Quantitative analysis of Trichodina denticlating characters and phylogenetic relationship studies on interspecies and intraspecies

Since Ehrenberg (1838) firstly reported Tricodina pediculus,there were two milestones in the research work on trichodinids. The first was the widespread acceptance of the uniform specific characteristics proposed by Lom (1958), which resulted in a standardization of the taxonomy of trichodinids. The second was the appliance of guidelines for elucidating the shape of denticles advanced by Van As & Basson (1989), which can also be used to re-evaluate previous work on trichodinids and especially to distinguish denticles between closely related species. As an important diagnosis marker, denticlating character has been widely used in species identification of the trichodine ciliates. In this paper,we firstly introduced a quantitative method of area percentage to describe denticlating. Quantitative description was achieved by measuring the percentages of the respective area of blade,central part and thorn to the denticle's and the total area of denticles to the denticlating ring's from aboral view. Basing on these quntitative values,first,we discussed the phylogenetic relationship of intraspecies of Trichodina nobillis from three populations; then we selected Trichodinella load as an outer group,and tentatively performed fuzzy clustering analysis on Trichodina nobillis, Trichodina heterodentata, Trichodina dormergui, and Trichodina fahaka, and studied the phylogenetic relationship of intraspecies among the four trichodinids. The results revealed the Pdr (Percentage of the area of denticles to the denticlating ring's) showed distinct diference in interspecies, and we also found Trichodina heterodentata and Trichodina dormergui with higher Ptd (Percentage of thorn area to dentice's) formed a sister group, and evolved lately, but Trichodina nobillis with lower Ptd evolved more early relatively. So, we concluded that the higher the Ptd was, the more lately Trichodina evolved. The conclusion approved the theory of evolutionary order of 6 types of denticles of Mobilina that Kuidong Xu et al. had put forward. It may not only describe quantitatively the structure of the three parts of the denticle and their interrelation, but also provide a method for the research of Trichodina phylogeny by this quantitative mean