Impact of size and food concentration on clearance and ingestion rates in the clam Ruditapes decussates (Linnaeus, 1758)

The impact of food concentration (C) and water flow on the clearance (TA) and ingestion (TI) rates of the clam Ruditapes decussates (Linnaeus, 1758) was studied, using different-sized specimens. We found no relationship between C and TA, whereas there was a significant relationship between C and TI (TI = 24.757 + 0.576 C). The relationship between TA and the clams' live weight (PV) was also significant (TA = 4.292 PV0.683). A close relationship between PV and TI was found only when food availability (AD), a parameter that includes food concentration and flow, was constant. When it was not, the equation TI = 64.089 + 0.015 PV + 0.546 AD appears to explain 96.1% of TI variability.Se estudia el efecto de la concentración de alimento (C) y el flujo sobre las tasas de aclaramiento (TA) e ingestión (TI) de Ruditapes decussatus (Linnaeus, 1758) con ejemplares de diferentes tamaños. En esta especie no se observa relación entre C y TA, mientras que entre TI y C la relación es significativa: TI = 24,757 + 0,576 C. Igualmente es significativa la relación entre TA y el peso vivo (PV): TA = 4,292 PV0,683. PV y TI guardan una estrecha relación sólo en caso de que el alimento disponible (AD), variable que engloba la concentración de alimento y el flujo, se mantenga constante. En caso contrario, se propone la utilización de la ecuación TI = 64,089 + 0,015 PV + 0,546 AD que explica el 96,1 % de la variabilidad de TI.Instituto Español de OceanografíaVersión de editor

Microplastic and an associated metal contaminant (Palladium) impair the immune response against pathogenic bacteria of the marine bivalve Mytilus galloprovincialis

Microplastics (MPs) are widely distributed in marine environments and have been reported to cause harmful physiological effects in marine bivalves including immune modulation. While Mytilus galloprovincialis is a model species in environmental monitoring studies, little is known regarding the effects of MPs and palladium (Pd), an emerging contaminant, metal on the immune functioning of this species. In this study, gills and gland samples of specimens of M.ytilus galloprovincialis which were exposed to the same particle concentration (2.5 x 10 66 μm3μm /mL) of Control (microalgae), MP (virgin microplastics) and MP-Pd (Pd spiked microplastics) once an hour during 4 hours. Thus, mussels were exposed to 6095 ng of Pd/mussel. Samples analyzed were collected after 4 and 24 hours of exposure and after 24, 48 and 144 hours of depuration. Several innate immune activities (lysozymes, peroxidase, protease, antiprotease, and bactericidal activities) were analyzed. Our data demonstrated that after 24 hours of exposure to MP, a decrease in lysozymes and peroxidase activities occurred, but not in the bactericidal activity which increased. However, when MP-Pd was used, an increase in all these activities was observed compared to MP levels group. These data suggest that when MP are spiked with Pd, the latter compound might induce an inflammatory process that will results in higher levels of most of all the immune activities analyzed. In the gland, however, most of the activity levels were decreased upon MP-Pd treatment compared to MP levels at different time point of exposure depending on the activity. Interestingly, after 24 hours of removing the pollutants from the water, most of the activity levels in both tissues, gills and gland, were recovered to control levels, but not the bactericidal activity. Considering this impairment of the bactericidal activity against possible pathogenic bacteria, a potential threat to mussels population in a polluted scenario is highly plausible

Energy balance of the clam Ruditapes decussatus (Linnaeus, 1758)

