• Aarhus Bay
• cox1
• cytb
• ecology
• genetics
• ILVO
• ITS
• microsatellites
• Mnemiopsis leidyi
• zooplankton

ABSTRACT

Mnemiopsis leidyi A. Agassiz 1865 is an American ctenophore that has invaded European waters in the last decades. The reliable, but still debated, relationship between this invasion and the collapse of the stocks of anchovy Engraulis encrasicolus (Linnaeus, 1758) in the Black Sea has concerned managers and scientists because of the possible damages on the fish stocks in the new invaded areas, involving several scientists in researches about this combjelly. The lack of data about Ctenophora has hampered this research effort in the past years, but important results have been reached. The pattern of invasion has been clarified, with the identification of two subclusters (one in North Europe and a second one in Mediterranean, Black and Caspian Sea) arising from two invasions of individuals coming from different native populations along American coasts. Moreover, publications of the complete sequences of nucleic and mitochondrial DNA have made this species the model organism for genetics in its Phylum.
In this study M. leidyi is analyzed with two different approaches. At first an ecological descriptive survey is carried out in Denmark in the Aarhus Bay where water masses from Baltic Sea and North Sea overlap and mix each other. The presence of two populations with different size distributions within this stratified water column is showed. Also the abundance variations are related with biotic (zooplankton abundance) and abiotic (temperature) factors to explain the pattern.
The second approach involves analysis carried out in Belgium with ten DNA markers. These have been used for M. leidyi In particular for population genetics and for molecular identification, since the presence of the morphologically similar Bolinopsis infundibulum that can be misidentified. ITS region is the marker used to point out the species, while seven microsatellites give data for population genetics and to be compared with previous studies. Also new primers for cytb and cox1, markers on mtDNA, are successfully created to investigate the presence of SNPs.