Transformation and Depuration of Paralytic Shellfish Toxins in the Geoduck Clam Panopea globosa From the Northern Gulf of California

In January 2015, a harmful algae bloom (HAB) of the dinoflagellate Gymnodinium catenatum occurred in the Northern Gulf of California (NGC). This species produces paralytic shellfish toxins (PSTs), a group of potent neurotoxins. The harvesting and commercialization of geoduck Panopea globosa are important economic activities in this region and were prohibited for several months due to the accumulation of PSTs in clam tissues. We analyzed PSTs concentrations in P. globosa collected on a weekly basis during 2015 near San Felipe, Baja California. The aim of the study was to evaluate the transformation and depuration characteristics of PSTs in different geoduck tissues. The PST content was evaluated in the visceral mass and in the siphon by high-performance liquid chromatography with post-column oxidation (HPLC-PCOX). Additionally, 10 selected samples were analyzed by hydrophilic interaction chromatography coupled to tandem mass spectrometry (HILIC-MS/MS). Toxicity in all siphon samples was lower than the regulatory limit (RL) for PSTs of 800 μg STX eq kg-1. In contrast, the maximum toxicity of 16,740 μg STX eq kg-1 detected in the visceral mass exceeded 21 times the RL and it took 210 days to reach values below 800 μg STX eq kg-1. Therefore, P. globosa can be considered a slow detoxifier bivalve with a depuration rate of 4.3% day-1 (calculated by an exponential decay model; R2 = 0.80). The N-sulfocarbamoyl toxins C1 and 2 were the most abundant analogs in the siphon and viscera samples collected close to the HAB occurrence. The concentration of these analogs decreased and GTX5 and more toxic analogs such as dcGTX2 and dcSTX were detected. M-type analogs were detected by HILIC-MS/MS and represented up to 75% of total PSTs in some samples. M-type analogs contributed to 48% of toxicity estimated in the sample. We report for the first time the depuration rate, PSTs profile, and its change over time in P. globlosa. This information is essential to characterize the metabolism of toxins in this economically important bivalve but also to develop management plans for fisheries if the organism is going to be recurrently exposed to PSTs producing blooms, as seems the case for the NGC

Mass Mortality of Cultivated Northern Bluefin Tuna Thunnus thynnus orientalis Associated With Chattonella Species in Baja California, Mexico

In 2016 a mass mortality period (MMP) of cage cultured tuna occurred in the northwest coast of Baja California, Mexico. Nine die-offs occurred from May 31st to August 2nd in Todos Santos Bay, Salsipuedes Bay and Coronado Islands. The organisms were disoriented, gasping, swimming erratically, and died hours after these signs were detected. Necropsies and histopathological analyses were performed on dead organisms. Abundant mucus and congestion was observed in the gills. Histopathological analysis of the gills showed hyperplasia, fusion of gill filaments and lamellae, telangiectasia, edemas, increased numbers of mucus cells, and in some cases severe hemorrhage. Water samples were analyzed and a sampling campaign was implemented in some cultivation areas to evaluate the presence of ichthyotoxic microalgae. Chattonella spp. (mainly C. cf. marina) were detected in the water column during the MMP. At the end of May abundances of 5 × 103 cells L−1 were detected in sea surface samples and Chattonella spp. represented ~20% of the microphytoplankton community. Abundance of these species at surface increased to 33 × 103 cells L−1 in June and represented 85% of the phytoplankton community. No other environmental stressful variables were detected during the MMP. The presence of Chattonella spp. in the water column explains the dead of the tuna since behavior, necropsies, and histopathological analyses of the gills indicate a severe reaction to an environmental noxa that could be related to the characteristic toxic effect of these species. Before the MMP, ichthyotoxic species have not been reported in the phytoplankton community of the region. Accumulation of Chattonella spp. was probably associated with abnormally high temperatures present during the two previous years before the MMP. Surface temperature anomalies of 3°C were registered during 2015. Mesoscale oceanographic and atmospheric phenomena brought the environmental conditions for a change in the phytoplankton community in the region. Phytoplankton biomass was low and associated with a decrease in the abundance of diatoms and dinoflagellates. The absence of diatoms together with upwelling events followed by stratification before the MMP probably favored the accumulation of Chattonella spp. that affected importantly tuna ranching activities in Northwest Baja California

DESCRIPCIÓN MORFOLÓGICA DE LOS ÓRGANOS DE MAYOR IMPORTANCIA DE CONUS (CONUS) PRINCEPS VAR. LINEOLATUS (LINNEO, 1758) Y CONUS (CONUS) BRUNNEUS (WOOD,1828)

Tesis de Licenciatur

Towards the Early Detection of <i>Gymnodinium catenatum</i> Algal Blooms in the Northern Gulf of California

