Right side

Description:

Portrait (right side) of the pleurostomatid ciliate, Siroloxophyllum utriculariae (Penard,1922) Foissner,1995. Siroloxophyllum was erected as a new genus based on the "oral bulge" which encircles almost the entire circumference of the cell, a single dorsolateral brush kinety and morphologically distinct right and left dorsolateral kineties different from other somatic kineties. The strongly laterally compressed cell is lancet shaped in outline. The cell is slightly contractile and highly flexible. The rounded anterior end is curved dorsally. The posterior is bluntly tapered. The flat right side bears 13-20 longitudinal kineties. The basal bodies of one of the perioral kineties are seen well here along the ventral (viewer's right) margin. The left side has 3-8 prominent longitudinal ridges bearing short cilia. The slit-like cytostome is located along the anteroventral edge. A hyaline band borders the cell. There is a distinctive structure which looks like a helix or twisted cord bordering the entire edge of the cell except for a short length of the anterior dorsal end. This is best seen at the anterior end in this image. The perpendicularly arranged peripheral extrusomes appear to anchor their exterior ends in this structure except in a short portion of the dorsal anterior edge where extrusomes and the string-like structure bordering the cell edge are absent. SEM studies suggest that all pleurostomatid ciliates have a string-like structure on the cell margin but in other genera this occupies 1/2 the cell circumference or less. There are two contractile vacuoles (seen here), the anterior one just ventral to the macronuclei and the posterior one located dorsally. The central macronucleus is bipartite. The inconspicuous micronucleus (seen here) is located between the two parts of the macronucleus. S. utriculariae swims slowly, gliding gracefully over the substrate. Differentiated from the similar L. helus by absence of trichocyst warts along the dorsal surface. Most easily confused with Amphileptus species which lack the distinctive bordering cord-like structure around most of its circumference and also have an anterior kinetal suture (spica) on the right surface. S. utriculariae may also be confused with Litonotus species in which the oral bulge is limited to the anterior end of the ventral side. Collected from a freshwater dredge pond near Boise, Idaho October 2004. DIC.