve Mytilus chilensis capture pelagic stages of Caligus rogercresseyi: A potential controller of the sea lice fish parasites.

The copepod Caligus rogercresseyi is an ectoparasite of several salmonid species. The pumping activity of filter-feeding molluscs could reduce the abundance of copepod dispersive larval stages in the water column. In this research, nauplius II and copepodid larvae of C. rogercresseyi were exposed to filtering mussels (Mytilus chilensis) of different sizes. These mussels were able to filter both larval stages, although they were more efficient in catching nauplius II. The fact that nauplius II were ingested more efficiently could be explained by their smaller size, lower swimming velocity (escape) and longer resting times between movements, when they were exposed to the influx of water around the inhalant area of the mussels. Larger mussels were more effective filtering C. rogercresseyi larvae due to their larger inhalant area and the related water influx. Additionally, the results suggest that larvae captured by the mussels can be incorporated into pseudofaeces or ingested and then released as part of the faeces. Thus, high concentrations of M. chilensis surrounding salmon farms may act as biological barriers, reducing the density of copepod dispersive larval stages and, thus, salmon infestations.

Transradial Comaneci-assisted coiling of a direct carotid-cavernous fistula.

Direct carotid-cavernous fistula is a communication between the internal carotid artery and the cavernous sinus, most of the times established following trauma or rupture of a cavernous aneurysm. The most commonly used treatments (coils, detachable latex balloons, stents, or liquid agents) carry ischemic or hemorrhagic risks, related to hemodynamic diversion of cerebral blood flow or permanent dual antiplatelet therapy. We report a case of coiling of a carotid-cavernous fistula assisted by the Comaneci, a temporary adjustable bridging mesh (Rapid Medical, Israel), to avoid transarterial or -venous migration. In our experience, Comaneci-assisted coiling represents a feasible solution to maintain patency of the distal vessels during coiling and avoid dual antiplatelet medications, even using a transradial approach.

Reproductive biology of the encapsulating, brooding gastropod Crepipatella dilatata Lamarck (Gastropoda, Calyptraeidae).

Among calyptraeid gastropods, males become females as they get older, and egg capsules containing developing embryos are maintained beneath the mother's shell until the encapsulated embryos hatch. Crepipatella dilatata is an interesting biological model considering that is an estuarine species and thus periodically exposed to elevated environment-physiological pressures. Presently, there is not much information about the reproductive biology and brooding parameters of this gastropod. This paper describes field and laboratory observations monitoring sex changes, brooding frequencies, sizes of brooding females, egg mass characteristics, and embryonic hatching conditions. Our findings indicate that C. dilatata is a direct-developing protandric hermaphrodite, changing from male to female when individuals were between 18 and 20 mm in shell length. At our study site in Quempillén estuary, females were found to be brooding almost continuously throughout the year, having an average maximum of 85% of simultaneous brooding, with a short rest from April through June. No relationship was found between the number of capsules per egg mass and the size of the brooding female. However, capsule size and the number of embryos and nurse eggs were strongly related to female size. The offspring hatched with an average shell length > 1 mm. About 25% of the hatched capsules were found to contain both metamorphosed (juveniles) and non-metamorphosed (veliger) individuals. The sizes of the latter were < 1000 µm. The length of hatching juveniles was inversely related to the number of individuals per capsule, which seems related to differences in the availability of nurse eggs per embryo. Although fecundity per reproductive event of this species is relatively low (maximum approx. 800 offspring per egg mass) compared with those of calyptraeid species showing mixed development, the overall reproductive potential of C. dilatata seems to be high considering that females can reproduce up to 5 times per year, protecting their encapsulated embryos from physical stresses until well-developed juveniles are released into the population, avoiding a dangerous pelagic period prior to metamorphosis.

Trophic transfer of paralytic shellfish toxin (PST): Physiological and reproductive effects in the carnivorous gastropod Acanthina monodon (Pallas, 1774).

