Calcium pathways such as cAMP modulate clothianidin action through activation of α-bungarotoxin-sensitive and -insensitive nicotinic acetylcholine receptors.

Clothianidin is a neonicotinoid insecticide developed in the early 2000s. We have recently demonstrated that it was a full agonist of α-bungarotoxin-sensitive and -insensitive nicotinic acetylcholine receptors expressed in the cockroach dorsal unpaired median neurons. Clothianidin was able to act as an agonist of imidacloprid-insensitive nAChR2 receptor and internal regulation of cAMP concentration modulated nAChR2 sensitivity to clothianidin. In the present study, we demonstrated that cAMP modulated the agonist action of clothianidin via α-bungarotoxin-sensitive and insensitive receptors. Clothianidin-induced current-voltage curves were dependent to clothianidin concentrations. At 10 μM clothianidin, increasing cAMP concentration induced a linear current-voltage curve. Clothianidin effects were blocked by 0.5 μM α-bungarotoxin suggesting that cAMP modulation occurred through α-bungarotoxin-sensitive receptors. At 1 mM clothianidin, cAMP effects were associated to α-bungarotoxin-insensitive receptors because clothianidin-induced currents were blocked by 5 μM mecamylamine and 20 μM d-tubocurarine. In addition, we found that application of 1mM clothianidin induced a strong increase of intracellular calcium concentration. These data reinforced the finding that calcium pathways including cAMP modulated clothianidin action on insect nicotinic acetylcholine receptors. We proposed that intracellular calcium pathways such as cAMP could be a target to modulate the mode of action of neonicotinoid insecticides

The discovery of a novel sodium channel in the cockroach Periplaneta americana: Evidence for an early duplication of the para-like gene

International audienceVoltage-gated sodium channels (Na(v) channels) belong to a superfamily of ion channels which play an essential role in membrane excitability. Only one gene encoding Na(v) channels has been characterized so far in insects. Here, we have cloned one full-length cDNA encoding a conventional insect Na(v) channel (PaNa(v)1) and two full-length cDNAs encoding putative insect Na(v) channels (PaFPC1 and PaFPC2) in Periplaneta americana, a model insect for neurophysiological studies. The ORFs of PaFPC1 and PaFPC2 contained 4662 bp and encoded 1553 amino acid residues, and the ORF of PaNa(v)1 contained 6153 bp and encoded 2051 amino acid residues. PaFPC1 and PaFPC2 are two isoforms, which differ by eight single amino acid substitutions. PaFPC1 shares 37.5-55% protein identities with known insect Na(v) channels, while PaNa(v)1 shares 70-97.5% protein identities with these latter. Both PaFPC1 and PaFPC2 possess the molecular hallmarks of Na(v) channels except the motif involved in fast inactivation. Contrary to PaNa(v)1 transcripts which are expressed mainly in the central nervous system, those ones of PaFPC are also expressed in non-neuronal tissues (muscles, gut and mushroom-shaped accessory glands). A detailed phylogenetic analysis confirmed that PaNa(v)1 and PaFPC are evolutionarily closely related to insect Na(v) channel genes

Benthic foraminiferal responses to anthropogenic manipulation on a wild oyster reef

International audienceBenthic foraminifera are known to respond quickly to environmental changes. Biological indices are used in marine subtidal areas (Barras et al., 2014) to monitor impacted marine environments (Mojtahid et al., 2006, 2008). Such indices could be useful in transitional marine environments such as estuaries and mudflats where no accurate indices are available. To develop such to ols and to improve our knowledgeon b enthic foraminifera in intertidal environments, we followed the spatial and temporal distribution of b enthic foraminifera in Bourgneuf Bay, a coastal bay with a large mudflat situated south of the Loire estuary on French west coast. At this location, wild oyster reefs are present. Partial release of organicand inorganic nutrients through oyster excretion enriches the nutrients flow leading to microphytobenthosbloom around the reef. To show this relation and to understand the relation between the different biological compartments,we analysed the foraminiferal composition of the sediment around the reef before and after ananthrop ogenic manipulation. In July 2014, the oysters of the reef were removed inorder to assess their impact on microphytob enthos and meiofauna. In this study, we showed a strong impact of this anthrop ogenic manipulation on benthic foraminiferal densities and species composition.These results confirmed the strong and quick responses of benthic foraminifera from intertidal areas toenvironmental changes and showed that intertidal benthic foraminifera can be used as an index to monitor transitional marine environments.</p

Characterization of tyramine -hydroxylase, an enzyme upregulated by stress in Periplaneta americana

