The nematode community of two Italian rivers (Taro and Ticino)

The Taro and Ticino rivers were sampled (maximum 15 cm depth) for nematodes during I year at three sites for each river and some ecological parameters were measured. The yearly mean abundance of nematodes in the river Taro was 23 individuals/ 10 cm 2 and in the river Ticino 79 individuals/10 cm(2). In the two rivers five to 15 and three to ten species, respectively, were found. The highest station (Taro 1) of the river Taro was significantly different from all the other Taro and Ticino stations both for number and species composition: bacterial feeders were the dominant group in Taro I (mean Maturity Index (MI) was 2.25), whereas unicellular eukaryote feeders dominated the other Taro and Ticino sites (mean MI of 2.85). Chromadorina bioculata was the most common species in both rivers, except at Taro 1, where Eumonhystera dispar dominated. Significant correlations were found between conductivity and unicellular eukaryote feeders and bacterial feeders. For the first time the Distinctness Index Delta(+) is used for freshwater nematodes. Comparing our communities with other Italian rivers (data taken from the literature), we detected significant differences between polluted and not polluted habitats.