Moerisia maeotica (Ostroumov, 1896)

Moerisia maeotica imageSynonyms: Thaumantias maeotica Ostroumov, 1896; Moerisia inkermanica Paltschikowa-Ostroumova, 1925; Ostroumovia inkermanica Valkanov, 1933; Pontia ostroumovi Paspalev, 1936; Odessia maeotica Paspalev, 1937.

Common names: None.

Order (Scientific): (HYDROZOA) LEPTOLIDA.

Family (Scientific): MOERISIIDAE.

Taxonomic descriptions: The species has form of both polypus and planktonic medusa. The polypi may be as isolated or bipolar colonies, formed through a fusion the bases basis of two polypi. The body has 3-12 tentacles with an irregular arrangement. Medusa develops only on polypus’ body. It has a spherical shape with a diameter up to 20 mm (at sexual maturity). On the borders of umbrella, there are up to 36 tentacles which have oceli at their base. Medusa with 4 radial ducts and an oral cavity with 4 lobs. The gonades on the basis of the oral cavity descend in radial ducts to the margins of the umbrella. A thick and transparent mesoglea.

Moerisia maeotica arealIUCN Status:
    World level:
    Black Sea Regional level: VU
    Subregion level: EN (Romanian sector), VU (Romanian and Ukrainian sector)

Distribution: In the Sea of Azov, Black Sea, limans of the Azov-Black Sea basin. Range includes freshwater areas of the Mediterranean Sea (in particular the eastern part of its basin - Adriatic Sea), Atlantic coast of Africa. After the opening of the Volga-Don Canal in 1952 the species penetrated into the Caspian Sea.

Habitat type, Critical habitats, Limiting factors: Polyps occur in the upper sublitoral. Can attach to rocks, broken wood, different floating objects. Jellyfish inhabit the near surface layers of the water body.

Biology: Live at temperatures of 15-25°C and a salinity of 0.5-3.5 ppt. Feed on zooplankton. The life cycle includes a succession of polypoid and jellyfish stages. In the Black Sea produces by the budding of polyps in August - September, forms weakly branched laminated colonies. The polyp has a thin long stalk. The jellyfish becomes mature in 30-40 days after separating from the polyp.

Population trends: Exact numbers unknown. Rarely encountered.

Threats: Increase in salinity, pollution of water bodies.

Conservation measures taken: Included in Red Data Books of Ukraine and the Black Sea.

Conservation measures proposed: Create conditions for normal species reproduction, including the prevention of pollution of freshwater areas of the sea.


  1. Naumov, D.V., 1960. Gidroidy i gydromeduzy morskikh, solonovatovodnykh i presnovodnykh basseinov SSSR (Hydroids and hydromedusas of marine, brackish and freshwaters reservoirs of the USSR), Moscow-Leningrad: Nauka Publ., 626 pp.
  2. Stepanyants, S.D., Murina, V.V., 1994. Moerisia maeotica. Chervona Knyga Ukrayiny (Red Data Book of Ukraine). Kijiv: Ukrajinska enciklopediya Publ., P. 17 (in Ukrainian); Opredelitel fauny Chernogo i Azovskogo morey (Key to Black Sea and Sea of Azov fauna). Kiev, Naukova dumka Publ., 1, 437 pp. (in Russian).
  3. Teodorescu-Leonte, R., 1977 - Le complex Raelm-Sinoe une system typiquement saumâtre. MAMBO/IRCM, 2: 78-92.
  4. Borcea, I., 1930-1931 - Nouvelles contributions a l’étude de la faune benthonique dans la mer Noire, pres du littoral roumaine. Ann.Sci.Univ.Jassy. 16: 655-750.
  5. Müller, G.I., 1991 - Composition of benthic fauna from the Black Sea littoral lakes Sinoe and Istria, in the conditions of the increasing eutrophication. (Annual study, RMRI, Constantza) (In Rom.).

Compiled by: B.G.Alexandrov, A.Petranu.