Harmful algal blooms can adversely affect different levels of the trophic chain, from primary consumers, such as bivalve molluscs, to higher links such as large fish, birds and mammals, including humans. Among secondary consumers, it has been described that carnivorous gastropods can accumulate these toxins when they prey on bivalves that have been exposed to toxic microalgae; these could also harm human health. In Chile, frequent events of harmful algal blooms caused by the dinoflagellate Alexandrium catenella have been described. This organism produces paralytic shellfish toxin (PST) which has been identified in some carnivorous gastropods. The objective of this research was to identify the physiological and reproductive response of the carnivorous gastropod Acanthina monodon fed on the Mytilid Perumytilus purpuratus, which had previously been maintained on a diet containing PST. Specimens of A. monodon showed a decrease in ingestion and absorption rate when they consumed PST indirectly through their diet. The oxygen consumption rate was also affected by the diet-time interaction. The variations of these parameters were reflected in the scope for growth, since the available energy was lower in gastropods exposed to toxic diet. Consumption of PST had a negative effect on the reproduction of A. monodon, since intoxicated adults presented lower egg-masses and delayed start of oviposition. We observed a delay in the development of the embryos inside the capsules, and a lower number of hatched juveniles, although these few juveniles from intoxicated parents accomplished higher growth rates during the next 6 months. We may therefore suggest that toxin transfer, from harmful microalgae through the trophic chain, can generate deleterious effects on the physiological energetics of the organisms that consume them, affecting their reproductive capacity and early ontogenetic development.

Ocean acidification exacerbates the effects of paralytic shellfish toxins on the fitness of the edible mussel Mytilus chilensis.

High latitudes are considered particularly vulnerable to ocean acidification, since they are naturally low in carbonate ions. The edible mussel Mytilus chilensis is a common calcifier inhabiting marine ecosystems of the southern Chile, where culturing of this species is concentrated and where algal blooms produced by the toxic dinoflagellate A. catenella are becoming more frequent. Juvenile Mytilus chilensis were exposed to experimental conditions simulating two environmental phenomena: pCO2 increase and the presence of paralytic shellfish toxins (PST) produced by the dinoflagellate Alexandrium catenella. Individuals were exposed to two levels of pCO2: 380 µatm (control condition) and 1000 µatm (future conditions) over a period of 39 days (acclimation), followed by another period of 40 days exposure to a combination of pCO2 and PST. Both factors significantly affected most of the physiological variables measured (feeding, metabolism and scope for growth). However, these effects greatly varied over time, which can be explained by the high individual variability described for mussels exposed to different environmental conditions. Absorption efficiency was not affected by the independent effect of the toxic diet; however, the diet and pCO2 interaction affected it significantly. The inhibition of the physiological processes related with energy acquisition by diets containing PST, may negatively impact mussel fitness, which could have important consequences for both wild and cultured mussel populations, and thus, for socioeconomic development in southern Chile.

Pre-ingestive selection capacity and endoscopic analysis in the sympatric bivalves Mulinia edulis and Mytilus chilensis exposed to diets containing toxic and non-toxic dinoflagellates.

This study investigates the effects of toxic and non-toxic dinoflatellates on two sympatric bivalves, the clam Mulinia edulis and the mussel Mytilus chilensis. Groups of bivalves were fed one of three diets: (i) the toxic paralytic shellfish producing (PSP) Alexandrium catenella + Isochrysis galbana; (ii) the non-toxic Alexandrium affine + Isochrysis galbana and (iii) the control diet of Isochrysis galbana. Several physiological traits were measured, such as, clearance rate, pre-ingestive selection efficiency and particle transport velocity in the gill. The clearance rates of both M. chilensis and M. edulis showed a significant reduction when fed a mixed toxic diet of 50% Alexandrium catenella: 50% Isochrysis galbana. Similarly, when both species of bivalves were fed with the non-toxic diet (50% A. affine: 50% I. galbana), clearance rate was significantly lower compared with a diet of 100% I. galbana. Under all the experimental diets, M. chilensis showed higher clearance rate values, slightly more than double that of M. edulis. M. edulis and M. chilensis have the ability to select particles at the pre-ingestive level, thus eliminating a larger proportion of the toxic dinoflagellate A. catenella as well as the non-toxic A. affine in the form of pseudofaeces. Higher values of selection efficiency were registered in M. edulis than in M. chilensis when exposed to the toxic diet. Similar results were observed when these two species were exposed to the diet containing the non-toxic dinoflagellate, explained by the fact that the infaunal Mulinia edulis is adapted to dealing with larger particle sizes and higher particle densities (Navarro et al., 1993). The lower transport particle velocity observed in the present work for both species, is related to the reduced clearance rate, the higher particle concentration, and the presence of larger, toxic dinoflagellates. In addition, the species differ in their feeding responses to diets, with and without A. catenella or A. affine, largely reflecting their adaptations to different environmental conditions. The results suggest that the presence of a dinoflagellate bloom, whether toxic or non-toxic spp in Yaldad Bay, is likely to have a greater impact on the Mytilus chilensis than the infaunal Mulinia edulis, based on the combined effects on clearance rate, selection efficiency and particle transport velocity.