| The phylum Rotifera is with three classes:Seisonidea,Bdelloidea and Monogononta.Seisonidea only reproduce sexually;Bdelloidea reproduce exclusively by asexual parthenogenesis;Monogononta reproduce alternating these two mechanisms?"cyclical parthenogenesis"or"heterogony"?.Parthenogenesis?amictic phase?dominates the monogonont life cycle and usually occurs at good environmental conditions,promoting fast population growth and colonization.In this phase males are absent and amictic females produce diploid eggs by mitosis which develops parthenogenetically into females that are clones of their mothers.Some amictic females can generate mictic females that will produce haploid eggs by meiosis.Mixis?meiosis?is induced by different types of stimulus depending on species.Haploid eggs develop into haploid dwarf males if they are not fertilized and into diploid“resting eggs”?or“diapausing eggs”?if they are fertilized by males.As rotifers and nematodes share many similarities in structural characteristics?for example,the cuticle of the body wall,the constant number of individual cells and the primary body cavity?,they were once classified as rotifers in Phylum Nematoda.The current animal classification system USES rotifers as Pseudocoelomata,when Pseudocoelomata,together with nematode animals and other animals with seven primary coelomata,are Pseudocoelomata.With the development and application of new molecular biology research technologies,the current international counterparts have begun to use rotifers as experimental materials to carry out the regulation of heat shock proteins involved in senescence related signaling pathways,in order to reveal whether rotifers can prolong their life by regulating the relevant signaling pathways involved in HSP70.At present,the genome of Adineta vaga and the genome of Daphnia pulex with similar life history and reproductive patterns to rotifers have been published,and the characteristics of heat shock protein activity and its regulation through relevant signaling pathways have gradually attracted people's attention.Among lophotrochozoans?annelids,Platyhelminthes,rotifers,molluscs?,rotifers are among the most experimentally tractable,with a rich body of natural history and ecological research going back hundreds of years.They make up one of the largest micro-invertebrate phyla in terms of biomass,ecological importance,and number of species,and are major components of inland and coastal aquatic ecosystems throughout the world.Most rotifers are smaller than 1 mm,but have ganglia,muscles,photo-,chemo-,and tactile sensory organs;structures for crawling,feeding,and swimming;digestive and secretory organs;and ovaries.Due to their wide distribution,small side,fast reproduction,ease of cultivation,short lifespan,vast availability and the resting eggs which could get large numbers of same individuals in short time,rotifers also became useful model system for aging studies as elegans.Previous studies have demonstrated that the evaluated expression of MnSOD and CAT plays an important role during the aging process in Brachionus calyciflorus,and is probably more important than in that of Caenorhabditis elegans.The finds in aging studies using rotifers made great contributions to the development of animal aging theories.1.Effects of quercetin on rotifer lifespan,reproduction and antioxidant activityResults show that the suitable concentration of quercetin?20?M?has significant effects on the lifespan of Brachionus calyciflorus.While in high concentration?50?M?,quercetin shows an acute toxicological effect on B.calyciflorus and seriously interferes the reproduction.When the concentration was 20?M,the lifespan of the treatment group was significantly higher than that of the control group?15%?.Moreover,the expressive quantity of MnSOD mRNA and CAT mRNA in rotifers'bodies showed a significant up-regulated tendency.Under oxidative stress caused by high temperature?35°C?,quercetin treatment can reduce ROS content in rotifers'bodies and increase the survival rate.This conclusion emphasizes that quercetin can lengthen the lifespan of rotifers mainly by improving their antioxidant capacity.2.Based on RNAi technology,the mechanism of SIR2 gene in the regulation of rotifer longevity was revealedIn this experiment,we proved that when the SIR2 gene is interfered,quercetin and dietary restriction,two effective life-extending methods for rotifers,were no longer significant?P<0.05?.This indicates the SIR2 gene is involved in the metabolic pathway stimulated by dietary restrictions and antioxidants in rotifers,and plays a role in extending the lifespan of rotifers.Our results have established the role of SIR2 gene in regulating the life span of rotifers for the first time.As rotifers become a model organism for studying aging,the study of the mechanism of action of SIR2 gene in Brachionus rotifers will be further improved.3.Thermodynamic effects and gene regulation of low temperature extending Brachionus calyciflorus's lifespanThrough the experiments in this chapter,we found that the lifespan of B.calyciflorus could be extended and their tolerance could be improved by decreasing temperature appropriately?P<0.05?.Extending the lifespan of B.calyciflorus by low temperature is not passively and completely temperature-controlled.At the beginning of rotifer life,low temperature may regulate the expression of specific genes.The effect of low temperature on extending the lifespan of rotifers is persistent?P<0.05?.Even if we changed the treatment temperature to 25°C on the fourth day,the lifespan-extending effect could be preserved?P<0.05?.In RNA interference experiments,we found that the effect of low temperature on extending the lifespan of rotifers decreased after gene interference,which showed that in this phenomenon gene regulation played a more important role than thermodynamic effects.4.Correlation study of calcium homeostasis during aging of rotifersIn this chapter,we examined the changes of SERCA gene expression during the aging process of rotifers.We found that the expression of SERCA gene decreased with the increase of senility.Nifedipine prevents calcium ions from entering rotifers'cells,reduces malondialdehyde content in rotifers,and increases rotifers'lifespan.These results suggest that calcium ions play a key role in the aging process of rotifers,especially in later life,and that cell damage caused by this calcium homeostasis can be improved by adding drug treatments.5.Effect of parental temperature on the tolerance of offspringIn this experiment,we examined the effects of two kinds of maternal effects?maternal age and food?on the offspring of B.calyciflorus.We found that the age of the mother affects the longevity and size of the offspring,and that dietary restrictions in the mother can reduce these effects to some extent.When CR treatment was applied to the offspring of the treated group,the offspring had a longer life span,indicating that the life-extending effect caused by CR treatment could be passed on to the next generation.The results showed that the energy distribution mechanism of B.calyciflorus could be inherited to the next generation under the dietary restriction.It remains to be seen whether rotifers will develop stable genetic mechanisms to cope with chronic food shortages if they go through several generations of dietary restriction,since the present experiment only involves the second generation.6.Changes in life span and stress defense gene expression of rotifers in different age groups under high CO2 concentration were analyzedThe results of this chapter show that acidification has a negative effect on population growth rate and average spawning amount of B.calyciflorus.Although there was no significant difference between the experimental group and the control group,the net reproductive rate was significantly reduced due to water acidification?P<0.05?.We found that in different age groups of rotifers,the mRNA expression levels of catalase CAT and heat shock protein HSP70 were affected by water acidification.There were also significant differences in mRNA expression levels in the same age group under different treatment conditions?P<0.05?.It is revealed that the age structure of the population is an important factor when rotifers are affected by acidified water bodies,because the age structure may change the redistribution of energy and the tolerance of organisms to the environment. |
PDF Full Text Request