International audienceOctopamine (OA) is an important neuroactive substance that modulates several physiological functions and behaviors of various invertebrate species. This biogenic monoamine, structurally related to noradrenaline, acts as a neurotransmitter, a neuromodulator, or a neurohormone in insects. The tyramine β-hydroxylase (TBH) catalyzes the last step in OA biosynthesis and thus plays a key role in the regulation of synthesis and secretion of OA in neurons. The aim of this study was to characterize TBH in the cockroach Periplaneta americana and to get a better understanding of its regulation under stress conditions in this insect. First of all, five full-length cDNAs encoding TBH isoforms were cloned from the nerve cord of the physiological model P. americana. PaTBH transcripts were found mainly expressed in nervous tissues and in octopaminergic dorsal unpaired median neurons. In addition, a new ELISA assay was developed so as to allow determination of both OA level and TBH activity in stressed cockroaches. Mechanical stressful stimulation led to a significant increase in TBH activity after 1 and 24 h, with a higher induction after 1 h than after 24 h. Thus, TBH could be considered as a promising biomarker of stress in insects rather than OA

Trophic strategies of intertidal foraminifera explored with single-cell microbiome metabarcoding and morphological methods: What is on the menu?

International audienceIn mudflats, interactions and transfers of nutrients and secondary metabolites may drive ecosystems and biodiversity. Foraminifera have complex trophic strategies as they often rely on bacteria and eukaryotes or on potential symbionts for carbon and nitrogen resources. The capacity of these protists to use a wide range of adaptive mechanisms requires clarifying the relationships between them and their microbial associates. Here, we investigate the interactions of three foraminiferal species with nearby organisms in situ, by coupling molecular (cloning/Sanger and high-throughput sequencing) and direct counting and morphological identification with microscopy. This coupling allows the identification of the organisms found in or around three foraminiferal species through molecular tools combined with a direct counting of foraminifera and diatoms present in situ through microscopy methods. Depending on foraminiferal species, and in addition to diatom biomass, diatom frustule shape, size and species are key factors driving the abundance and diversity of foraminifera in mudflat habitats. Three different trophic strategies were deduced for the foraminifera investigated in this study: Ammonia sp. T6 has an opportunistic strategy and is feeding on bacteria, nematoda, fungi, and diatoms when abundant; Elphidium oceanense is feeding mainly on diatoms, mixed with other preys when they are less abundant; and Haynesina germanica is feeding almost solely on medium-large pennate diatoms. Although there are limitations due to the lack of species coverage in DNA sequence databases and to the difficulty to compare morphological and molecular data, this study highlights the relevance of combining molecular with morphological tools to study trophic interactions and microbiome communities of protists at the single-cell scal

Trophic strategies of intertidal foraminifera explored with single-cell microbiome metabarcoding and morphological methods: What is on the menu?

International audienceIn mudflats, interactions and transfers of nutrients and secondary metabolites may drive ecosystems and biodiversity. Foraminifera have complex trophic strategies as they often rely on bacteria and eukaryotes or on potential symbionts for carbon and nitrogen resources. The capacity of these protists to use a wide range of adaptive mechanisms requires clarifying the relationships between them and their microbial associates. Here, we investigate the interactions of three foraminiferal species with nearby organisms in situ, by coupling molecular (cloning/Sanger and high-throughput sequencing) and direct counting and morphological identification with microscopy. This coupling allows the identification of the organisms found in or around three foraminiferal species through molecular tools combined with a direct counting of foraminifera and diatoms present in situ through microscopy methods. Depending on foraminiferal species, and in addition to diatom biomass, diatom frustule shape, size and species are key factors driving the abundance and diversity of foraminifera in mudflat habitats. Three different trophic strategies were deduced for the foraminifera investigated in this study: Ammonia sp. T6 has an opportunistic strategy and is feeding on bacteria, nematoda, fungi, and diatoms when abundant; Elphidium oceanense is feeding mainly on diatoms, mixed with other preys when they are less abundant; and Haynesina germanica is feeding almost solely on medium-large pennate diatoms. Although there are limitations due to the lack of species coverage in DNA sequence databases and to the difficulty to compare morphological and molecular data, this study highlights the relevance of combining molecular with morphological tools to study trophic interactions and microbiome communities of protists at the single-cell scal

Trophic strategies of intertidal foraminifera explored with single-cell microbiome metabarcoding and morphological methods: What is on the menu?

