APPIANO. Monticolo? It is a lake populated by little stinging male jellyfish and therefore harmless for swimmers. They were first spotted in summer 2015 and have been present in the hottest months from July to September ever since. The type of jellyfish sighted has a diameter of a couple of centimeters, comes from China and was the focus of a study, published in an international journal.

The discovery in August 2015.

Andrea Falcomatà, from the Bolzano Sub Fotosub team, spotted and photographed them for the first time during a training session in view of the Italian digital underwater photography championships. His diving buddy, Massimo Morpurgo, biologist of the Museum of Natural Sciences, has captured two specimens, immersed them in a small aquarium of the Bolzano Museum in via Bottai and since he was very keen to reassure the swimmers already at the time he put us in a hand to see if they pinched or not. And the result was more than comforting. To make sure he had identified the species, Morpurgo then contacted the highest authority in the field, the curator of the world hydrozoan database, Dr. Peter Schuchert of the Natural History Museum in Geneva. The latter, studied the images, confirmed the identification.

Lo studio in team.

Biologists Massimo Morpurgo of the Museum of Natural Sciences, Peter Schuchert of the Natural History Museum of Geneva, Samuel Vorhauser and Renate Alber, both of the Biological Laboratory of the Provincial Agency for the Environment and Climate Protection, collaborated in the study of new arrived as part of the research project of the Museum of Natural Sciences Hydrozoans and Bivalves of the lakes of Monticolo and Caldaro.

The results of their research are now presented in the international scientific journal Journal of Limnology. The article is titled “Occurrence of two distinct lineages of the freshwater jellyfish Craspedacusta sowerbii (Hydrozoa: Limnomedusae) in Italy” (in Italian: Presence of two distinct genetic lines of the freshwater jellyfish Craspedacusta sowerbii (Hydrozoa: Limnomedusae) in Italy ) and is published on the magazine website https://www.jlimnol.it/index.php/jlimnol/issue/view/74.

The results: jellyfish and … polyps.

The jellyfish Craspedacusta sowerbii Lankester 1880 is a small species – it reaches a maximum of a couple of centimeters in diameter – it feeds on tiny plankton crustaceans and is not very stinging and therefore harmless for swimmers. It is allochthonous, therefore not native to the Great Lake of Monticolo. It comes from China. Of particular interest is the biological cycle of the species which occurs in two different forms: octopus and jellyfish. “Polyps, up to one millimeter long, live alone or in small colonies on the bottom of the lake. Polyps reproduce asexually to form other polyps. At the beginning of the summer the polyps then produce the jellyfish », explains Morpurgo. Jellyfish live only in summer, while polyps survive all year round. Jellyfish were particularly abundant in summer 2019, the third hottest summer since 1850 in South Tyrol. Both jellyfish and polyps of this species have been found in the Great Lake of Monticolo, while only the polyps have been found in the Small Lake of Monticolo.

Male jellyfish only.

All the jellyfish examined are male. Populations of single-sex jellyfish are common for this species outside of China. In these cases the sexual reproduction of the jellyfish does not occur, but the populations are maintained thanks to the polyps. Finally, molecular analyzes suggest the existence in the world of at least three distinct genetic lines of Craspedacusta, two of which also live in Italy: one in the Monticolo Lakes and one in Sicily.

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