Mercury bioaccumulation in the long-fin squid Loligo forbesi near the Mid-Atlantic Ridge: Implications to human exposure

Due to growing commercial interest as a fishing resource and its intermediate position in the marine trophic chains as both prey and predator, cephalopods can play an important role in mercury (Hg) transfer along the marine food webs, since they can bioaccumulate this metal in its tissues. Our study aims to analyze Hg accumulation in Loligo forbesi caught in the Azores Archipelago (Portugal) quantifying Hg in different tissues (mantle and stomach), as well in the squid stomach content, in order to evaluate the efficiency of Hg transfer from prey to predator. Hg data from the tissues was used to estimate the weekly tolerable Hg intake due to squid consumption. Overall data indicate that Hg measured in the stomach tissue (0.1 ± 0.01 μg g^-1) was significantly higher than Hg levels found in the mantle (0.04 ± 0.001 μg g^-1) and stomach contents (0.01 ± 0.001 μg g^-1). BMF (bioaccumulation factor) was >1 for all the samples, indicating a biomagnification process from prey to predator. Hg concentration in the mantle tissue was correlated with mantle size; although females present higher Hg levels than males, the difference was found to be not related to gender but rather to the fact that females had larger bodies. Finally, considering the Hg concentration found in the mantle and the permitted Hg levels, it is advisable to consume up to 1050-1890g of squid per week, according to the regulatory agencies. Thus, our results indicate that, since these doses are respected, consumption of squids from the Azorean waters do not pose a risk to humans.

Halogenated natural products and anthropogenic persistent organic pollutants in chokka squid (Loligo reynaudii) from three sites along the South Atlantic and Indian Ocean coasts of South Africa

Chokka squid (Loligo reynaudii) from three sites along the South African coast were analyzed for halogenated natural products (HNPs) and anthropogenic persistent organic pollutants (POPs). HNPs were generally more than one order of magnitude more abundant than POPs. The most prevalent pollutant, i.e. the HNP 2,3,3',4,4',5,5'-heptachloro-1'-methyl-1,2'-bipyrrole (Q1), was detected in all chokka squid samples with mean concentrations of 105, 98 and 45 ng/g lipid mass, respectively, at the Indian Ocean (site A), between both oceans (site B) and the South Atlantic Ocean (site C). In addition, bromine containing polyhalogenated 1'-methyl-1,2'-bipyrroles (PMBPs), 2,4,6-tribromophenol (2,4,6-TBP, up to 28 ng/g lipid mass), polybrominated methoxy diphenyl ethers, MHC-1, TBMP and other HNPs were also detected. Polychlorinated biphenyls (PCBs) were the predominant class of anthropogenic POPs. PCB 153 was the most abundant PCB congener in chokka squid from the Indian Ocean, and PCB 138 in samples from the South Atlantic Ocean and between both oceans.

Multifunctional and biodegradable self-propelled protein motors

A diversity of self-propelled chemical motors, based on Marangoni propulsive forces, has been developed in recent years. However, most motors are non-functional due to poor performance, a lack of control, and the use of toxic materials. To overcome these limitations, we have developed multifunctional and biodegradable self-propelled motors from squid-derived proteins and an anesthetic metabolite. The protein motors surpass previous reports in performance output and efficiency by several orders of magnitude, and they offer control of their propulsion modes, speed, mobility lifetime, and directionality by regulating the protein nanostructure via local and external stimuli, resulting in programmable and complex locomotion. We demonstrate diverse functionalities of these motors in environmental remediation, microrobot powering, and cargo delivery applications. These versatile and degradable protein motors enable design, control, and actuation strategies in microrobotics as modular propulsion sources for autonomous minimally invasive medical operations in biological environments with air-liquid interfaces.

