Abstract:

Copepods and protozoans often co-exist in marine rotifer mass cultures. Interspecific interaction between the rotifer Brachionus rotundiformis Tschugunoff and eight other zooplankton species, namely Brachionus plicatilis O. F. Muller (rotifer), Diaphanosoma celebensis Stingelin (cladoceran), Tigriopus japonicus Mori, Acartia sp. (copepod), Euplotes sp., Vorticella sp., an unidentified protozoan species (P1 strain) (protozoan) and Artemia sp. (anostracan) at two developmental stages (nauplii -0.95 mm, 0 days old; adults -3.3 mm, 19 days old) were investigated in the laboratory.There was no contaminating species that contributed to an increase in rotifer population growth during the experiments. Four types of interspecific interactions were seen between B. rotundiformis and other co-existing zooplankton species. These include effects on population growth: (1) both species declined, (2) one species is promoted while the other is not influenced, (3) one species is declined while the other is not influenced and (4) one species is promoted while the other declined. The first type was exhibited by B. rotundiformis vs B. plicatilis, B. rotundiformis vs D. celebensis and B. rotundiformis vs Artemia sp. The second type was exhibited by B. rotundiformis vs Vorticella sp. and the third type by B. rotundiformis vs Euplotes sp. and B. rotundiformis vs T. japonicus. The fourth type was exhibited by B. rotundiformis vs Acartia sp. and B. rotundiformis vs P1 strain.
(Nagasaki Univ., Grad. Sch. Marine Sci. and Engn., Bunkyo Machi 1- 14, Nagasaki 852, Japan)
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