Confocal Micro-Raman Spectroscopy Detection Of Shell Of Mussels

Mussels are widely distributed in the deep-sea(cold springs and hydrothermal fields)and offshore areas because of their strong adaptabilities to these environments.Mussels consume materials and energies in the environments to sustain the metabolism and to secrete calcium carbonate minerals to form shells for protecting the soft tissues.As a biomineral,the mineral shell is sensitive to environments,which results in the shells ideal subjects to study the physiochemical changes of their living environments during the formation processes.Generally,the previous researches mainly focus on the mechanism of the biomineralization processes and the microstructure of the shells,based on the traditional technical methods that require complex sample pretreatments,and cause damages to the shell samples.Here,we introduce laser Raman spectroscopy,a kind of"fingerprint"spectroscopy,to study the material structures of the shells.The laser Raman spectroscopy has many advantages,such as in-situ measurements,non-destructive to the samples,no need of sample pretreatment,and multi-component detection at a time,etc.Therefore,it is very suitable for the study of mussel shells minerals.In this paper,confocal micro-Raman spectroscopy was used to analyze and compare the mussel shells in different environments(offshore areas,cold seeps,hydrothermal fields).Based on the characteristics of the Raman spectra,significant changes in the minerals of mussel shells in different environments were revealed and the following conclusions are obtained:(1)Differences exist in the mineralization of mussel shells of offshore areas.Organic matters appear in the shells of Mytilus galloprovincialis.The crystallinity of three mussel shells are different.The prism layers of the shells of the Modiolus elongatus and Modiolus kurilensis are calcite,while the nacre layers is composed of aragonite.The prism layer of Mytilus galloprovincialis in Qingdao-offshore is calcite,the nacre layer is dominated with aragonite.The growth area contains calcite,and the organic molecule polyene is found with the Raman shift at 1019,1131,1301,1519?2235 and 2635 cm^-1.The polyene in the shell is closely related to mineralization and the Raman intensity directly proportional to the color of the growing area.The FWHM(full widt h at half maximu m)of calcium carbonate at 1085 cm^-1 of three types of mussel shells nacre aragonite was counted.The FWHM reflects the change of crystallinity.No obvious differences between the maximum growth direction and the vertical crystallinity of Qingdao Mytilus galloprovincialis were observed within and between individuals.The maximum growth direction of the aragonite in Modiolus elongatus is higher than that of the vertical direction,and no obvious differences between individuals were displayed.The crystallinity of Modiolus kurilensis is higher than that of above mentioned two types of mussels in Qingdao-offshore,and the aragonite crystallinity of the maximum growth direction is higher than that of the vertical direction.Different crystallinity in different growth directions may result from the strict control of shell mineralization by biological macromolecules.(2)The minerals of Bathymodiolus platifrons in the cold seep in the Fomosa Ridge(Site F)are aragonite and calcite.The mineral in the prism layer of Bathymodiolus platifrons is calcite,and the nacre layer is aragonite.The Raman shifts of the two minerals are not different from those of mussels in offshore environment.There is no obvious difference in the FWHM of t he main peak o f calc iu m car bo nat e bet ween Bathymodiolus platifrons and Modiolus elongatus,Mytilus galloprovincialis.The cr yst a llinit y o f t he maximu m growt h dir ect io n is higher t han t hat of t he vert ical direct io n.Bathymodiolus platifrons adapt to the cold seep environment.In the areas with high methane concentrations,the growth rate is comparable with that in the offshore areas.No obvious differences in miner alizat io n wer e obser ved.(3)The hydrot her ma l enviro nment has a significant influence on t he miner als o f Bathymodiolus manusensis.The mineral in the prism layer of Bathymodiolus manusensis in DESMOS hydrothermal is calcite,and the nacre layer is aragonite.The FWHM of nacre layer in the mussel shells is larger than that in other environments.And there are significant differences among individuals.The crystallinity of aragonite is poor,and the mineralization of shells is closely related to the complexity of hydrothermal environment.The temperature gradient of hydrothermal field is large.Various kinds and different concentrations of heavy metal ions affect the survival of the mussels.