Intraspecies Variability in the Esterases and Acid Phosphatases of Paramecium jenningsi and Paramecium multimicronucleatum: Assignment of Unidentified Paramecia; Comparison with the P. aurelia Complex'

Enzyme electrophoresis was exploited to identify stocks of paramecia previously not identified to particular species. Stocks collected in India and one from Panama belong to Paramecium jenningsi, while others collected in Panama or in Brazil are assignable to syngen 2 of P. multirnicronucleatum on the basis of similarity of their esterase and acid phosphatase phenotypes. Inclusion of these doubled the numbers of stocks available in the two species, thereby facilitating examination of intraspecies variation and comparison of particular features of intraspecies variation found for the P. aurelia complex. Variant stocks were observed in P. jenningsi and in syngens 2, 3, and 4 of P. multimicronucleatum. In some cases the variant lacked the enzyme; in others, a change in mobility of the enzyme occurred that resulted in an electrophoretic form similar to one common in another species. Unique phenotypes were displayed by the variants of syngen 2 in P. multimicronucleatum. Hypervariability for Esterase B was observed in this syngen, where, in addition, several subtypes were seen for three other esterases. Unique phenotypes and hypervatiability were also noted in P. biaurelia. Clustered variations were observed in these species and in the P. aurelia species. Unlike the situation for members of the aurelia complex, where lack of geographical differentiation between stocks in the same species is a unique feature, some such differ- entiation does occur in P. multimicronucleatum-2. The frequency of variant stocks in P. jenningsi was similar to that observed in the aurelia sibling species. In contrast, a significantly higher frequency of variant stocks was found in syngens 2, 3, and 4 of P. multimi- cronucleatum. NZYME electrophoresis has been exploited to identify stocks E belonging to different species in the Paramecium aurelia complex (4, 12, 22, 23). Provided the frequency of enzyme phenotypes shared by different species is low, assignment of stocks to species can be carried out unambiguously (2, 23). Separate species status was given to the syngens of (the old) P. aurelia when it became possible to identify stocks by enzyme electrophoresis and they could be frozen and stored in liquid nitrogen (19). Each species has a distinctive array of enzyme phenotypes. Comparison ofenzyme phenotypes between species has shown that the molecular distances between species are large despite their lack of morphological differentiation (2). A number of stocks collected in Panama, Brazil, and India in 1957 to the mid-1960's were suspected of belonging to either Paramecium jenningsi or P. multirnicronucleatum, but for rea- sons no longer possible to determine, they had never been as- signed to species (Sonnebom and Schneller, personal commu- nication). These stocks were sent to us so we could identify them using the enzyme electrophoresis techniques. This has been ac- complished, and we will show that some of these collected stocks belong to P. jenningsi and others to syngen 2 of P. rnultimi- cronucleatum. Five different esterases in members of the aurelia complex can be distinguished on the basis of their substrate specificity, sensitivity to the inhibitor eserine sulfate, and their response to different conditions of growth (5, 8, 11). All, or most, of these five esterases are also present in species of the P. jenningsi, P. rnultirnicronucleaturn, and P. caudatum species complexes (1 3): Esterase A (EstA), Esterase B (EstB), Cathodal Esterase C (EstC,), Anodal Esterase C (EstC,), and Esterase D (EstD). Each type of esterase was found to vary independently, with genetic as well as environmental factors determining the electrophoretic mobility or activity of individual esterases (6-8, 11, 13, 14). For eash esterase, each species has a commonly observed sub- type (of a particular mobility) that may, or may not, be shared with other species. Each species (or syngen) has a distinctive ~~