Search

With the intensification of maritime traffic, recently emerged infectious diseases have become major drivers in the decline and extinction of species. Since 2016, mass mortality events have decimated the endemic Mediterranean Sea bivalve Pinna nobilis, affecting ca. 100% of individuals. These events have largely been driven by Haplosporidium pinnae's infection, an invasive species which was likely introduced by shipping. While monitoring wild populations of P. nobilis, we observed individuals that survived such a mass mortality event during the summer of 2018 (France). We considered these individuals resistant, as they did not show any symptoms of the disease, while the rest of the population in the area was devastated. Furthermore, the parasite was not detected when we conducted a PCR amplification of a species-specific fragment of the small subunit ribosomal DNA. In parallel, the transcriptomic analysis showed evidence of some parasite RNA indicating that the resistant individuals had been exposed to the parasite without proliferating. To understand the underlying mechanisms of resistance in these individuals, we compared their gene expression with that of susceptible individuals. We performed de novo transcriptome assembly and annotated the expressed genes. A comparison of the transcriptomes in resistant and susceptible individuals highlighted a gene expression signature of the resistant phenotype. We found significant differential expressions of genes involved in immunity and cell architecture. This data provides the first insights into how individuals escape the pathogenicity associated with infection. [ABSTRACT FROM AUTHOR]

Background: The pen shells Pinna nobilis and Pinna rudis are large wedge-shaped bivalve molluscs. Both species are threatened by different anthropogenic pressures. In the last few years, P. nobilis populations have significantly reduced due to massive mortality events. The complete mitochondrial DNA sequences of these congeneric species have been determined and compared for the first time. Results: The mitogenome sequences of P. nobilis and P. rudis were 18,919 bp and 18,264 bp in length, respectively. Each mitogenome is composed of 12 protein-coding genes, 2 ribosomal RNA, 22 transfer RNA (tRNAs) genes and non-coding regions. A putative Adenosine Triphosphate synthase subunit 8 gene could only be proposed for P. nobilis. Both newly sequenced mitogenomes present a conserved gene order between them, comparable to the closely related Atrina pectinata, but global arrangement greatly differs from other available bivalve mitochondrial sequences. Multiple copies of tRNA-Cys were identified, located in different positions probably due to mechanisms of mitochondrial genome rearrangements, and detected 2 and 3 times in P. rudis and in P. nobilis, respectively. Conclusion: A close relationship was shown between Pinna species and Atrina pectinata and a consistent clustering showing a monophyletic origin of Pinnidae family sequences was evidenced. The mitochondrial genomes will provide a valuable genetic resource for further studies on population genetics and species identification. [ABSTRACT FROM AUTHOR]

17α-ethinylestradiol (EE2), the female contraceptive pill, has been detected in mediterranean coasts where seahorse populations, Hippocampus guttulatus, live. Low environmental concentrations have the potential to disrupt growth but also endocrine metabolism, and this imbalance is all the more critical in early life stage. To investigate the impact of EE2 in reared seahorses, we exposed aged 2 months and sexually undifferentiated seahorses to an environmental concentration of 21 ng/L of EE2 for a period of 30 days. EE2 exposure led to a 19% reduction in weight, but also a mortality rate of 27%. This exposure predicted demasculinization of male individuals with a late onset of secondary sexual characteristics. EE2 exposure led to an increase of the free androgen index, but significant reductions of estradiol and testosterone in males were observed. This low estrogen concentration seemed to impact the positive feedback on luteinizing hormone (LH) with a decrease in LH production. Added to this, synthetic estrogen had a negative impact on the production and the release of follicle-stimulating hormone. Contrary to all expectations, females demonstrated a significant decrease in vitellogenin, following exposure to EE2 at 21 ng/L, while no changes were detected in males. This first study on the European long-snouted seahorses confirmed the deleterious impact of the female contraceptive pill with a real impact on growth, sexual differentiation, and maturation in young immature seahorses. [ABSTRACT FROM AUTHOR]

