Effects Of Light And Temperature On Cardiac Hemodynamic Parameters Of Tridacna Crocea

In this study,color Doppler flow imaging technique（CDFI）was used to detect the heart rate（HR）,stroke volume（SV）,cardiac output（CO）,ejection fraction（EF）,ejection time（ET）and peak systolic velocity（PSV）of Tridacna crocea to explore the diurnal variation of these indicators and the influence of light and temperature on the diurnal variation.It lays a good theoretical foundation for study on the regulation mechanism of the cardiac hemodynamic parameters of T.crocea,and also provides important information for the artificial breeding of T.crocea,the protection of natural resources and choosing potential suitable habitats.The main research contents and results are as follows:1.Establishment and optimization of monitoring methodsIn this study,CDFI technology was used for detection of the structure of heart and blood flow pathways of T.crocea,precisely presenting the cardiac cycle and monitoring its frequency.It showed real-time observation of the blood flow direction,velocity,etc.under non-destructive conditions.In this study,the use of Image J software for post-processing shorten the time used to monitor samples,which help quickly treat several experimental individuals within a certain period of time,and increase the reliability of replicates.2.Diurnal variation of various indicators of T.crocea（1）The research has revealed the diurnal variation of the cardiac hemodynamic parameters of T.crocea at the optimal temperature.It was found that it has relatively diurnal variation,low heart rate,high ejection time,and high stroke volume,cardiac output and ejection fraction at night,while the case was just opposite during the day.However,the peak systolic velocity did not show any significant diurnal variation.（2）Different individuals had different diurnal variation ranges of each index.Heart rate ranged from 5.16 to 13.67 bpm.Ejection time ranged from 0.30 to 0.96 s.stroke volume ranged from 4.87 to 13.53×10^-3m L.Cardiac output ranged from 93.12 to 160.92m L/min.Ejection fraction ranged from 0.31-4.55%.Peak systolic velocity ranged from1.46 to 10.04 mm/s.（3）The analysis of the wet weight and the trend of each index showed that the heart rate,ejection time,stroke volume,cardiac output and ejection fraction had obvious regularities.The cardiac output,stroke volume and ejection time showed an upward trend with the increase of the individual’s wet weight.The heart rate and ejection fraction showed a downward trend with the increase of the individual’s wet weight.3.The effect of light on the cardiac dynamics parameters of T.crocea（1）It is found that four different photoperiods which include 12L:12D（a）（lighting time 06:00-18:00）,12L:12D（b）（lighting time 18:00-06:00）,0L:24 D（no light）,24L:0D（24h light）have effect on the cardiac hemodynamic parameters of T.crocea.The cardiac hemodynamic parameters of T.crocea is decided by the photoperiod.（2）Light-dark switching experiment proved that it can affect the cardiac hemodynamic parameters of T.crocea quickly,which illustrates that T.crocea is sensitive to the change of light.When the light is off,heart rate dropped rapidly,ejection time rose gradually,peak systolic velocity rose first and then dropped,the stroke volume and cardiac output rose rapidly.When the light is re-illuminated,heart rate rose rapidly,and ejection time,peak systolic velocity,stroke volume and cardiac output decline rapidly,and all of them returned to the initial level before the light off.4.The influence of temperature on cardiac hemodynamic parameters of T.crocea（1）We studied the cardiac kinetic indexes of T.crocea at gradient temperature（24℃,25℃,26℃,27℃,28℃,29℃,30℃）.It is found that within the temperature range,the cardiac hemodynamic parameters of T.crocea showed a consistent diurnal variation.Gradient temperature had a significant impact on the cardiac hemodynamic parameters of T.crocea.When the temperature rises,T.crocea responded by increasing heart rate,shortening the ejection time,and reducing the stroke volume and cardiac output.Peak systolic velocity was relatively stable to maintain blood supply.（2）We studied the cardiac hemodynamic parameters of T.crocea under fast heating stress（26-32℃,1℃/h）.The heart rate and PSV increased with the fast rising temperature,while ejection time,stroke volume and cardiac output showed a downward trend.Stroke volume,cardiac output and peak systolic velocity rose to a peak at 31℃,and then dropped slightly at a high temperature of 32℃,indicating a clue of heart failure.