Does neutral red suit the requirements of being a reliable indicator in clearance rate measurements of suspension-feeding bivalves? An empirical refutation

One basic requirement in the measurements of feeding rates in suspension-feeding bivalves when using clearance methods is that the suspended particles that are used in the determination of these rates must reach size compatibility with full retention by the gill. In spite of this requirement, clearance of neutral red (NR) -a soluble vital dye- has long been used for this purpose and recourse to this method has even increased over the last years for determining the filtration rate as a specific physiological response to stress in ecotoxicological and biomonitoring studies. The aim of this study was to produce empirical evidence that would dismiss the suitability of the NR method for providing reliable measurements for feeding rates in suspension feeders. Experiments that were designed to this end in the blue mussel Mytilus galloprovincialis led to three main conclusions: 1) Temporal dynamics of NR retention by the mussels point to a diffusion mechanism whereby the marker would be up-taken by gill tissue rather than filtered by the muco-ciliary action of this organ. 2) The NR method largely underestimates the clearance rate (by 90% on average) when compared with conventional methods that use microscopic particles in the size-range of gill retention. 3) The close similitude between rates of retention of NR by intact mussels and mussels that had been sacrificed by sectioning apart the valves adductor muscle proves outright the lack of a quantitative relationship between this retention process and the pumping activity.This research was funded by the GIU 17/061 project from the UPV/EH

Metabolic size scaling reflects growth performance effects on age-size relationships in mussels (Mytilus galloprovincialis)

Body-size scaling of metabolic rate in animals is typically allometric, with mass exponents that vary to reflect differences in the physiological status of organisms of both endogenous and environmental origin. Regarding the intraspecific analysis of this relationship in bivalve molluscs, one important source of metabolic variation comes from the large inter-individual differences in growth performance characteristic of this group. In the present study, we aimed to address the association of growth rate differences recorded among individual mussels (Mytilus galloprovincialis) with variable levels of the standard metabolic rate (SMR) resulting in growth-dependent shift in size scaling relationships. SMR was measured in mussels of different sizes and allometric functions fitting SMR vs. body-mass relationships were compared both inter- and intra-individually. The results revealed a metabolic component (the overhead of growth) attributable to the differential costs of maintenance of feeding and digestion structures between fast and slow growers; these costs were estimated to amount to a 3% increase in SMR per unit of increment in the weight specific growth rate. Scaling exponents computed for intraindividual SMR vs body-mass relationships had a common value b = 0.79 (~ ¾); however, when metabolic effects caused by differential growth were discounted, this value declined to 0.67 (= ⅔), characteristic of surface dependent processes. This last value of the scaling exponent was also recorded for the interindividual relationships of both standard and routine metabolic rates (SMR and RMR) after long-lasting maintenance of mussels under optimal uniform conditions in the laboratory. The above results were interpreted based on the metabolic level boundaries (MLB) hypothesis.Funder1 MINECO (https://sede.mineco.gob.es) Project FIGEBIV (AGL2013-49144-C3-1-R) Awarded: E.N., I.I. and P.M. Funder2 UPV/EHU (www.ehu.es) Project: GIU20_064 Awarded: I.I. and K.A. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Variable Capacity for Acute and Chronic Thermal Compensation of Physiological Rates Contributes to Inter-Individual Differences in Growth Rate in Mussels (Mytilus galloprovincialis)

The aim of this study was to ascertain if the capacity for acute and chronic compensation of thermal effects on physiological rates represents a trait contributing to inter-individual growth rate differences in the mussel Mytilus galloprovincialis. Juvenile mussels (10– 11 mm shell length) were collected, transported to the laboratory, and divided into two groups: one group was maintained at 20 C (warm treatment), and the other at 10 C (cold treatment). The mussels were reared at these two temperatures (continuously fed), until clear size differences allowed us to select fast- (F) and slow (S)-growing individuals from both groups (F20/S20 at 20 C and F10/S10 at 10 C). Selected F and S mussels were then exposed to three experimental temperatures (10, 15, and 20 C), and the time-course of their response, in terms of clearance rate (CR: L/h) and routine oxygen consumption (VO2: mLO2/h), was monitored. The overall growth rate of mussels in the warm treatment group was significantly higher than in the cold treatment group. For both treatments, significant differences were found in key physiological parameters between F and S mussels: F mussels had a higher CR and a larger gill surface area than their S counterparts. Although no significant differences in the thermal sensitivity of the clearance or metabolic rates were observed between F20 and S20 mussels reared at 20 C, when exposed to acute temperature changes, experiments with mussels reared at 10 C revealed a different outcome: in response to acute warming (from 10 C to 15 and 20 C), F10 were capable of compensating for the thermal effect on CR and VO2; however, no such compensatory response was observed in S10. We conclude that two significant factors contribute to endogenous differences in the growth rate of mussels: (i) the capacity to exhibit intense filtering activity, which appears to be functionally correlated with the gill surface area and (ii) the capacity to compensate for the effects of temperature on filtration and metabolic rate. The second trait does not appear to make a significant contribution to the inter-individual size-differentiation observed in mussels maintained in warm environments, but explains a significant proportion of inter-individual growth rate differences in cold environments.DP was funded by an FPI grant from the Basque Government. A part of this study was also funded by the Spanish Ministry of Economy and Competitiveness (Reference: AGL2013-49144-C3-1-R)

