Superclone Expansion, Long-Distance Clonal Dispersal and Local Genetic Structuring in the Coral Pocillopora damicornis Type β in Reunion Island, South Western Indian Ocean.

The scleractinian coral Pocillopora damicornis type β is known to present a mixed reproduction mode: through sexual reproduction, new genotypes are created, while asexual reproduction insures their propagation. In order to investigate the relative proportion of each reproduction mode in P. damicornis type β populations from Reunion Island, Indian Ocean, clonal propagation along the west coast was assessed through four sampling sites with increasing geographical distance between sites. Coral colonies were sampled either exhaustively, randomly or haphazardly within each site, and genotypic diversity was assessed using 13 microsatellite loci over a total of 510 P. damicornis type β determined a posteriori from their mtDNA haplotype (a 840 bp sequenced fragment of the Open Reading Frame). Overall, 47% of all the sampled colonies presented the same multi-locus genotype (MLG), a superclone, suggesting that asexual propagation is extremely important in Reunion Island. Within each site, numerous MLGs were shared by several colonies, suggesting local clonal propagation through fragmentation. Moreover, some of these MLGs were found to be shared among several sites located 40 km apart. While asexual reproduction by fragmentation seems unlikely over long distances, our results suggest a production of parthenogenetic larvae. Despite shared MLGs, two differentiated clusters were enclosed among populations of the west coast of Reunion Island, revealing the necessity to set up appropriate managing strategies at a local scale

Isolation and characterization of 22 microsatellite loci from two coral species: Acropora muricata (Linnaeus, 1758) (Scleractinia, Acroporidae) and Porites lutea Milne-Edwards & Haime, 1851 (Scleractinia, Poritidae): Microsatellite records

International audienceTotal genomic DNA of eight colonies for each of the two species, Acropora muricata and Porites lutea, sampled on the west coast of Reunion Island, was isolated using DNeasy Blood & Tissue kit (Qiagen™) following the manufacturer’s instructions and sent to GenoScreen, Lille, France (www.genoscreen.fr)

Influence of water temperature and food on the last stages of cultured pearl mineralization from the black-lip pearl oyster Pinctada margaritifera

International audienceEnvironmental parameters, such as food level and water temperature, have been shown to be major factors influencing pearl oyster shell growth and molecular mechanisms involved in this biomineralization process. The present study investigates the effect of food level (i.e., microalgal concentration) and water temperature, in laboratory controlled conditions, on the last stages of pearl mineralization in order to assess their impact on pearl quality. To this end, grafted pearl oysters were fed at different levels of food and subjected to different water temperatures one month prior to harvest to evaluate the effect of these factors on 1) pearl and shell deposition rate, 2) expression of genes involved in biomineralization in pearl sacs, 3) nacre ultrastructure (tablet thickness and number of tablets deposited per day) and 4) pearl quality traits. Our results revealed that high water temperature stimulates both shell and pearl deposition rates. However, low water temperature led to thinner nacre tablets, a lower number of tablets deposited per day and impacted pearl quality with better luster and fewer defects. Conversely, the two tested food level had no significant effects on shell and pearl growth, pearl nacre ultrastructure or pearl quality. However, one gene, Aspein, was significantly downregulated in high food levels. These results will be helpful for the pearl industry. A wise strategy to increase pearl quality would be to rear pearl oysters at a high water temperature to increase pearl growth and consequently pearl size; and to harvest pearls after a period of low water temperature to enhance luster and to reduce the number of defects

Summary statistics for the four <i>Pocillopora damicornis</i> type <i>β</i> populations.

<p>Summary statistics for the four <i>Pocillopora damicornis</i> type <i>β</i> populations.</p

Network of multi-locus genotypes (MLG) based on shared allele distance.

<p>The number of colonies sharing each MLG is indicated inside each node and the geographic origin of the colonies is represented by colors. The node shape represents the result of the clustering analysis: circles, MLGs assigned to cluster 1 (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0169692#pone.0169692.g004" target="_blank">Fig 4</a>) with a probability ≥ 0.90; squares, MLGs assigned to cluster 2 (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0169692#pone.0169692.g004" target="_blank">Fig 4</a>) with a probability ≥ 0.90; triangles, MLGs assigned to one cluster or the other with a probability ≤ 0.90.</p

Detection, counting and characterization of nanoplastics in marine bioindicators: a proof of principle study.

Plastic particulates in the environment pose an increasing concern for regulatory bodies due to their potential risk to higher organisms (including humans) as they enter the food chain. Nanoplastics (defined here as smaller than 1 μm) are particularly challenging to detect and analyze at environmentally relevant concentrations and in biological matrices. The tunicate Ciona Robusta is an effective bioindicator for microplastics and nanoplastic contamination in the marine environment, due to its capacity to filter substantial volumes of water and to accumulate particulates. In this proof-of-principle study that demonstrates a complete methodology, following controlled exposure using spiked samples of a model nanoplastic (100 nm diameter polystyrene spheres) the nanoparticles were separated from an enzymatically digested biological matrix, purified and concentrated for analysis. The described method yields an approximate value for nanoplastic concentration in the organism (with a limit of detection of 106 particles/organism, corresponding to 1 ng/g) and provides the chemical composition by Raman spectroscopy. Furthermore, this method can be extended to other biological matrices and used to quantitatively monitor the accumulation of nanoplastics in the environment and food chain

Spatial representation of <i>Pocillopora damicornis</i> type <i>β</i> colonies sampled in (a) REU1 (<i>N</i> = 158) and (b) REU2 (<i>N</i> = 264).

<p>Each symbol represents a colony. Multi-locus genotypes (MLG) occurring only once are represented with “+”. Colonies sharing the same MLG are represented with the same color and each repeated MLG is represented by a different color. MLGs shared by both sites are represented with circles (MLG01: red, MLG02: blue, MLG03: white, MLG04: green, MLG05: black) and MLGs specific to a unique site with squares.</p

Genetic differentiation between <i>Pocillopora damicornis</i> type <i>β</i> populations estimated with Weir and Cockerham’s <i>F</i>_<i>ST</i> [58] and with Jost’s <i>D</i>_<i>est</i> (in parentheses, [59]).

<p>Genetic differentiation between <i>Pocillopora damicornis</i> type <i>β</i> populations estimated with Weir and Cockerham’s <i>F</i>_<i>ST</i> [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0169692#pone.0169692.ref058" target="_blank">58</a>] and with Jost’s <i>D</i>_<i>est</i> (in parentheses, [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0169692#pone.0169692.ref059" target="_blank">59</a>]).</p