Assessment of coralline algal species diversity and composition at European CO₂ seeps using DNA barcoding

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Morphological and molecular assessment of Lithophyllum okamurae with the description of L. neo-okamurae sp. nov. (Corallinales, Rhodophyta)

Lithophyllum okamurae has been widely reported in the Pacific Ocean with identification based on morpho-anatomical observations. Two infraspecific taxa, L. okamurae f. okamurae and f. angulare, described from Japan, have been recorded in the temperate region of Japan. We assessed branched Lithophyllum samples morphologically referable to L. okamurae using morpho-anatomical data and DNA sequences (psbA, rbcL and partial LSU rDNA) obtained from herbarium specimens, including type material, as well as recently field-collected material in Japan. The molecular analyses showed that these ‘L. okamurae’ samples contained two species: L. okamurae and a cryptic new species which we describe as L. neo-okamurae sp. nov. Because the holotype of L. okamurae f. angulare was conspecific with original material cited in the protologue of L. okamurae, it is a heterotypic synonym of L. okamurae f. okamurae. Lithophyllum okamurae and L. neo-okamurae were morphologically similar in having warty, lumpy and fruticose thalli and in often forming rhodoliths. Lithophyllum okamurae can be morpho-anatomically distinguished from L. neo-okamurae by the thallus with tapering or plate-like protuberances (knobby protuberances in the latter) and by having smaller tetrasporangial conceptacle chambers (167–314 μm; 248–380 μm in L. neo-okamurae). Our LSU rDNA sequence data from L. okamurae f. angulare (=L. okamurae f. okamurae) was identical to that of the type of L. margaritae, which has nomenclatural priority over L. okamurae. However, considering that psbA and rbcL sequences of L. margaritae type material could not be generated in the present study, we refrain, for the moment, from proposing the taxonomic synonymy between these two taxa until the status of L. margaritae and its synonyms from the type locality (Gulf of California) are clarified.This research was mainly supported by Japan Society for the Promotion of Science (JSPS KAKENHI Grant Number 26850123, 17K07908) to AK

Major loss of coralline algal diversity in response to ocean acidification

Calcified coralline algae are ecologically important in rocky habitats in the marine photic zone worldwide and there is growing concern that ocean acidification will severely impact them. Laboratory studies of these algae in simulated ocean acidification conditions have revealed wide variability in growth, photosynthesis and calcification responses, making it difficult to assess their future biodiversity, abundance and contribution to ecosystem function. Here, we apply molecular systematic tools to assess the impact of natural gradients in seawater carbonate chemistry on the biodiversity of coralline algae in the Mediterranean and the NW Pacific, link this to their evolutionary history and evaluate their potential future biodiversity and abundance. We found a decrease in the taxonomic diversity of coralline algae with increasing acidification with more than half of the species lost in high pCO2 conditions. Sporolithales is the oldest order (Lower Cretaceous) and diversified when ocean chemistry favoured low Mg calcite deposition; it is less diverse today and was the most sensitive to ocean acidification. Corallinales were also reduced in cover and diversity but several species survived at high pCO2; it is the most recent order of coralline algae and originated when ocean chemistry favoured aragonite and high Mg calcite deposition. The sharp decline in cover and thickness of coralline algal carbonate deposits at high pCO2 highlighted their lower fitness in response to ocean acidification. Reductions in CO2 emissions are needed to limit the risk of losing coralline algal diversity

Physiological Status Drives Metabolic Rate in Mediterranean Geckos Infected with Pentastomes

Negative effects of parasites on their hosts are well documented, but the proximate mechanisms by which parasites reduce their host's fitness are poorly understood. For example, it has been suggested that parasites might be energetically demanding. However, a recent meta-analysis suggests that they have statistically insignificant effects on host resting metabolic rate (RMR). It is possible, though, that energetic costs associated with parasites are only manifested during and/or following periods of activity. Here, we measured CO2 production (a surrogate for metabolism) in Mediterranean geckos (Hemidactylus turcicus) infected with a lung parasite, the pentastome Raillietiella indica, under two physiological conditions: rested and recently active. In rested geckos, there was a negative, but non-significant association between the number of pentastomes (i.e., infection intensity) and CO2 production. In recently active geckos (chased for 3 minutes), we recorded CO2 production from its maximum value until it declined to a stationary phase. We analyzed this decline as a 3 phase function (initial decline, secondary decline, stationary). Geckos that were recently active showed, in the secondary phase, a significant decrease in CO2 production as pentastome intensity increased. Moreover, duration of the secondary phase showed a significant positive association with the number of pentastomes. These results suggest that the intensity of pentastome load exerts a weak effect on the metabolism of resting geckos, but a strong physiological effect on geckos that have recently been active; we speculate this occurs via mechanical constraints on breathing. Our results provide a potential mechanism by which pentastomes can reduce gecko fitness