The effect of food ingestion and clam size on absorption efficiency, absorption rate and oxygen consumption of the clam Ruditapes decussatus (L., 1758) was studied. Absorption efficiency (AE) was related to the ingestion rate (IR) following the non-lineal equation AE = 0.836 + e-0.64/IR (P 0.01; n = 26; r² = 0.321) No significant relationship as found between AE and clam live weight, whereas there was a relationship between absorption rate (AR) and IR, following the expression AR = 0.8248 IR - 0.0344 (P 0.001; n = 26; r² = 0.964) The maintenance food ration for a 2 g (live weight) clam was estimated as 1.528 J/h, equivalent to a daily food ration of 0.08 mg organic matter/g clam live weight.Se estudia el efecto de la ingestión de alimento y el tamaño de las almejas sobre la eficiencia de absorción, la tasa de absorción y el consumo de oxígeno de Ruditapes decussatus (L., 1758). La eficiencia de absorción (EA) se relaciona con la tasa de ingestión (TI) siguiendo el modelo no lineal EA = 0,836 + e-0,64/TI (P 0,01; n = 26; r² = 0,321) Entre EA y el peso vivo de las almejas no existe una relación significativa, mientras que sí la hay entre la tasa de absorción (TA) y TI, y responde a la ecuación TA = 0,8248 TI - 0,0344 (P 0,001; n = 26; r² = 0,964) La ración de mantenimiento de una almeja de 2 g de peso vivo es de 1,528 J/h, que se corresponde con una dieta diaria de 0,08 mg de materia orgánica por gramo de peso vivo.Instituto Español de Oceanografí

Seasonal variability of antioxidant biomarkers in mussels Mytilus galloprovincialis from the Spanish N-NW coast.

Marine organisms are highly seasonal animals in relation to their physiology which depends, among other factors, on their annual cycle of reproduction. In bivalves, reproductive cycle is regulated by two main environmental factors: temperature and food availability. Specifically, bivalves are undergoing high variable environmental conditions. Integrated pollution monitoring carried out by the IEO along the N-NW coast of Spain has evidenced that the variability of the environmental conditions produce spatial differences in mussel condition which seems to mask the biomarker responses to pollution. Thus, there is a need to study the natural variability of biological responses used as pollution biomarkers at different seasons and in different habitats in order to establish an adequate link between chemical pollution and biological responses. This study aims to assess the natural variability of some biomarker responses on the mussel Mytilus galloprovincialis in 5 different sites from the Spanish Marine Pollution Monitoring Program which are differentiated in their natural ecology and their anthropogenic pressure. The potential influence of environmental and endogenous factors that can cause biomarker´s seasonal fluctuations was examined. Biomarkers analyzed in this study are considered among the most usefull biological tools applied in pollution monitoring programs, including exposure indicators (superoxide dismutase –SOD-, catalase –CAT-, glutathione reductase –GR-, glutathione peroxidase –GPx-, glutathione-s-transfersase –GST-) and a damage indicator (lipid peroxidation –LPO-). Mussel biological characterization from a histological and anatomical point of view was also performed. Results evidenced that biomarkers were clearly influenced by the annual cycle (all of them were affected by the season) but also significant differences between sites were found in some biomarkers (GR and GST). Thus, not only environmental but also endogenous factors must be considered in monitoring programs in the study of biomarkers responses.Society of Environmenta Toxicology and Chemistry (SETAC

Physiological responses of the fan mussel Pinna nobilis to temperature: ecological and captivity implications

The fan mussel Pinna nobilis is experiencing a mass mortality event throughout the Mediterranean Sea. The survival of the remaining isolated populations and the maintenance and reproduction of individuals in captivity could determine the future of the species. This paper examines the clearance rate (CR) and oxygen consumption (VO2) of fan mussel individuals measured under 5 different temperatures (8.5, 14, 18, 23 and 28ºC). The measurements of both physiological variables revealed a threshold limit of thermal tolerance at both extreme temperatures, indicating the critical situation of the remaining populations, which are located in coastal lagoons and shallow bays where these extreme temperatures usually occur. Besides, the high clearance rates observed highlight the significant ecosystem service provided by the species in terms of water filtration, especially in confined waters with low renewal rates. Routine control of the clearance rate as an early warning system is proposed for detecting ailing individuals. Such a system could also be used to improve captivity conditions.info:eu-repo/semantics/publishedVersio

