Studies On Vertical Migration Rhythm Of Two Species Of Pseudodiaptomus

The vertical migration of copepods is a common ecological phenomenon.The vertical movement pattern of copepods may change according to the species and the environments copepods lived,therefore,the vertical movement of copepods is characterized by complexity.The vertical movement of copepods may be affected by many factors,and many researchers believe that this phenomenon is related to endogenous rhythm.In this research,the vertical migration rhythm of Pseudodiaptomus annandalei and Pseudodiaptomus sheni was studied by using advanced biorhythm analysis methods such as autocorrelation analysis,Fourier analysis,maximum entropy spectrum analysis and wavelet transform,and the biorhythm calculated from rising frequency and rising height of copepods.Meanwhile,several factors that may affect the vertical migration rhythm of copepods were investigated.The main findings are as follows:1.The vertical migration rhythm of Pseudodiaptomus annandalei and Pseudodiaptomus sheni:Pseudodiaptomus annandalei mainly performed circadian rhythm under constant dim condition(DD),and the power of circadian rhythm and circatidal rhythms were both strong under normal photoperiod conditions(LD),but circatidal rhythms were stronger than circadian rhythms.The enhancement of the tidal rhythm of Pseudodiaptomus annandalei under LD condition is probably caused by the interaction between circadian rhythm and circatidal rhythms,and the oscillations of circadian rhythm oscillators promote the expression of tidal rhythms.Under both DD and LD conditions,the vertical migration of Pseudodiaptomus sheni was dominated by circadian rhythms,and the power of circatidal rhythm lowered than circadian rhythm.The difference in the vertical migration rhythm of these two species Pseudodiaptomus is probably due to the different adaptive strategies adopted by the two experimental animals which live in different environments.2.Effects of light on vertical migration of copepods:Under the constant light condition of 72-100 lx(LL),the vertical migration rhythm of Pseudodiaptomus annandalei and Pseudodiaptomus sheni was continuously attenuated.Pseudodiaptomus annandalei and Pseudodiaptomus sheni were sensitive to light,and under this illumination,the periodic vertical migration of Pseudodiaptomus both increased.The vertical migration periods of Pseudodiaptomus annandalei and Pseudodiaptomus sheni were disordered under the influence of both light and endogenous rhythm.3.Comparison of vertical migration rhythm in male and female copepods:The vertical migration rhythm of both sexes Pseudodiaptomus annandalei was dominated by circadian rhythm,but the results of wavelet transform showed that the intensity of the main rhythm(circadian rhythm)of two sexes Pseudodiaptomus annandalei was different,and the intensity of the main vertical migration rhythm of Pseudodiaptomus annandalei was higher in females than in males.The components of the vertical migration rhythm of the female Pseudodiaptomus sheni and the male Pseudodiaptomus sheni were different,and the circadian rhythm and circatidal rhythm of the female Pseudodiaptomus sheni were stronger than the male Pseudodiaptomus sheni.4.Effects of starvation and feeding on the vertical migration rhythm of copepods:The main rhythm components of the vertical migration of feeding and food deprived Pseudodiaptomus annandalei were same,both of which had a circadian rhythm.Feeding and food deprived Pseudodiaptomus sheni also mainly performed circadian rhythm,and the power of circatidal rhythm lowered than circadian rhythm.However,the results of wavelet transform revealed the difference in the intensity of the main vertical migration rhythm(circadian rhythm)between feeding and food deprived Pseudodiaptomus annandalei,and the intensity of main vertical migration rhythm of food deprived Pseudodiaptomus annandalei was higher than the feeding animals;however,the intensity of main vertical migration rhythm of food deprived Pseudodiaptomus sheni was lower than the feeding animals.