Nausicaa’s Jellyfish

Jellyfish are able to float and swim but cannot maintain their position against ocean currents, so they are considered to be a constituent of plankton.

Like their close cousins sea anemones and coral, jellyfish are stinging animals. Scientists classify them among the Cnidarians (from the Greek knidèknidè, nettle).

There are more than 9,000 species of cnidarians, including hundreds of species of jellyfish.

What is a jellyfish made of?

Mainly of water (in general more than 95 %).

It nonetheless possesses a digestive system with a mouth between its tentacles, light sensitive organs, muscles and nerves.

Its stinging cells are like miniature harpoon guns, each one with its own supply of venom.Every jellyfish has thousands of such cells.

Why does Nausicaa have jellyfish?

They can be viewed in the centre of the plankton zone, because they such beautiful representatives of this family of animals. You only have to see them being carried by the current, drifting aimlessly or swimming to the surface to understand what plankton is.

Which jellyfish are there at Nausicaa?

There are 2 main species. Aurelia (scientific name Aurelia aurita) and Phyllorhiza jellyfish (scientific name Phyllorhiza punctata). The Aurelia jellyfish can be viewed in the large tank of zone 1 of the visit called ”The Worlds of the Sea”. The Phyllorhiza can be viewed in the small tank in the same zone.

Aurelia Aurita

Aurelia jellyfish are known as “moon jellyfish” and belong to the family Ulmaridae. They can be found in all oceans as well as in the Strait of Dover. Aurelia jellyfish feed on small animal plankton. At Nausicaa, they are fed small Brine shrimp larvae, which are reared especially for the purpose. Brine shrimp larvae are a salmon-pink colour. When the moon jellyfish feed on them you can see their transparent stomachs turn pink.

Phyllorhiza Punctata

It gets its species name (punctata) from the spots on its bell. In the wild, Phyllorhiza inhabits the Pacific Ocean. It belongs to the family Mastigiidae and can reach 50 cm in diameter in adulthood. Phyllorhiza punctata’s transparent body is home to symbiotic algae: the jellyfish provides a shelter to algae and in exchange the algae produces oxygen and sugars which the jellyfish feeds on. This means that rearing Phyllorhiza in captivity requires special lighting designed to foster the growth of plants. NB: symbiosis means a reciprocal relationship between two species, in this case based on essential nutritional symbiosis.

How do jellyfish reproduce ?

The lifecycle of jellyfish is complex but goes through one fixed lifecycle stage: a tiny polyp. Their polyps live on the sea bed, attached to a rock where they multiply through a process of budding to create a colony. With the change of season, the polyp transforms and its crown of tentacles detaches to become a tiny jellyfish larva, which will eventually grow into the jellyfish we can all recognise. They can reach 40cm in diameter. Jellyfish are both male and female and inseminate each other. After insemination their larvae are deposited on the sea bed where they turn into a new polyp, and the cycle can begin again!

Mythology

The jellyfish’s strange shape earned it the name of the mythological character, Medusa. In Greek mythology the Medusa was one of the three Gorgons, winged demons with female body and snakes for hair. Medusa’s stare turned her adversaries into a statue of stone. Perseus killed her by cutting off her head and from her blood Pegasus, the winged horse, was born.

BOOKS (available for consultation in Nausicaa’s library)

• Jacqueline GOY. Les Miroirs de Méduse : biologie et mythologie. Ed. Apogée, 2002
• Jacqueline GOY, Yves LAISSUS, Charles Alexandre LESUEUR. Les Méduses de PERON et LESUEUR. Ed. CTHS, 1995
• Guido MOCAFICO. Medusa. Ed. Steidl, 2006
• Chang-Tai SHIH. Guide des méduses des eaux canadiennes de l’Atlantique. Ed. Musées Nationaux du Canada, 1977
• Encyclopédie Larousse des Animaux – Vie Sauvage – Tome 7 – Chapitre sur les méduses, Ed. Larousse, 1994 Mise à jour de décembre 2007
• Alexandra BUTEUX. Etude du cycle d'Aurelia aurita (Linné) en milieu ouvert dans les bassins du port du Havre. Mémoire de Maîtrise d’Ecologie Marine, Université Pierre et marie Curie, Paris VI, 2000

Articles (available for consultation in Nausicaa’s library)

• Thierry AUFFRET VAN DER KEMP. Les Méduses : sources de nuisances ou ressource biologique à exploiter ? Paru dans : Sciences Ouest, n°180, septembre 2001, p 9
• La Méduse pullulante (tentative d'explication des phénomènes de pullulation de Pelagia noctiluca, en Mer Ligure). Paru dans : Pour la Science, n°108, octobre 1986, pp 9-10
• Sophie COISNE. Nager avec les méduses... sans se faire piquer. Paru dans : Science et Vie Junior, n°134, novembre 2000, pp 28-30