Abstract
Samples of the Moinairrasa were collected in Gudang irrigation cana,l a small canal for agriculture in Hangzhou,Zhejiang Province(30b17cN, 120b07cE), and were given abundant food(fed with Scenedesmus obliquus at about thedensity of 3 @ 105 cells/mL).The juveniles from the female parentwere isolated and cultured in different temperatures(15±1)℃,(20±1)℃,(25±1)℃,(30±1)℃,(35±1)℃) respectively.The expermi entwas carried out under aconstant light regmie of 12h light: 12h dark.Observed four tmies each day, the body length wasmeasured, the instars duration and the brood size were recorded.M ature age ofM.irrasa was related to w ater tem perature in inverse ratio, the relationship betw een mature age andw atertemperature at 15-35℃ could be expressed by formula: h= 7231.4t-1.6167, and the mature age was delayed to 19.3 dvisibly at(11±1℃). It was found thatM.irrasa has 3 pre-adult instars, 3-8 adult instars at 15℃, 30℃and 35℃respectively, 12-13adult instars at 20 and 25℃.The mean longevity of ind ividualswas estmiated to be 13.6±2.1 days or 12.2±3.1 instarsat 25℃ and 36.2±5.2 days or 6.8±3.1 instars at 15℃ 1A t 15-35℃, the low er tem perature, them ore brood size of the first adult instars1Them axmium egg product ion of the first adult instars was 19.8±1.7 at 15±1℃.From the 4th instars(part of individual from the 5th at(15±1℃),M.irrasa began to reproduce, the egg production increased with the instars, but began to declined after the maxmium egg production appeared. The expermient showed, the instars that reached the most fecundity were different in each temperature1Usually, the maxmium brood size was observed from the third to the fifth adult instars1The body length was 1.12)1.45mm at(15±1)℃, 1.06-1.47mm at(30±1℃ and 1105) 1143mm at(30±1)℃, the fecundity increased with the body length.The body length at(20±1)℃and(25±1) ℃ and the brood size were longer than the other temperatures1Under the condition of the 5 different temperatures(15℃, 20℃, 25℃, 30℃and 35℃), the maxmium size reached1193mm at 25e 1From juvenile stages to adult instars at 5 different temperatures, it needed 4d, 2.36d, 1.4d, 1.31d and1.00d respectively.The average number of egg production peradult was 24.78±4.29, 19.1±2.42, 26.25±5.71, 27.62±2.72 and 19.47±3.29; and the average individual cumulative egg production was 87±26, 159±39.5, 239±21.9,130.9±36.1, 81.6±17.0, respectively.ToM.irrasa, the most appropriate temperature for production was during of 25-30℃ and them axmium individual cumulative at 25℃, which egg production was 239±21.9.The average cumulative number of egg product ion was less than 100 at(15±1)℃ and(35±1)℃, only a few of individual reach to 151 and 117. It show ed that althoughM.irrasa could produce, it could not reach to them axmium fecund-ity in this case.The expermient showed that the temperature. s upper lmiited forM.irrasa at 38e for bear and at 40e for living1Onthe condition of 11℃, theM.irrasa were not suitable for production in their parthenogenetic generation1Reproduction capacityand bio logical phenomenon in several close species toM1irrasa in Genus Moina were also discussed in present.
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