The annual occurrence of harmful algal blooms (HABs) of the dinoflagellate Gymnodinium catenatum in the northern Gulf of California (NGC) during winter and spring has negative ecological, economic, and social impacts on the local coastal population. G. catenatum produces paralytic shellfish toxins, and a robust monitoring program of the species is necessary to sustain mitigation actions against their detrimental effects. Here, we applied the maximum-likelihood classification (MLC) method to classify satellite images from MODIS and Sentinel-3 to evaluate their effectiveness to detect G. catenatum. Different classes associated with the presence of the species were developed from data of two HABs that occurred in 2015 and 2017. Two classes derived from Sentinel-3 data from the 2017 HAB allowed the detection of this species. These Sentinel-3 classes adequately represented the temporal and geographical distribution of G. catenatum in the region and the no-bloom condition during the summer. The concordance between the detection of the Sentinel-3 classes on the west coast of the NGC and the recorded presence of G. catenatum (75% of concordance) in the area indicates that the MLC method could be applied for early detection of the species in the NGC, using Sentinel-3 full resolution images

Hells Bells – unique speleothems from the Yucatán Peninsula, Mexico, generated under highly specific subaquatic conditions

We here report on a type of meter-sized pendant speleothem growing under water in the submerged El Zapote sinkhole (cenote) west of Puerto Morelos on the Mexican Yucatán Peninsula. These conical, mantle-shaped downward expanding and diverging calcareous structures, here termed as Hells Bells, are yet unreported in the scientific literature. They are characterized by bell- or trumpet shaped longitudinal and circular, elliptical or horse-shoe-like horizontal cross-sections. Hells Bells grow downward, based on the downward divergence of the structures and the horizontally laminated internal texture of both blade-shaped spar calcite and microspar laminae. Age dating confirms that Hells Bells are young (\u3c 4500 yr) and formed in a subaquatic environment. They grow under lightless conditions in a stratified water body, which is characterized by a fresh water body overlying a salt water body with a stagnant transition zone (halocline) of several meters. We hypothesize that the growth of these structures is mediated by specific physical and biogeochemical conditions above and in the halocline. Stagnant hydraulic conditions led to extensive diffusion profiles of several nutrients including calcium originating from the salt water body. Dissolved organic carbon from the fresh water is microbially oxidized in the upper part of the halocline, where a distinct redox zonation was identified from oxic to anoxic conditions. Degradation processes combined with slightly alkaline pH values as well as the diffusive transport of calcium into this zone may induce an increase in calcite oversaturation. Phylogenetic analysis of the community on the surface of the Hells Bells suggests the presence of microorganisms involved in the nitrogen-cycle, from which some potentially have the capability to increase the pH by autotrophic growth and denitrifying activity, thus supporting calcite precipitation. The growth of Hells Bells is strictly dependent on the elevation of the halocline. This offers a wide potential for the use of Hells Bells as

Evolution over Time of Ventilatory Management and Outcome of Patients with Neurologic Disease∗

OBJECTIVES: To describe the changes in ventilator management over time in patients with neurologic disease at ICU admission and to estimate factors associated with 28-day hospital mortality. DESIGN: Secondary analysis of three prospective, observational, multicenter studies. SETTING: Cohort studies conducted in 2004, 2010, and 2016. PATIENTS: Adult patients who received mechanical ventilation for more than 12 hours. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Among the 20,929 patients enrolled, we included 4,152 (20%) mechanically ventilated patients due to different neurologic diseases. Hemorrhagic stroke and brain trauma were the most common pathologies associated with the need for mechanical ventilation. Although volume-cycled ventilation remained the preferred ventilation mode, there was a significant (p &lt; 0.001) increment in the use of pressure support ventilation. The proportion of patients receiving a protective lung ventilation strategy was increased over time: 47% in 2004, 63% in 2010, and 65% in 2016 (p &lt; 0.001), as well as the duration of protective ventilation strategies: 406 days per 1,000 mechanical ventilation days in 2004, 523 days per 1,000 mechanical ventilation days in 2010, and 585 days per 1,000 mechanical ventilation days in 2016 (p &lt; 0.001). There were no differences in the length of stay in the ICU, mortality in the ICU, and mortality in hospital from 2004 to 2016. Independent risk factors for 28-day mortality were age greater than 75 years, Simplified Acute Physiology Score II greater than 50, the occurrence of organ dysfunction within first 48 hours after brain injury, and specific neurologic diseases such as hemorrhagic stroke, ischemic stroke, and brain trauma. CONCLUSIONS: More lung-protective ventilatory strategies have been implemented over years in neurologic patients with no effect on pulmonary complications or on survival. We found several prognostic factors on mortality such as advanced age, the severity of the disease, organ dysfunctions, and the etiology of neurologic disease

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field