Studies On The Ultrastructure Of The Hypotrichous Ciliate Pseudourostyla Cristata

Hypotrichous ciliates are a kind of ciliates whose cortical systems and cellular structure are relatively complex,the study on the cortical ciliature and its variation during morphogenesis are important to reveal the development model of life cycle of ciliates and the relationship between the new and old structures and also has important theoretical and practical meaning to phylogenetics,comparative taxonomy and genetics of eucaryote.There were so much study on morphology and morphogenesis of ciliates,but the data of ultrastructure of some common ciliates like Pseudourostyla cristata is insufficient,and it also has some problems about the formation of adoral zone of membranelles during morphogenesis.In this paper,using scanning electron microscope and transmission electron microscope,the ultrastructure of ciliate Pseudourostyla cristata was observed and got its ultrastructural features of morphogenetic process of cortical ciliature,the accessory microtubules and fiber systems.It offered new data to understand the morphogenetic mechanism and characteristics of structural differentiation.1 The morphology and morphogenesis of cortical ciliature of Pseudourostyla cristataThe characteristics of cortical ciliature of ciliate Pseudourostyla cristata were indicated by using scanning electron microscope.Including the morphology of adoral zone of membranelles(AZM),undulating membrane(UM),frontal cirri(FC),marginal cirri(MC)and dorsal cirri(DC).It was sure that each membranelle of the AZM included four rows of paramembranelles.Besides,the first row only included three basal bodies and arranged closely with other three rows in the lapel part(AZM-L),while it was located in the ridge of separating two adjacent membranelles in the collar part(AZM-C).The AZM-L had lateral cilia of different length.The left and right marginal cirri were different in the numbers and arrangement of basal bodies:the RMC had 11 basal bodies,the first row had 3 and the other two rows had 4 each other;but the LMC had 14 basal bodies,the first row had 4 and the other two rows had 5 each other.The basal bodies of MC,DK and FC are all had something special connected with pellicle.The author also observed the intact process of morphogenesis of ventral and dorsal ciliature.During morphogenesis,the AZM-L and the ends of AZM-C of the proter were renewed,while the other part of AZM-C were remained.And something new were found in the study of forming of AZM of proter and opisthe.The primordia of AZM of opisthe were formed at the left of left row of mid-ventral cirri.Moreover,some membranelles at the posterior end of old AZM were left during morphogenesis and moved backwards to the most anterior end of AZM of opisthe.These membranelles of old AZM may supply some substances and may take part in the formation of AZM of the opisthe with mid-ventral cirri,which may a new mode of stomatogenesis in hypotrichs.2 Transmission electron microscopic observation on the cortex,ciliature and nucleus of Pseudourostyla cristataUsing transmission electron microscope,the ultrastructure of pellicle,cortical ciliature,nuclear in the vegetative period and nuclear of the division stage were revealed.The V-shaped microtube bundles connecting membranelle of AZM became wider and coarser from the horizontal direction to the vertical direction and connected to submembranellar fiber finally.The bottom of basal bodies of AZM were connected as transverse rows by anterior and posterior connection.The middle part were connected as transverse rows by anterior and posterior connection and as longitudinal rows by left transverse and right transverse tubules.The inner preoral membranelle possessed only one row of basal bodies,the outer preoral membranelle was consisted of 3-4 rows.The accessory microtubules of LMC included the anterior longitudinal fibers,posterior longitudinal fibers,surrounding fibrillar basket,kinetodesmal fibril and small sub-ectoplasmic rootlets formed.The basal bodies of LMC were connected by two transverse connection(1 anterior connection and 1 posterior connection),1 diagonal connection and 1 longitudinal connection.The nucleus had 2 layers of nuclear membranes,and nuclear matrix presented connecting with cytoplasm due to missing of nuclear membranes in this part.A replication band could be seen during the division stage and had two different areas.There were closely arranged microtubules behind the pellicle,which formed microtubule layer together with the accessory microtubules of the cirri.The connection of basal bodies of AZM showed high similarity among the same genus and certain difference of the different genus.But the Pseudourostyla cristata and the Paraurostyla weissei showed great similarity among the AZM,UM and MC,so the Paraurostyla weissei might be a kind of ciliate which between Oxytricha and Urostyloidea,so I it was advised that it should be divided from Oxytricha.So the study of the connection of basal bodies of ciliature of Pseudourostyla cristata not only riched the data of ultrastructure of ciliates and indicated the diversity and complex nature of eukaryotic cell,but also provided theoretical basis for the study of taxonomy and phylogeny in the view of ultrastructure.In addition,the arrangement of microtubules behind the cortex indicates that the higher the level of evolution of ciliates,the more complicated of arrangement of microtubules.