About 550 pairs of birds of the family Ardeidae nest on the Swan islands in the Karkinit Gulf of the Black Sea, the most numerous colonies being of grey heron and little egret. These birds form an important part of the Karkinit Gulf ecosystem, and are of particular interest as hosts for some helminth worms. The present study investigated the species composition of trematodes parasitizing these birds, and the main routes by which infection can occur. From 1992 to 1997 helminth collections were examined from 67 birds of 6 species: Botaurus stellaris (bittern), 3 individuals; Nycticorax nycticorax (night heron), 6; Egretta alba (great white egret), 1; Egretta garzetta (little egret), 16; Ardea cinerea (grey heron), 31; Ardea purpurea (purple heron), 10. 73% of the birds were infected, and 10 species of trematodes from 5 families were observed:
Invasions take place when birds are feeding. Analysis of the life cycles of the recorded trematode species, and study of different invertebrates near the Swan Islands revealed that the most frequent food for Ardeidae in this region is freshwater fish, sea fish, more rarely Crustacea and, very rarely Mollusca. Ardea cinerea and Egretta alba are invaded by Pygidiopsis genata, Cryptocotyle concavum, Cryptocotyle lingua and Maritrema subdolum, a clear indication that on the Swan Islands thay prefer sea habitats. The species composition of trematodes found in Egretta garzetta (Echinostoma revolutum, Echinoparyphium recurvatum, Mesorchis denticulatus, Apharyngostrigea cornu) shows that this bird prefers fresh water habitats and only visits the sea coast more rarely. In terms of parasitology the Ardeidae are closely linked with fish and members of the Crustacea. Links with Mollusca seem to be random: only 8 of 67 birds were invaded by a trematode species (Echinoparyphium recurvatum) in which the life cycle is completed in the Mollusca.
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Ukraine, Kaniv, Biodiversity Conference: home page | Translation: V.P. Hayova |