Tetrahymena of the T. pyriformis complex collected from varied habitats in Malaysia, Thailand, and The People's Republic of China include strains of the micronucleate species T. americanis and T. canadensis and the amicronucleate T. pyriformis and T. elliotti. Two new breeding species are described-T. malaccensis from Malaysia and T. asiatica from China and Thailand. Two wild selfers from China and some of the amicronucleate strains from all three countries fall into isozymic groups similar to named micronucleate and amicronucleate species. The T. patula complex is represented by two groups of clones from Malaysia that fit the morphological description of T. vorax. They, however, have radically different isozymic electrophoretic patterns and both groups differ from those of previously described T. vorax. As their molecules indicate relationships to other "T. vorax" strains as distant as that between T. vorax and T. leucophrys, they are considered to be new species, T. caudata and T. silvana. A third new breeding species, T. nanneyi, was identified among strains previously collected in North America. Viable immature progeny were obtained from the new strains of the five breeding species. Maximum temperature tolerances were determined for the new strains of four of the breeding species.
The rickettsial disease of man found only in Asia is mite-borne (scrub) typhus, caused by Rickettsia tsutsugamushi. Unique to southern Japan is a little-known human mononucleosis-like disease caused by Rickettsia sennetsu. In 1981 and 1982, there was a remarkable resurgence in the number of reported cases of mite-borne typhus in Japan after some years of virtual absence. Recent studies of R sennetsu have resulted in its reclassification to the genus Ehrlichia, members of which until now have been exclusively pathogens of animals. The historical background of ecologic investigations, in Malaysia and elsewhere, of these two developments suggest directions for future research.