Preliminary Study On Rare Earth Elements Particles And Its Formation Factors In Compound Eyes Of The Antarctic Krill (Euphasia Superba Dana)

As an important part of the Antarctic ecological environment,no matter how to measure it,the Antarctic krill can be called the most successful species on the planet.The Antarctic krill can survive in the harsh Antarctic because of its adaptation to the environment and gradual evolution.The compound eyes are the important photoreceptor of the Antarctic krill,which has unique structural characteristics and complex physiological functions,and play an extremely important role in the survival of the Antarctic krill.This paper is mainly to conduct a preliminary study on the special structure—particles,which found in compound eyes of the Antarctic krill.The compound eyes of the Antarctic krill,muscle tissue,photogenic organs'chromatophores and chromatophores under the carapace were observed by electron microscopy scanning(SEM).Lots of particles were found outside the chromatophores.The particles were not observed in muscle tissue,photogenic organ chromatophores and chromatophores under carapace,which is the different between the chromatophores in compound eyes and other two kinds of chromatophores in the Antarctic krill.In order to further explore the formation of the particles in the compound eyes,the further SEM and energy dispersive spectrum(EDS)were performed on the particles of the Antarctic krill with different ages and genders.From the observation of SEM,from stage 1 to 4 of the Antarctic krill,the diameter and density of the particles gradually increased.The diameter of the maximum particles in stage 1 is 4-5?m,the diameter of the maximum particles in stage 2 is 9-10?m,and the diameter of the maximum particles in stage 3 and 4 is 25-30?m.At the stage 3 and stage 4,the diameter and density of the particles reached the maximum and at stage 5,the diameter and density of the particles decreased as a whole,the diameter of the maximum particles in stage 5 is 8-11?m.There were no significant changes of the Antarctic krill of different genders.The changes of particles are consistent with the growth and development trend of the Antarctic krill.In the EDS,the muscle tissue of the Antarctic krill had single elements and no rare earth elements(REEs),but in the particles of the compound eyes,we detected the presence of a large number of elements including REEs.Therefore,the presence of a large amount of REEs is a prominent feature of the particles in the Antarctic krill.The statistical analysis shows that the particles of the Antarctic krill in different ages and gendersall contain C,N,O,Y,Tm,Yb,Ho and etc.The total average content of C,N,O and Y is 80.98±4.28%,and the total average content of Y,Tm,Yb and Ho is80.91±10.26%.The element detection shows that the content of elements in chromatophores of compound eyes was similar to that in corresponding particles.The main factors of particle formation in compound eyes of Antarctic krill were speculated by EDS.First,it was related to the growth and metabolism of chromaphores in compound eyes.Second,REEs have similar physical and chemical properties and often coexist.The aggregation of a large number of REEs may lead to the formation of particles.Third,REEs have active chemical properties,which can produce interactions with proteins or nucleic acids.The existence of such interactions has a tendency to cluster REEs.Fourth,the content of Y is highest in REEs,Y is most likely to combine with O.^2-to form Y₂O₃,which has a low solubility and a strong tendency of aggregation or precipitation to form particles in the solution.The magnetic detection of Antarctic krill compound eyes,compound eyes'paraffin,the standard Y and Y₂O_3,which proved that the Antarctic krill compound eyes,compound eyes paraffin section,Y and Y₂O₃ have paramagnetism,which further illustrates that the particles cotain REEs.It is speculated that Y and other REEs have the same characteristics of paramagnetism,which is also one of the factors of particles formation.Through tests of the Antarctic krill oil compound eyes and other tissue,found that the Antarctic krill compound eyes contain abundant PC,astaxanthin,astaxanthin esters,astaxanthin esters,respectively,compared with other organizations in more than 348 mg/g,2488.5?g/g,7217.2?g/g,6318.4?g/g,respectively.It is speculated that the formation of the particles in the compound eyes is related to abundant lipid,such as PC,astaxanthin,astaxanthin monoester,astaxanthin diester.Because PC,astaxanthin and its esters are antioxidant,which speculates that the particles in the compound eyes may have antioxidant activity,which plays an important role in the survival of Antarctic krill in Antarctica.The study makes preliminary study on the particles in the compound eyes of the Antarctic krill,and speculates several factors of the formation and effects of particles in compound eyes.Future research should start from the aspect of optics and vision,and further explore the functional characteristics of particles by combining the optical effect of particles in compound eyes with the visual development of the body.In addition,the special enrichment mechanism of REEs in compound eyes particles and the existence characteristics of nucleic acids and proteins in these particles will also be the future research direction.