There are 30 jellyfish species in the Black Sea, the majority of which (26 species) are small – not more than 1-20mm in diameter. The large ones are common jellyfish or moon jellyfish (Aurelia aurita) – up to20 cm in diameter, barrel jellyfish (Rhizostoma pulmo) – up to 60cm in diameter, and the very rare lucernaria (Calvadosia campanulata). In 2009, compass jellyfish (Chrysaora hysoscella) from the Mediterranean were found for the first time in the Black Sea, not far from the Turkish coast. This nettle-fish if touched leaves red marks on human skin resembling chemical burns. Moon jellyfish sometimes leave light burns, which pass in an hour or so, and bigger barrel jellyfish can very painfully damage skin, though the burns generally disappear in a few days.
Jellyfish are mainly predators eating small planktonic animals. They grasp food with their mouths, which also serve to discharge food remains. The manubrium also has gonads attached to it. They produce reproductive cells, which are directly involved in the breeding process.
The Black Sea is a friendly sea, for there are very few hazardous marine animals- even for children. A few species that can be annoying are listed below.
Rhizostome jellyfish Rhizostoma pulmo can sting your skin with its thread-cells located on the lacy peristomal tentacles. It is better to avoid it when swimming; Though nettle stings stronger than this jellyfish.
Moon jellyfish Aurelia aurita is another Scyphozoan medusa common in the Black Sea. Its thread-cells located on the canopy fringe tentacles are less potent weapon than those of Rhizostoma; they cannot penetrate even children’s skin. Contact of this jellyfish with eyes still should be avoided.
Compass jellyfish
A translucent yellowish-white jellyfish with brown markings around the fringe and on the top of the bell. Those atop the bell resemble a compass, with V shapes radiating out from a central point. They have a bunch of frilled oral arms below the bell and long thin marginal tentacles around the fringe of the bell. Don’t get too close to those tentacles though, they give a nasty sting.
Jellyfish immobilize or even kill their prey (small planktonic animals mostly) with the use of thread-cells containing venom capsule with a sharp, saw-edged coiled harpoon attached to it.
The spring uncoils and hit the prey when it touches sensitive hair on the thread-cell surface. Spike of the hollow dart breaks inside the victim body, and paralyzing venom pours out. Thread-cell is a disposable weapon.
Coelenterate thread cell action
Interesting is that newly hatched silvery horse-mackerels often crowd between Rhizostoma tentacles, and travel with jellyfish. Thread-cells do not harm these tiny fishes – just like tentacles of tropical actiniae don’t act on clown-fish living between them.
Bibliography
http://blacksea-education.ru/e3.shtml
wildlifetrusts.org/wildlife-explorer/marine/jellyfish/compass-jellyfish
Author: Giuglea Raul – President of ECOM
