PROGRESS IN PROTOZOOLOGY

254 D. L. NANNEY
Table 6
Estimates of the mean DNA contents of Tetrahymena strains in programs
DNA per G2 macronucleus
Species Mean
Coefficient of
Variation (%)
T. pyriformis complex
Amicronucleate species
T. pyriformis (A) 30 25
T. elliotti (B) 15 17
T. furgasoni (C)
Micronucleate species
13* 16
T. thermophila (1) 20 20
T. americanis (2) 30 20
T. canadensis (7) 20 20
(6)
T. pigmentosa ^
25
36*
25
20
T. hyperangularis (10)
T. rostrata complex
35 20
T. rostrata 40 25
T. corlissi
T. patula complex
50 25
T. patula 40 12
T. vorax 30 30
D o e r d e r et al. (1981).
* indicate extreme values.
philci, T. americanis, T. hegewischi, T. pigmentosa and T. tropicalis) and
concluded that the five pairs of chromosomes observed in each were
indistinguishable. Similarly, Elliott (1973) notes the "remarkable
homogeneity" of the species he surveyed for nutritional requirements.
Although occasional deviant strains have been reported, and mutations
have been induced, the standard nutritional pattern of the 10 species
studied is to require 11 amino acids, 7B vitamins, a purine and a pyrimidine.
In all the gross organismic characteristics — size, shape, karyotype,
biosynthetic processes — the T. pyriformis complex is monolithic. It is
against this organismic homogeneity that we have to consider the
question of molecular diversity.
(4) The T. pyriformis Complex is Enormously Diversified in its
Molecular Characteristics
The impression of phenotypic invariance, or at least of tightly constrained
phenetic variability, is sharply in conflict with essentially every
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