No abstract

Over the past three decades the colonial ascidian Didemnum vexillum has been expanding its global range, significantly impacting marine habitats and aquaculture facilities. What biological features make D. vexillum so highly invasive? Here, we show that juxtaposed allogeneic D. vexillum colony fragments (‘ramets’) may, initially, form chimeric entities. Subsequently, zooids of the differing genotypes within such chimeras coordinately retreat away from fusion zones. A few days following such post-fusion retreat movements there is further ramet fission and the formation of zooid-depauperate tunic zones. Using polymorphic microsatellite loci to distinguish between genotypes, we found that they were sectorial at the fusion zones and the subsequent ramet movements resulted in further spatial separation of the paired-genotypes indicating that the fusion events observed did not lead to formation of long-term, stable chimeras. Thus, movements of D. vexillum colony ramets from initial fusion zones lead to progressive segregation of genotypes probably minimizing potential somatic/germ-cell competition/parasitism. We speculate that relatively fast (≤10 mm/day) movement of D. vexillum colonies on substrates along with frequent, and perhaps unrestrained, transient allogeneic fusions play significant roles in this species’ striking invasiveness and capacity to colonize new substrates.

No abstract

Accurate identification of scleractinian coral species is fundamental for proper biodiversity estimates, for aiding in efforts of reef monitoring, conservation, restoration, and for the management of coral reefs. Here, we provide the first DNA barcoding reference library for coral species in Eilat, Red Sea, based on the mitochondrial gene cytochrome c oxidase subunit I (COI), targeting the identification of stony coral species from shallow (0–12 m) reefs. A total of 191 specimens were collected, depicting 14 families, 39 genera, and 94 species (all are new full species records to the BOLD system). Three species (Sclerophyllia margariticola, Cyphastrea magna, and Psammocora profundacella) are first records for Eilat’s coral reef. The results presented here strengthen the claim that COI is not universally informative for delimitation of stony coral species, a notion reinforced by the constructed maximum likelihood phylogenetic tree. This library is the first step in a long journey towards elucidating coral biodiversity in the coral reef at Eilat and for improving future management and monitoring efforts.

Nineteen microsatellite loci, obtained by the whole genome sequencing approach, were developed and validated for the ‘smooth cauliflower’ coral Stylophora pistillata, a widespread Indo Pacific branching coral species. A sample size of 40 colonies collected at five reef sites along the northern Gulf of Eilat, the Red Sea, were genotyped, revealing loci reproducibly and suitable outcomes for wide applications, including population genetic studies. The 19 new microsatellite loci in this sample were composed of 4–20 alleles/locus, of which 10 microsatellites are highly polymorphic (≥10 alleles/locus). The observed and expected heterozygosity ranged between 0.289 and 0.957 (mean 0.597) and 0.101 and 0.911 (mean 0.726), respectively, and the Fixation Index (F), which also indicates the inbreeding coefficient, ranges between −0.174 and 0.569 (mean 0.207). The polymorphic information content (PIC) ranges between 0.100 and 0.904 (mean 0.699). This new set of microsatellite loci will be employed for population genetics studies as for identifying the distribution of various genotypes within S. pistillata chimeras.