Ocean warming enhances malformations, premature hatching, metabolic suppression and oxidative stress in the early life stages of a keystone squid

Background

The knowledge about the capacity of organisms’ early life stages to adapt to elevated temperatures is very limited but crucial to understand how marine biota will respond to global warming. Here we provide a comprehensive and integrated view of biological responses to future warming during the early ontogeny of a keystone invertebrate, the squid Loligo vulgaris.

Methodology/Principal Findings

Recently-spawned egg masses were collected and reared until hatching at present day and projected near future (+2°C) temperatures, to investigate the ability of early stages to undergo thermal acclimation, namely phenotypic altering of morphological, behavioural, biochemical and physiological features. Our findings showed that under the projected near-future warming, the abiotic conditions inside the eggs promoted metabolic suppression, which was followed by premature hatching. Concomitantly, the less developed newborns showed greater incidence of malformations. After hatching, the metabolic burst associated with the transition from an encapsulated embryo to a planktonic stage increased linearly with temperature. However, the greater exposure to environmental stress by the hatchlings seemed to be compensated by physiological mechanisms that reduce the negative effects on fitness. Heat shock proteins (HSP70/HSC70) and antioxidant enzymes activities constituted an integrated stress response to ocean warming in hatchlings (but not in embryos).

Conclusions/Significance

The stressful abiotic conditions inside eggs are expected to be aggravated under the projected near-future ocean warming, with deleterious effects on embryo survival and growth. Greater feeding challenges and the lower thermal tolerance limits of the hatchlings are strictly connected to high metabolic demands associated with the planktonic life strategy. Yet, we found some evidence that, in the future, the early stages might support higher energy demands by adjusting some cellular functional properties to increase their thermal tolerance windows.

Effects of ocean acidification on trace element accumulation in the early-life stages of squid Loligo vulgaris

The anthropogenic release of carbon dioxide (CO(2)) into the atmosphere leads to an increase in the CO(2) partial pressure (pCO(2)) in the ocean, which may reach 950 μatm by the end of the 21st century. The resulting hypercapnia (high pCO(2)) and decreasing pH ("ocean acidification") are expected to have appreciable effects on water-breathing organisms, especially on their early-life stages. For organisms like squid that lay their eggs in coastal areas where the embryo and then paralarva are also exposed to metal contamination, there is a need for information on how ocean acidification may influence trace element bioaccumulation during their development. In this study, we investigated the effects of enhanced levels of pCO(2) (380, 850 and 1500 μatm corresponding to pH(T) of 8.1, 7.85 and 7.60) on the accumulation of dissolved (110m)Ag, (109)Cd, (57)Co, (203)Hg, (54)Mn and (65)Zn radiotracers in the whole egg strand and in the different compartments of the egg of Loligo vulgaris during the embryonic development and also in hatchlings during their first days of paralarval life. Retention properties of the eggshell for (110m)Ag, (203)Hg and (65)Zn were affected by the pCO(2) treatments. In the embryo, increasing seawater pCO(2) enhanced the uptake of both (110m)Ag and (65)Zn while (203)Hg showed a minimum concentration factor (CF) at the intermediate pCO(2). (65)Zn incorporation in statoliths also increased with increasing pCO(2). Conversely, uptake of (109)Cd and (54)Mn in the embryo decreased as a function of increasing pCO(2). Only the accumulation of (57)Co in embryos was not affected by increasing pCO(2). In paralarvae, the CF of (110m)Ag increased with increasing pCO(2), whereas the (57)Co CF was reduced at the highest pCO(2) and (203)Hg showed a maximal uptake rate at the intermediate pCO(2). (54)Mn and (65)Zn accumulation in paralarvae were not significantly modified by hypercapnic conditions. Our results suggest a combined effect of pH on the adsorption and protective properties of the eggshell and of hypercapnia on the metabolism of embryo and paralarvae, both causing changes to the accumulation of metals in the tissues of L. vulgaris.

