Behavioral And Physiological Responses Of Mizuhopecten Yessoensis To Escape From Three Predators

Since 2017,scallop production has shown a downward trend,which has caused certain economic losses to the breeding enterprises.Predator predators has a great impact on scallop survival,so it is important to further investigate the escape mechanism of scallops.Mizuhopecten yessoensis is an important economic shellfish and cultured species in China.This study preliminarily observed and quantified the behavior and ability of scallops when the large(119.85± 3.23 mm),middle(89.24 ± 3.77 mm)and small(60.10 ± 3.23 mm)size scallop were respectively stimulated by predators(Asterias amurensis,Naptunea cumingii and Charybdis japonica).Comparing superoxide dismutase(SOD),catalase(CAT),arginine kinase(AK),and octopine dehydrogenase(ODH)activity changes in scallop gills,captalis,and mantle after continuous stimulation of predators,and transcriptome sequencing of the significant differences tissues.The following results have been obtained:(1)M.yessoensis response A.amurensis experiment:the pressure sensor-force gauge is used to measure the maximal force of closed shell(Fmax),contraction number of times(Tphasic,Ttonic),duration of contraction(ttonic),number of shell closures per minute and percentage regarding the number of closed shells(P30s)as predator presence conditions of M.yessoensis.The results showed that,with the amount of time,the movement ability of each scallop decreased,and the behavior patterns of different sizes were slightly different.The results of enzyme activity showed that all the different enzymes were different,and the four enzymes in the closed shell muscle were significantly different(p<0.05).Using muscle of medium scallop for transcriptome sequencing.In the transcriptome,the number of differentially expressed genes(DEG)was 514.|log2FC|≥ 3,p<0.05 for DEGs including PAH、β-GLB、BCAT1、KLF12、BRIP1、C1QL4、TRM112、C25B8.10、Rnf207、ASK.(2)M.yessoensis response N.cumingii experiment:Observe the cumingii selection of scallops,and quantifying scallop shell closure ability.Results show that when the size of the incense snail does not pose a threat to the scallop,it mainly avoids the prey by opening and closing the double shell for many times.However,the smaller the size,the smaller the muscle strength,if it is wrapped by the N.cumingii,it is difficult to escape.With the increase of the size,the ability to open and close the double shell is gradually enhanced,and the escape mode gradually changes to extend the closure time,and it is difficult to be wrapped or captured by the N.cumingii.The results of enzyme activity showed that the enzyme activity of medium scallop was quite different(p<0.05).Similar to the results of the N.cumingii-M.yessoensis experiment.Transcriptome sequencing identified a total of 405 DEGs,of which 289 were annotated to GO entries and 76 DEGs were enriched in the KEGG pathway.Wnt signaling pathway has the most enriched DEGs,including RYK、APC、BAMBI、WNT16、CACYBP and RUVBL1.(3)M.yessoensis response C.japonica experiment:Through video observation found that the scallop by continuous closed shell or movement to avoid crab predation,using the meter to quantify the movement,and the A.amurensis or N.cumingii experiment change trend is similar,the response mode are different when the specifications are different.The escape mode changes from multiple closed shells to continuous closed shells,with the increase of specifications.The results of enzyme activity showed that the enzyme activity of medium scallop was quite different(p<0.05),and the transcriptome analysis was conducted,780 genes were differentially identified.Combined with the results of three experiments,the differential genes showed that C1ql4,CHRNA2,KIF13B,HMCN1 and PROM1A were differentially expressed in the three predator stimuli.It is speculated that these genes might be related to the movement and regulation of scallop muscle after stimulation.