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. (8)
05/09/2026
Vélez-Málaga
05/09/2026
Vélez-Málaga
03/09/2026
03/09/2026
Visible uniquement au toucher
19/08/2026
North Myrtle Beach
19/08/2026
North Myrtle Beach
14/08/2026
Monte Argentario
14/08/2026
Monte Argentario
11/08/2026
La Turballe
11/08/2026
La Turballe
07/08/2026
07/08/2026
It doesn’t sting and feels like jelly and
It doesn’t have stinging tentacles
05/08/2026
05/08/2026
Plein de Ctenaphores sur le bord et dans l'eau, notamment vers la plage surveillée (pas b'bol :-D). Totalement inoffensifs. Grumeaux dans la soupe.
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.