| In this paper, the activities of digestive enzymes and population ecology of the Splraeroma retrolaevis were analyzed by researches taken in Hainan Dongzhaigang Mangrove from March to December in2011. We explored the relationship between activities of digestive enzymes and Splraeroma retrolaevis feeding habits by detecting activities of protease, lipase, amylase and cellulase. In addition, we observed the physical, chemical, biological and environmental factors of seawater in different regions, and also the distribution characteristic, age structure and sex ratio of Splraeroma retrolaevis containing station A, B, C, D and E. The results are as follows:(1) Activities of digestive enzymes in Splraeroma retrolaevisIt showed that the range of protease activity was from32.07to105.86U/mg, and average activity was83.18U/mg. The relation function of protease activity represented both larvae and adult was "y=15.461x+5.0509"(y=Protease activity, x=Body length, the same below). The average protease activity of adult male and female were86.22±0.80U/mg and125.01±0.69U/mg respectively. The relation function of protease activity was "y=3.787x+94.103". The range of amylase activity was from26.63to54.41U/mg, and average activity was44.63U/mg. The relation function of amylase enzyme activity from larvae to adult was "y=-3.268x2+24.784x+12.943". The average amylase activity of adult male and female were39.34±1.73U/mg and36.65±2.04U/mg respectively. The relation function of average enzyme activity was "y=-9.8599x+117.91". The range of lipase activity was from11.21to12.78U/mg, and average activity was12.07U/mg. The relation function of lipase activity from larvae to adult was "y=0.01x+12.05". The average lipase activity of adult male and female were12.10±0.06U/mg and12.15±0.05U/mg respectively. The relation function was "y=0.0252x+11.945". The range of cellulase activity was from18.46to48.62U/mg. The relation function of cellulase enzyme activity from larvae to adult was "y=-0.5173x3+3.6173x2-3.9102x+39.43". The average cellulase activity of adult male and female were30.00±1.57U/mg and27.35±1.72U/mg respectively. The relation function of cellulase enzyme activity was "y=-7.5915x+89.914". The lipase activity of Splraeroma retrolaevi was lowest either in larvae or adult, and it kept the same in different body length or different gender. With growth of bodies, protease activity was significantly higher than other digestive enzyme activity, and it was higher in female. Amylase and cellulase activity was reduced with growing of bodies. These changes in activities of digestive enzymes suggested that the larval and juvenile bodies feed more foods that containing higher cellulose and starch, such as phytoplankton, less foods that containing higher fat. The mature individuals feed more zooplankton or phytoplankton that containing higher proteins to meet the reproductive and developmental needs.(2) Environmental factors that affects distribution of Splraeroma retrolaevisThere was no significant difference in physical factors between stations A, B, C, D, and the control station E. Physical factors of seawater did not affect distribution of Splraeroma retrolaevis. Chemical factors of seawater such as salinity, pH, dissolved oxygen (OD) and chemical oxygen demand (COD) had no obvious influence on the distribution of Splraeroma retrolaevis either. Interestingly, total nitrogen and total phosphorus are limiting factors for the distribution of Splraeroma retrolaevis. The higher nitrogen and phosphorus increased phytoplankton bio mass and content of chlorophyll a in stations A, B, C and D compared to the control station E, which in turn provided abundant food for Splraeroma retrolaevis, therefore promoted Splraeroma retrolaevis breeding abundantly. In conclusion, the content of total nitrogen and phosphorus, the amount of plankton and chlorophyll a are critical environmental factors that influence the distribution of Splraeroma retrolaevis.(3) Splraeroma retrolaevis population ecologyThe Splraeroma retrolaevis population spatial distribution characteristics results show that Splraeroma retrolaevis population belongs to the cluster distribution type which trunk distribution center to the surrounding.The population quantity more large degree of industry cluster more higher. Largest population density at about20-25cm height from the basement that it near the high mark. In March, the Splraeroma retrolaevis population is fastest growing population that age structure for growth. The population age result becomes stable population in June and September. The age structure for Splraeroma retrolaevis is declining in December.Splraeroma retrolaevis population age structure of growth is the fastest in March and population growth to June, the age structure of the population becomes stable time Splraeroma retrolaevis reaches the maximum, in December, the Splraeroma retrolaevis population age structure of the inverted pyramid recession-type, in the most unstable recession phase. June water temperature, Splraeroma retrolaevis population in the highest population density, population most stable period, high and low temperature impact throughout the year group the Splraeroma retrolaevis population density and age structure.Splraeroma retrolaevis populations annual average ratio of55.02%to66.02%what close to population sex ratio is about1:1to1:2. Each month ratio level were in March> June> September> December。Adult Splraeroma retrolaevis total average ratio is lower than the rest of the year, which is about55.02%in December. This may be due to the Splraeroma retrolaevis male body is longer than the female body, so the body longer than6.5mm male ratio higher. Splraeroma retrolaevis populations in the recession, the sex ratio of the population older individuals. So the December is the best time for Splraeroma retrolaevis pest control. |
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