In mudflats, interactions and transfers of nutrients and secondary metabolites may drive ecosystems and biodiversity. Foraminifera have complex trophic strategies as they often rely on bacteria and eukaryotes or on potential symbionts for carbon and nitrogen resources. The capacity of these protists to use a wide range of adaptive mechanisms requires clarifying the relationships between them and their microbial associates. Here, we investigate the interactions of three foraminiferal species with nearby organisms in situ, by coupling molecular (cloning/Sanger and high-throughput sequencing) and direct counting and morphological identification with microscopy. This coupling allows the identification of the organisms found in or around three foraminiferal species through molecular tools combined with a direct counting of foraminifera and diatoms present in situ through microscopy methods. Depending on foraminiferal species, and in addition to diatom biomass, diatom frustule shape, size and species are key factors driving the abundance and diversity of foraminifera in mudflat habitats. Three different trophic strategies were deduced for the foraminifera investigated in this study: Ammonia sp. T6 has an opportunistic strategy and is feeding on bacteria, nematoda, fungi, and diatoms when abundant; Elphidium oceanense is feeding mainly on diatoms, mixed with other preys when they are less abundant; and Haynesina germanica is feeding almost solely on medium-large pennate diatoms. Although there are limitations due to the lack of species coverage in DNA sequence databases and to the difficulty to compare morphological and molecular data, this study highlights the relevance of combining molecular with morphological tools to study trophic interactions and microbiome communities of protists at the single-cell scale

Trophic strategies of intertidal foraminifera explored with single-cell microbiome metabarcoding and morphological methods : What is on the menu?

In mudflats, interactions and transfers of nutrients and secondary metabolites may drive ecosystems and biodiversity. Foraminifera have complex trophic strategies as they often rely on bacteria and eukaryotes or on potential symbionts for carbon and nitrogen resources. The capacity of these protists to use a wide range of adaptive mechanisms requires clarifying the relationships between them and their microbial associates. Here, we investigate the interactions of three foraminiferal species with nearby organisms in situ, by coupling molecular (cloning/Sanger and high-throughput sequencing) and direct counting and morphological identification with microscopy. This coupling allows the identification of the organisms found in or around three foraminiferal species through molecular tools combined with a direct counting of foraminifera and diatoms present in situ through microscopy methods. Depending on foraminiferal species, and in addition to diatom biomass, diatom frustule shape, size and species are key factors driving the abundance and diversity of foraminifera in mudflat habitats. Three different trophic strategies were deduced for the foraminifera investigated in this study: Ammonia sp. T6 has an opportunistic strategy and is feeding on bacteria, nematoda, fungi, and diatoms when abundant; Elphidium oceanense is feeding mainly on diatoms, mixed with other preys when they are less abundant; and Haynesina germanica is feeding almost solely on medium-large pennate diatoms. Although there are limitations due to the lack of species coverage in DNA sequence databases and to the difficulty to compare morphological and molecular data, this study highlights the relevance of combining molecular with morphological tools to study trophic interactions and microbiome communities of protists at the single-cell scale

Unravelling the distribution of three Ammonia species (Foraminifera, Rhizaria) in French Atlantic Coast estuaries using morphological and metabarcoding approaches

International audienceAssessing the distribution of species in natural environments is essential for their use in environmental surveys. Here, we investigate the distribution of three pseudo-cryptic species formerly lumped in the morphospecies Ammonia tepida (Cushman, 1926), commonly found on estuarine mudflats along the European coasts: Ammonia veneta Schultze, 1854 (T1), Ammonia aberdoveyensis Haynes, 1973 (T2) and Ammonia confertitesta Zheng, 1978 (T6). We studied their distribution at 51 sites located in seven estuaries of the French North Atlantic coast (Elorn, Aulne, Odet, Crac'h, Auray, Vilaine, Vie), using both morphological and molecular identification methods. Ammonia veneta was detected by both approaches at most of the stations. While A. aberdoveyensis was frequently identified by the morphological method but not detected with metabarcoding, the presence of A. confertitesta in the eDNA data often contrasted with its absence in the morphological analysis. The absence of A. aberdoveyensis in eDNA of sites where it was identified morphologically could be the consequence of its relative scarcity, and eventually a patchy distribution. Concerning A. confertitesta, we hypothesise that these contradictory results can be explained by the supposedly invasive character of this species. Despite the widespread presence of A. confertitesta genetic material (including adults, juveniles and propagules), a mature population has not yet fully developed everywhere. The seven investigated estuaries seem to represent different stages of replacement of the autochthonous species A. veneta and A. aberdoveyensis by A. confertitesta. Our study demonstrates that the combination of visual observations and molecular approaches is ideal for monitoring the progressive spreading of exotic species