Methods for assessment of body tissue composition as an indication of the energetic status in bivalve populations: A comparison of biochemical and elemental analysis

Elemental (CHN) and proximate biochemical compositions of body tissues are useful tools among the ecological indices most commonly used in evaluation of the energetic status of animal populations. Gnaiger and Bitterlich (1984) supplied procedures for the interconversion between both these measurements based on stoichiometric relationships, that were further tested using gut contents and body tissue samples of freshwater fishes. Despite a lack of validation studies, the reported conversion factors have been broadly applied in the field of body composition analysis of marine invertebrates, especially bivalve mollusks. The aim of this study was to test the applicability of those conversion equivalents in analysis of the body tissues of two congeneric clam species (Ruditapes decussatus and Ruditapes philippinarum). To this end, proximate biochemical composition, as analyzed by fractionated extraction of tissues samples and quantification using spectrophotometric methods, was converted to elemental composition, and the resulting figures were compared with those of direct CHN analysis. The results of this comparison indicate good agreement within the ranges reported, provided that ninhydrin positive substances (NPS) are incorporated in the biochemical composition analyses. The magnitude of the nonprotein N component in bivalve tissues appears to complicate the reverse computation of biochemical components from elemental composition because no accurate estimation of proteins from N contents might be possible. Additionally, a specific correction of residual water in dried samples of bivalve tissues for CHN analysis should be applied. The absence of broad differences found between species reflects the morphological, evolutionary and functional proximity between them, whereas tissue differences display the differential role that each organ plays in the organism, although other sources of variability such as diet and sex should be addressed in future research.This work was supported by the Spanish Ministry of Economy and Competitiveness (AGL2013-49144-C3-1-R). K. Arranz was funded by a predoctoral research grant from Universidad del Pais Vasco/Euskal Herriko Unibertsitatea (UPV/EHU). SGIker technical and human support (UPV/EHU, MICINN, GV/EJ, ESF) is gratefully acknowledged

Autoantibodies against type I IFNs in patients with critical influenza pneumonia

In an international cohort of 279 patients with hypoxemic influenza pneumonia, we identified 13 patients (4.6%) with autoantibodies neutralizing IFN-alpha and/or -omega, which were previously reported to underlie 15% cases of life-threatening COVID-19 pneumonia and one third of severe adverse reactions to live-attenuated yellow fever vaccine. Autoantibodies neutralizing type I interferons (IFNs) can underlie critical COVID-19 pneumonia and yellow fever vaccine disease. We report here on 13 patients harboring autoantibodies neutralizing IFN-alpha 2 alone (five patients) or with IFN-omega (eight patients) from a cohort of 279 patients (4.7%) aged 6-73 yr with critical influenza pneumonia. Nine and four patients had antibodies neutralizing high and low concentrations, respectively, of IFN-alpha 2, and six and two patients had antibodies neutralizing high and low concentrations, respectively, of IFN-omega. The patients' autoantibodies increased influenza A virus replication in both A549 cells and reconstituted human airway epithelia. The prevalence of these antibodies was significantly higher than that in the general population for patients 70 yr of age (3.1 vs. 4.4%, P = 0.68). The risk of critical influenza was highest in patients with antibodies neutralizing high concentrations of both IFN-alpha 2 and IFN-omega (OR = 11.7, P = 1.3 x 10(-5)), especially those <70 yr old (OR = 139.9, P = 3.1 x 10(-10)). We also identified 10 patients in additional influenza patient cohorts. Autoantibodies neutralizing type I IFNs account for similar to 5% of cases of life-threatening influenza pneumonia in patients <70 yr old

SARS-CoV-2 susceptibility and COVID-19 disease severity are associated with genetic variants affecting gene expression in a variety of tissues

