Harmless
Mnemiopsis leidyi
Ctenophore (Mnemiidae)
Known as the "sea walnut", it is not a true jellyfish but a ctenophore. Native to America, it has become highly invasive in Europe, particularly in the Netherlands.
Sting symptoms
Completely harmless. Does not sting, lacks stinging cells.
Identification
Small transparent and oval organism, resembling a lobe or walnut. Rows of cilia often light up with rainbow reflections as it moves.
Size
Body: 7 to 12 cm
Habitat
Coastal waters, bays, estuaries. Tolerates wide salinity variations.
Scientific family
Ctenophore (Mnemiidae)
Community photos
Photos submitted and verified by Meduseo users. (1)
05/07/2026
Saint-Gildas-de-Rhuys
05/07/2026
Saint-Gildas-de-Rhuys Idem que plage du Kerver, ressemblance à de petits sacs plastiques. Pas de tentacules visibles.