Marine microalgae and cyanobacteria have largely been studied for their biotechnological potential and proved their ability to produce a wide array of bioactive molecules. We investigated the antifouling potential of unexplored benthic tropical microalgae using anti-adhesion and toxicity bioassays against two major micro- and ma crobiofoulers, namely bacteria and barnacles. Fifty strains belonging to six phyla [Cyanobacteria, Miozoa (Dinoflagellata), Bacillariophyta, Cryptophyta, Rhodophyta and Haptophyta] were isolated from southwestern Islands of the Indian Ocean. They were chosen in order to represent as much as possible the huge biodiversity of such a rich tropical ecosystem. The associated chemodiversity was highlighted by both NMR- and LC-MS-based metabolomics. The screening of 84 algal fractions revealed that the anti-adhesion activity was concentrated in methanolic ones (i.e. 93% of all active fractions). Our results confirmed that microalgae constitute a promising source of natural antimicrofoulants as 17 out of the 30 active fractions showed high or very high capacity to inhibit the adhesion of three biofilm-forming marine bacteria. Dinoflagellate-derived fractions were the most active, both in terms of number and intensity. However, dinoflagellates were also more toxic and may not be suitable as a source of environmentally friendly antifouling compounds, in contrast to diatoms, e.g. Navicula mollis. The latter and two dinoflagellates of the genus Amphidinium also had interesting anti-settlement activities while being moderately toxic to barnacle larvae. Our approach, combining the bioprospecting of a large number of tropical microalgae for their anti-settlement potential and metabolomics analyses, constituted a first step towards the discovery of alternative ecofriendly antifoulants. [ABSTRACT FROM AUTHOR]

The antifouling (AF) properties of phytochemicals isolated from the Mediterranean brown seaweed Taonia atomaria have been assayed against several colonizing organisms. Eight compounds were isolated and their chemical structures characterized by spectroscopic techniques (NMR, MS) and comparison with literature data. The phytochemical composition of the extracts of T. atomaria was found to be mainly attributable to sesquiterpenes. Accordingly, a new germacrane, germacra-4(15),5,10(14)-trien-9-ol ( 1), is described together with five other sesquiterpenoids (-)-gleenol ( 2); α-cadinol methyl ether ( 3), (-)- trans-calamenene ( 4), (1 S, 5 E, 7 S) 1-acetoxygermacra-4(15),5,10(14)-triene ( 5), and 4-peroxymuurol-5-ene ( 6). Moreover, two lipidic compounds, a polyunsaturated fatty acid, (5 Z, 8 Z, 11 Z, 14 Z, 17 Z)-eicosa-5,8,11,14,17-pentaenoic acid ( 7), and a glycerol derivative, sn-3- O-(geranylgeranyl)glycerol ( 8), were also isolated. The known compounds 3, 6- 7 are described here for the first time from this alga. In comparison with commercial antifoulants [tributyltin oxide (TBTO), zineb, and copper pyrithione (CuPT)], compounds 1, 2, 4, 6, and 8 were evaluated for their toxicity and capacity to inhibit the settlement of five bacteria isolated from marine biofilms. Toxicity and anti-settlement activity of 1, 2, and 6 were also assessed against two barnacle species ( Amphibalanus amphitrite and Balanus perforatus). Regarding bacteria, a significant anti-adhesion effect was recorded for 8 (EC between 25 and 50 μM) with moderate associated toxicity. Considering the settlement inhibition of barnacle cyprids, (-)-gleenol ( 2) exhibited a strong AF efficacy (EC < 5 μM) with moderate toxicity. In addition, as B. perforatus showed similar responses to the reference A. amphitrite with all compounds, this species may be proposed as an alternative model for anti-macrofouling assessment, especially in temperate areas. Overall, these results suggest that a number of the tested compounds could, alone or in combination, play a critical role in limiting the fouling at the T. atomaria surface. [ABSTRACT FROM AUTHOR]

Glyphosate-based herbicides are the most frequently used herbicides in the world. We evaluated the effect of Roundup 360 SL on the expression of interleukin-1β ( il- 1β), interleukin-10 ( il- 10) and heme-oxygenase-1 ( ho- 1) in the gills, intestines and spleen of young European sea bass ( Dicentrachus labrax L.), aged 8 mo. A group of fish was exposed to 647 mg/L of Roundup for 96 h. This treatment did not alter gene expression levels of il-1β and il- 10 cytokine in the intestines, but significantly lowered both levels in the gills ( p = 0.02 and p = 0.04 respectively). Expression levels of ho- 1 were increased significantly in the three organs of fish from the treated group (the gills p = 0.04, the intestines p = 0.004 and the spleen p < 0.001). These changes may in turn negatively impact the immune system of European sea bass exposed to Roundup. [ABSTRACT FROM AUTHOR]