Rhopilema nomadica
(nomad jellyfish)

Preferred Common Name

• nomad jellyfish

Local Common Names

• Israel: hutit nodedet

• Domain: Eukaryota
•     Kingdom: Metazoa
•         Phylum: Cnidaria
•             Class: Scyphozoa
•                 Order: Rhizostomeae
•                     Family: Rhizostomatidae
•                         Genus: Rhopilema
•                             Species: Rhopilema nomadica

R. nomadica is a medium-sized rhizostomid medusa. It has a nearly hemispherical umbrella, thickest centrally, thinning gradually towards margin. Exumbrella minutely granulate, granules fewer and blunter near margin. Margin of umbrella divided into 64 rounded velar lappets. Ocular lappets small, lanceolate, one third as wide as velar lappets. Subumbrellar circular muscles well developed, uniform. Arm disc prismatic, about one third of bell diameter, oral pillars quadrate. Distal corners of oral pillars prominently tuberculate. Subgenital ostium at each interradius kidney-shaped, as wide as oral pillar. A pear-shaped, tuberculate papilla interradially on subumbrella, opposite ostial opening. Eight pairs of large, deeply bowed scapulets arise from adradial sides of armdisc; underside concave, smooth; upper side bearing frilled mouths and numerous filaments. Distal part of scapullets bearing long filaments, sometimes twice as long as scapulets. Each scapulet is divided, midlength, into two, with five appendages on each side. Eight adradial mouth arms stout, smooth, fused to midlength. Lower part of mouth arm divided into two triangular flaps, each flap distally tripartite and terminating in claw-like digitate processes. Ventrally, mouth arms bear numerous frilled mouths and long filaments. Lowermost end bearing a vermicular appendage terminating in a thin filament. Stomach cavity nearly octagonal. Gastrovascular system consisting of four perradial, four interradial and eight adradial canals interconnecting in a complex network of anastomosing vessels extending almost to bell margin. Four principal canals extend from lower part of stomach to radii entering each scapulet and mouth arm, then branching to numerous minute canals leading to mouths (Galil et al., 1990).

Colour in life icy blue. It can reach up to 100 cm umbrella diameter, but is commonly 30-50 cm in diameter.

In 1976 it was first collected of the coast of Israel (Galil et al., 1990), in 1989 it appeared off Lebanon (Lakkis et al., 1990), in 1995 it appeared off the southeastern Turkey (Kideys and Gücü, 1995), in 1998 off Izmir, in 2002 off Syria (Ikhtiyar et al., 2002), in 2003 off Cyprus, and in 2006 off Lakonikos Gulf, Greece (Siokou-Frangou et al., 2006).

Natural Dispersal (Non-Biotic)

R. nomadica has a negative impact on the southern Levantine fisheries. Coastal trawling and purse-seine fishing are disrupted for the duration of the swarming due to net clogging and inability to sort yield: “It is not uncommon that fishermen, especially purse seines, discard entire hauls due to the overwhelming presence of poisonous medusae in their nets” (Golani and Ben Tuvia, 1995). Jellyfish-blocked water intake pipes pose a threat to cooling systems of port-bound vessels and coastal power plants: in the summer of 2001 Israel Electric removed tons of jellyfish from its seawater intake pipes at its two largest power plants, at estimated costs of US $50,000 (Galil, 2007).

• Proved invasive outside its native range
• Highly mobile locally
• Fast growing
• Has high reproductive potential
• Gregarious
• Has propagules that can remain viable for more than one year
• Reproduces asexually

• Altered trophic level
• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Infrastructure damage
• Negatively impacts cultural/traditional practices
• Negatively impacts human health
• Negatively impacts animal health
• Negatively impacts livelihoods
• Negatively impacts aquaculture/fisheries
• Negatively impacts tourism
• Reduced amenity values
• Reduced native biodiversity
• Threat to/ loss of native species
• Negatively impacts animal/plant collections
• Damages animal/plant products

• Causes allergic responses
• Competition - monopolizing resources
• Herbivory/grazing/browsing
• Predation
• Rapid growth

• Difficult/costly to control

Economic Value

R. nomadica is cogeneric with the edible jellyfish, Rhopilema esculenta, a popular food in South-East Asian cooking (Hsieh et al., 2001). The latter species is also used for medicinal purposes (Omori and Nakano, 2001), such as treatment of high blood pressure and bronchitis and have been commercially exploited along the coasts of South-East Asia for more than 1,000 years (Morikawa, 1984; Hsieh et al., 2001; Omori and Nakano, 2001). The fishery is characterized by considerable fluctuations in annual catch and very short fishing season. Attempts to process and export R. nomadica from the Mediterranean to South-East Asian markets have not been successful thus far.