Anatomy of gonads and propagation of Ctenophore Mnemiopsis in the Black Sea.

V.Ye.ZAIKA., N. K. REVKOV

From HYDROBIOL.-J.-1995.-vol.31, no.3, pp.9-14.
(Originally published in Zool.zh. 73(3), 1994: 5-10.)

In an invading ctenophoran species of from the Black Sea (Mnemiopsis sp.) the gonads lie only in the walls of 8 meridiorial canals but in the walls of auricular canals under the flagellar rows as well. Up to 2—3 thousands to eggs can be simultaneously produced by a large clenophore. Under the natural light regime and temperature of 19 to 24°C the signs of the formation of testicles appears at 18h, eggs at early stage of oogenesis — after 20h, the spawning take place from 23h to 01 a. m. With augmentation of temperature from 19—21 to 24—28°C the duration of embryogenesis decreases from 19.5—21 to llh. A mass spawning of Mnemiopsis sp. in the Black Sea begins when the surface temperature of water reaches 23°C.

Fig.1. Mnemiopsis: a - ovaries localization, b - gonads, 20 h p.m., c - gonads, 22 h p.m., m.k. - meridional canal, a.k. - auricular canal, o - ovary, t - testis k - ctens.

Fig. 2. Daily cycle of gonads development: a- in experimenental conditions with different light-dark regimes (A,B,C,D), b - in natural conditions (at the Sea) 1 - testis forming, 2 - ovum forming, 3 - spawning.