Hatchery seed production of flat oysters from the Mar Menor lagoon

The Mar Menor lagoon (SE Spain) suffers a severe eutrophication process aggravated since the collapse of the lagoon in 2016. Together with it, the populations of the flat oyster Ostrea edulis have been decimated in the lagoon, but also in the European seas, where the species and the habitats provided by it have mainly disappeared. The Mar Menor Oyster Initiative’s main objectives are gaining knowledge on the nutrient extraction capability of the Mar Menor flat oyster and developing the required tools for restoration and bioextraction actions. The project RemediOS, within the framework of the Mar Menor Oyster Initiative, aims to obtain flat oyster seed using the decimated local broodstock to provide the initiative with an oyster population to work with. The present work describes the results of the first attempt of Mar Menor local broodstock reproduction in captivity. Larvae produced in the hatchery accounted for 57.5 million, of which 11.8 million were cultured and 0.68 million survived to settlement and metamorphosis

Impact assessment of agricultural inputs into a Mediterranean coastal lagoon (Mar Menor, SE)

The Mar Menor is a coastal lagoon threatened by the development of intensive agriculture in the surrounding areas. Large amounts of pesticides from these areas are discharged into El Albujón, a permanent watercourse flowing into the lagoon. We have used a multi-biomarker approach to assess the biological effects arising in bivalve species affected by agricultural pollution. Biomarkers indicative of neurotoxicity (acetylcholinesterase, AchE), oxidative stress (catalase, CAT; glutathione reductase, GR and lipid peroxidation, LPO), phase II biotransformation of xenobiotics (glutathione S-transferase, GST) and physiological stress (scope for growth, SFG) were measured in clams transplanted to four sites of the lagoon (two reference sites and two sites affected by the dispersion of the effluent of the El Albujón), for exposure periods of 7 and 22 days. The hazards of this effluent were also examined by simultaneously measuring up to 83 contaminants (pesticides, PCBs, PAHs and others) in samples of fresh water from the watercourse mouth and seawater from the deployed sites, as well as the bioaccumulation of organochlorinated compounds and PAHs in the transplanted animals. Biomarker responses showed marked differences between reference and affected sites after 7 and 22 days. However it was only after 22 days that Principal Component Analysis (PCA) of the biomarker responses distinguished between clams deployed in sites affected by the dispersion of the effluent of the watercourse and those from the reference sites. The chemical analysis of water showed high concentrations of pesticides close to El Albujón watercourse mouth, with the greatest input flux corresponding to the organophosphate chlorpyrifos, followed by pendimethalin and naphthalene, and at lower levels acenaphthene, terbuthylazine-desethyl and chlorpyrifos-methyl. In this regard, PCA analysis showed that the biological effects of the mixture of pesticides in caged clams after 22 days were reduced levels of AchE and SFG and increased levels of GR and phase II GST activity. An Integrated Biomarker Response index was calculated from the combination of these biomarkers, proving useful for the assessment of the impact of agricultural pollution in caged clams.Preprint3,761

Scope for growth and dietary needs of Mediteranean Pinnids maintained in captivity

Abstract Background: The measurement of the energy available for growth (scope of growth, SFG) can be used in bivalves to make a long-term prediction in a short-term experiment of the condition of the individual. In order to tackle the best conditions for captive maintenance of Mediterranean Pinnids, a SFG study was conducted using Pinna rudis as a model species. Three diets were examined to test the viability of live microalgae and commercial products: i) a control diet using 100% of live microalgae based on the species Isochrysis galbana (t-ISO), ii) a 100% of commercial microalgae diet based on the product Shellfish Diet 1800®, and iii) a 50/50% mix diet of I. galbana (t-ISO) and Shellfish Diet 1800®. Results: SFG results showed significant differences among diets in the physiological functions measured and suggested lower acceptability and digestibility of the commercial product. Negative SFG values were obtained for the commercial diet which indicates that it should be rejected for both Pinnid maintenance. The mixed diet showed improved physiological performance compared to the commercial diet, resulting in a higher SFG that had no significant differences with the control diet. However, in the long-term, the lower digestibility of the mixed diet compared to the control diet could lead to a deterioration of individuals’ conditions and should be considered cautiously. Conclusions: This work represents the first case study of SFG in Pinna spp. and provides fundamental data on dietary needs for the critically endangered species, P. nobilis.En prens