Hypotrichidium tisiae(Gelei,1929)Gelei,1954:a unique hypotrichid ciliate having a highly specialized developmental pattern during binary division

In sharp contrast to their pelagic relatives,the oligotrichs,the overwhelming majority of hypotrich ciliates inhabit the benthos.Only a few species,including those of the genus Hypotrichidium Ilowaisky,1921,have adapted to a planktonic lifestyle.The ontogenetic mode of the highly differentiated ciliate,Hypotrichidium tisiae(Gelei,1929)Gelei,1954,is unknown.In this study,the interphase morphology and the ontogenetic process of this species are investigated.Accordingly,the previously unidentified ciliary pattern of Hypotrichidium is redefined.The main morphogenetic features are as follows:(1)The parental adoral zone of membranelles is inherited completely by the proter and the oral primordium of the opisthe arises in a deep pouch.(2)Five frontoventral cirral anlagen(FVA)are formed:FVA I contributes to the single frontal cirrus,FVA II–IV generate three frontoventral cirral rows,FVA V migrates and forms postoral ventral cirri.(3)All marginal cirral row anlagen develop de novo:each of the two left anlagen forms a single cirral row,while the single right anlage fragments into anterior and posterior parts.(4)Two dorsal kinety anlagen occur de novo,with the right one fragmenting to form kineties 2 and 3.(5)Two long caudal cirral rows are formed at the ends of dorsal kineties 1 and 3.On the basis of the morphogenetic features and phylogenetic analyses,the assignment of Hypotrichidium to the family Spirofilidae Gelei,1929 within Postoralida is supported.The establishment of separate families for the slender“tubicolous”spirofilids and the highly helical spirofilids is also validated.

Ontogenesis and systematic position of a new hypotrichous ciliate,Chaetospira sinica sp.nov.,with an improved diagnosis of the poorly defined family Chaetospiridae Jankowski,1985(Protozoa,Ciliophora,Hypotrichia)

Ciliates are unique single-celled organisms that play important roles in ecological,environmental,evolutionary,and ontogenetic research.In the present study,phylogenetic analyses based on 18S rRNA gene sequence data reveal that Chaetospira sinica sp.nov.clusters with Stichotricha aculeata with strong to full support(97%ML,1.00 BI),but is not closely related to members of Spirofilidae Gelei,1929 to which Chaetospira and Stichotricha have previously been assigned.Phylogenetic analyses,together with morphological and morphogenetic data from Chaetospira sinica sp.nov.,support the validity of family Chaetospiridae Jankowski,1985.Chaetospira and Stichotricha are here assigned to the family Chaetospiridae,the improved diagnosis of which is as follows:non-dorsomarginalian Hypotrichia with flask-shaped body;oral region extending along narrow anterior neck region;lorica usually present;two ventral and two marginal cirral rows,all distinctly spiraled or obliquely curved;pretransverse and transverse cirri absent.The basic morphogenetic features in C.sinica sp.nov.can be summarized as:(1)the oral primordium for the opisthe develops de novo and the parental adoral zone is completely retained by the proter;(2)all ventral cirral anlagen and marginal anlagen developed intrakinetally;(3)three dorsal kineties anlagen formed intrakinetally in each daughter cell;and(4)macronuclear nodules fuse into a single mass.Exconjugant cells were also isolated and their morphologic and molecular data are provided.