Exploring the sequence-function space of microbial fucosidases

Microbial α-l-fucosidases catalyse the hydrolysis of terminal α-l-fucosidic linkages with diverse substrate/linkage specificities and can be used in transglycosylation reactions to synthesise oligosaccharides. Based on sequence identity, α-l-fucosidases have been classified in distinct glycoside hydrolases (GHs) families in the carbohydrate-active enzymes (CAZy) database. Here, we explored the sequence-function space of fucosidases from GH29 family. Based on sequence similarity network (SSN) analyses, 16 GH29 α-l-fucosidases were selected for functional characterisation. Using activity assays combined with HPAEC-PAD and LC-FD-MS/MS analyses, we determined the substrate and linkage specificities of these enzymes against a range of defined oligosaccharides and glycoconjugates, revealing a range of specificities for α1,2, α1,3, α1,4 and α1,6 linked fucosylated ligands. The structural basis for the substrate specificity of GH29 fucosidase from Bifidobacterium asteroides towards α1-6 linkages and FA2G2 N-glycan was further determined by X-ray crystallography and saturation transfer difference NMR. TLC combined with electrospray ionization – MS and NMR confirmed the capacity of this enzyme to carry out transfucosylation reactions with GlcNAc and Fuc1,3GlcNAc as acceptors. Taken together, these experimental data validate the use of SSN as a reliable bioinformatics approach to predict the substrate specificity and transfucosylation activity of GH29 fucosidases.<br/

Exploring the sequence-function space of microbial fucosidases

Microbial α-l-fucosidases catalyse the hydrolysis of terminal α-l-fucosidic linkages with diverse substrate/linkage specificities and can be used in transglycosylation reactions to synthesise oligosaccharides. Based on sequence identity, α-l-fucosidases have been classified in distinct glycoside hydrolases (GHs) families in the carbohydrate-active enzymes (CAZy) database. Here, we explored the sequence-function space of fucosidases from GH29 family. Based on sequence similarity network (SSN) analyses, 16 GH29 α-l-fucosidases were selected for functional characterisation. Using activity assays combined with HPAEC-PAD and LC-FD-MS/MS analyses, we determined the substrate and linkage specificities of these enzymes against a range of defined oligosaccharides and glycoconjugates, revealing a range of specificities for α1,2, α1,3, α1,4 and α1,6 linked fucosylated ligands. The structural basis for the substrate specificity of GH29 fucosidase from Bifidobacterium asteroides towards α1-6 linkages and FA2G2 N-glycan was further determined by X-ray crystallography and saturation transfer difference NMR. TLC combined with electrospray ionization – MS and NMR confirmed the capacity of this enzyme to carry out transfucosylation reactions with GlcNAc and Fuc1,3GlcNAc as acceptors. Taken together, these experimental data validate the use of SSN as a reliable bioinformatics approach to predict the substrate specificity and transfucosylation activity of GH29 fucosidases.<br/

Major loss of coralline algal diversity in response to ocean acidification

[Abstract] Calcified coralline algae are ecologically important in rocky habitats in the marine photic zone worldwide and there is growing concern that ocean acidification will severely impact them. Laboratory studies of these algae in simulated ocean acidification conditions have revealed wide variability in growth, photosynthesis and calcification responses, making it difficult to assess their future biodiversity, abundance and contribution to ecosystem function. Here, we apply molecular systematic tools to assess the impact of natural gradients in seawater carbonate chemistry on the biodiversity of coralline algae in the Mediterranean and the NW Pacific, link this to their evolutionary history and evaluate their potential future biodiversity and abundance. We found a decrease in the taxonomic diversity of coralline algae with increasing acidification with more than half of the species lost in high pCO2 conditions. Sporolithales is the oldest order (Lower Cretaceous) and diversified when ocean chemistry favoured low Mg calcite deposition; it is less diverse today and was the most sensitive to ocean acidification. Corallinales were also reduced in cover and diversity but several species survived at high pCO2; it is the most recent order of coralline algae and originated when ocean chemistry favoured aragonite and high Mg calcite deposition. The sharp decline in cover and thickness of coralline algal carbonate deposits at high pCO2 highlighted their lower fitness in response to ocean acidification. Reductions in CO2 emissions are needed to limit the risk of losing coralline algal diversity.Fieldwork in the Mediterranean was supported by the EU ‘Mediterranean Sea Acidification under a changing climate’ project (MedSeA; grant agreement 265103; MM, JH-S

CORALLINE ALGAE AT INCREASED CO2: A GLOBAL RESPONSE TO OCEAN ACIDIFICATION

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Trans-Neptunian objects and Centaurs at thermal wavelengths

The thermal emission of transneptunian objects (TNO) and Centaurs has been observed at mid- and far-infrared wavelengths - with the biggest contributions coming from the Spitzer and Herschel space observatories-, and the brightest ones also at sub-millimeter and millimeter wavelengths. These measurements allowed to determine the sizes and albedos for almost 180 objects, and densities for about 25 multiple systems. The derived very low thermal inertias show evidence for a decrease at large heliocentric distances and for high-albedo objects, which indicates porous and low-conductivity surfaces. The radio emissivity was found to be low ($\epsilon_r$=0.70$\pm$0.13) with possible spectral variations in a few cases. The general increase of density with object size points to different formation locations or times. The mean albedos increase from about 5-6% (Centaurs, Scattered-Disk Objects) to 15% for the Detached objects, with distinct cumulative albedo distributions for hot and cold classicals. The color-albedo separation in our sample is evidence for a compositional discontinuity in the young Solar System. The median albedo of the sample (excluding dwarf planets and the Haumea family) is 0.08, the albedo of Haumea family members is close to 0.5, best explained by the presence of water ice. The existing thermal measurements remain a treasure trove at times where the far-infrared regime is observationally not accessible.Comment: Review chapter in "The Trans-Neptunian Solar System" (D. Prialnik, M.A. Barucci and L. Young, eds.), accepted for publication in January 2019, 3 Tables, 2 Figures, 27 Page