The Bdelloidea rotifer, a kind of asexually microscopic invertebrate, is the largest Metazoan group that reproduces only through parthenogenesis. Here the potential evolutionary species composition was analyzed using a coalescent approach to infer independently evolving entities from a phylogenetic tree obtained from cytochrome oxidase I sequences. Three clones (HX4, HX8 and HX19) of Bdelloidea Rotaria rotatoria were selected to be the representatives of three sympatric putative cryptic taxa for detecting the effects of temperature (24, 28 and 32 ℃) on their life history traits. The results showed that the responses of life table parameters to increasing temperature were different among the three evolving entities. Evolutionary species, temperatures and their interaction significantly affected all life history parameters except that evolutionary species did not significantly affect the durations of post-reproductive period and mean lifespan. In addition, the interaction of evolutionary species and temperatures did not significantly affect the durations of postreproductive period, offspring production or net reproductive rate. No matter what the evolutionary species was, the age-specific survival curves tended to decrease earlier and more quickly, and the peak of age-specific fecundity curves appeared earlier with increasing temperature. The three potential cryptic R. rotatoria taxa adopted variable life history strategies, low reproduction and high survivorship at low temperature, as well as high reproduction and low survivorship at high temperature. The similar adaptation abilities of HX4, HX8 and HX19 to water temperatures could be the best explanation for their coexistence in the subtropical shallow pond at a high temperature.

Rotifers are the most important live food organisms for use as starter food in aquaculture. The population growth and resting egg production dynamics of Brachionus calyciflorus sibling species BNA13 from lake Baixiang and BNB3 from lake Kongque, in Xishuangbanna city, Yunnan, China at four temperatures (16, 20, 24, and 28°C) and four algal (Scenedesmus obliquus) densities (0.5, 1.0, 2.0, and 4.0 9 10 6 cells/ml) were studied. The results showed different responses with rotifer sibling species. Sibling species, temperature, algal density and their interactions significantly affected the maximum population density, population growth rate and resting egg production except that both the interactions of temperature and algal density and the interaction of sibling species and temperature as well as algal density did not significantly affect maximum population density. Regardless of the effects of temperature and algal density, maximum population density, population growth rate and resting egg production of the B. calyciflorus sibling species BNA13 were greater than those of BNB3, suggesting that B. calyciflorus sibling species BNA13 was more suitable than BNB3 for fish larviculture. The maximum population density and resting egg production of sibling species BNA13 were the highest at the combination of 20°C and 4.0 9 10 6 cells/ml algal density and 28°C and 4.0 9 10 6 cells/ml algal density, respectively, indicating that the two combinations of temperature and algal density represented the optimum conditions of mass culture and resting egg production of B. calyciflorus sibling species BNA13 for fish larviculture respectively.

The bdelloid rotifer is an important component of freshwater zooplankton, exhibiting the features of parthenogenesis and anhydrobiotic capability. Heat shock proteins (Hsps), acting as molecular chaperones, are a highly conserved, ubiquitously expressed family of stress response proteins. In this study, the thermal optimums for heat-shock response and the levels of Hsp70 in Rotaria rotatoria (bdelloid rotifer) under different stress conditions were evaluated using survival assays and western blotting with fluorescent detection. The results showed that: (1) The survivorship in R. rotatoria were 100% throughout the temperature range of 12°C to 40°C, and the population growth rate reached its culmination at 28°C, suggesting the retardation of growth and reproduction at the other temperatures; (2) While stressed under 40°C, the levels of Hsp70 in R. rotatoria increased significantly over time, correlating with the duration of the stress; (3) As responses to different temperatures, the synthesis of Hsp70 could be induced significantly in R. rotatoria under both of high (40°C) and low (16°C) temperatures; (4) After removal of the thermal stress and recovery at 28°C, the levels of Hsp70 continued to rise for a period of time, peaked at 12 h, and then slowly declined with the extension of recovery duration, until there is no significant difference of Hsp70 levels. Summarily, with the fluctuations of stress duration and temperature, the rotifers could adapt to the environments sensitively by regulating the synthesis of Hsp70.