Physiological And Transcriptional Responses To Thermal Stress Among Different Populations Of Nerita Yoldii

Intertidal zone is affected by both marine and terrestrial environments.Intertidal environment fluctuates violently and is easily sensitive to climate change.With the construction of artificial infrastructures along the Chinese coastline,more and more natural coasts are replaced by artificial coasts.In the present study,we conducted field survey and physiological studies on a rocky intertidal gastropod Nerita yoldii,traced their northern migration and analyzed the physiological and transcriptional responses among its different populations.After a six-year ecological survey of several artificial and natural coastal areas in Zhejiang and Jiangsu provinces(once in winter and once in summer in each year),it was found that the northern distribution of Neritayoldii migrated to Zhong'anpeng in 2016 and to Wanggangzha in 2017.Distribution data also showed that Dongtou,Lvsi and Yangguangdao populations were divided into a group,Zhong'anpeng and Wanggangzha populations were divided into another two groups.Density of snails decreased in Yangguangdao but increased in Zhong'anpeng.The coverage of Nerita yoldii on artificial hard-substrate seawalls(Lvsi,Yangguangdao and Zhong'anpeng)showed a seasonal trend of low in winter and high in summer,however,this pattern could not be found in the population of natural rocky shore(Dongtou).These results indicated that the artificial seawalls built on the coast of Jiangsu province provided a substrate for the northward spread of Nerita yoldii,making its geographical distribution rapidly changing,but populations showed different seasonal variation trends among habitats.Temperature is the most critical environmental factor affecting the survival of organisms.In this study,four populations of Nerita yoldii were collectded from two natural rocky shores(Xiamen and Dongtou)and two artificial hard-substrate seawalls(Lvsi and Zhonganpeng).After two months of common garden at 25?,the cardiac performance curve was measured.The results showed that Arrhenius break point temperature(ABT)increased with the increase of latitude,while the flat line temperature(FLT)and FLT minus ABT showed no such trend.There were significant differences in ABT and FLT between different populations,but no significant difference in FLT minus ABT.The ABT and FLT of natural rocky shore populations were lower than those of artificial hard-substrate seawall populations,and there was a significant difference in ABT between different habitats.The generalized additive model(GAM)analysis showed that there were significant differences in heart performance curves within and between populations.These results indicated that the thermal tolerance of Nerita yoldii increased with the increase of latitude,and there were significant differences among different populations and individuals.The more severe thermal stress environment on the artificial seawalls might be the reason for the improvement of the thermal tolerance of the species.The microevolution of intertidal organisms adapting to different latitudes is closely related to their distribution.In this study,the transcriptome of different populations of Nerita yoldii was sequenced at different temperatures(25,37 and 45?).Sequencing results showed that with the process of heating up,heat shock response occurred in Nerita yoldii,a lot of heat shock proteins were synthesized to resist the cellular damage.The ubiquitin-proteasome hydrolysis process was enhanced,related genes presented higher expression in 37 and 45?.The expression of inhibitor of apoptosis proteins also increased with the increase of temperature.The annotated results also included some genes of the antioxidant system,showing a trend of up-regulation followed by down-regulation.Under the condition of 45?,genes associated with glycometabolism were downregulated,suggesting that the cells devoted a lot of energy to resisting heat stress.The transcriptomic response patterns of different populations were different,and differences between Xiamen population and the other three populations were the most significant,which might be the result of local adaptation to the habitat temperature.