Phylogeny and Systematics of Leptomyxid Amoebae (Amoebozoa, Tubulinea, Leptomyxida).

We describe four new species of Flabellula, Leptomyxa and Rhizamoeba and publish new SSU rRNA gene and actin gene sequences of leptomyxids. Using these data we provide the most comprehensive SSU phylogeny of leptomyxids to date. Based on the analyses of morphological data and results of the SSU rRNA gene phylogeny we suggest changes in the systematics of the order Leptomyxida (Amoebozoa: Lobosa: Tubulinea). We propose to merge the genera Flabellula and Paraflabellula (the genus Flabellula remains valid by priority rule). The genus Rhizamoeba is evidently polyphyletic in all phylogenetic trees; we suggest retaining the generic name Rhizamoeba for the group unifying R. saxonica, R.matisi n. sp. and R. polyura, the latter remains the type species of the genus Rhizamoeba. Based on molecular and morphological evidence we move all remaining Rhizamoeba species to the genus Leptomyxa. New family Rhizamoebidae is established here in order to avoid paraphyly of the family Leptomyxidae. With the suggested changes both molecular and morphological systems of the order Leptomyxida are now fully congruent to each other.

[Morphometric analysis of six natural populations of Difflugia tuberspinifera].

The morphometrical variability of six natural populations of Difflugia tuberspinifera was investigated using the statistic methods based on 374 samples from Yangtze River and Pearl River valleys. The size frequency distribution analysis indicated that D. tuberspinifera is a size-monomorphic species with normal distribution of shell height, shell diameter and aperture diameter. The size of spine length, collar height, foreside length and number of conical spines are the most variable. The correlation analysis showed that most characters are inter-correlated with P<0.05. The shell height, shell diameter, aperture diameter, spine length, collar height, rear end length, foreside length, number of aperture tooth-like structures and number of conical spines differed significantly between different populations (P<0.0001), but principal component analysis (PCA) did not clearly distinguish the six populations based on the morphometric data. However, the cluster analysis separated the six populations into two groups, the Pearl River-Yangtze River group and the Yangtze River group. Further, the populations with different shell characters can coexist within the same river valley. Thus, there is a high morphological variability or diversity within the populations of D. tuberspinifera which is related with local environmental conditions.