当前位置： SCI文献检索 > INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY期刊下所有文献 > Systematic position of Discocephalus-like ciliates (Ciliophora: Spirotrichea) inferred from SSU rDNA and ontogenetic information.

Systematic position of Discocephalus-like ciliates (Ciliophora: Spirotrichea) inferred from SSU rDNA and ontogenetic information.

Abstract：

:The Prodiscocephalus-like ciliates, or discocephalines, are cephalized organisms that are traditionally considered to be hypotrichs (sensu lato) but whose precise systematic position has long been uncertain. The main reasons for this are that these organisms exhibit several intermediate morphological and morphogenetic features and that hitherto none has been investigated using molecular methods. In the present study, the cortical development of Prodiscocephalus borrori was observed during binary division and this can be summarized as follows: (i) in the parental adoral zone of membranelles, only the posterior end is renewed by dedifferentiation of the old structures; (ii) the oral primordium in the opisthe occurs de novo on the cell surface as seen in other typical stichotrichs; (iii) in both dividers, the undulating membranes anlage does not split longitudinally in the usual way but, instead, divides transversely to form the paroral and endoral membranes; (iv) usually seven frontoventral transverse cirral anlagen are formed in the primary mode which then divide into two sets, one each for the proter and opisthe; (v) both left and right marginal rows divide into two parts, thus giving rise to a post-lateral marginal segment at the posterior end of each; (vi) invariably five caudal cirri are formed at the posterior end of the three rightmost dorsal kinety anlagen. Thus, it was found that, like other related discocephalines, P. borrori exhibits more similarities to stichotrichs than to euplotids. Based on a combination of morphological and morphogenetic data, a phylogenetic tree was constructed which suggests that the discocephalines group within the stichotrichs and separate from the euplotids. In addition, the complete small-subunit rRNA gene (SSU rDNA) of P. borrori was sequenced and analysed. In the resulting SSU rDNA tree, the discocephalines represent an intermediate group between the euplotids and the Stichotrichia-Oligotrichia-Choreotrichia assemblage, albeit with low bootstrap support. From these data, we conclude that the discocephalines might be a divergent, or possibly an ancestral, group within the Stichotrichia. Furthermore, our findings further support the suggestion that these organisms should be considered as a distinct order, i.e. Discocephalida Wicklow, 1982, in the subclass Stichotrichia Small & Lynn, 1985.

journal_name

Int J Syst Evol Microbiol

journal_title

International journal of systematic and evolutionary microbiology

authors

Shao C,Song W,Li L,Warren A,Al-Rasheid KA,Al-Quraishy SA,Al-Farraj SA,Lin X

doi

10.1099/ijs.0.65781-0

subject

Has Abstract

pub_date

2008-12-01 00:00:00

pages

2962-72

issue

Pt 12

eissn

1466-5026

issn

1466-5034

pii

58/12/2962

journal_volume

pub_type

杂志文章

在线工具

Systematic position of Discocephalus-like ciliates (Ciliophora: Spirotrichea) inferred from SSU rDNA and ontogenetic information.