Range of Variation in the Somatic Infraciliature and Contractile Vacuole Pores of Tetrahymena pyriformis

SYNOPSIS. Meridian ranges and contractile vacuole pore patterns were determined for 36 strains of Tetrahymena pyriformis, including most of the “classic” amicronucleate and micronucleate strains used by many investigators, plus a dozen other strains not previously characterized with respect to these two morphological features. Uniform axenic culturing and staining techniques were employed. Meridian ranges and modes are analyzed with strain-by-strain comparisons to the reports of previous investigators. The overall inclusive range of the 36 strains was 15–25 meridians. Modes for individual strains varied from 16 to 23. Broader ranges and, especially, higher modes and higher limits are recorded than those reported by Corliss (1953) for strains grown in bacterized hay cultures. Two postoral meridians are characteristic, although a single individual having only one and a few having three postorals were observed. Three postorals were found only in those strains having the higher number of total meridians. A few individuals, showing an anterior half or a posterior half of a bipolar meridian missing, indicate a possible explanation of how a single dividing individual could produce a proter and an opisthe differing in the total number of meridians. Meridian ranges of individual strains do not overlap each other in all cases, but they do constitute a progressively overlapping series which does not warrant taxonomic separation of strains at either extreme from each other. Contractile vacuole pores varied from 1 to 3, with 2 pores (1 each in meridians 5 and 6) being characteristic of 22 of the strains. The 2-pore 6-7 pattern was modal for 8 of the strains. Presence of 3 pores (in 5, 6 and 7) was typical of only 2 strains, but 3 pores were found occasionally. Another pattern of 3 pores (in 6, 7 and 8) was observed occasionally in 10 strains. Double pores (in 6 and 7 or 7 and 8) and the triple pore patterns were observed only in the strains having the highest total number of meridians. These variations are not considered adequate justification for taxonomic separation. Strains Ki and Aq are affirmed to be T. pyriformis. Strains V¹ PP and V, formerly regarded as strains of T. vorax, are considered to be T. pyriformis, supporting the view of Shaw and Williams (1963).