Variability in SARS-CoV-2 susceptibility and COVID-19 disease severity between individuals is partly due to genetic factors. Here, we identify 4 genomic loci with suggestive associations for SARS-CoV-2 susceptibility and 19 for COVID-19 disease severity. Four of these 23 loci likely have an ethnicity-specific component. Genome-wide association study (GWAS) signals in 11 loci colocalize with expression quantitative trait loci (eQTLs) associated with the expression of 20 genes in 62 tissues/cell types (range: 1:43 tissues/gene), including lung, brain, heart, muscle, and skin as well as the digestive system and immune system. We perform genetic fine mapping to compute 99% credible SNP sets, which identify 10 GWAS loci that have eight or fewer SNPs in the credible set, including three loci with one single likely causal SNP. Our study suggests that the diverse symptoms and disease severity of COVID-19 observed between individuals is associated with variants across the genome, affecting gene expression levels in a wide variety of tissue types

A first update on mapping the human genetic architecture of COVID-19

peer reviewe

Stoichiometry of growth under variable scenarios of nutrient limitation: Differential homeostasis of body composition among growth phenotypes of the Manila clam

Fast- and slow-growing phenotypes from two separate breeding families of the Manila clam (Ruditapes philippinarum) were alternatively fed two monoalgal diets with high and low N content (C:N ratios of 4.9 and 13.5, respectively). After 35 days of food conditioning, clams were sacrificed, and the soft body was dissected out into five different tissue fractions to determine the corresponding ponderal ratios (tissue wt./body wt.) and a separate analysis of the elemental composition of these tissues. Previously reported C and N balances performed with the same conditioning diets were integrated and compared with tissue composition of the same phenotypes in order to assess the efficacy of mechanisms elicited to compensate for N deficit. Broad differences in dietary N content resulted in only minor changes in whole-body C:N composition which suggests a noticeable degree of homeostatic regulation of nutrient balances. This regulation was found to be stricter in fast-compared to slow-growing phenotypes and differed among the various body tissues. Using the threshold element ratio approach, physiological mechanisms were identified that partly compensate for large stoichiometric mismatches between low-N food and body tissues.This work was supported by the Spanish Ministry of Economy and Competitiveness through project AGL2013-49144-C3-1-R. K. Arranz was funded by a predoctoral research grant from Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU). SGIker technical and human support (UPV/EHU, MICINN, GV/EJ, ESF) is gratefully acknowledged.info:eu-repo/semantics/publishedVersio

Stoichiometric characterization and physiological bases of differential growth in the congeneric clam species Ruditapes decussatus and R. philippinarum

253 p.En la presente Tesis se plantea el estudio del crecimiento en dos especies de almejas de alto interés acuícola, pertenecientes al mismo género: la almeja japónica Ruditapes philippinarum (Adams and Reeve, 1850) y la almeja fina Ruditapes decussatus (Linnaeus, 1758). Dicho estudio se aborda desde una doble perspectiva que remite a dos importantes temas de la acuicultura relacionados con el control del crecimiento: a) El análisis de la dependencia entre crecimiento y factores nutricionales, basado en la manipulación experimental de la composición bioquímica de las dietas y centrado principalmente en la determinación de los efectos potenciales de la alteración del balance de nutrientes y de los correspondientes mecanismos compensatorios desplegados por los bivalvos en forma de respuestas fisiológicas específicas. b) La caracterización fisiológica de un componente endógeno del crecimiento responsable de la variabilidad inter individual del crecimiento observada al comparar diferentes fenotipos generados mediante selección de familias y de tallas individuales dentro de cada familia.Así, el tratamiento con dietas ricas tanto en proteína como en lípidos generó balances de energía y nutrientes (C y N) superiores a las dietas de calidad pobre, lo cual se tradujo en tasas de crecimiento superiores; debido a unas mayores tasas de ingestión y eficiencias de absorción. Asimismo, en los tratamientos con la dieta pobre en N se observó una regulación homeostática parcial en todos los fenotipos a nivel absortivo y post-absortivo. La composición bioquímica de los tejidos de ambas especies de almeja resultó similar, dada su proximidad taxonómica. Las diferencias endógenas fueron manifiestas en todos los experimentos realizados, donde invariablemente las almejas con mayores tasas de crecimiento alcanzaron mayores tasas de adquisición de energía y nutrientes, presentaron una mayor capacidad para la elaboración de respuestas fisiológicas a corto plazo adecuadas a las fluctuaciones ambientales; e incluso en la almeja japónica se observó una mayor eficiencia metabólica en los grupos de crecimiento rápido