Thermodynamic Aspects of the Heterogeneous Deacetylation of β-Chitin: Reaction Mechanisms

This paper aims at giving a better understanding of the reaction mechanisms involved in the heterogeneous deacetylation of beta-chitin in relation with the influence of soda concentration (30-55% (w/v)) and the type of sodium hydroxide hydrates formed in solution. The role of temperature (35-110 degrees C) and of the amount of sodium acetate generated in the reaction medium was also investigated. We demonstrated that the type of soda hydrate formed before deacetylation starts and its relative abundance drive the reaction efficiency. Thus, in the first part of this work, we evidenced that activation energies and the global reaction order associated to sodium hydroxide varied as a function of soda concentration. Therefore, we revealed that deacetylation efficiency was emphasized when the less hydrated soda was used, whereas anhydrous soda showed no or very low activity. We also pointed out that various parameters could be responsible for the progressive dehydration of the reaction medium, responsible for the transformation of the most reactive hydrates into less effective species. We underlined that this progressive dehydration could be caused by either one or all of the three following phenomena: alkaline hydrolysis of the polymer, the delivery of sodium acetate in the medium, and the evaporation of water when we process deacetylation at high temperatures and in open reactors. Beside kinetics reasons, we revealed that the transformation of soda hydrates as the deacetylation proceeded was also ascribable for the low reaction efficiency at long reaction times. Thanks to our investigations, we concluded that the amount of water present in the system chitin/soda/water/sodium acetate was the angle stone of complex equilibriums governing the reaction, and we propose soda mono- and dihydrates to be the most active reactants for the chitin deacetylation.

Receptor-coupling properties of the invertebrate visual guanine nucleotide binding protein iGqalpha

Invertebrate visual iG(q)alpha is homologous to mammalian mG(q)alpha in two of the three domains important for G protein interaction with receptors; the C-terminus and the linker regions that connect the helical and ras-like domains of the alpha subunit. The third receptor-interacting domain, the N-terminus, contains a six amino acid extension MTLESI in mG(q)alpha that is not present in iG(q)alpha. In co-expression studies we assessed the promiscuity and efficacy of receptor coupling to phospholipase C (PLC) by iG(q)alpha, a non-palmitoylated mutant iG(q)alpha(C3,4A), mG(q)alpha and G(15)alpha. The invertebrate G proteins and mG(q)alpha only coupled to G(q)-coupled receptors (m1 muscarinic acetylcholine receptor (mChR1), alpha(1A)-adrenergic receptor (alpha1-AR)) and not to the G(i/s)-coupled receptors (CCR1 receptor, beta2-adrenergic receptor or dopamine D1 receptor) while G(15)alpha coupled to all receptors. iG(q)alpha and iG(q)alpha(C3,4A) both had double the efficacy for PLC activation compared to the mammalian G proteins when co-expressed with mChR1 and alpha1-AR. The increased efficacy of iG(q)alpha compared to mG(q)alpha was also seen downstream of PLC with carbachol stimulation of the mitogen-activated protein kinase, ERK1/2. Addition of the MTLESI extension onto the N-terminus of iG(q)alpha decreased its efficacy by 35% whereas deletion of this sequence from mG(q)alpha increased its efficacy by 60% in the PLC and ERK1/2 assays. iG(q)alpha, iG(q)alpha(C3,4A) and mG(q)alpha all displayed similar receptor-independent AlF(4)(-)activation of PLC and guanosine triphosphate hydrolysis (GTPase) activity. iG(q)alpha, and iG(q)alpha(C3,4A) both had increased receptor-activated guanosine 5'-[gamma-[(35)S]thio]triphosphate ([(35)S]GTPgammaS) binding when compared to mG(q)alpha when co-expressed with the mChR1. These results demonstrate that G(q) protein efficacy is at least partially determined by the presence of the amino-terminal MTLESI extension. Comparison of [(35)S]GTPgammaS binding rates helps explain the increased efficacy of the invertebrate G proteins.