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Appendix 9 workshop 1

Results of experimental works on Mnemiopsis leidyi and Beroe ovata in the Caspian Sea

Ivanov V. P., Sokolskiy V. P., Abdulmejidov A., Vorobyova A. A.

Objective: to identify viability of B. ovata in the Caspian water, its relevance to Mnemiopsis Leidyi and plankton.

Ctenophora B. ovata were first caught in August 2001 in the Black sea (experimental base of Bolshoy Utrish) and in 50-litre barrels with the Black sea water (17%). 10 species per barrel were successfully delivered to the Caspian coast, experimental base of Turali-2 of KaspNIRKH’s Dagestan Division and later placed in 20-litre aquariums with the Black sea water.

Two species of B.ovata were placed in the aquarium with the Caspian water (12%). Big species (? 4 cm) immediately died while smaller one (<1,5) – died only in two days. In Black sea water B.ovata were active and reproductive.

For adaptation purposes of B. ovata 1 litre of Caspian water was daily added in aquariums with the Black sea water for a month. Ctenophora were then transferred into clean Caspian water (3 October), where they kept living, feeding and intensively growing.

With temperature decrease they were transferred in a heated room, however, in 2 days both B.ovata and Mn.leidyi died (24 October).

Studies conducted on nutrition of Ctenophora helped to identify the following data:

Mn.leidyi intensively feeds in the Caspian water at t =28° N, swallowing up to 30 species of Calanoida (30 %) and digesting them within 2.5-3 hours. Nutrition peak was recorded in the evening (18 hours) with this being less intensive at night (22 hours). Upon temperature decrease nutrition intensity decreased as well.

At t =28° N of the Caspian water (early October) B.ovata actively fed on Mnemiopsis within a day and most actively in the first half of the day. At t =25°N the species intensively fed throughout day and night periods and at t =20° N – only during nighttime. Digestion time at t=25-28°N made up 1 hour 15 minutes and at t =20°N – 1 hour 47 minutes. Daily consumption of Mnemiopsis by B.ovata amounted to 5-7 species.

Even in conditions of durable starvation B.ovata did not feed on plankton (Caspian organisms and Artemia salina) and upon abundance of plankton tightly squeezed its oral cavity assuming an oval form. B.ovata did not fed on small coelelminths.

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